bghazzal

Agree with all the above. And keep in mind that all "cheaper" clamps are not made equal. Speaking from experience, do stay away from non-branded generic products. The alloys (?) / material and sheer design of the super-cheap generic ones will lead problems after a while (corrosion, fusion of screw / washer elements etc) as they are not made of the proper material for salt-water use. Be very very careful with these, wash, vinegar, lubricate (WD40) regularly and never ever leave them tightened for extended periods of time (or you might have to hacksaw it...) Overall, best stay away unless you're ok with "disposable" clamps for experimenting / testing your setup (especially floats), and then get properly made ones as soon as that's settled. What you can also do is stay away from the cheapest-generic ones and get intermediate branded ones like Kraken, Weefine, Big Blue, Carbonarm instead... These might not be as solid as ULCS or Nauticam, but are roughly half the price, design is coherent, and they offer options sometimes not available in Nauticam (open clamps, especially 4 or 3 ball open-ended clamps, which are super useful for some applications...). If necessary, you can upgrade these gradually once your kit is set. That said, carbon-fiber floatation arms don't seem to have the same issues. I've been using a Puluz 900gm float and other generic floats for a few years now and they're perfectly fine. There are no-moving parts, and other than the rubber ring wearing down (you get spares with Puluz) especially when usign open-clamps, there have been no issues whatsoever with the carbon arms (cracks, etc) - as new. So this piece of kit might not be as critical. Just look for proper buoyancy data and brands that label their products (Puluz does), as most online vendors will have no clue as to what they are selling... cheers ben

SUMMARY Returning to the filtering / transmission info we now have on the UR-Pro Cyan filter, we can try to summarize the data as is: - In terms of spectrum, the UR-Pro Cyan does indeed function like fluorofilter, with a similar profile. The filter blocks the UV spectrum, and strongly restricts cyan to green transmission, while maintaining a medium transmission of dark/purple blues, and strong transmission of orange/red wavelengths, thus having a marked warming effect and smoothing spectrum alterations of ambient light in blue water (which helps the camera white balance). Practically, the working result is that UR-Pro Cyan preserves some deep blues for the water column, while nudging the cyan/green cast to a warmer yellow-orange tones, which gives a good base for colour grading to aesthetically pleasing results. In this, it is not the most colour-accurate (the Keldan Spectrum filter is clearly more accurate), but is nonethless great and very practical for underwater video use (which explains its popularity). - The UR-Pro Cyan induces a general light loss in the roughly -1.6 to -2 stop / Ev range (being a colour filter, this is also relative to wavelength transmission, as discussed here) - Physically, the UR-Pro Cyan was made of acrylic or glass (not gel), with an orange to reddish tint, and was the steepness of the curve seems to indicate that it was an optical grade filter. If we take the available transmission data from the filter patent and order it on the wavelength/colour spectrum, we end up the following: UR-PRO CYAN FILTER WAVELENGTH TO TRANSMISSION, MAIN DATA POINTS Below 370 nm: 0% UV ULTRAVIOLET: BELOW 400 nm Below 400 nm: 25% VIOLET: 400-450 nm Below 410 nm: 27% Below 450 nm: 12% BLUE: 450-500 nm Below 470 nm: 8% Below 500 nm: 4% CYAN: 500-550 nm Below 520 nm: 7% Below 550 nm: 18% GREEN: 550-580nm Below 570 nm: 50% YELLOW: 580 - 600 nm Below 600 nm: 87% ORANGE: 600 - 650 nm Below 700 nm: 90% RED: 650 - 700 nm - We are also given a rough visual representation of the UR-Pro Cyan filter's transmission curve, which can be rendered as is on the wavelength spectrum: UR-PRO CYAN FILTER SPECTRUM TRANSMISSION CURVE - Combining these data sets, we can add the following projections for wavelength transmission cut-off (known data point are in bold type, projections are in italic type) UR-PRO WAVELENGTH TO TRANSMISSION, KNOWN DATA POINTS AND PROJECTIONS ALTERNATIVES In terms of possible alternatives, there seems to be a marked difference between optical grade photographic filters, which have might tighter, precise cut-off points, and design specificities like fully cutting off the UV spectrum, and lighting filter gels, which have a more sloped curve, with less marked cut-off points. - A relatively cheap and somewhat more accessible option would be to combine existing lighting gels such as fluorescent filters (FL) / orange colour temperature adjustment filters (CTO), or orange to pale red colour conversion filters (CC), with a UV blocking filter to steepen the curve. This seems promising, as illustrated above. However, one thing to look out for when combining lighting gels would be light exposure / stop loss. A loss -3 stops / Ev would be a reasonable limit. For smaller sensor cams like action cams, it would be best to stay in the -1.5 to -2 Ev / stop range, as anything stronger would introduce to much noise when shooting in ambient light. Some options to look into would be Lee and Rosco filters, such as the (discontinued...) Lee Pale Red 166 combined with the Lee 266 UV, or the Rosco Cinegel 3310 Fluorofilter, or other CTO / CC filters of their respective ranges (Rosco 166 Pale Red, Roscolux and Cinegel CTOs, etc.) - Another option would be to look into existing optical grade filters for photography (color correction, fluorescent filters, such as the Tiffen 47B filter for example) or those designed for other optical applications (microscopy, astronomy...). These would require no additional UV filters, but these will usually be in glass form, so less flexible, and more expensive. - Lastly, there would be the option of trying to tweak existing photo filter gels (Magic Filter or Keldan) to bring them closer to the UR-Pro Cyan, combining them with a minus green lighting gel for instance. From my tests on grading flat action-cam footage, Magic Filter's handling of magenta (inverted, when to other filters) is problematic at depth for my video grading use (more details here and here) but a filter like the Keldan Spectrum SF-1.5, combined with a gel giving it a bit more "bite" (a minus green gel?) seems like a promising base for experimentation. cheers! ben

Thanks for sharing this, really interesting. AF is doing a great job at staying on the crab and ignoring the smaller shrimps and bigger clownfish. However at 53 seconds in it loses focus as the crab is moving to top left of the frame, and regains focus when the camera moves in. Same at 1:56, would you know what is going on here? In the first instance, it looked a bit like the crab has reached the dof limit, but seems too shallow for this critter size - for the last one I'm wondering if AF is confused by camera movement? It almost looks like there's a weak artificial light source at the begining (I'm guessing it's sunlight), so I'm wondering if it's actually changes in illumination angles that throw it off balance twice. Do you think using a video light would have helped the AF lock-in on the crab by increasing contrast data? Anyway, it’s very interesting to see AF in action, doing a good job 5 years ago already.

from no-picture=didn't-happen to I-think-this-happened=picture 😁

IIRC the Nauticam GH6 housing works for the GH7.

Wow - AI augmented footage, or to quote the article Imax will "utilize its AI algorithm to explode the images". Boom 💣 The revolution is well underway - guess we can go soon go back to shooting in 1080p and let AI do the rest (including bringing bleached coral back to life and turning that trout into a bull-shark perhaps?). It will be interesting to see how we transition from capturing reality as best as we can to generating a computer-assisted reality we like better (and if we go all Black-Mirror, eventually choosing to see, inhabit and intereact in some sort of filtered and customized enhanced reality ).

Perhaps – in this type of scenario, where you’re following fast moving medium-sized action, not having to worry about focusing would certainly be a relief, but I’m also not convinced results would be that different. It would for sure make life easier if it works, but I think there might also be a risk of AF loss and tracking when the subject is out of the frame / lighting - which is bound to happen at some point - in which case staying focus-locked-in might actually be easier. Hard to tell – I know on my cam it wouldn’t work, but if Sony AF is as good for video as it is for stills, it could be very nice indeed in some cases! I chose this specific example as it was technically more challenging because of the fast moving of medium sized subjects, with little time to adjust. This might sound a little paradoxical, but for smaller macro to supermacro subjects I find it somewhat easier (MF examples of all sizes here or here). Based on my experience and the setup I use, but in the 10mm to 5mm critter size-range and below, depth of field gets so shallow that AF doesn't have much to offer. You basically have to move (nudge) the camera if the critter moves out, there’s just not enough range to focus-follow. But for fast-moving middle-range subjects (which are not that common actually), and also more tricky applications like small subjects free-swimming in the water column (black-water beckons...), I can definitely see the appeal of fast and efficient AF tracking. Tricky enough following the show and being stable! 😅 Bring back 80s home-video zoom-shots! 😁 Joke aside, I agree, it would be great to have some illustrations of latest AF tracking-technology being put to good use for underwater video. Animal-eye AF on the eye of fish moving in a school would be amazing, and I would love to have access to the extended-range / helping hand an efficient Sony AF system could give if it works as it's rumored to. AF seems like a no-brainer for stills, since you are effectively freezing the movement, but for video nailing the 10-seconds-minimum of focused, stable footage required for moving pictures ofen requires a different type of control over the camera. Really curious as to how others approach the issue and what works best for them.

As a follow-up to the Ultimate Filter Quest, the Rosco Cinegel 3310 Fluorofilter also seems like a good base for UR-Pro cyan recreation. Here are the specs: UR-Pro Curve is close – however a major difference I see with the Cinegel 3310 (as with the Lee Pale Red) is UV transmission. The UR-Pro cuts transmission below 370 nm to 0% helping with the strong blue/magenta cast we have underwater. Transmission of the greens, which is another big cast-generating headache underwater is down to 4% at 500 nm, so the UR curve is a bit sharper. I think combining the Cinegel 3310 with a UV filter gel (something with less than 50% transmission at 410 nm dropping to 0% at 350 nm or so, similar to the Lee CL 226 UV) should help with this as well, and give very close results.

Wow, indeed - I wasn’t aware DJI had a cine-cam range... 😅 This is good, as there is an in-house link to more professional applications, spanning beyond that of the stereotypical action cam user-base. Let's see if this feeds into their action range. Professional productions use action cams as backups, B/C cams and for dedicated application (the BBC /blue planet crew I saw in Palau in 2023 had GoPros setup for certain boat mounted angles, I think it was the GP5 and GP9), so DJI might be on to something if they ease up on the be-a-hero pov immersive-social-media angle and offer a more-rounded “rough-cam”… That said, regarding sensor-size/focus I’m a little worried at how workeable AF would be on such a cam underwater (particles…) – seems perfect for correctly tracking a “talking head” like in the Insta360 clip, but it could also mean trouble in our less than ideal underwater conditions…

Hear, hear! I'm also placing my hopes on DJI - 1" with AF please -- overall, judging by the user manuals, the DJI seems more like the kind of product I would want (for shooting in flat) for an upgrade than the Insta360. Speaking of the DJI Osmo Pocket 3, what's up with this product? looking into it, there's no underwater housing for it - is it just the shape factor, and DJI focusing the bulk of UW product offer on its waterproof action cam line?

Very interesting subject indeed, looking forward to reading more real life feedback, especially from Sony-AF users! I don't have much experience/feedback to contribute, as while not being professional nor having a cinema rig I also shoot in manual focus both for wide and macro. This is not because I think using AF is amateurish in any way, but because in my case AF just doesn't work underwater. Lumix LX10 autofocus is slow, and CAF tracking uses up way too much of the cam's very limited battery power. Other major issue is particules in the water, water movement, there are simply too many things leading AF to tracking in the void and missing shots. What works best for me is manual with back-button focus AF (AF/AE lock, set to single area AF) and focus peaking for visual feedback. - For wide angle, it's mostly hyperfocal and not an issue at f/8 to f/11 with the Inon UWL-H100, just back-button lock and good to go, reefs, sharks, mantas etc... I shoot wide in ambient light with a filter, so peaking info is more limited, but there's usually enough feedback to judge how much is in focus. - For macro/supermacro, there's more going on on the focusing front, and getting small critters both in focus and properly lit is critical - I acquire general focus, and then use peaking to see where I'm at. I was using the focus knob at first, but while it's very useful for fine-tuning the focus point on an already acquired focus, it doesn't really work for acquiring focus for tiny critters - backbutton AF and nudging the camera (on its quadripod) really works best. So it's usually nudge/backbutton acquire> nudge > fine tune In macro shooting's full artificial light, focus peaking is generally wonderful, and once the focus point is acquired you can really adjust to your liking. For tiny critters, DoF is super shallow already, so aperture considerations tend veer to the artistic (the how-shallow-can-you-go focus-limbo dance 😁)... If there's a little surge, most tiny critters will swing in and out of focus and DoF is so shallow CAF wouldn't make much of a difference... - Focusing is, however, much more tricky for closeups/portraits of medium-sized critters in movement - but I find this is also very much size/behaviour dependent. This crab clip was in constant fast motion, roughly 10cm wide critters, but there was use sufficient leeway to keep things in focus, following the show and reaquiring critical focus with backbutton AF when needed, and while this wasn't really macro, it was sufficiently artificial-dominant lighting for peaking to work great and see when I was nailing it. Even if playing with aperture and depth of field, UW action is usually slow enough to reaquire focus and get a decent clip, especially with larger to medium subjects like turtles, octopuses etc - The trickiest bit, and one where I would love a super-fast autofocus, is tracking fast-moving small critters, say in the 5cm range, especially of the free-swimming variety... This is hellish, as it's combining shallow DoF with fast movement, and this is where I'm missing the most number of shots. I haven't found a good solution, and if the critter doesn't slow down it's very difficult to get usuable footage - and even if it's in focus and stable, on my cam zoomed-in shallow dof + movement makes for some very sea-sickness inducing clips, as the sharp/stable critter is moving in front of a blurry fast moving background, and quite the roller-coaster ride.... Fun watch (weeee!), but I've never used those shots, as it's just too much... Would probably need a lens with more depth of field to shoot something less psychedelic and useable... Classic free-swimming critters like ghostpipefish (usually in the 5 to 10 cm range) can be tricky, as while they don't move around too much, staying close to their camouflaged habitat, they can have a tendency to move in and out of focus - partial hand-held, ie using one or to legs for support but allowing follow movement works well (or fully handheld if stable). But then it also depends on conditions and the subject itself - some are also nice and cooperative and stay in one place to allow for multiple shots with different focus areas (eye closeup, mouth closeup, shallow dof...), nice and easy. I'm also concerned about black-water video shooting scenarios, which combine hand-held, small moving, critters and lighting considerations (critical with transluscent critters). This is where efficient AF definitely sounds like a good idea (so you can focus-pun intended - on lighting), and I'm not sure how things will go IRL. I do have a hunch that a "light-box" type config might be good enough - if you know that the central part of your "light box" square is in focus, then it's mostly a question of keeping the critter in there as you follow the movement. But this is just a theoretical projection for now, never-try-never-know as they say... All this to say that MF + backbutton AF works for me, and tracking animal eyes hasn't been much of an issue - if it's big enough, you can follow peaking points handheld, and if smaller then a semi-handheld solution allows for the small movement required to do so... Then again, I've also never been in more cinematographic shooting scenarios where I had to track the face of diver swimming towards me for instance, for which a good autofocus or solid manual tracking option would be absolutely necessary.... *** I'd like to add that while the video forum clearly has a really limited reach, it's really refreshing to take part in this type of concrete, practical technical discussion! I really wish there was more of that (along with more aesthetic/artistic discussions to even things out, of course...). I've been reading into WeP archives recently, digging for historical info on a filter, and there was a bit more of this going on 20 years ago, when you had a lot of users experimenting with video rigs and sharing practical, technical info with their peers. Then it all seems to have died out a few years back, with video discussion flatlining, paradoxically exactly when sharing video was finally becoming possible... I have a feeling this is linked to the rise of bandwidth-enabled commercial video content, where semi-professional video-shooters started working as "content creators" sharing their content online (liveaboard-based videos, for instance, were no longer limited to trip-recap videos sold to customers, but became promotional content actively shared online, like professional advertising content for resorts or locales), and were thus much less inclined to share information (maybe not so much out of pride as out of protectionism?) This dying-out of practical discussion also happened at the same time as the rise of social-mediable clips of vloggers and YTubers, which probably accounts for 80% or more of video content found online, and mostly 1-shot-stand affairs. Industry, truly professional UW cinematographers have always been more secretive, and working in a world of their own, with techniques closely linked to the equipment (and teams...) they have access to - inspiring, but a little out-of-reach...

As a follow-up, sales-pumping "rumours" strategically circulated online hint at the upcoming DJI Action5 having a 1" sensor, like the InstaAce or the already existing DJI Action3.

Looking into alternatives, on the Lee Filter side, the Lee 166 Pale Red is somewhat similar: Lee filter's customer service suggested this gel could be combined with the 226 Lee UV to block the UV spectrum, combination which would give the following curve: There are differences - the 600nm wave length with its warm yellow/oranges, is already at 87% transmission on the UR-Pro, as opposed to 64% on the Lee Pale Red 166 + 226 Lee UV combination. In the blues the UR-Pro's 410nm peak at 27% transmission is moved to a greener 420nm at 22% transmission, but otherwise it's quite close (with some blues but also a strong filtering of the 400nm greens, 5% for the UR-Pro for 4% for the combo). I'm guessing it will be a little cooler and with a bit more green, which doesn't sound too bad! Anyway, should be worth a try... b

Following up, I tried to find a blank light spectrum file I could plot values onto to give a visual rendering of the filter data, but couldn't find anything to work with... So I made the most of my fragile photoshop skills and adapted the filter curve given above by scaling it to an existing filter spectrum graph... (if anyone knows practical way to render the available data in a more accurate manner, do let me know!) Anyway, here are the results: UR-Pro Cyan filter spectrum transmission, based on available patent data As a reminder, known values for light wavelength (nm) to % of incident light transmitted are: Below 370 nm: 0% Below 400 nm: 25% Below 410 nm: 27% Below 450 nm: 12% Below 470 nm: 8% Below 500 nm: 4% Below 520 nm: 7% Below 550 nm: 18% Below 570 nm: 50% Below 600 nm: 87% Below 700 nm: 90% **** While this quick-and-dirty visual is far from perfect, it does give a good idea of how the filter is acting in blue water, and affects spectrum transmission and colours making it to the camera sensor. Some observations: - As noted in empirical tests, filtering of the blue-green spectrum is quite pronounced, with only 4% transmission at 500 nm (which removes the greenish hues, pushing them to yellow-orange) - There is a strong transmission of the orange-red spectrum, 90% transmission at 700nm+ (warming effect, to compensate for the filtering effect of water and restore colour balance) - The filter does let some deeper blues hues through (25 to 27% transmission in the 400 nm zone, likely to avoid losing water-column blue tones), while also strongly filtering out darker blues and,importantly, almost all the purple/magenta hues (0% transmission below 370 nm!) This strongly marked section of the curve seems to be the UR-Pro's most characteristic spectrum filtering feature, and would be the one to focus on when looking for alternatives: cheers! ben

Good to know, thanks - I have the AOI wide lens and find it almost too wide, but image quality gain is worth the transfer to a wider-angle / smaller subjects than what I've been using over the years (medium, then linear fov - the AOI lens, like the two others is designed to be used in wide mode).

As a follow-up, I ran some tests today on the GoPro with a combination of two stacked gels, one original Magic Filter gel and one Keldan Spectrum SF-15. Tests were done on an overcast morning, in murky greenish-blue water, in tropical ambient light only (east Bali). As in the previous tests, GoPro7 was on flat profile (WB native and GoPro colours), auto ISO locked at min 100 and max 1,600 (which is what I usually use for wide angle tropical ambient light shooting with the GoPro, max 800 if possible), 4K, 60fps, medium fov. Note: AOI wide lens was not used as the person handling the camera for these tests - who happens to be my wife - couldn't be bothered with the extra weight 😅 Quick summary: not usuable / a practical solution at depth. - good in the shallows (the Keldan gel evens out the Magic Filter), but too much light loss at depth (combined exposure loss should be Keldan -1.5 Ev and Magic -1.6 Ev so a total of roughly -3 ev - too much to handle for the GoPro at depth in today's murky conditions, footage was grainy, meaning the camera probably pumped up to 1,600 ISO around 15m) The other issue is the Magic Filter's orange/magenta spike at depth, already noticed on the previous test. The Keldan gel doesn't help with this, and simply reduces the colours data making it to the sensor. Here are some quick screenshots: - 8m depth, on a flat plateau worked well given conditions - white balanced and quickly graded in FCPX (looked good just after setting the WB, plenty to work with...) However, deeper and with less light on the slope, things got ugly... 18m depth, on the slope While the footage isn't pure garbage, it's quite desaturated (which looks ok-ish) but the issue is really that's there's really not much left to work with. The marked orange/magenta dayglo boost of the Magic, already noticed on the previous tests, is still there, waiting to be revealed.... All it takes is boosting the highlights+midtone saturation to the max, to see what colour info we really have to work with: Ouch... The other issue being the grain - ok, conditions were really not great and got worse during the dive, low light and particules, but it's still very grainy - other footage is worse in this respect. This is something to keep in mind when working on stacked filters - on my aging GP7 at least, -3Ev is too much for the camera to be practical, unless staying above 10m in tropical light. I guess a loss of -1.5 to -2 Ev is the sweet spot.

Here is some news -following up on Nick Hope's idea, I ran a patent search for UR-Pro's Kirk Kreutzig in the US. patent data base and got 3 hits for optical filters. Among the 3 three filter patents, 2 actually concerned night-vision devices, but one was of particular interest: patent US-4542959-A "Color correction filter and method of taking underwater photographs therewith", filed on July 25, 1983 and published (patented) on September 24, 1985 Here is the downloadable patent file: 4542959.pdf Not sure if this is UR-Pro Cyan filter patent or not, but maybe there's some related information within. Here is the abstract: 6 pages of rather interesting reading, and while it's difficult to know if it is the UR-Pro Cyan we're familiar with, it does sound like a blue-water/cyan underwater photo filter... To summarize in copy-pastable form, the light wavelength (nm) to % of incident light transmitted is as follows: Below 370 nm: 0% Below 400 nm: 25% Below 410 nm: 27% Below 450 nm: 12% Below 470 nm: 8% Below 500 nm: 4% Below 520 nm: 7% Below 550 nm: 18% Below 570 nm: 50% Below 600 nm: 87% Below 700 nm: 90% EDIT- looking into it, it seems like this is indeed the UR-Pro Cyan, or at least one of its early versions Here is another related patent filed by W TUCKERMAN BIAYS, refering to U.S. Pat. No. 4,542,959 as covering the "UR/Pro Marine CY Filter" https://patents.google.com/patent/US5719715A/en It is well known that light is made up of electromagnetic radiation having a range of wavelengths usually considered to be between 0.4 and 0.7 microns. Underwater color correction is described in U.S. Pat. Nos. 4,542,959; 3,588,215 and 3,929,487. In addition, the following publications discuss the "UR/Pro Marine CY Filter" (which may be described in U.S. Pat. No. 4,542,959) Frink, "Warmer U/W Photos", Skindiver, December 1983; Herbst, "New Filter Banishes the Undersea Blues", May 1986 and Holland, "Filters May Improve your U/W Photography", February 1988. Murphy, in "Shark Eye", appearing in Skindiver, May 1987, apparently describes a filter which may be related to U.S. Pat. Nos. 3,588,215 and 3,929,487. Adams, in "Exposure Control for Underwater Photography", appearing in ElectroOptical System Design Conference, 1971, at page 336, discusses the use of color correcting red filters, as does Rowlands, in The Underwater Photographer's Handbook, pages 74-75, Van Nostrand Reinhold Co. Cardone, in "Clearoptic Lenses", in Skindiver, May 1989, describes a yellow filter, sometimes known as "shooters" glasses. As a bonus, here is a link to a local Chicago Tribune article published in 1999 on Kirk Kreutzig's various filter-related inventions, titled "FILMING 100 FEET UNDER SEA " cheers ben

Thanks for this, interesting product - in the discussions, Craig Jones and Nick Hope also bring up the glass vs plastic issue. To quote Craig's article again: First, your choice of filter depends on whether you are deep or shallow and whether the water is blue or green. The stronger FL-B filters are only suitable for blue water and moderate to deep depths (20-70 feet). Use the FL-D type filters for green water or shallow depths. For any given lens or housing, you may be able to use thread-on filters, rectangular filters (externally) or gels. Some combinations may be supported only by a UR Pro filter in which case your choice is fairly obvious. For those that can use thread-ons I prefer the Singh-Ray FL-B, the Hoya FL-D and the B+W FL-D. I have not used the Hoya FL-W but it may be desirable for very green water. For those who can mount a 4 inch/100mm Lee filter holder externally, the Lee FL-B filters provide essentially a shallow/medium/deep solution. I have also adapted a UR Pro CY resin filter to the Cokin X-Pro filter system. I personally avoid the Tiffen filters and the UR Pro glass filters due to their sandwich glass construction. Sandwich filters have many more light boundries that make them more susceptable to flare. For those lenses that have rear gel holders your choices are more interesting since you can roll your own. First choose your magenta gel. I would use 20 to 50 units depending on depth and clarity of the water. You can then optionally add a warming gel. I would bring an 81C, and 81EF, and a 85 for example. The benefit of the warming gel is that it brings the balance of the light closer to matching the optimal balance of the imaging sensor. The downside is that you give up light sensitivity. On bright days and deep dives use a strong warming gel. Otherwise use a weaker gel or leave it out entirely. Note from the editor - According to Craig, a good starting point is to purchase two strengths of magenta (say, 30 and 50 or 20 and 40), and then add two strengths of warming (81EF and 85). For shallow shots use the weak pair. For deep the strong pair. For green water use the strong magenta with or without the 81EF. You can combine the weak pair or the CC30M alone with strobes if you carefully control strobe power. Reduce strobe power by 1-2 stops to start. Filtering strobes is ideal, but we have some more experimentation to do before anything conclusive can be said.

A little snippet on fluorescent filters (especially the UR-Pro) by Dr. Mustard from this 2005 thread: I have noticed quite a big difference between CC filters and Fluorescent filters is in the cameras ability to auto white balance. Fluor filters (specifically the UR-Pro series that I have used) tend to work really well on AUTO-WB (even when they actually don't look too good on the LCD screen when they are underwater). Whereas CC filters tend to need custom white balancing either in situ with a grey/neutral card or in RAW conversion in post processing. This shot, for example, was shot on Auto WB and can out of the camera looking pretty much like this. The only way I can get such good colour balance straight from the camera with a CC filter is in situ WB. The obvious answer to this is that fluor filters are better. But I am not convinced about this because at certain depths the camera uses more extreme white balance (colour temp and tint) settings for the UR Pro than are needed for the CC filter. It is just that the camera (well my cameras D100 and D70) have found it easy to get the right white balance (in Auto) with the Fluor filter as opposed to the CC filter. And also from this 2006 thread where Nick Hope is pondering UR-Pro vs. Magic for video The Magic Filter does work with Video, but requires manual white balance - which is not always advantageous with moving images. I can only comment on their use on stills, but the Magic filter is actually quite different from the UR Pro. I can tell a UR Pro shot from a Magic shot straight away (on stills). On stills the UR Pro tends to produce more Magenta blue water, while the Magic tends to more to cyany blues. On general reef topography I find the Magic much more neutral coloured (I find the UR Pro CY more muddy looking). The UR Pro also renders Anthias much more red rather than orange (I have just been in the Red Sea shooting them both - hence the Anthias comment). On the plus side for the UR Pro, I think that the UR Pro filter gives more contrasty images than the Magic Filter. Which tends to help moving images. All that said, I am reluctant to persue the video market with the Magic Filter. We set up Magic Filters to provide a solution for photographers than didn't already exist (namely a gel format UW filter). And it is not our intention to take on UR Pro (or others) in the video market. That said we are happy to supply filters to those who want to try them. Alex and also here in 2006 You cannot judge filters just by looking at them. Filters are rather more complicated that the colour that they look. For example UR Pro CY and SW-CY look identical but they are not. It is the details of the transmission spectra that are important. Another example is that the original magic filter looks orangy, but the transmission spectra is nothing like a standard orange filter. http://wetpixel.com/forums/index.php?act=A...pe=post&id=2619 This is the magic transmission spectra and it lets through lots of red, orange and yellow light, some green and very little blue. And orange filter, which may look quite similar, has a much more defined peak in the orange (although I don't have an example). The 2006 UWP article on the inception of Magic Filters is also definitely worth a read: http://www.magic-filters.com/download/UWP26a.pdf Here's an extract I found particularly interesting (highlights by me) : I have used many filters over the last few years and firm favourites have been Kodak’s Wratten CC (Colour Compensation) Red series and UR Pro’s CY and SWCY filters. Both have strengths but neither was the perfect solution for me and this is what started me on the path to Magic. The main limitation of CC Red filters is that only work in very narrow depth range, for example I have found that the CC0R only produces pleasing images between 2 and 6 metres, even with adjustable white balance). This makes them impractical unless we know the exact depth of the subject before we dive. UR Pro’s filters are designed specifically to counteract the filtering effect of seawater and work very well. They are an excellent choice for videographers and work over a wider depth range (I find the CY works best on stills between and 12 metres). Frustratingly, for the still photographer UR Pro filters are only available as glass or thick optical plastic, which means that they cannot be physically fitted on the most popular SLR wide angle lenses such as fisheyes (which can only take gel filters). I designed the Magic Filter to work over as wide a depth range as possible. The Magic filter differs from other UW filters as it is not designed to perfectly counteract the filtering effect of seawater because this is highly variable. Instead it adjusts colours to produce a colour balance that is easily corrected by the camera’s white balance as is this 2007 article And fast-forwarding to a very interesting 2010 thread with a bit of spectrometer action: Nick Hope: The Lee, Rosco etc gel filters are designed to just change the colour of electric lights and are allegedly not "optical" quality (whatever that means), although I have seen point-and-shoot users get away with them. You can get a swatch book from them with loads of samples. Apparently the Magic Filters are somehow different in a way that makes them "optical" quality, but exactly what that is, I have no idea. The archived UR-Pro site (last archived in 2019) is also accessible here: http://web.archive.org/web/20191209011451/http://www.urprofilters.com/content.do?region=FilterInstructions#tips This dive into this pre-Keldan, film to digital, SD to HD history is pretty fascinating - to me anyway 😅 Really worth looking into discussions/input by Craig Jones (author of the "filters and ambient light photography" article I posted extracts of above), Nick Hope and Alex Mustard. We've come a long way but also, in others, full-circle (with non-manually white-balancing cameras like action cams) Technological advances (sensors, RAW, and LED technology, with the availablity of powerful UW light sources) have changed certain aspects (MWB was a hot-topic back in the days, and I hadn't heard of the Expodisc...), but some technical questions remain when it comes to handling the UW colour spectrum, especially for UW video. Just look at Nick Hope's UW-MWB tests in 2007 Trying to figure out what the now extinct UR-Pro CY/ SWCY were feels a little like trying to figure the coca-cola recipe 😝 It's a little sad that such valuable information has seemingly vanished with the company and its patent (?). cheers

Digging into the archives, i found this interesting 2003 article comparing UR-Pro filters to fluorescent filters, and giving "recipes" for some combo filters including the UR Pro ones. https://wetpixel.com/articles/filters-and-ambient-light-photography/ Here is an extract: Color Conversion filters. Color conversion filters come in two varieties, warming and cooling. For this discussion the warming filters are valuable since they can be used to counteract the cooling effects of the water. White light is characterized by its color temperature, specified in Kelvin, where warm light has low values around 3000K and cool light has higher values around 5500K. Although Kelvin is the measure photographers are accustomed to, it is more useful to speak of light in terms of mireds, or micro-reciprocal degrees. You can convert Kelvin to mireds by inverting and mutliplying by 1000000. color temperature equivalent mireds 2800K 357 3000K 333 3200K 313 3800K 263 4100K 244 4700K 213 5500K 182 6500K 154 There are two series of warming filters, the 81 series and the 85 series. They are characterized as follows: filter mireds 81 9 81A 18 81B 27 81C 35 81D 42 81EF 53 85C 81 85 112 85B 131 There are two analogous series of cooling filters, the 80 and 82 series, and they have matching but negative mired values. For our application they are uninteresting but they can be used to adjust the color of strobes or halogen lights. When applying a filter to light simply add the filter value to the light value to get the result. Water generally needs 2-5 mireds per foot to compensate for its cooling effects with turbid water requiring less compensation. Fluorescent Filters. Up until now we've talked about filters that are primarily available as gels that you have to combine and mount yourself. As it turns out, photographers have had to deal with another light source that is overly green and that's fluorescent lighting. Because of that we have at our disposal a limited range of thread-on and rectangular filters that are combinations of the filters that we desire. Additionally, many underwater photographers are familiar with UR Pro, a company that specializes in filters for underwater use. The UR Pro filters are functionally like fluorescent filters. Below is a table that I've compiled characterizing these filters. filter mireds CC M UR Pro glass CY 140 75 UR Pro glass VLF 145 60 UR Pro resin GR 25 30 Tiffen glass FL-B 100 50 Tiffen glass FL-D 40 65 B+W FL-D glass 20 20 Singh-Ray resin FL-B 147 50 HiTech resin FL-B 96 75 HiTech resin FL-D -12 30 Hoya glass FL-D 34 30 Hoya glass FL-W 9 60 Lee resin FL-B 3600K 35 40 Lee resin FL-B 4300K 69 45 Lee resin FL-B 5700K 134 40 Lee resin FL-D 3600K -50 70 Lee resin FL-D 4300K -16 70 Lee resin FL-D 5700K 14 60 ---- This 2007 discussion is also worth a glance: It that the UR-Pros were sold as plastic that you can cut to size or glass, both are exact same underwater but plastic gets scratched really easy. and also describing UR Pro filters as simply FL-B filters repurposed. If you can find FL-B filters in your size they will work well and be much cheaper than UR PRo. UR-Pro was apperently run by Kirk Kreutzig (and were not always easy to reach) It also turns out Nick Hope was looking into the makeup of UR-Pros at the time as well: A few years ago I trashed a big UR-Pro plastic external filter on it's first ever dive (staghorn coral). In subsequent discussions with them about re-polishing etc. I was genuinely interested in what UR-Pro had managed to patent about their filters, and what makes them so unique. I had a search for the patent (was involved with patent stuff in my old career) but couldn't find it, and I could never get a specific answer or a patent number out of them. Just that they "sill hold the patents" and that other filters will not give the same performance. Would still love to know what's so special about them. Other old threads discussing the UR-Pro / Magic filters worth a read include this one here as as well as this one here I'll keep digging around, see if anything else comes up. cheers b 

This is a summary of observations / data gathered from filter tests based on raw files shot on the LX10. Parameters: LX10 raw files, WB set to 6000K (like the theoretical value of the MW4300 light), exposure ISO 125, f/8, 1/60 (some exposure change due to the vignetting caused by the filter mount) - WB point is taken on the same spot on a Whibal calibrated grey card. - Light source is a Backscatter MW4300 video light used in wide mode, theoretically calibrated to 6000K (in reality, seems closer to 5000K), CRI 71.1 - colour data is samled in Lightroom Classic (colour slate used isn't a calibrated colour checker) LX10, unfiltered, WB uncorrected (temp 5350K, tint Magenta +19) wb rebalanced in post to check (temp 5000K, tint Magenta +27) Unfiltered colours observed: LR Histogram: UR-Pro acrylic 55mm filter, WB corrected (temp 2350K, tint Magenta -14 - warms by 3000K) Filtered colour modification observed: LR Histogram: - Known filter light loss values for UR-Pro Cyan (measured by Interceptor121): -1.6 Ev Original Magic filter, WB corrected (temp 2950K, tint Magenta +23 - warms by 2400K) Filtered colour modification observed: LR Histogram: - Known filter light loss values for the Magic Filter (measured by Interceptor121): -1.6 Ev Keldan SF -1.5 gel, WB corrected (temp 3000K, tint Magenta -28 - warms by 2350K) Filtered colour modification observed: LR Histogram: - Known filter light loss values for the Keldan SF -1.5 gel: -1.5 Ev (Keldan SF -2: -2 Ev) UR-Pro glass filter, WB corrected (temp 2250K, tint Magenta -10 - warms by 3100K) (note: filter in better condition than the acrylic UR-Pro) Filtered colour modification observed: LR Histogram: - Known filter light loss values for UR-Pro Cyan (measured by Interceptor121): -1.6 Ev Side-by side filtered colour modifications observed in LR: Unfiltered: Ur-Pro Glass : Ur-Pro Acryl: Orig. Magic: Keldan SF1.5: Based on these observations, most significant variations occur on the yellow (warmer on the UR-Pros), green (stronger filtration by UR-Pro, as expected) and also on the handling of the slate-gray tones by each filter. Magic handles the blue channel quite differently - which probaly relates to the magenta boost when rebalancing the WB. Keldan and Magic are actually quite close, but differ on the cooler end of the spectrum, greens, blues and slate-grey. Temperature-wise, the UR-Pro Cyan has the strongest warming effect (roughly 3000K and 3100K for -1.6 Ev), followed by the original Magic Filter (2400K for -1.6 Ev) whereas the Keldan SF-1.5 has the weakest (2350K for -1.5 Ev, in the same range as the Magic). Only the Magic filter requires boosting the Magenta tint to rebalance the WB, whereas all other filters require a reduction of the Magenta tint to rebalance.

Thanks, that makes total sense, the green to brown conversion of the UR-Pro CY just works as a base for grading. On one hand, a filter like the Keldan spectrum seems more accurate in its colour handling, but on the other, the UR-Pro offers an easy to work with base-colour palette, which just works for grading to visually pleasing results in most blue water situations. The Magic's handling of magenta (+23 on a readjusted WB) also explains the spike I was seeing at depth, and makes it difficult to handle imo - for video at least... Really looking forward to seeing the gel test results! One other thing i've been considering, given that the Keldan gels are -1.5, is to stack two (the standard glass filter is -2, the next strength gel is -3.5) This should give a rough -3, which probably can be handled by the GoPro in sunny tropical conditions, and maybe offer a good base as well, since the Keldan doesn't rebalance with magenta boost like the Magic filter does. I've worked on the LX10 raw files to extract colour data, and will post a summary of the observations for the 3 filters.

Yes definitely -now that the WB is clearer, the idea is just to try to see what parts of the color spectrum are the most affected by each filter, and how. The example you just posted fits nicely with the grading data - as Dreifish noted in his mixed lighting / ambient filter tests, and also as I remarked when grading the footage, the greens are much less affected with the Magic Filter than the UR-Pro. The brownish tint is also consistent, with the look and feel of the ungraded footage posted here For sure, these numbers are difficult to deal with, but they also do show roughly how the filters affect the colour spectrum, beyond the white balance / magenta temperature reading. When grading, the UR-Pro and Magic are really quite different in the rendering of certain parts of the colour spectrum. It would be more accurate if I could work on the raw files instead of the JPGs, and the LX10 test shots are more standardised Better still would be using testing with a standardised colour checker and a 100 CRI strobe, instead of an 70 CRI video light and an AOW slate, but I think there's still workeable data to be gained. These are screeshots of the lightroom WB and histogram data from the LX10 raw files, WB set to 6000K (like the light), exposure ISO 125, f/8, 1/60 (some exposure change due to the vignetting caused by the filter mount) WB is taken on the same spot on the Whibal calibrated grey card - LX10, unfiltered, WB uncorrected (temp 5350K, tint Magenta +19) unfiltered, wb rebalanced in post to check (temp 5000K, tint Magenta +27) UR-Pro acrylic filter, WB uncorrected (temp 5350K, tint Magenta +19) UR-Pro acrylic filter, WB corrected (temp 2350K, tint Magenta -14) Magic filter, WB uncorrected (temp 5350K, tint Magenta +19) Magic filter, WB corrected (temp 2950K, tint Magenta +23) ******* These are extras, but here is an original glass UR-Pro (not damaged like the acrylic UR-Pro), which shows a reading very close reading to the acrylic UR-Pro, and also a Keldan -1.5 Spectrum Filter gel. UR-Pro glass, WB uncorrected (temp 5350K, tint Magenta +19) UR-Pro glass, WB corrected (temp 2250K, tint Magenta -10) Keldan SF -1.5 gel, WB uncorrected (temp 5350K, tint Magenta +19) Keldan SF -1.5 gel, WB corrected (temp 3000K, tint Magenta -28) It would be nice to grab the colour square data from these raw files instead, but I don't know how to do this in the version of lightroom I have (there's no "colour pipette") and my photoshop CS6 is too old to handle Panasonic RW2 files... EDIT - I found a way to display the RGB info in lightroom (switching to "soft proofing"), and will work on the raw files filtered RGB values, which should be more precise.

Yes, there's clearly a lot going on. I couldn't find a way to do this with the raw files in Lightroom, and my Photoshop CS6 can't seem to handle raw files (probably some camera raw issue), but to give an rough idea of what's going on with the colours with the two filters, I worked on the JPGs in Photoshop, and grabbed the colour data from each square, but from the GoPro files set to 6000K WB (theoretical calibration of the video light used) If anyone knows how to do this with raw files (I'm guess my image software is too old), it would be more accurate... The (very rough) data I have is as follows: GOPRO UNFILTERED - WB 6000K RED SQUARE: R187 G100 B93 ORANGE SQUARE: R193 G118 B87 YELLOW SQUARE: R200 G212 B0 GREEN SQUARE: R62 G153 B96 BLUE SQUARE: R105 G110 B168 SLATE-GRAY SQUARE: R111 G100 B117 GOPRO + URPRO - WB 6000K RED SQUARE: R243 G132 B113 ORANGE SQUARE: R244 G149 B117 YELLOW SQUARE: R252 G208 B49 GREEN SQUARE: R171 G144 B91 BLUE SQUARE: R183 G129 B143 SLATE-GRAY SQUARE: R197 G140 B123 GOPRO + MAGIC - WB 6000K RED SQUARE: R229 G125 B96 ORANGE SQUARE: R234 G139 B95 YELLOW SQUARE: R237 G213 B29 GREEN SQUARE: R153 G168 B87 BLUE SQUARE: R168 G142 B127 SLATE-GRAY SQUARE: R176 G142 B117 If we reorder this per square to track the global changes the filtration induces, we get: RED UNFILTERED R187 G100 B93 UR PRO R243 G132 B113 MAGIC. R229 G125 B96 ORANGE UNFILTERED R193 G118 B87 UR PRO R244 G149 B117 MAGIC R234 G139 B95 YELLOW UNFILTERED R200 G212 B0 UR PRO R252 G208 B49 MAGIC R237 G213 B29 GREEN UNFILTERED R62 G153 B96 UR PRO R171 G144 B91 MAGIC R153 G168 B87 BLUE UNFILTERED R105 G110 B168 UR PRO R183 G129 B143 MAGIC. R168 G142 B127 SLATE-GRAY UNFILTERED R111 G100 B117 UR PRO R197 G140 B123 MAGIC R176 G142 B117 This, combined with the histogram and white balance / temp data, should give a rough ideal of how each of the two filters is affecting the colour spectrum (and, hopefully, what needs to be adjusted on the Magic gel to more closely match the UR-Pro).

To develop the comparison between the UR-Pro SW Cyan (55mm acrylic SRP-Blurfix model) and the original Magic filter gel, based on the GoPro raw still files (LX10 raw files gave similar results, we can make the following observations: When it comes to white-balance, other than the UR-Pro being slightly warmer, the main difference between the two filters comes from the handling of magenta. As observed on the GoPro (and the LX10), rebalancing with UR-Pro gives a negative Magenta reading, whereas rebalancing with the Magic gives a positive Magenta reading. GoPro raw files, WB set to Native, 6000K light (results are similar with camera WB set to 6000K) UR-Pro Cy, unbalanced WB UR-Pro Cy, rebalanced WB: 3100K Magenta -44 Original Magic filter gel, unbalanced WB Original Magic filter gel, rebalanced WB: 3500K Magenta +20 *** Based on these readings, there is a 400K warming effect difference between the two filters, which is not much, however when it comes handling of Magenta, the UR-Pro increases magenta by +31 (+13 to -44) whereas the the original Magic decreases Magenta by -31 (+13 to +20) As an experiment, if we try to match the two filters by warming up the Magic filter and boosting the Magenta, we get a very similar result between the unbalanced UR-Pro filter and the modified unbalanced original Magic filter: UR-Pro Cy, unbalanced WB Modified Magic filter gel, unbalanced but with WB warmed to 5900K and Magenta increased to 76: Results are now visually quite close for such rough measurements. But while the results are visually similar, the histogram still shows significant differences in colour distribution. To fine-tune this, it would be interesting to get readings on main individual colour channels (squares) as well, see how both filters affect them, but I'm not sure how to approach this.