Chris Ross

This is the adapter I use with the Canon 8-15 fisheye on the OM-1. I have tried it with a few EF lenses and it seems to work well on all I have tried. You will see the compatible camera/lens list of course on the page you linked, these are generally reliable as I understand it.

The first part is correct light is absorbed by wavelength unevenly, that is well established. Secondly speed of light in water is identical for all wavelengths, however this has no impact on the current subject. In any photography above or below water you have a continuous flux of photons from a continuous light source such as the sun, by this I mean photons/square meter/second as long as the light source remains constant - which the sun does as long as a cloud doesn't move across it. To get the number of photons multipy flux by time: photons/sqm/sec x sec = photons/sqm. The absorption doesn't come into it except to set the ratio of red to green to blue photons that exists due to the distance the light has travelled from the surface to the subject, through the lens into your camera and falling on the sensor. Changing the shutter speed doesn't change the the ratio of red/green/blue photons, just the total number of photons that arrive. This is not opinion, it is indisputable fact. It is important to get this right to avoid confusion when discussing these topics. What the camera data does with this set of photons it has recorded is a different issue and is buried in the proprietary algorithms used to take the sensor data recorded and calculate a RGB value for each and every pixel. Any such changes are global, though WB adjustments could potentially be non linear treating shadows WB slightly different to highlights WB. Any thing that is due to the camera processing is specific to that brand and potentially even the hardware/firmware of that particular model.

Nice pics Chris, I agree with your argument - Retra understands what is going on with lighting UW. Yes as distance increases the impact of strobe colour decreases somewhat- the solution ---- Shift the light further to the red and that way you still get the enhancement from using a warm strobe. While it is true that red light doesn't travel as far as blue light , there is still a lot of blue light in the strobe light and overall the loss of light is not that great and certainly not great enough to need to change to using a strobe with a cooler colour balance. Of course this only applies to clean blue water, temperate waters you generally don't see the benefits. The use of cooling filters for video is a different issue all together - they are trying avoid the issue where the WB varies dramatically with distance with video lighting, the effect is where are subject swims close and looks very red.

While I don't doubt you see this effect when taking your photos, I don't see it myself and this is likely down to perception. On these points : 1. yes the WB may vary my experience is that is varies only minimally on autoWB with my cameras. Adjusting the WB in my RAW converter to compare images taken at various shutter speeds within the range that it varies WB, the adjustments are so small that I can see no change in the WB. The WB may also generally be influenced by the subject and the light received from the flash. If the subject is large in the frame this may well dominate and be the larger impact. Different camera brands may respond to this differently of course but my OM-1 seems quiet consistent with similar subjects. 2. While the spectral absorption is correct, the camera knows nothing of this and only records the photons it receives. If you shorten the exposure the blue light is reduced by the same extent that the green and indeed the red light is reduced. All that happens is that the is the total luminosity is reduced. The only way for the colour tone to change is to change the WB and We've established that doesn't change much with exposure. There's no room for argument on this the RAW file has the same red/green/blue ratios as you reduce the exposure, just less total photons. 3. Perception of colour can indeed change - I don't see any change in colour tone with exposure. You might see something and I won't argue with that. It's purely subjective. 4.Using camera profiles with RAW processing only provides a preset or a starting point for processing. If you find one you like it certainly saves processing time. These are proprietary to each camera brand and anything discerned from them applies purely to this camera brand. They could well be non linear and do weird stuff that is not expected, but again if this is advantage you see it only applies to your camera model and possibly others of the same vintage using that same algorithm to work out how to adjust the preset for your image. The underlying RAW image remains the same.

You are claiming moving only the shutter speed will shift between green and blue water? which way am I supposed to move exposure to make green water look blue? Please explain the physics behind this. Changing the shutter speed can only change how much light of all wavelengths gets through. This can only make the water lighter or darker- the colour has to remain the same - all other factors remaining equal. Colour in this case is the relative amount of red/green/blue. As I understand things the Canon landscape profile - they call it picture style makes blues and greens more vivid. This is baked into a JPEG file but is used as a preset for a Raw file and in Canons DPP at least you can turn it off and choose a different picture style as if you had set it in the camera - it's just a set of instructions that includes changes to the saturation to make these colours more vivid. The RAW file is not impacted.

I must disagree with this statement, if you are looking at Nauticam housings for example the price of the housing for a full frame Z8 is near enough double that of an OM-1 (m43). Domes are generally smaller cheaper and easier to travel with and the lenses can be around half the price depending on the model and are significantly smaller. If you are shooting wide angle because you are shooting at f8 on m43 rather than f11-16 on FF you can use less powerful strobes which can be lighter and cheaper as well. Plus wit h APS-C you can use a Tokina 10-17 and m43 the Canon 8-15 for a very flexible zoom setup that just is not available on FF unless you go with the very expensive FCP port.

The colour temperature or WB in camera only impacts the starting point for the the RAW file and impacts how it looks when you first open the file as I understand things and in theory you can adjust the WB in post to get to any of the settings. As I understand things in lightroom, adobe standard, landscape etc are presets which apply a standard adjustment to the file and again are a starting point. Colour space such as AdobeRGB or sRGB when set in camera is also a starting point it sets the range of colours the raw converter can map to from your RAW data. The other thing all these in camera settings are used for is to make the in camera JPEG which is used to display the image. RAW processing can get around all of this, however it does help if you are trying to check for clipping in your file for example. With the wrong settings the 8 bit in camera JPG will clip before the RAW file clips and give you misleading information when adjusting your settings.

Here's an actual example, this shot was taken in PNG at Walindi resort. First I have the as taken shot, only sharpening has been done, here it is in Adobe RGB profile - it should look fine as long as you use a colour profile aware browser: Unprocessed in Adobe RGB and here it is sRGB with blues tweaked a little you can see the cyans are suffering: Unprocessed in sRGB You can see in the unprocessed image that the subject is rendered quite warm as it is illuminated by 4500K light while the frame is balanced at about 5900K. Next is global adjustments to colour balance and contrast , first in AdobeRGB then in sRGB, I quite like the blue in Adobe RGB but not so keen on the sRGB version.: Processed in Adobe RGB Processed in sRGB I've linked them from Google drive as any image posted here is processed further and for some reason when I upload them the colours go way off. Should be able to open them in tabs to flip between.

This is true, but the same strobe light is illuminating both the subject and the backscatter, so if the backscatter doesn't move the pixels where it is recorded receive the same relative amount of light as the subject portion that is occupying the same slice of the image where the shutter is open. If the subject is the same brightness in the final image the backscatter must also be the same brightness. The only way it can be less bright is if it is recorded again on a different pixel or group of pixels on the sensor. Another way to think of it is that the very high frequency pulsing on and off approximates continuous lighting so the result is similar to increasing the natural light coming in albeit from different directions and coverage. To take the astro photo stacking analogy, if you get a satellite trail through one frame of a 20 frame stack it's only 1/20th as bright in that stack as it was only recorded on those pixels in that frame. But you don't get that in backscatter unless the particle moves enough to not be recorded again on those pixels in the next frame.

You are likely correct for a lot of the shots in my IG, but I would also suggest being cautious with images on IG. I process my images in Adobe RGB and get reasonable blues but converting to sRGB they go off and I haven't discovered a magic formula to bringing them back. In addition Facebook I know and I assume IG strips the colour profile for the image and converts it to uRGB, which is their own profile - they do this to reduce the size of the profile attached to the image, with the millions of images uploaded it saves significant bandwidth. If I am honest I think a lot of images I'm not close enough so they don't get enough flash light - I can compensate for that but the blues probably suffer a little as a result. I shoot RAW, (no JPG) out of camera, autoWB, using two Z240 with the 4600K diffusers for some of the images - mostly the tropical ones, I have a huge number of images from Sydney using the standard diffusers. Don't use lightroom, I use Capture One feeding into photoshop. in camera it's Adobe RGB profile. If you are shooting Raw the colour profile in camera is somewhat irrelevant, it just sets the starting point when you open in your Raw processor. Of course shooting JPEGs are a different story and profile in camera is important. The only way to remove greens though is through the tint adjustment on WB - the starting point you get will certainly vary with the camera you are using and the colour profile you set but changing the shutter speed only makes it lighter or darker. The point of the images I posted previously was to show that the water colour does not change with shutter speed only the brightness. Certainly increasing your shutter speed can improve the look of your image by darkening the background providing more contrast. A lot of this is going to vary with how your camera deals with WB. Some cameras if they know a flash is attached will set to a constant value others will adjust WB based upon the pre-flash, my OM-1 seems to produce images with around 5900-6100 K WB setting at least in Sydney waters. I have found my best shots seem to come from ones that are minimally processed. Just a quick tweak of levels/curves and WB adjustment.

The real power of these connections is that you don't have to open the housing, I got one for my OM-1 housing and on my last trip I charged the camera each evening and downloaded all the images for review without opening the housing. Very handy for that setup as I had an adapted 8-15 which I would need to pull the port and remove the lens to get the camera out. One thing to note is that charging through the camera seems a bit slower than using a dedicated charger, may or may not be the case for other brands. If you get one from Nauticam, be sure to get the specific 28mm bulkhead designed for the USB-C connection, the Nauticam cable doesn't fit through the other one.

Sorry, but that is not how it works, changing the shutter speed changes the amount of every wavelength of light the same amount, it doesn't preferentially cut off certain wavelengths. What can happen is on Auto WB the camera might shift the WB around on each frame or shooting a different subject might provide a bigger shift in auto WB. I was out diving this morning in greenish water and took a series of shots of just the water, then copied a square out of the centre of each frame and pasted into a single file. I did this first as shot, you can see I didn't get the same aim in each frame so exposure wasn't equal. I then equalised exposures on all frames and pasted another set of squares. YOu can see the equalised brightness squares are all pretty much the same. The water was under exposed a little so I then increased exposure of each frame by 1.3 stops and also pasted them into the file. You can see that the colour doesn't really vary among the frames. I also noted the colour temperature and tint from each frame and it moved a little bit, but undoing this I could see no change in frame colour. The way to shift greenish water to blue is increase tint which adds magenta. This may or may not be feasible depending on how the the subject reacts when you do a global tint adjustment. Not saying that darkening the background water doesn't improve things, it just doesn't change colour. Shooting with warming filters does however shift the colour of the water towards blue/cyan, removing yellow and red.

One option is to break them down into clip lengths, have some short and sweet and others longer, maybe keep them in separate folders? As for me a short sharp clip is nice, and if it has exceptional content etc I'll watch for longer.

Hopefully we'll see something official soon, wonder if he'll also go to Boot dive show in Düsseldorf?

I've already factored that in by calculating the the amount a particle would need to move at 0.3x magnification to move one pixel width on the sensor which is 3.3 microns/0.3 x = 11 microns.

I would check how easy the focus peaking is to use in practice. I know it can be problematic on my Olympus, it will depend on how it's implemented in camera or on the monitor. I have a an Atomos Shinobi and find the monitor is more optimistic about what is in focus compared to the camera when using on land. You could probably try all of this on land before committing to a housing for the monitor.

Sounds like the claim is that each pulse of HSS light is very short and if the particle moves between pulses it will receive less light. The problem is that HSS pulses are at very high frequency in the kHz range and likely the particle won't move very far between pulses. A quick analysis, assume a 20MP m43 sensor shooting at 0.3x . Pixel pitch is 3.3 microns and the backscatter particle needs to move one full pixel which is 3.3/0.3 = 11 microns to not appear on the same pixel at the next pulse. Assume the HSS is operating at 20 kHz so each flash is 1/20000 = 0.00005 sec. To move 11 micron in this time particle needs to move at 0.000011m/0.00005 sec = 0.22 m/s. Not particularly fast, that is 0.42 knots. However the particle is probably bigger than 11 micron to be conspicuous, lets say it's 1mm across so it needs to move 1/2 a mm so it doesn't cover any of the same pixels in the next pulse, so that's 0.0005mm/0.00005 sec, so that's 10 m/sec which is 20 knots. Any slower and it leaves a short trail as it is illuminated each time the flash pulses. This analysis is not exact of course and only gives you an idea of how quickly things need to move to be not be recorded by more than one flash pulse. In a HSS image at 1/250 shutter speed and HSS at 20 kHz, the total time the shutter is open is 0.004 sec and at 20 kHz that's 80 flashes. You do get a moving window of the focal plane shutter and that means each bit of image receives only some of these pulses, but the total light must be the same if the subject is to be exposed correctly.

To be fully accurate, changing shutter speed doesn't change the colour of the water, it makes it brighter or darker. Changing the colour temperature means there is more or less yellows in the blues. The tint can also have a big impact on how the blues appear, adding magenta makes them appear deeper in colour. Making the water darker however can improve the look of the water, providing higher contrast with the subject. I agree masks can be a problem - it's always better IMO to get it right in camera. It's so easy to get carried away when processing and produce something you want to throw out when you see it the next day with fresh eyes, so keeping your processing simple is always a good thing.

The issue with the 180mm dome is it is not a fisheye dome and it only covers the field of a 16mm lens with the entrance pupil at the dome centre of curvature. This means you have to place this lens well forward in the dome to avoid vignetting and it will not be as sharp as it would be if properly placed and the filed of view will change somewhat. Fisheyes are more tolerant of incorrect placement compared to rectilinear lenses, there will be some image degradation but without actually testing it hard to predict how much and if it's acceptable. You see vendors like Ikelite offering shallower 8"domes than the 180mm for use with the 8-15 for CFWA work and it still works and produce fairly decent images. I would expect the 180mm dome to be close to this in performance. THis link has some test shots which will give you some idea: https://www.ikelite.com/blogs/buying-guides/when-to-use-a-compact-8-dome-port-underwater?srsltid=AfmBOoq7cYAIaQzEIVTEl0zBJ5dC71nshLjTj2nHBSLCxy_wFBWMEuqy

Wondering what specifically you might concerned about with your vision and how you think a monitor might solve that? For myself my closeup vision is not so good so struggle to details up close a little. I use a separate monitor on land for judging sharpness when the camera is low to the ground and for it to be a all helpful I need my reading glasses on. So my take on that is you need good closeup vision to take advantage of the monitor or supplementary lenses on your mask, because by it's nature the monitor will be quite close in. UW is use a Nauticam 45° viewfinder and it provides a full bright image and it has diopter adjustment to allow me to see the details sharply and it's my preferred way of shooting. Admittedly I don't shoot video, but the distance vision problems are the same.

Welcome on board, assume your hesitation is the cost, it's a fairly big step to house a full frame camera and everything is more expensive with larger sensors - housings, potentially domes, lenses etc. You may want to look at all the components you will need and also compare them to other brands to see what makes the best deal facially. Yu can of course ask questions of the members here to help you with decisions.

The point of warming diffusers is that only the flash light is warmed, the light from the strobe has zero impact on the water. To get the right balance on your subject, generally 4500K light would look too warm and you need to cool the colour temperature a little in post, this means the water will be cooled down as well if you do a global colour temperature adjustment. You end up with deeper blues in the water as a result. As far as the original question goes in Raw files it doesn't really matter if you use a preset 4500K WB in manual or an auto WB. The correct WB for the subject remains the same regardless and you can adjust this very easily as a global adjustment in post. I tend to use AUTO WB and find that it works just fine, use the one that ends up closest to correct when you open it in Raw. The whole point of the warming diffusers is it takes advantage of the fact that the subject is flash lit and the water is not. This way a global WB adjustment ends up cooling the temperature of the water. Yes you could do this with masks but my preference is to minimise post processing if possible.

While masks are very good, my view is it is always better to not mask, it's less work in post processing for a start and unless you adjustments are limited getting transition between masked can be an issue.

The Tokina if it's a Canon mount can be used on m43, Canon EF and R series APS-C and Sony APS-C and the dome would come along with it. Unfortunately the hazard of going with a very good but lower volume camera brand is the ability to keep it housed. THe 10-17 is as future proof as anything in the sub full frame sector.

No problems, regarding the Tokina 10-17 the process is to check the Metabones website to see if they have tested it. You will see here that they haven't but they have tested the Canon 8-15mm: https://www.metabones.com/products/details/MB_EF-X-BT1 The fact that it is established using the tokina 10-17 on mounts such as Sony E mount, m43 among others where the Canon 8-15 and Tokina 10-16 also work is documented so I'd be surprised in the 10-17 didn't work. You could always use the Canon 8-15 which has a zoom limiter for APS-C and is documented to work on Fuji. Then check with Nauticam on their recommendation for using adapted EF lenses with Sony x- mount. Typically with adapted lenses Nauticam used to have a line on the port charts that included a port adapter to use N120 ports using a zoom knob on the adapter in combo with the Canon EF zoom gear. I can't recall if Nauticam ever had this for the Fuji port chart. It has been done before with adapted EF lenses on Fuji, this article from the old wetpixels site has details: https://wetpixel.com/articles/compatibility-report-fuji-x-t3-by-tino-brandt