Chris Ross

As I understand things strobes emit a full spectrum centred around their colour temperature and they do this by generating a plasma which glows giving a black-body type continuous spectrum centred on a particular wavelength. Technically it produces grey body radiation which is transparent to its own radiation. This wavelength is what defines the colour temperature produced. The temperature achieved inside the tube corresponds to plasma temperature achieved so 4500-6000 degrees kelvin (Kelvin = degrees C plus 273) The peak wavelength moves to shorter wavelengths as the current density increases due to the plasma getting hotter. If the strobe is using small linear tubes the current density needs to be higher to match the output produced from a larger tube so light is bluer. The light produced is proportional to the volume of gas that is excited into a plasma. So physically large tubes can use lower current densities and their light tends to be warmer. Similarly a shorter pulse will shift warmer as the shorter duration means less energy is added to tube so peak temperature reached is lower, color temperature lower and peak wavelength longer.

It's good that they do standard comparison tests of strobes, but when I last looked the only way to find them was buried in individual videos be nice if they had a central site where you could find their data to directly compare strobes you are interested in. I find I am really not a fan of video reviews they are nice enough to watch but I'd much rather have a written review where I can skim to the interesting bits.

I'm as baffled as you about green water turning blue, you can do it in post processing but the diffuser has little to do with it.

I'm not sure how this relates to my comment (quoted by you) I made no mention of turning green water blue - perhaps it applies to another comment.

Indeed, It's really WB method independent and requires no more thought than doing the standard WB adjustment on your subject. The main point if that it really only is a big benefit in clean tropical waters. I've left the 4600K diffusers on in temperate Sydney water and the photos come out just fine, but I don't see a big benefit for it in that situation.

Advertised Guide numbers are somewhere between a general guide and works of fiction, most seem to report centre brightness in air and previous studies have shown some strobe models are quite bright in the centre with more than average fall off. It sounds like the S220 should be on my list to replce my Z-240s one day! If you have all of this data it would make a great write up to give people some objectivity when choosing strobes. Would you consider writing it up as an article for the site?

Which is exactly the application they are suited for, warm strobes really give you no advantage in cold dirtier waters.

I would think the problem lies within the camera/UWT trigger combination. When in manual the INON strobe just fires when it receives a light pulse. You might be best to message Pavel if he doesn't chime in.

Welcome on board Gerald, hope you find the forums useful. On your question about the Nikonos lens perhaps you could ask the question in this post where it might get more visiblity?

What I have seen if they are forward is the lens sees the particles very close to the strobe which then become very bright and intrusive. perhaps I didn't express it right. The main point of the post really is to point out that stating that you can't avoid backscatter by using edges because you can see unilluminated particles in the image is being pedantic. The whole point is not to illuminate them so you don't notice them.

There's the physics of course, but this ignores the aesthetics, using blue filters on your light source does indeed provide an even colour profile throughout and it does suit some subjects. But it mutes the reds through yellows and looks kind of flat - it suits some subjects but not others IMO. For skin tones, vibrant soft corals the images look kind of dull that I have seen. One of the big things underwater is to restore reds - all the warm colours but putting a blue filter on your light source kind of defeats the purpose. I would agree that you don't necessarily need a warm strobe, but you might want one.

I would argue you care about both, the sun does a fine job of illuminating the upper surfaces but the sides of fish, corals etc don't get much illumination, then of course there's the undersides, you only have to look at how dark it is under even a small overhang.

Technically yes you can see the particles but I would argue that un-illuminated particles are not backscatter. The meaning of backscatter is light reflected back towards the camera and these particles are very close to the strobe so are very bright and objectionable. Particles you avoid illuminating may or may not be noticeable depending upon what is behind them many times I can zoom into 100% and see stuff floating around but the final image you really don't see them. For all practical purposes they have no impact on the image. I've positioned my strobes badly often enough that I can say for certain that avoiding illuminating the particles is a real positive for the photo. the most important parameter seems to be to pull the strobes well back behind the plane of the dome port.

Back to the original question, regarding strobe selection, The small INONs are nice strobes, however my experience is with Z-240 I find that shooting at f8 on m43 lenses I am at 1/2 power or the next level which is 1/2 stop less than full. at ISO200 I find lighting big scenes a struggle at times. On full frame you will be stopping down to F11-13 most likely. You can bring your ISO up to 400 but might find you are running into your sync speed if shooting sunballs or even bright surface waters. 1/250 @ f8 ISO 200 is the same as 1/250 @ f11 ISO400. I've just finished diving at Walindi in PNG shooting Barracuda schools etc. I didn't really want to go full power as I was ready to shoot again quite quickly at the powers I used. I kind of felt I'd like a little more strobe power. You could probably get away with the S220 if shooting at less than 1 m distance and using full power, but might find them wanting when shooting big scenes.

This is correct, if you white balance with a warmer strobe to make your subject neutral you cool the image overall which means the water is colder/bluer, no masks required. This happens because the strobe illuminates the subject and not the water. Though I would say there is no harm in 4600K light, I've used in clean tropical waters and results are fine.

A few points, you seem to want to do wide angle shots, firstly be aware that a fisheye is is not apples to apples with a RX100 with a wide lens. The fisheye is a lot wider and challenging to fill the frame with compared to a typical wide angle lens on the Sony. With fisheyes for general wide angle work the AF won't be a problem and any combination should just snap in, you may notice some problems with CFWA work where you are in very close. I would look at an RX-100 V if the primary interest was wide angle. I would also suggest that photography while snorkelling at least to me when compared to diving is quite different. Apart from seals and animals that might want to interact with you fish often swim off as you swim over them. I was struck by how approachable fish were when diving in comparison. the m43 systems have a good range of UW lenses, better than Sony APS-C IMO and the lenses are a lot smaller. see for example this macro comparison: https://admiringlight.com/blog/macro-battle-sony-90mm-vs-olympus-60mm-vs-fuji-60mm/ Smaller lenses often means smaller ports and are certainly lighter to travel with. I would suggest looking at second hand EM-1 MkII systems in either Nauticam or Isotta, they can often be picked up for a bargain price and have more flexibility in lens and port choice. They also use fibre optic flash triggering with the accessory flash to trigger which works really well. On the ikelite housings, they certainly work, however the dome offered for fisheye is an 8"dome that can't be positioned optimally as it's not a full hemisphere and is not so good for CFWA due to the size. The m43 fisheyes however work very well with the little 4"Zen dome or the Nauticam 4.33"dome much smaller and easier to deal with in the water. If you are snorkelling getting a housing that allows using a vacuum system is a big plus, counter-intuitively leaks on housing are more likely at the surface. Vacuum systems pre-load the o-rings making a leak at the surface less likely.

One thing you might want to try is if you are editing your videos you might be better placed to get full resolution frame grabs which you could then crop a little and post as a JPEG. I would guess that selecting a frame may be easier in a video editor. Freeze framing the youtube video doesn't provide a particularly high resolution image.

You might try moving your large float arm to under the housing instead of on top, then check the trim in a tub as Davide suggests. the basic principle is to get the centre of buoyancy near to the centre of mass. Other ways to do it might be to extend two equal floats out horizontally at about the same level as the lens. What you can accomplish will be distated by your tray configuration most likely.

I find that videos are less than ideal for ID purposes unless it's something obvious as the fish just wriggles around making it hard to compare to reference pics. Having said that to me it looks like a dragonet of some type, possibly this, but could well be way off: https://www.fishbase.se/summary/Callionymus-bairdi.html

Hi @SwiftFF5, The system is actually supposed to block video uploads now. The concern is cost of storage when many videos get uploaded. The best solution will be to upload externally, probably to Youtube and link it to the post. Don't know why it's not showing the video, but seeing as how it's not working I deleted the video from the post. Let me know if you need assistance linking the video externally.

Fishbase can be useful, I searched for Haemulidae (grunts) and narrowed to Indonesia and started looking at pics, you find the link to show species images and then click on the species and click on the pictures link above the the photo on the species Page. I found this, it's white rather than silver however the patterns seem to match: https://www.fishbase.se/photos/PicturesSummary.php?resultPage=3&ID=4465&what=species

if you just want to buy new o-rings rather than go to a store or try to measure yours, I think you will find that all S&S ports that fit your S&S housing will take the same o-ring. there is no reason they would change between different ports. as they all need to fit into and seal against any housing that takes that port type.

Unfortunately even if you didn't turn it on, when you tell the repair centre it's water damage they will often refuse to repair. The problem is that they could replace failed components only to have corrosion take out others a few weeks after they return the camera. If salt water touches electronics it's generally toast. As for the housing internals you could try to re-use them but they will likely suffer the same fate.

This is not the reason people wish to use warmer strobes. The reasoning is that a warm strobe when white balanced back to daylight colour balance will render the water bluer. The water is not illuminated by the strobe so it has no impact on the water directly. You can't get this effect by just white balancing cooler as the subject will then be too blue. It's the same problem you get for example shooting flash of for example a sunset with with a flash lit foreground subject. The WB will only be "right" for one subject as you are mixing 5000K flash light with 2000K sunset light. The WB can only be "right"for one - not both. Not sure if all cameras do this but as I understand it at least some set the WB to standard colour temperature for flash assuming it will match and produce pleasing skin tones. So Auto WB when shooting flash defaults to 5000K or whtever the manufacturer uses. Tend to agree on LR, I don't use it but as I understand it you can set it up to use your WB and other settings as a preset to give you a starting point.

I use INON Z-240s and have generally used the 4600K diffusers that came with the units in tropical blue waters and I've been happy with the results. I have not done extensive comparisons using different diffusers though. Agree it's about colour temperature balance, not tint. If you are using INON strobes, diffusers I think are a given whether they are the standard ones or the warming diffusers. For myself I would rather get it right in camera, there are various ways of addressing the blues without impacting upon the main subject including masks, but If I can get away without drawing masks on my images I will, depending on subject they can be fiddly and you always risk edge effects around your subject.