Adventurer

Well, it depends what you define as "awful". 😉 This is usually a very subjective expression of the situation. More objective would be: miimeter distance of the entrance pupil milimeter distance of the port (required vs available extension rings) stronger image compression able to shoot the lens more oben (F4 or F8 instead of mandatory F11 or F16) priority on zoom flexibility priority on corner sharpness priority on avoiding chromatic aberrations priority on travel weight lightness In physics and underwater photography there is usually no free lunch. Meaning there is one death you have to die (as we say in German). My approach will be to verify the theoretical moved position of the entrance pupil, with a paralax test on a nodal rail. For that I do not need to go diving or get the system wet. Again, thanks for sharing your results @RomiK ! However, I think there are combinations that will perform much better considering IQ in your rig. I hope you will also be able to benefit from the findings in this thread.

Coming back to the initial question and topic, the theory and some formulas suggest that by using the TC the entrance pupil (common name nodal point) will move into the direction of the cameras sensor plane. So if the Kenko Teleplus HD 2x DGX for Canon has 35mm length, an additional extension ring of just 15mm might be enough; if you keep using the same dome and it was absolute precisely positioned before you added the teleconverter. In this example we assume the entrance pupil moved 19.78mm towards the sensor. This is just an example to give you a general idea on how it works and what might be going on, with the real 15mm port extension not computed nor tested / verified.

Can you double check that Chris? My Kenko 1.4x PRO 300 DGX for Canon is just 18mm thick. This also corresponds with INONs Extension Ring 18mm which was especially developed for that Teleconverter.

True! With Canon MIL cameras that dome might work even in the 16mm diagonal fisheye setting that you archive when using the 2.0 TC - might be worth trying on your Sony A1 as well.

Thanks @RomiK for posting the examples. For correct optical performance you have to get the dome size and positioning exactly right on a millimeter level. You are introducing quite a bunch of variables by changing dome size and TC at once. Knowing that Nauticam and Marelux 180mm domes are not full spheres your test was destined to fail. The 180mm dome with conical rear part was simply not made for that lens. The Canon 8-15 FE without the TC is very likely to perform better behind the 140mm dome, which is (almost) full sphere and suitable for fisheye lenses.

I will be utilizing 2.0x and 1.4x Teleconverters with a fisheye zoom lens behind a dome. Currently doing the math for optimum dome positioning and sizing. I am under the assumption that the entrance pupil will move by adding a TC. And I mean by that, not equivalent to the 31mm physicial space that the teleconverter adds between camera and lens. Can you share your thoughts and maybe even the math for this endeavor?

Initially I was looking for some smart inputs to ditch cto gels or warming diffusers on strobes with cooler color temperatures and harvest the maximum photon energy of these cooler illuminators while still getting decent blues in tropical waters. I can adjust the hue and tint in my cameras auto white balance by several mired. In fact more mireds then some of the suggested gels or diffusers mentioned in this forum. I have the assumption that the additional color dynamic range when firing warm light into the foreground may not be needed (anymore) with recent full frame mirrorless cameras.

I am a huge fan of your spreadsheets works @DreiFish but the MARELUX value looks wrong to me. I think I measured 51mm could someone i.e. @Phil Rudin confirm this? I think sensor to bayonet distance in Marelux Canon housings is exactly 70mm.

Fantastic, just as fantastic that your manual triggers auto-switch to HSS mode once you shoot faster than 1/250sec. I would love to have this as a feature in a manual smart trigger for my Marelux MX-R6 II housing. However your trigger design keeps me away from using it, as I cannot fit the box on top. There is a physical camera holding element hindering me from using anything larger than a very thin hot shoe cable in the Marelux housing. I tried the manual trigger of a friend and like the functionality. My friend said I should get your mobie version to get around that problem, but you do not seem to offer that for your latest trigger generation anymore.

I like the Seahorse with blue bokeh very much and also the red bokeh behind yellow fish 🐟… but these two are not done with the TTArtisan 100mm soap bubble bokeh lens, are they? Is the last one with the nudi really trioplan copy ? It does not exhibit the typical soap bubble bokeh you can archive with it. Also I am curious how you got along with the working distance of that 100mm vintage lens. In total a very impressive trip portfolio. Nice work Chris, as usual.

In HSS we are not in the long exposure realm as with astro satellites moving across the frame. We are in a very fast space of collecting light, as a reference look at: sensor read speeds HSS pulse frequencies sensor size pixel pitch on sensor derived line read speed Also consider that there are two dimensions for a strobe to be bright*: the timescale the peak energy output * the strobes total brightness is the integral under that curve. With „normal“ relatively long exposures and classical max x-sync speeds of 1/200sec or 1/160sec strobes may have a loooooong burntime to archive a high guide number. In HSS all that is different.

When I corrected Wolfgang @Architeuthis I especially refered to his wrong general statement about RAW files: RAW files contain color information, as the the bayer array has sorted light into all three channels. This is usually encoded in the manufacturers unprocessed file written to the buffer and card. Wolfgang is right though when he talks about the initial sensor before photons go through the bayer array, but at that stage no RAW file in the camera has been stored. This is from Wikipedia, for the non-believers: Source: https://en.wikipedia.org/wiki/Raw_image_format So now let's discuss the following statement which some of the previous authors cling to here. …when we talk about the blue or green water column, not illuminated by a strobe, in the background of our wide-angle underwater photos, let’s consider the following to think this through one more time. I’m referring to the early stage of photon collection, without any white balance, profile adjustments, or final color space corrections, etc. This process is very similar to the days of chemical film, where light hit your unprocessed slide, and underwater photographers had only 36 shots per dive. Imagine you have a light source emitting the following simplified RED, GREEN, and BLUE values of light (photons): Light travels at the same speed underwater for all wavelengths, but RGB values don’t decrease proportionally when underexposing because of wavelength-dependent absorption. In tropical seawater, the absorption coefficient for green (~525 nm) is ~0.04 m⁻¹, while for blue (~475 nm) it’s ~0.015 m⁻¹. Green is absorbed ~2.67 times faster than blue, which corresponds to a logarithmic difference of 1.42 stops. When you underexpose by minus 1 stop (halving the light), green weakens further compared to blue due to this absorption difference. For example, starting with (R, G, B) = (0, 120, 255), underexposing by minus 1 stop results in (R, G, B) = (0, 22, 127), as green fades significantly. With minus 2 stops (quartering the light), the values become (R, G, B) = (0, 11, 64). This demonstrates that blue light dominates as green diminishes more rapidly with underexposure, disproving the idea that RGB values decrease proportionally. The key factor here is the wavelength-dependent absorption of light in water.

Yes, but for three channels! 🤦‍♂️ R G B RED GREEN BLUE Your long text is highly misleading for the sake of making an argument. Wrong. Because of cited absorption coefficients in water and distance of blue/green background water column. Just try it , and talk to a knowledgeable underwater photographer who still shot chemical film, if you know one, for confirmation.

Hi @ChrisH I totally see your point and in your specific configuration and setup it all makes perfect sense. You are very strong fisheye user, hence your warm strobes (ex-factory warm) play out perfectly. Next influencing factor: the Nikon blues in AWB got you covered. Also a (minor) last factor: Your SiGMA Fisheye, instead of a Nikon or Canon FE. I previously owned this and remember that when even shooting this topside this lens would render the shots a little more golden than a Canon or Tokina FE. Anyway, just change your perspective to the average Joe who does it different and bought one of the cooler strobes out there, internationally sold in multiple quantities. Even Nikons, Sony and Canons System strobes are manufactured with quite cool color temperatures. So let’s look at my initial statement quoted again above. Does it always make sense to „rape“ your strobes energy output with warming diffusors ? I would like to hear more different opinions from others. You and @Chris Ross have made your point.

Double needs to be deleted

Sorry Chris, but this is wrong and I need to correct you for physical facts. Water absorbs light in a wavelength-specific manner: • Blue (~450–495 nm): Absorbed the least and penetrates the deepest. • Green (~495–570 nm): Absorbed more strongly than blue but less than red. • Red (~620–750 nm): Absorbed almost completely within a few meters. Absorption Coefficients • For blue light (~475 nm): Absorption coefficient ≈ 0.015 m⁻¹. • For green light (~525 nm): Absorption coefficient ≈ 0.04 m⁻¹. This means that green light is absorbed at approximately 2.67 times the rate of blue light in pure water. While the speed of light in water is nearly identical for both wavelengths, the absorption rates dictate how much light remains visible, making green “fall out” of underwater photos more quickly than blue. You can utilize this effect by underexposing. The green part of the histogram will overproportionally be underexposed if you lower your exposure by one stop. Sidenote: underexposing slightly for decent blues underwater is a technique coming from the film days where underwater photographers had no control over white balance in a non-digital camera. It‘s a proven relict. However if you do not meter and expose in a proper way you may be unable master this technique with your camera. Unfortunately it blows the scope of an Internet forum to teach this here and the thread is on it‘s way to go off-topic.

When a photo is underexposed, it alters how colors are rendered in the image. The effect of greenish water appearing blue in an underexposed photo can be explained by several factors: 1. Camera White Balance Cameras adjust white balance automatically or manually to ensure colors appear correct. In underexposed conditions, the camera’s white balance often shifts toward cooler tones (blues), as green and yellow tones reflect less light in dark conditions, making blue tones more dominant. 2. Spectral Light Absorption in Water Water absorbs red light more strongly than blue light. This natural property makes water appear bluish, especially in low light (e.g., during underexposure). When the image is darkened, the green component of the water reflects less light, allowing the blue hues to stand out more. 3. Perception and Color Saturation Underexposed photos tend to increase the perception of color saturation and contrast. This can enhance any slight bluish tint in the water while muting green or yellow tones. 4. Camera Color Profiles Digital cameras have specific sensitivities in their sensors. These sensors often respond more strongly to blue light under low-light conditions, which can make greenish water appear more blue when underexposed. In summary: Due to the physical properties of water, the camera’s processing (e.g., white balance), and sensor behavior, greenish water often appears bluer in underexposed images.

Interesting Balage, two questions: 1.) After setting this up via the computer you are stuck in strobo mode for the whole dive until you connect it to USB PC/MAX again and edit it ? 2.) As a Canon user, any chance this is also coming / available for the e-TURTLE 2 MANUAL trigger ?

Don‘t get me wrong (Camera/RAW)Profiles (Portrait,Landscape,Neutral,Standard, Adobe Landscape etc) + ColorProfiles (AdobeRGB, sRGB) are to a large amount available in both, camera and raw converter. So with your phrase above I now struggle to understand if you refer to ColorProfiles or (Camera/RAW)Profiles. The fact that (Camera/RAW)Profiles also heavily influence color balance does not make it easier for everyone to communicate about this 🤭🤣. @Chris Ross the fact that you shoot OM-1 explains a lot. Color science varies hugely among camera brands and even models in some cases. But if you get exposure right you will also be able to shift between green and blue background without touching white balance. I stay with that advice and experience on many different brands I had to shoot over the years. Give it a 2nd try and watch that you do not underexposure too heavily, otherwise you will not notice the effect. @ChrisH let’s come back to warm strobes or gels topic. Mr. Ross pointed out that sometimes he might not be close enough with his Z240s. This is an important factor. I see with you that you are mainly mastering the fisheye lense which usually gets you ultra close! In this case I would subscribe to your algorithm. The warm color temp of the strobes will definitely hit the foreground and also use the warm spectrum. But now let’s imagine you have to be more far away and will use a more tele end lens, such as 17-55 or 14-35. You want to shoot it on the zoomed in end of wide angle underwater photography. This is not uncommon when shooting portraits of mid sized pelagics such as sharks or dolphins or shy reef sharks with strobes. There the warm color in the foreground will be quickly absorbed and have no use, because you are simply not close enough. Same applies when you do not have sufficient stuff to fill the frame in the foreground. In that scenario I would opt in on the cooler strobes and try to avoid diffusers, as I want the maximum energy of the strobes to penetrate the water column as far as possible. Cool color temp of the strobes spectrum will travel more far than the reddish parts emitted or filtered. There is a second thread going on right now where that concept is discussed and exaggerated by even adding cooling filters to video lights or strobes. This is also the reason why Backscatter offers blue Diffusors for there HF-1 strobe. However if you want maximum energy penetration through the water column then cool native color temp strobe, without any diffusors or filters is the way to go.

Camera profiles are a strange beast and were for a long period the origin of high color discrepancies between your camera (Canon/Nikon/Olympus/Sony) and Adobe Lightroom. In Lightroom you can pick stuff such as „Adobe Standard“,… „Adobe Landscape“, … „Camera Standard.“ ,.. „Camera Landscape“ - many photographers agree that the profile should be picked early in the editing workflow. They should not be mistaken with Creative Filters (of Cameras), Presets (Lightroom) or Color Profiles (AdobeRGB, sRGB etc). (Camera) Profiles are the way how the camera or raw converter interpretes the early data in your RAW file. This can lead to huge variance in color and contrast.

I think everyone’s intuition that particles or subjects have to move to emit less backscatter reflection is not mandatory. If you are familiar with astro photography image stacking you might develop a good intuition on what might be enough for the initial statement to be true. In HSS the light pulses are usually less strong so they will cause a less strong reflection compared to a classic single strobe pulse (equaling the quantity of light that all HSS pulses together have). As the shutter travels down (line by line) during the (less strong) pulses, less backscatter reflection is captured, compared to a single strong strobe burst, giving out all at once and not in tiny slices.

Nice pictures @ChrisH - must be magic „Nikon Blues“ in AutoWB 😉👌without postprocessing. @Chris Ross I would like to get us all on the same page and look what’s different. I assume that both of you do not shoot RAW+JPEG out of cam, are you? So all your image go through the Adobe (Lightroom) workflow? What color profile do you have set in your cam? In my Canon‘s I occasionally like to use the magic „Landscape“ profile. This might be one of the reason, why we come up with different results and experiences. Next to that, I‘d like to stick with my statement that if not correctly exposed for the blue water, the image may get a green tint or cyanized. This also results the phenomenon that you can tweak greenish water into the blue spectrum with traditional in camera technique (exposure) on auto white balance. Even though Chris Ross came up with a fresh lab test argument/example about greenwater, I do not agree with his results and conclusion. I took a look at your Instagram account, Chris Ross and my impression is that you did not nail the blue in the majority of your shots. When compared to Christian‘s results, Mr. Horras has definitely very pleasing blues in his examples. There are different levers that you can push in your camera to get the desired blue background. With the AutoWB and general color science camera brands act very differently, so this may also come into play.

I do not (fully) agree Chris. Actually you can turn green water background into blue color by just alternating the cameras shutter speed. If you look at a prism / color spectrum you will find that blue and green live next to each other on that scale. By cutting off wavelengths you can move slightly in this gradient.

„HSS will minimize Backscatter compared to a single strong pulse of the underwater flash.“ What do you think about this?

classic terms in photography is quality and quantity of light, not really including the color temperature. The quantity is referring to light output, but that can be also very concentrated on a single spot. The most extreme example would be a laser pointer. Quality of light refers to the distribution of that power. Hence you can imagine it‘s less in important in macro photography than wide angle. All underwater strobes today and even many torches have enough quality of light for underwater macro scenes. But as many don’t have enough quality of light for large wide angle scenes it likely you buy a second strobe or two new strobes once get into serious underwater wide angle photography. Dr. Alex compared it to the jam on your toast. You want it evenly spread and not all in one corner of the bread 😉