Photo Synthesis

Even the clearest water has at least some particles suspended in it — sand, silt, plankton, who knows what — and most of the time, in most places, the water isn’t really all that clear. In fact, during a plankton bloom or after a storm that has caused a lot of runoff, you might just as well leave your camera on the boat. Light from a camera strobe has a nasty habit of bouncing back from any particulate matter that it encounters between the camera lens and the subject. The result is the bane of underwater photography: backscatter. Your images will look as though they were taken in a blizzard.

The backscatter problem can be mitigated in several ways. Being as close as possible to the subject is one strategy. Nearness minimizes the volume of water between the lens and the subject, so the number of suspended particles is proportionately reduced as well.

Another strategy is to take advantage of the Law of Reflection by aiming your strobe(s) at an angle such that the light rays emitted will bounce (reflect) off any particles in some direction other than back toward your lens. Usually this means lighting the subject with one or more strobes positioned off to the side(s) of the subject, as opposed to aiming them straight ahead.

Remember, though, that the Law of Reflection assumes that the incident ray will be reflected from a flat, mirror-like surface. I think it’s safe to say that, in the underwater world, the particles from which the light rays will be reflected are likely neither mirror-like nor flat. Instead they can be virtually any shape, and that irregularity will affect the angle of reflection. So, this strategy won’t completely eliminate the potential for backscatter, but it can go a long way toward minimizing the problem.

Of course, these days you can use photo editing software to correct for backscatter, at least up to a point. A few ‘dots’ here and there usually can be made to disappear, but if you have an image that really does look like it was shot during a blizzard, eliminating all the backscatter can be a monumental — and sometimes impossible — task.

Below are four macro images that originally had at least some backscatter. Each has been corrected using the Microsoft Digital Image Editor scratch removal tool.

The first image had only a few dots of backscatter that were very easily removed. The subject is an arm of a crinoid — probably Heterometra savignyi — from the Red Sea.

i-e1660ad086f6b427db0fed2e08065f3e-Heterometra-savignyi76(c)BNSullivan.jpg

The second image, below, is a White Speckled Hermit Crab (Paguristes punticeps), a Caribbean species. It was photographed in the Cayman Islands.

i-2ba6c6cbfeb8119f21feb9c0b386ea0c-Paguristes-punticeps10(c)BNSullivan.jpg

Next is a Bryozoan species from Hawaii, Crisina radians, also known by its common name, Tuning Fork Bryozoan. These fan-like colonies are very small; the one pictured was approximately 1.5 cm (about a half inch) wide.

i-fa98f42808f88980646593f2ae35e621-Crisina-radians240-15(c)BNSullivan.jpg

The final image shows one of the most common nudibranchs found in Hawaii, Phyllidiella pustulosa. By the way, in natural light those pink nodules look green. The pink color is apparent only when the creature is lighted artificially underwater. This individual was about 5 cm (2 inches) long.

i-bc112ed00b8e7936f04cf2ceb3f3f163-Phyllidiella-pustulosa240-16(c)BNSullivan.jpg

Comments

  1. #1 Jason
    August 7, 2009

    Thanks for the post! Very neat pictures.

    Regarding the green/pink nodules of the nudibranch – do you notice if this is a common (maybe even frequent?) phenomenon? It never dawned on me that such contrasts would exist – especially when you see some sea critters whose pelagic coloration / cryptic coloration is so obvious?

  2. #2 B. N. Sullivan
    August 7, 2009

    Hi Jason

    Regarding the green/pink phenomenon: Check out my earlier post on lighting underwater photos. The red wavelengths of the visible light spectrum are absorbed by the water, so those colors are not visible at depth in natural light. The remaining components — green, in this case — are still visible. Providing artificial light from a near source (e.g., camera strobe, dive light, etc.) allows the diver/photographer to see the ‘real’ color of the critter, rather than what’s left to see in natural light after the longer wavelengths have been absorbed.

    In general, if you see a photo of a colorful marine critter — esp. one with lots of reds/oranges/ — you can assume that it was artificially lit. Both the crinoid and the hermit crab in the above photos looked a dull, muddy brown before they were artificially lit to bring out the reds.

  3. #3 Janne
    August 8, 2009

    How do polarizers work underwater? Can they still be used to minimize unwanted reflections?

    Oh, and any advice for shooting BW underwater (apart from “don’t do it”)?

  4. #4 Kris L.
    August 9, 2009

    Hi, Bobbie! First let me say that I love your blog, The Right Blue! I always learn so much from it. So, I am very excited to find this website where I can learn even more about underwater photography! I would have really liked to have seen the “before” pictures of the above “”after” pics so that I could have had an idea of how much work you went to to get rid of the backscatter! I use Photoshop to improve my pics, but am a real amatuer at it! I hope to do a lot of improving and you are a real role model for me! Thanks for all the info you provide!

  5. #5 B. N. Sullivan
    August 9, 2009

    @ Janne – I use a circular polarizer on land, but I have never used a polarizing filter underwater, so I’m afraid I cannot answer your question. Also, I can’t think of too many situations that would benefit from shooting BW underwater.

    @ Kris L. – Thank you for the kind words. I am blushing. Re photography and editing, EVERYONE begins as a beginner! The best advice I can give is to pay close attention to any errors you make so that you will be less likely to repeat them — and then practice, practice, practice.

  6. #6 oyun hileleri
    May 9, 2010

    Hi, Bobbie! First let me say that I love your blog, The Right Blue! I always learn so much from it. So, I am very excited to find this website where I can learn even more about underwater photography! I would have really liked to have seen the “before” pictures of the above “”after” pics so that I could have had an idea of how much work you went to to get rid of the backscatter! I use Photoshop to improve my pics, but am a real amatuer at it! I hope to do a lot of improving and you are a real role model for me! Thanks for all the info you provide!

    thanks…

  7. #7 metin2 hile
    August 23, 2010

    The Right Blue! I always learn so much from it. So, I am very excited to find this website where I can learn even more about underwater photography! I would have really liked to have seen the “before” pictures of the above “”after” pics so that I could have had an idea of how much work you went to to get rid of the backscatter! I use Photoshop to improve my pics, but am a real amatuer at it! I hope to do a lot of improving and you are a real role model for me! Thanks for all the info you provide!thank you

  8. #8 Tineke
    November 20, 2010

    Dear reader,

    One of my pictures from Sulawesi is a Crisina radians. But when I look in WoRMS I can’t find it. Is this the right name of the Bryozoan? Or does there exist an other name?
    I cann’t send you a picture in this email, but I will be happy to send you one.
    Regards,
    Tineke

The site is currently under maintenance and will be back shortly. New comments have been disabled during this time, please check back soon.