Saturday, November 26, 2011

Diving Photography

Taking decent underwater photographs is a challenge. This post is about my experience this trip. Warning: it gets technical.

I was surprised on our diving live-aboard boat trip how many people had elaborate underwater camera setups. I'm used to being the keen photographer in a group, but I was definitely outgunned this time.

I have a much better camera now than I used to - a Canon G12 instead of the little Powershot. It has much better low light abilities and can shoot raw which allows a lot more adjustment afterwards.

The big difference with the more sophisticated setups was the lights. It's dark underwater and the colors get washed out. I don't use the built-in flash on my camera because flash on camera like that is harsh unnatural lighting, and the little built-in flash isn't very powerful anyway. A better setup is to have multiple (two or more) separate strobes (powerful flashes). But this kind of setup is heavy and bulky and awkward (not to mention, expensive).

You can get underwater cases for SLR's but if the case leaks that's a lot of money down the drain. One of the people on our trip had borrowed a fancy underwater camera and it flooded on the very first dive - ouch!

Because I don't have lights I prefer to take photos fairly shallow where there is still light and color. But most of our dives on this trip were around 20m (70ft). For this, shooting raw and using software like Lightroom is key to getting some color back.

I started the trip shooting fully automatic, but the G12 tries hard to use a low ISO (light sensitivity) because that gives a better quality photo (less noise or "grain"). The problem is, that means a slow shutter speed. But underwater, everything is moving - you're moving and the fish are moving and the only way to "freeze" that movement is with a fast shutter speed. (Another reason why flash is better - it also helps freeze the movement.)

Next I tried shooting at the G12's maximum ISO of 3200. That resulted in faster shutter speeds and less motion blur, but a lot of noise. Next day I tried 1600, and then the next 800, where I left it for the rest of the trip. It seemed the best compromise between sensitivity and noise. Part of it is diving skill - how well you can "hover" in one spot and hold steady while taking a shot. I'm gradually getting better at that but I still find it a challenge. Sometimes you can find a spot to put a finger against which helps a lot.

At shallower depths, like 10m, when the light is relatively bright, I was finding the highlights were often burning out. You can recover some of this, especially if you're shooting raw, but not if it's totally white. In these conditions I found it worked better to override the exposure to be darker by one stop. This is where the G12 is nice because it has a separate dial for exposure adjustment, rather than having to poke around in the menus (especially underwater!) There's also a separate dial for ISO. The downside of forcing the images to be darker is that it increases the noise. But I'd rather have more noise than have totally burnt out areas.

Although other people on the live-aboard had better cameras, or at least better lights, they didn't seem to be as familiar with adjusting the photos on the computer afterwards. Using software like Lightroom or Aperture is the modern day equivalent of having and using your own darkroom. Just accepting the default processing that the camera does is like accepting drugstore prints in the days of film. (And if you're going to adjust them you really need to shoot raw, assuming your camera is able.)

In Lightroom my normal adjustments would be: Clarity +50 (sometimes all the way to 100, although that can look unnatural), Luminance Noise 50 (depending on ISO), Strong Contrast Tone Curve, sometimes increased Vibrance, sometimes Recovery. If one side or corner is too bright I'll use an exposure gradient to adjust it. Other than parts that get too bright, the images almost always look murky and washed out and I'll increase the Black and Exposure settings to improve the contrast. (I should probably directly adjust the tone curve more, but I haven't got to that point yet.)

If there's something neutral in the image, like a black wetsuit or (relatively) white sand, I'll try using that to set the white balance. If not, or if that doesn't look right, I'll adjust it manually. Underwater photos taken with natural light are very blue. Getting rid of that and bringing back some reds often requires extreme white balance adjustments, pushing Temperature and Tint to the max. But it really is blue underwater, so sometimes it looks better to just let it be blue and not try to remove it all.

I always smile when people claim their photos are "unprocessed". There's no such thing as an unprocessed digital image. All it means is you are keeping the default processing your camera (or computer) does. That processing isn't necessarily any more "true" than when you adjust it manually. Of course, you can push the processing to extremes and end up with something unreal. The closest thing to an "unprocessed" image would be a raw image with all the settings zeroed. But that looks awful and won't be anything like what it "really" looked like. Unless I'm deliberately trying to achieve some abstract artistic result, I try to make the images look as close as I can to how it "felt" to see it in person (with, admittedly, variable results).

Of course, apart from all these technical issues, the subject and composition are still critical. No matter how technically excellent an image might be, it still needs to be interesting and pleasing to the eye. And there's still a lot of luck involved in being at the right place at the right time.

Photos from the week coming soon, as I select and process them.

PS. You can see why so many computer geeks get into photography - there's plenty of technical details to obsess over!

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