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Underwater White Balance

Red Light Absorbtion

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#1 Lobalobo

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Posted 15 August 2012 - 09:30 AM

The research I've done so far suggests that a problem with taking photos under the ocean's surface is that sea water absorbs red light and that other than a strobe there are two solutions, one, to use a filter that converts some light to red and, two, to adjust the white balance (or otherwise adjust color levels). But if the water is absorbing the light, then it is doing so to the light that reaches the human eye as well as to the light that reaches a sensor. So my first question is this: Is the goal in adding red in underwater photos to alter the photos and make the images look better than they do to the naked eye (and there would be nothing wrong with that), or is the eye more sensitive to red light than film or a digital sensor and so by adding red, the image better approximates what the eye sees?

This leads me to my second question. Panasonic point-and-shoot digital cameras have a natural light scene setting for "snorkeling and beach." This confuses me. A digital Snorkeling setting, I take it, adjusts the white balance to emphasize red that the water removes (just a small adjustment, as compared to what would be required at depth). Ok, but why in the world would the same adjustment be used for a beach scene? A beach may be bright and may have an unusual mix of colors, much different from neutral gray, that, like snow, could fool the camera's auto-exposure suggestion, but what does that have to do with water's absorption of light, which is what, I take it, an underwater setting is all about? Thanks in advance.

#2 3ricj

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Posted 11 September 2012 - 10:11 AM

I'm still new to under water shooting, but I have worked with optics and light quite a bit.

This graph:

...might shed some uhh light on the topic. The "red" filters don't add anything, they subtract. Specifically, they reduce the amount of blues and greens from hitting your sensor, giving what reds might not be blocked by the water a chance to be seen. This in effect, balances your images better, as without the filter the reds would be below the noisefloor (eg: no way to fix in photoshop, as the red just simply isn't in the file). However, this also requires that you shoot at a higher iso or longer shutter speed to make up for the reduced light. This is true of 99% of the filters out there - they just reduce bands of light, via high-pass, low-pass or band-pass.

However, the deeper you go the less likely a filter will help, as there simply isn't much red left to see. In that case, a flash is needed such that the other colors will seen.

I hope this helps,
-3ric

#3 3ricj

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Posted 11 September 2012 - 10:14 AM

The automatic "snorkeling" or "underwater" mode on the camera is just a preset for white balance (as you pointed out). I have no idea what "beach" mode is, but I suspect it's just poorly labeled underwater whitebalance.

This leads me to my second question. Panasonic point-and-shoot digital cameras have a natural light scene setting for "snorkeling and beach." This confuses me. A digital Snorkeling setting, I take it, adjusts the white balance to emphasize red that the water removes (just a small adjustment, as compared to what would be required at depth). Ok, but why in the world would the same adjustment be used for a beach scene? A beach may be bright and may have an unusual mix of colors, much different from neutral gray, that, like snow, could fool the camera's auto-exposure suggestion, but what does that have to do with water's absorption of light, which is what, I take it, an underwater setting is all about? Thanks in advance.



#4 tdpriest

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Posted 11 September 2012 - 03:01 PM

In the end, artificial lighting is needed at any depth much below 5m.
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#5 Lwang

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Posted 28 September 2012 - 08:02 PM

Our eyes usually adjusts to the underwater scene, so corals and fishes less blue/greenish and more like if they were in 10 ft of water (the same way if you put one of those blue/red 3D glasses, and after a while when you take it off, one eye will see everything in cyan and the other yellow). But the sensor doesn't auto-compensate, so if you shoot everything with natural light, all your pictures will be blue or green. I guess it is for the purpose of showing its true colors. If a submersible goes down 1000 ft and everything is dark, they can't just say that's the way it is and take a whole bunch of pictures of darkness.

#6 Timccr

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Posted 05 December 2012 - 04:16 AM

I took a grey scale down with me once which I shot at various depths in available light and then colour corrected in PP. What I learnt from that was that our brains actually do a lot of colour correction and I had to reduce the corrections done in PP by about 50%. If you are really into available light shooting it is worth really studying what you can do in PP because it gets pretty complicated. In the Red Sea I could use available light down to around 30 metres. This involved some pretty massive corrections so you need a lot of colour depth to start with. These days I am diving in the Med and am still trying to cope with the green water. Much as I am a big fan of available light shooting I think I am going to end up with a strobe or two soon.

#7 rtrski

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Posted 05 December 2012 - 06:39 AM

I just started using Lightroom (finally got a good deal) and have played around with topside pics with the gradient filter, darkening or increasing saturation for skies on landscapes and the like, and noticed that you could apply a white balance adjustment as well. I've always struggled with setting my near-subject white balance sometimes making the water look muddy due to my preferencial setting being a bit too 'warm' for the ambient light, especially if my strobe lighting is rather imperfect and I'm trying to warm up the regions I didn't really light up enough as well. I haven't played with it yet, but since underwater the 'white balance' is actually a shifting thing, unlike above - the further objects are from you the less red they're going to be, whether you're using ambient light or strobes - I can't help wonder if using a gradient white balance adjustment would help image recovery in some cases. It would be best if you had more options than just a linear gradient across the frame, e.g. create a mask of some sort around a near field subject and a gradient that 'halos' around that...

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#8 Damo

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Posted 06 December 2012 - 12:36 AM

Hi Lol,

Can ur camera shoot RAW?
Re: white base- I always shoot in Auto white balance, and adjust RAW file after in Lightroom afterwards if I need to correct colours.
Of course, this is just my own personal preference.

Best

D
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#9 TomR1

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Posted 06 December 2012 - 02:33 PM

Actually you can open a jpg in RAW and correct the color. The problem will be that there is less to work with because the camera throws away info in .jpg. A solution is to use a red filter that, as explained above, actually blocks the non-red wavelength requiring more light (lower F/stop, slower shutter or higher ISO) to get a properly exposed picture from the camera's perspective. You can then correct in RAW.

In fact I always council a beginner to buy a camera that can shoot in RAW because it makes the task loading underwater simpler. Adjustements that need to be done underwater can be done on the surface using RAW in Photoshop or Lightroom. I demonstrate this by taking a shot of mine that was poorly lit and adjusting in RAW to show how a poor shot can turn into a decent shot.

#10 Angychesler

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Posted 24 January 2013 - 07:39 PM

the deeper you go the more red you will loose in your images. If you stay at one depth you can do a custom white balance if your housing allows for that on a white dive slate.
A red filter helps at a certain depth, but everything will look to red if you are in shallow water.
I have been shooting in RAW with automatic white balance and corrected in post production, that worked best when I shot at a lot of different depths.
You other choices are strobes as mentioned above. I also have used very strong video lights, the advantage is that you can see how the light affects the scene.

#11 Grg

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Posted 25 January 2013 - 03:35 AM

In the end, artificial lighting is needed at any depth much below 5m.


That.

You'll win greatly in colors if you use artificial lights. White balance can be set afterward if you are shooting in raw, so you may be able to see and adjust directly on the picture and see with your eyes how it works, but in the end, artificial lights will simply open your horizon with a surface spectre of lights. The farer the light is from the subject and the farer the subject is from you, the less you'll have red.