Stabilizer or faster lens?

[CT Sean]

IMO you're wrong here. If you're at intermediate depth, a red filter will reduce the blue and green channels, require more exposure and make the red channel a bit stronger since you expose more without blowing out the B and G channels. That means you can recover whatever's left of red without suffering that much noise in the R channel.

If you're so deep that there's no red light left, you're only increasing the shutter speed...


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So you're getting a theoretically cleaner image but at the cost of a slower shutter speed. If a slower speed works, that's good but if you have to up the ISO to compensate you just add noise to all channels so in the end it's probably a wash.

 

[Storker]

If a slower speed works, that's good but if you have to up the ISO to compensate you just add noise to all channels so in the end it's probably a wash.

More or less. TANSTAAFL.

There's one additional, albeit minor, advantage, though. In some programs, like LR, heavy color balance corrections are difficult unless you start editing individual channel curves. A somewhat better balance between the channels makes color balancing a bit simpler.


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[Tigerman]

The closer to correct white balance (and exposure) you shoot, the easier and quicker the post-processing will be, regardless of what format you use - but you will have MUCH MUCH more data to work with, making the end result even better with RAW.
We have enough issues with light below the surface to begin with that reducing it even more really is a "last resort" rather than the preferred option. The preferred option is always to bring your own, personal sun to get the light back

 

[CT Sean]

More or less. TANSTAAFL.

There's one additional, albeit minor, advantage, though. In some programs, like LR, heavy color balance corrections are difficult unless you start editing individual channel curves. A somewhat better balance between the channels makes color balancing a bit simpler.


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Fair enough - I manual WB everything so I've never had something so bad that I couldn't get the right WB without the eye-dropper in LR. A bit OT, but I have been pretty impressed with what LR can deal with as a "one click correction" though. Its underwater WB capabilities is why I bought it. Canon's DPP is woefully inadequate in some situations (backlit scenes being one)

 

[Interceptor121]

If you shoot without strobes there is some value in white balancing underwater as the shift in the colour channels may move the histogram and you may evaluate exposure incorrectly however this is marginal and generally for raw i don't bother balancing as the latitude of change is much better in post also never use filter for stills
For video different story filter on and auto white balance as I found that with certain cameras custom white balance creates more problems than what it solves

Aldo forgot to mention white balance picker only works with light behind you backlit shots end up magenta and need to be adjusted directly on the hues or channel gains if you have those

 

[String]

So you're getting a theoretically cleaner image but at the cost of a slower shutter speed. If a slower speed works, that's good but if you have to up the ISO to compensate you just add noise to all channels so in the end it's probably a wash.

As above, its into (rapidly) diminishing returns with increasing depth. There is a sweet spot and that tends to be very shallow.

Obviously shooting JPG or lacking the ability to manually white balance filters are very useful. However in RAW especially with modern cameras that have a decent dynamic range (most will easily pull back 2 stops of difference now) and relatively low noise you can pretty much balance a photo without a filter as easily as with unless you're at the absolute extreme end of the scale and once you reach about 15m or so in clear water forget it, the filter is just making things worse.

All those pretty colourful reef shots you see - they're usually 5m or shallower. Ambient light photography is fun (i do a lot of it) but in terms of getting anything close to reality or even acceptable quality its worthless below about 10-15m or even shallower in murkier water. If you're happy to produce grainy, massively coloured tinted photos lacking in clarity and contrast then go for it deeper but if its close to reality you want, it wont happen.

---------- Post added December 16th, 2014 at 05:29 AM ----------

Canon's DPP is woefully inadequate in some situations (backlit scenes being one)

Interestingly ive found Canon's DPP using manually WB shots and indeed RAWs can produce MUCH MUCH better results than the identical shot in ACR or Lightroom. Any shots with ambient where the red range is minimal i can get far more scope for adjustment and better colour rendition now than i can with Adobe. I put this down to the proprietary reverse engineered RAW format in that Adobe are making guesses or not able to use all the data whereas the Canon SW is.
It's not just a picture style issue either. My new workflow annoyingly involves exporting the ambient light/manual WB photos as TIFF from DPP before editing in lightroom.

 

[olegk]

OK, in case anybody wants to try "messing" with my RAWs, I uploaded several ones:

(1) http://www.lazyconv.com/galleries/DEMO/UW_TMP/DSC03375.ARW
This is the input for DSC03375.JPG
The image shot at >20m with a wrong filter (FLD); this is the cause for excessive noise.
As I already wrote here, this image hits natural restrictions of available-light UW photography: it includes matters on different depths. While I claim the wreck and the diver got more or less correct colors (watch the white letters on his dive-suite, and the fins _are_ magenta), the water behind- and especially above him turned magenta. The way I explain it: most of the water seen here is at lower depth than the diver, and thus it would require less color correction. Still the picture suffered from the wrong filter, and I would not invest into it any more.

(2) http://www.lazyconv.com/galleries/DEMO/UW_TMP/DSC03579.ARW
This is the input for http://www.lazyconv.com/galleries/Root/Underwater_Israel_2014/DSC03579.html
Shot at 24.5m with FLB filter that is supposed to fit well.
I consider this shot a success (you may disagree). There is some magenta cast in the background water (for the usual reason), but it doesn't dominate the picture.

(3) http://www.lazyconv.com/galleries/DEMO/UW_TMP/DSC03665.ARW
This is the input for DSC03665.JPG
Shot at 28.7m with FLB filter. Again, the color-balance of the main subject is mostly correct, and there is no excessive noise. The picture would benefit from a RAW converter with local-contrast-enhancement, but the one I use doesn't have it.

By the way, the original thread that brought me into available-light underwater photography is still available for read: Available light shots - Lights, Strobes, and Lighting Technique - Wetpixel :: Underwater Photography Forums

 

[Storker]

(1) http://www.lazyconv.com/galleries/DEMO/UW_TMP/DSC03375.ARW
The image shot at >20m with a wrong filter (FLD); this is the cause for excessive noise.

The noise isn't bad at all. I'll bet that if you made an 8"x10" print of that picture, you wouldn't need to bother with noise reduction. The picture is reasonably sharp, though. I ran it through LR "quick & dirty":

Processing:
WB temp: 20000
WB tint +150
Exposure: +2.0
Blacks -70
Clarity: +20
Some adjustment of the tone curve for the blue channel (one adjustment point 64%->47%, i.e. a concave curve shape)
Luminance noise adjustment: 25
Sharpening amount: 50 (to recover some lost acuity during noise reduction)

(2) http://www.lazyconv.com/galleries/DEMO/UW_TMP/DSC03579.ARW

This picture isn't sharp. Looks primarily like motion blur even on the coral; work on holding the camera steady.

Processing:
WB temp: 10000
WB tint +150
Exposure: +0.70
Whites: +30
Blacks -20
Clarity: +20
Luminance noise adjustment: 0
Sharpening amount: 25 (LR standard)

(3) http://www.lazyconv.com/galleries/DEMO/UW_TMP/DSC03665.ARW
Shot at 28.7m with FLB filter. Again, the color-balance of the main subject is mostly correct, and there is no excessive noise.

Again, not sharp. Looks like motion blur plus missed focus. Very difficult to color balance correctly in the foreground and avoid a magenta hue on the background, so I resorted to using an adjustment brush on the background water. Not very well, it's really quick&dirty.


Processing:
WB temp: 50000
WB tint +150
Exposure: +1.5
Luminance noise adjustment: 0
Sharpening amount: 25 (LR standard)
Adjustment brush on background, in auto mask mode: Temp -100, Tint -20


EDIT: If you're worried about digital noise, the last thing you want to do is to underexpose and then plus-compensate ("push") in post. That can make even a base ISO image look noisy. Try your best to get your pictures correctly exposed, and if that means you have to up the ISO, so be it. It's better than pushing in post. And stop pixel-peeping. Evaluate your pictures when they're downscaled for screen display, or as prints.

EDIT2: IMNSHO, if you're doing ambient light UW photography, you should try to make use of the hues and colors underwater, perhaps modifying the color balance somewhat to mimic our brain's auto color adjustment (it always looks worse in the camera than in our minds). That can give a very interesting look and feel, and you won't run into a brick wall trying for topside color balance. Because of the physics of light absorption, that's just not possible. If you want your reds and oranges to 'pop' like they do topside, you need artificial light.