How to fix over exposure from tank lights?

[kevinha]

I'm trying to shoot some of the coral in my tank with a Canon Digital Rebel and a tripod. The problem that I'm having is the pictures are overexposed to what I believe is due to the lighting in the tank.

I've tried a combination of f/stops, film speed and shutter speed all to little avail. I'm posting a couple of the pictures here to show what I mean.

Any advice would be greatly apprecaited!

[phistio]

it's tricky, but i would bracket the photos...

first of all, take one picture in full auto...just to show where the camera's meters think the aperature, and the like should be. your digital rebel should be able to show you exactly what f-stop, shutter speed/ISO, and aperature are set at...(and if memory serves me well, it even shows a white balance graph.)

so, say a random picture from your tank is taken at an f-stop of 11, and 1/40 sec. and an ISO of 200. try shooting in full manual mode...move one f-stop down, and then one up....try longer shutter speeds, try shorter. and last word of advice is: when in doubt underexpose, and alter the image on PC...you can always push the colors, and saturation; but if a subject in the frame is already over exposed, there's no way you can reduce the contrast. if you have an image that is under-exposed, you have a lot more room in the spectrum to play with.

almost all of my shots that i intend to manipulate digitally, i purposefully under-expose.

[kevinha]

Cool. I'll give it a shot. I also spoke with a couple of friends who do photography for a living and also happen to have reef tanks, and they stated that it's quite likely the camera's metering system is having a difficult time picking out a midtone, and therefore is blowing out the photo. The suggestion was to use a grey card and lock the exposure on the card, then shoot the tank.

I'll post some pics after I've tried both sets of advice and see what happens!

[phistio]

while a grey card may very well work...the spectrum is harder to read though the water due to a constant variance in light. refractions cause peaks and shadows at different times in the water, making it hard for the meter to correctively act.

also, try using the cameras auto compensation modes. (i.e for low lighting, indoor lighting etc.) also, try using the flash...it brings a whole new color/temp. into play.

[reefcrazy20]

I put my digital rebel on the Tv setting and set the speed to one of the long exposure settings, like 1 sec. or more (1" on the camera). You will need to use your tripod for this to work though. It WILL blur if it is not on a tripod. Attaching a remote would improve the clarity even more. If you are trying to get fish in the picture you will have to set the speed higher to "stop" them and then you will have to adjust the image afterward. It seems counter intuitive to set the exposure to such a long time period for such bright light....but it works. I absolutely love the pictures I get out of the camera though.

[Scubaman]

I've had good luck shooting my tank using f5.6, 1/60 shutter speed and 800 iso. It works well on my tank, but it depends a lot on the light your using. 1/60 shutter speed is okay, but going faster would be better. The main problem is that the lens that comes with the Drebel is really slow, so upgrading the lens to a better one will most certainly give good results.