Thanks Dave_2133
This is how I do it....
Preamble... I use a digital slr. Try use lowest iso(asa) possible. I leave the tank lights on to help focussing. The light in my tank will not be relavant at the shutter speed and apeture selected. The flash (most flashes) has a really short burst, something like 1/20000 sec and it freezes the movement.
I use a shutter speed of 1/60 sec and f8. With my tank lights, an exposure at these settings will be way way to dark and thus in effect the only relavant light sorce is the flash. If I had metal halide lighting, this would not be true as its much brighter and would play a part in the exposure of the image.
Using the "on camera" flash, I make sure I angle the camera slightly downwards so that the area of glass containing the flashes reflection is not in the frame. I usually hold the camera about 30cm from the glass and have the camera set to continuous autofocus. In this mode it does not 'lock on' to the subject but constantly tries to keep it in focus.
I set the camera to spot metering so that it reads what flash power is needed from the side of the fish and not from the dark background. If I use centre weighted or matrix metering I get a larger proportion of pics where the fish has 'blown out'.
I use a 17-55 lens, mainlyon 55 and follow fish around until they either pause, flare their gills, raite their fins etc and then take the pic.
The resultant photos are then looked at on the computer and culled ruthlessly. I select what I consider to be the best and then load them into photoshop.
The pics are leveled and contrast adjusted to represent the image I sam through the viewfinder. Floaties in the water are disposed of and finally the image is resized for posting to the forums. I resize to 640x480 pixels at 72 dpi. I then finally sharpen the image using photoshop settings of 100% .7 and 3. Usually I then slightly darken the edges as I feel it looks better.
Here is an example of an udadjusted image (only resized) and the resultant pic after a little photoshop work.
Original:
Adjusted image:
Hope this helps.... sorry for the long winded reply.
Cheers
Brian