Copper said:
One standard guideline for taking photographs through water is to use a light source seperate from the camera itself. I steady light source would be best as a flash may startle your fish causing unnecessary stress, but if you have nothing else. You'll want your light peferrably at a 45 degree angle to your camera.
That is sort of right but not exactly. Look at any handy sheet of glass or the surface of a pond. You can see the reflection of stuff that is closest to your head. A strong light source that is behind you could be a good long distance away and still cause reflections. If you want the physics lesson, do a google search of “critical angle” or “angle of incidence”. For the best pics, you probably want to have two or three light sources as far to either side as possible (three sources will essentially prevent any shadows).
Copper said:
Second, the faster the film settings (analog or digital) the better. Fish have a tendancy to keep moving causing blurs, so a faster speed with help freeze the picture.
Well, if you are using really expensive professional quality film (or a really crappy disposable camera), you are more likely to run into this effect. But if you just get some Kodak ASA 200 film you probably will never notice motion blurs. Heck, if the room you are in is decently lighted, 200 speed film is not likely to even trigger the automatic flash on most cameras. For reference, you can use ASA 400 to take stills of a galloping horse and ASA 1,000 is good enough to keep the blur from the legs of a cheetah running at 70 MPH. And just how fast are your fish swimming?
Also, allow me to note that ASA is a number that does not relate to digital photography. A couple of points:
ASA is not just the speed of the film but also the “grainyness” or in digital terms, the resolution in DPI. That is one setting on a camera (assuming that you have a “good” camera and not just a point and shoot model that is fine for taking on vacation).
Digital cameras produce the image on the sensor chip in the opposite manner to what film does. If an image is too faint, a longer exposure will “intensify” it but not for exactly the same reason. Again, there is a physics lesson here and I will try to hunt up something later.