Originally posted by Leana This is my first and best attempt after MANY deletions! Fish just move too quickly!
Leana,
You posted two shots. The second one is okay. Needs to be lightened up a little in post-processing.
The first one is not so okay, but the reason seems obvious. It's not that the fish move so quickly, it's that you used way too slow a shutter speed. Looks like your settings were:
shutter = 1/6th sec
ISO = 800
aperture = f/5.6
focal length = 300mm
Shutter speed of 1/6th sec might be a bit on the slow side for photographing a building on a calm day, especially if the focal length is 300mm. Photographing anything that moves, you need to get much faster. And the longer the focal length, the faster the shutter speed needs to be to eliminate camera shake. It probably wasn't the fish that were moving at all--it may have been you. (Or were you using a tripod?)
I'd suggest that you try a much shorter focal length, so you can get the largest aperture the lens is capable of. And by going to a shorter focal length, you'll also reduce the effects of lens shake. Try to get the shutter speed to be faster than the reciprocal of the focal length, in other words, if the focal length = 180mm, use a shutter speed of 1/180th sec
or faster (1/200th sec, etc.).
Push the ISO up to 1600.
I'd be trying for a shutter speed of at least 1/30th sec, better 1/60th sec. Aperture can be as wide as you can go. Fish are thin and you don't need much depth of field. If you had a Pentax 50 f/1.4, you could go to f/1.4. If you don't, and 1/30th sec + ISO 1600 + f/4 or whatever you got, still produces a dark photo, then you will just have to throw more light on the fish tank.
Good luck. And remember to get a signed release from the fish.
Will