mpoletti said:
I picked up my first prime a few months ago; it was the 50mm f/1.8. For the price, I think everyone should have one in their bag. I have been looking into the 85mm as I already the 105mm f/2.8 as well. I just can not capture the quick moving fish like I wish I could. Its either "just" out of focus or their is too much noise.
The 50mm F/1.8D is one of the best lenses I have. Sure it's cheap, but I use it all the time. Quality is awesome, great focal length, great for a lot of things. I never found the need to upgrade to a 1.4 or whatever, this one rocks as is. The lens you use the most is more valuable than any lens that just sits in the bag, regardless of sticker price.
The 85mm has a wider aperture, sure, but that won't get you the shots you want at the right focal length. The compositions that you'll get with the 85 are going to be completely different than your 105. I'm guessing it's a macro 105? The magnification on the 105 macro is about 1:1, meaning you can get really freaking close to what your human eye can see close up. The 85 is much different, you can't get that close by any means.
The solution you're looking for is basically more light, or higher ISO capabilities. You want a faster shutter speed for sure, such that you can capture the fish. But you also can't stop down enough the aperture to allow for good exposures. More light might be hard, as your tank really only has that much light, even 400watt halides right above the tank won't help really. Higher ISO capabilities means a new camera body =) I shoot with a nikon d700 which is amazing even in the lowest of light hand held, just for this reason. I think you're learning the limits of your camera's ISO?
Thanks to the professionals like you guys, I still have alot of room to improve.
Not a professional by any means, plus professionals really aren't that good at photography
It's the hardcore hobbyists that really define what photography really is, just like reef tanks!