It's a function of amount of light (ISO) and aperature for your depth of field. You want to have as much light as possible. So,
Set your ISO settings to as high as you can (as long as it still gives you reasonably clean images).
Step your lens down to f/5.6 or f/8, you're going to loose light as you stop down the lens but that's the only way you can gain depth of field.
Now your depth of field actually includes some space in front of your focal point and some space behind it. So you should set your focus point so it'll maximize your depth of field. (i.e. choose a focal point that is a little behind the closes point)
Also remember your focal plane is parallel to the sensor in the camera. So by tilting the camera you could get more of your subject in focus. (The only problem is if you shoot at an angle, the glass from the tank might give you distortions)
Now hold your breathe and roll your finger over the shutter button instead of pressing it and pray for the best results.
White balance is a little more difficult and you'll have to check with your manual and should allow you to adjust it. If you shoot raw, you should be able to change your white balance in the software. Good luck.
|