Hi Phillip- your not so far from me- just up the freeway a bit
I'd be happy to attempt to explain the differences between the exposure modes for you. You will also find a lot of answers to your photography questions in
these Reefkeeping Magazine articles. Ximina's tutorials are awesome too- highly recommended, especially since you are both Nikonians.
Hopefully by now you've read
this article and you know how the camera works.
This requires a lengthy explanation... hope you have some popcorn
One of the first things you want to comprehend is the relationship between the aperture and shutter. When a photo is taken the aperture opens to a certain size (often referred to as an f-number, like f8) and the shutter opens for a certain amount of time (referred to as the shutter speed). The aperture size determines the depth of field. Depth of field is described as the amount of the image that appears in sharp focus. While the aperture determines the depth of field, it also has a direct effect on the shutter speed because they are interdependent. Double the size of the aperture and you have to double the shutter speed to keep the amount of light passing thru the lens to the film [sensor] the same. Another way of looking at is-- if you make the hole the light passes thru twice as small you have to allow the light twice as much time to pass thru.
Regarding depth of field- the smaller the aperture the greater the depth of field, and as I just explained, the smaller the aperture the longer the shutter speed has to be.
If you want lots of depth of field you will need a long shutter speed most likely (if there's tons of light you can still have a fast shutter speed but in our aquariums there is not tons of light, no matter how many mh lights you have).
So back to your original question-- what is the difference between the exposure modes. "M" stands for manual exposure and when you are in that mode you need to set both the aperture and shutter speed. "A" stands for aperture priority and in that mode you set the aperture and the camera figures out the proper shutter speed to achieve a properly exposed image. "S" stands for shutter speed priority- in that mode you set the shutter speed and the camera will figure out the proper aperture. "P" mode is a bit like auto mode- the camera determines the shutter speed and aperture that will give you a proper exposure, but you still have control over those settings-- in full auto mode you can't adjust the settings the camera chooses (for the most part).
I think most photographers use aperture priority for the bulk of their shooting, leaving shutter speed priority for things like sports- where the most important thing is choosing a shutter speed that is fast enough to freeze the action. Ultimately it doesn't matter whether you're in a,s or m mode as long as you are paying attention to what the light meter says. Some people are more comfortable in a mode while others prefer s--- you say tomato and I say tomahto
There are some subtle differences in the different exposure modes that you will come to appreciate, but you'll need to get a handle on the whole aperture/shutter speed/depth of field thing first.
Regarding question number two:
What mode should I use to get the most accurate color?
The exposure mode (m,a,s or p are exposure modes) doesn't really have an effect on how accurate the colors turn out- that is a function of the white balance setting. One of the articles I linked to explains what a white balance is- give it a readthru and you'll have a much better understanding of why it's so tough to get accurate colors in aquarium photography. Hopefully you'll also learn how to manipulate your camera's white balance settings to get colors you're happy with.
I hope this wasn't too confusing... it may seem complicated but it's nothing compared to alkalinity and pH!
