Although I use most of the housing controls at one time or another, I think which controls you use the most often depends on your shooting style and whether or not you use TTL strobes. I do use TTL strobes for every strobe shot I take, wide-angle or macro, and feel it increases the number of one shot opportunities I get right. I also use auto-focus lenses on auto-focus much more often than I use manual focus, which I do like for some situations.
Given those parameters, the controls I use, in their frequency of use is as follows: (1) the trigger - both to take the picture and to initiate auto-focus. (2) the zoom control to vary what the lens is seeing. (3) the flash compensation button - to vary the strength of the flash depending on what the picture needs. (4) the aperture control knob - usually to vary aperture of the lens to provide the overall exposure to work with the ambient light and to control depth-of-field. Sometimes, when I shoot in shutter priority auto-exposure, this knob can be used to vary the overall exposure compensation. (See the Nikon custom function called "Easy Comp) (5) the shutter speed control - to vary the overall exposure and and to stop or blur subject movement. On many dives this just stays somewhere between 1/125 and 1250 for the whole dive. (6) the M-S-C control which I sometimes use to switch to actual manual focusing but more often use as a focus lock for repeated shots at the same distance. (7) The manual focus control for the lens, especially used with wide-angle lenses (8) the Function Button (on my D700) which I have programmed to turn off the flashes. This is much easier than trying to reach up to each strobe to turn it off or on. Sometimes I turn the flashes off for an intentional ambient light only shot. At other times to check ambient light metering before I add fill flash. (9) the ISO button. With the D700 I usually shoot at ISO 400 or 800 the whole dive. (10) the Focus Lock button (programmable on my D700) which I usually have set to utilize a Nikon function called Flash Value Lock. If you are a Nikon user and haven't looked into this capability I think you're missing out on a really good function. (11) The housing latches to open the housing at the end of the day to download shots and to change the camera battery.
Edited by divegypsy, 04 March 2013 - 12:47 AM.