howarde:
Simple question for UW photographers. Do you use TTL, Manual Strobes, or maybe a little of both. Explain and discuss...
I'll start by saying - I've been shooting in TTL 99% of the time. I keep my camera on Manual, and vary the shutter speed and F - stop according to the DOF I'm after and/or motion of the subject.
First recognize that the camera meter is TTL, so there is a difference between flash TTL, the TTL used by the camera meter. I know what you are asking, but I thought I'd throw this out for those that may not understand that yes, there are two seperate metering functions going on if one is using a Flash.
I would use flash TTL if I could, but while the housing I'm using has TTL capabilities, my strobe (an SS200) does not.
I will shoot UW just like I shoot topside once I have TTL control. That is to say that I'll shoot in Shutter or Aperture priority, or manual with TTL flash mode, and adjust the compensation on the back of the camera just like I do topside if the flash is not quite where it needs to be. If the ambiant light is strong often -1~-2 flash provides better modeling, and a more natural looking exposure.
When one has a manual flash, Aperture priority can work OK as long as there is plenty of light, which is to say not that often. In aperture priority the camera is going to use the meter to determine the ambiant light, and modify the shutter based on ambiant light. So one may end up with shutter speeds that are too slow to stop movement, or prevent camera shake.
With Shutter priority and M flash one has a similar problem in that the aperture is likely going to be wide open because the camera does not know about the flash, and again, available light will generally result in a wide open aperture at most shutter speeds which means little DOF, and the potential to blow out the subject once the flash fires.
This is a major reason that UW photographers shoot in manual mode, they really don't have much choice if they do not have TTL capabilities. If one is at a constant depth, and the subject distance remains consistant, then shooting in manual mode is not a problem. If one is shooting using the flash as a main source of light with a consistant subject distance, manual is not difficult. If one is varying aperture constantly, or is under changing lighting conditions or the subject distance is changing a lot from shot to shot, then shooting manual will require constant adjustment of the strobe output. This is not an overwhelming task, but one that TTL can help eliminate.
IMO TTL is the way to go regardless of if one shoots in Manual mode, A mode, or S (TV) mode. Just as photographers have come to rely on the built in TTL meter in the camera, they can rely on the TTL flash meter which is going to get the exposure correct in a large percentage of the shots. It still remains the job of the photographer to use settings that control DOF, and stop critter movement, but between the cameras TTL meter, and TTL flash meter the equipment makes things easy for photographers at all levels.
It should also be noted that the short duration of the flash will help freeze critter movement especially in shots where the flash is completely overpowering the ambiant light.
I don't miss it.
