Shutter speeds

There is a rule of thumb (is it called that in English?)

35mm => 1/35s

50mm => 1/50s

100mm => 1/100s

Under water I feel that everything (me) moves around a lot so I typically use one step faster speeds.

What about macro shots; is the rule still applicable when what you photograph is extremely close to the camera?

What shutter speeds do you use?

/Anders

Shutter speed controls the exposure of the background and the strobe controls the foreground. So you want a shutter speed that gets you the depth of blue you want in the background.

For me in my waters I typically use 1/80 to 1/100 second. However, I never go below 1/60 second because even at 1/60 second I sometimes get motion blur with moving subjects.

That rule of thumb applies to ambient light shooting. Basically, the smaller the field of view, the less the amount of camera shake that can be tolerated without visible blurring of the image. There are exceptions, such as when shooting with lenses/cameras that include an image stabilizer (for example, when I use my 100-400IS lens above water, I would normally have to follow the rule and try to stay at 1/400 for telephoto shots -- however, the image stabilizer has allowed me to get sharp images as low as 1/45 if I do a good job of stabilizing the camera).

As Peter implies, most underwater shooting is done with a strobe. The strobe "flash" is of very short duration and tends to freeze the action to a certain extent so it tends to make shutter speed less important. As long as you shoot above 1/60 or a bit higher for faster-moving subjects, you'll usually be able to stop the action underwater. I'll also add that, in additon to shutter speed, the aperture also affects the exposure of the background (however, it will also affect foreground exposure as well) . . .

Under water I use two artificial light sources – one video light and one strobe. I need to balance these two sources as well as the available light. Doing macro I need to set the slowest possible, non-blurring, speed. I want to balance the light from the strobe with as much light as possible from the video light. What speed is that, and how does it depend on focal length (zooming) and whether I use a macro conversion lens or not?

/Anders