AboutJohn and Chris Expertise We are both professional photographers, with over 15 years experience. We can answer questions about photography, as well as questions about cameras from the 60s to 90s. (extensive 35mm, quite a bit of other formats.) Please, no darkroom questions.
Expert: John and Chris Date: 7/17/2007 Subject: Quick Question
Question Hello,
In order for me to produce a sharp image when I hand hold a camera with 100 mm lens, what shutter speed would you recommend?
Last question; When using an SLR what is the function of the automatic diaphragm? Any help with these questions would be greatly appreciated. Regards-Skyler
Answer Skyler,
The rule of thumb is that your shutter speed should be the reciprocal of your focal length.... or "one over the focal length". In other words, if your at 100mm, then your shutter speed should be at least 100th of a sec. (the closest on most cameras would be 125th).
"Automatic Diaphragm" is an old term. It meant that the lens aperture blades were held in the full open position so you got the brightest possible view through the view finder and did not close to the metered "working" aperture until the moment of exposure. They really don't bother with the term anymore, because all cameras use this feature now. It would be like pointing out that a new car came with seat-belts. (I don't know how old your are, but I remember when there were cars that didn't)
