shutter speed rule of thumb?

I recall there being a rule of thumb with normal 35mm cameras with respect to minimizing hand shake.

ex: if you are at 100mm, then your min shutter speed (hand held, NOT tripod) should be 1/100 sec.

For a digital camera, does this also apply? ...or with a 100mm lens, does a 1.6x crop camera have to shoot a min of 1/160sec?


Thanks.

This question comes up every few weeks on photo message boards. The shutter speed rule of thumb is just a guideline. The rule of thumb does need to take sensor size into account - the rule of thumb would be based on the effective focal length of the lens, so 1/160 is correct.

While many people talk about resolution & crop factor to answer this question, it really has more to do with blur relative to sensor size. Let's say we made an 8x12" print from cameras with a full frame and 1.6x sensor. A certain amount of blur radius happens when shooting. The 1.6x chip is smaller relative to the print than the full frame chip (15x22 vs 24x36) and so the blur gets enlarged more.

So in theory, you need to account for sensor size. In practice, I personally shoot at shutter speeds of 1/lens focal length instead of 1/effective focal length, and I'm happy with my results.

I have to say that I, too, use the traditional rule of thumb without taking the sensor size into account, and since the crop factor is a crop factor and not a magnification factor, it works just as well on my 20D as it did on my film camera.

It's not really a crop factor either (any more than 35mm film is a cropped version of MF which is a cropped version of LF), and if you printed at 24 x 36 mm for your film and 15 x 22 mm from your 1.6 format factor camera, you'd be dead right about it not being a magnification factor, too.

If you printed your film to 8 x 12 and your 20D to 5 x 7.5, you'd see the same effect of blur in each print and you wouldn't need to figure in the crop factor in the rule of thumb.

Gomer, The best thing to do is develop your own rule of thumb - shoot a few attempts at each shutterspeed and see how slow a shutterspeed doesn't show the blur. Joe has established he is OK with handholding to 1/true focal length on a 1.6 camera. You may not have such steady hands, or you may have even steadier hands. You have to check for yourself.