1.6X, 1.3X, 1.5X, factor

The rule of thumbs in photography is to always use a shutter speed that is equal to, or greater to the focal length of your

lens. For example, if you are using a 100mm lens then your shutters speed should be set a 1/125 of a second or greater.

If you are using a 300mm lens, then your shutter speed should be set at 1/300 or greater. However, a 100mm lens on a

cropped sensor camera is the equivalent of a 160mm lens and a 300mm lens on a cropped sensor camera is the

equivalent of a 480mm lens. So what shoud we be setting our shutter speeds to, the actual focal lenght of the lens, or the

cropped equivalent ?

<p>Hi Harry,<br>

From experience, the rule does not work out so well when you have longer lenses! My main lens is a 58mm that works out to be a 84mm on my sony body. When I switch off IS I try not the get the shutter speed below 1/60th.</p>

<p>Cropped equivalent</p>

<p>It is the cropped equivalent, of course, as Bob said, but the "rule" is just a general guide. Whether or not you will get movement blur depends on your technique, inherent steadiness, how much coffee you had, whether you have something to lean on, adrenalin level, etc. Try getting chased up a tree by a bear and then photographing him at 1/the focal length. I haven't.</p>

When I shoot sports, particularly swimming, if I really want to stop action with a 70-200 2.8 I like a thousandth or faster. I try never to go below 1/400 because even at that speed you get blurred arm movement. Indoors is a problem. I am happiest at 1/2000 in bright sunlight. It depends upon what you are doing. Sometimes a little arm blur gives a feeling of motion. Even on full frame 1/200 is not fast enough at 200mm. At least for what I do.

<p>Usually I feel safe with 1/(4xfocal length). Even with full frame I don't like shooting at less than 1/(2xFL), although I can get sharp pictures with wide angles are ridiculously slow speeds. I tend to believe the 1/FL rule has its origins in rangefinder photography... most of my shots are wasted when I use it with an SLR.</p>

It also depends on how large you plan to present the final image. I found my 35mm transparencies (shot with a 50 mm lens) showed much better consistently when I used 1/250 sec instead of 1/100 sec ( my next slowest option). People rave about the images produced by the Oly Trip 35 (40 mm lens) I think mostly because 1/200 was the only shutter speed.

Great point Hector throw in an Image Stablizer(IS), or (VR) and things really start getting confusing.

<p>originally, the focal length/shutter speed rule was 1/focal length in mms. but the crop factor has altered this. the rule now is 1/focal length in mms X crop factor. the crop factor is used as a multiplier since that altered focal length is what the dslr is actually using.<br>

it should be be noted that the resulting shutter speed is to be regarded as the MINAMUM shutter speed. if you have a fast moving subject across the fov or you just had 8 cups of coffee then you would have to up the shutter speed to compensate. and do not go below 1/60sec unless you put the rig on a tripod. use 1/125 if you have any intention of doing larger prints. OR, if printing big, or max IQ is desired or needed, use a tripod period. and do not rely on IS/SR/VR too much; antishake only helps so far.</p>

<p>+1 for what Bob Atkins said, remembering the 'R.O.T.' is about avoiding unsharpness due to camera shake <em>under ideal conditions with ideal shooting technique</em>.</p>

<p>3rd most common question asked by beginners. It's covered 50 times/year in the EOS forum, I'd suggest the OP actually read the forum.</p>

<p>I tend to go one shutter speed faster because I'm one of those who actually has a harder time holding the camera steady, even with a Leica. Also that is, I think, based on an 8x10 print a given distance from your eyes on a wall. So if you make bigger prints or look at them closer, your personal rule of thumb could be considerably different.</p>

<p>I think Mr. Griffin has the answer. I depends greatly on the size you will eventually print the image, and what your viewing distance will be.<br>

If you crop an image from a full frame sensor to produce the same FOV you achieve with a cropped sensor then the amount of motion blur at any given shutter speed will be the same in both images.</p>