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11-28-2009, 03:34 AM   #16
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QuoteOriginally posted by B Grace Quote
Many of us learned the use of a camera by using a 35mm film camera and we learned the several rules of thumb that apply such as setting our minimum handheld shutter speed to the reciprocal of the lens focal length. When using a crop factored DSLR we must modify those rules of thumb by the crop factor so the minimum handheld speed for a 50mm lens would be 1/90th. SR sure helps.
Umm... no. According to this logic you could use a shutter speed of a full second hand held with an 8x10 camera that has a 50mm lens. The lens to shutter speed hand held ratio is an absolute. Film (or sensor) size does not matter.

(sarcasm warning)
As far as DOF scales are concerned I would suggest you take a look at the delightfully plesant thread from last week. There were people agreeing with each other even though they had directly conflicting opinions. Many trustworthy sources were quoted, such as wikipedia. When it was all over everyone involved had a good cry, and then a good laugh.

Seriosly though, you could ask tis question 10 times on this forum and get 10 different answers. The best way to answer this question for yourself is to test a couple of lenses with a tripod and a measuring tape.

11-28-2009, 01:11 PM   #17
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QuoteOriginally posted by Steve Beswick Quote
The lens to shutter speed hand held ratio is an absolute. Film (or sensor) size does not matter.
This is false. The old rule of thumb relating focal length to minimum shutter speed - which was always a best a rough approximation - is based entirely on *field of view*, not on any optical quality of the lens. It just so happened than on 35mm format, the FOV was lenses was such that 1 / focal_length worked out reasonably well as rough approximations go.

The main reason your 8x10 example falls apart is that we all know most of us cannot handhold an 8x10 camera at all. Also, the 1 / focal_length rule of thumb never worked very well for very short or very long lenses.

But consider a P&S camera with a a 6X "crop factor". On such a camera, a 50mm lens is actually a long telephoto in 35mm FOV terms. And indeed, you're going to need a correspondingly faster shutter speed to handhold that successfully.
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