RULE OF THUMB HANDHELD SHUTTER SPEED?

Yes, you are. Since the amount of blur at the sensor, which you correctly state won't be affected by the sensor size, gets magnified to different amounts when you print a given size print from an APS-C or a full frame 35 mm camera. It gets magnified 1.6x more, thus we include the 1.6x "crop factor" in the calculation. The "crop factor" also enters into DoF calculations for the same reason.

I tend to agree with Steve Hoffmann (quoted below) about the 1.6 crop/shutter speed and DOF theory.


Steve Hoffmann's Nature and Landscape Photography

DEPTH OF FIELD, PERSPECTIVE AND SAME FOV WITH TELEPHOTO LENSES

Image content has three major technical components that we are interested in for this article FOV (field of view), depth of field and perspective. These factors are optical in nature and have nothing to do with the digital side of photography.

DEPTH OF FIELD and SHUTTER SPEEDS
Depth of field decreases as you shorten the distance between the lens and subject. This is true for any given focal length lens and aperture. Depth of field is related to lens focal length, focused distance and aperture and has nothing to do with film format size or sensor size. If we must move closer to the subject with our larger sensor equipped cameras and same focal length lens to obtain the same FOV as the 20D, we should expect to see less depth of field for any given aperture used with the larger sensor equipped cameras. If you like an out of focus background, for any given lens focal length, aperture and FOV it will be easier to achieve with the larger sensor equipped cameras. Conversely the 20D with any given FOV, lens focal length and aperture will always have more depth of field.

I'd like to touch on the subject of appropriate hand held shutter speeds. There are some folks who claim the old 1/focal length rule isn't a good starting point for insuring sharp images when hand holding with smaller image sensor cameras. As an example of the current generally accepted rule, to minimize image softness due to camera shake use 1/250 sec as your minimum hand held shutter speed for a 250mm lens.

Some people are advocating 1.6 X focal length as your minimum hand held shutter speed with a 1.6 crop factored camera (1/400 sec for your 250mm lens). The reasoning given for theory is that the 1.6 crop image will ultimately have to be enlarged more than that same FOV image shot with with a full frame camera and therefore, any camera shake induced blur will be more magnified in enlargements. It seems to me that physics would tell us that image blur due to camera shake is related to three factors: the distance from the camera to subject, the lens's focal length (actual magnification power) and the shutter speed used. The full frame DSLR would require a slightly longer focal length lens (more magnification) at the same focused distance to achieve the same FOV or need to be closer to the subject if the same focal length lens was used to get the same FOV. Both of these conditions would theoretically enhance the chance for camera shake blur. In practice, I'd bet it would be a wash. I suspect that other factors such the strength of the shooter, the weight of the lens/camera and just plain old technique would be more important factors in reducing handshake induced image blur.

I will say that all of these digital cameras are producing relatively high resolution images. The big prints that people are now more willing to make with their clean high resolution DSLR images will show off photographic skills (or lack thereof) and lens quality issues in startling fashion. I've found from experience that at my advanced age and decrepitude I can't hand hold my 1Ds Mark II and 400mm lens at much less than 1/800 second if I expect to get all the resolution that this lens is capable of. That's twice the old rule of thumb of 1/focal length.

If we take Steve Hoffman's theory into the realms of compact cameras, then you could hand-hold a 60mm lens at 1/60th second. This would be good news, because that lens would have an equivalent focal length of about 400mm on a full frame camera, so you could get some pretty good action and nature shots with it, all hand held a 1/60th.

I don't think so.

Couple of points he's got wrong - camera-subject distance doesn't matter for camera shake discussions. Until the light rays hit the lens they're traveling in a straight line, and aren't exposed to a "shaking" medium (ignoring the effects of thermal refraction). It's only when they hit the lens that there's any shake issue to deal with, because the camera is what's moving, not the outside air. Actually the light rays are still traveling in a straight line (subject to refraction in the lens); camera shake causes the sensor to move over the duration of the exposure. All any anti-shake mechanisms do is try to deflect, either physically or logically, the incident light rays to counter the camera motion.

The argument's being made that since you use a longer lens on FF, there will be more shake. Yes, but, this is a red herring. The actual linear distance may be greater, but the angular motion tends to be pretty consistent across focal lengths. Your shake may be 0.01 deg. of arc over a 1/200 sec. exposure. If you map 0.01 deg. of arc to the actual "smear" of your point on the sensor, it'll cover 0.035 mm over 200 mm. If you map 0.01 deg. of arc from the 300 mm lens to the actual "smear", it's a blur of about 0.05 mm. When you enlarge these two to get an 8x10 print, you enlarge the "negative" 13.5x for an APS-C camera, but only 8.47x on the FF camera. That gives a print "smear" from a 200 mm lens on an APS-C sensor of 0.47 mm; on a FF with 300 mm, it's 0.42 mm. And a "point" that's about 0.5 mm is blurred enough to be "unsharp". So you really do need to figure in the "crop" in calculating hand-holdable speed. For the same reason, "crop" (or final print size) has to be considered in determining depth of field. The "circle of confusion" varies with the sensor format. The more you enlarge a print, the smaller the acceptable circle of confusion in the original negative, subject to viewing distance (which tends to be consistent fro any given size print).

NSWESP wrote in post #4079810
I can hand hold 300mm at f5.6 taking a shot of a slow moving car with IS at 1/60th at ISO100.

100% crops please. You must be bionic.

J.

JohnJ80 wrote in post #4082200
100% crops please. You must be bionic.

J.

I dont pixel peep so 100% Crops dont worry me. When i get home on Saturday night i will post some for you guys.

You have to remember though if the subject is moving and if so how fast. If you have a 35mm lens and wanna shoot about 1/50 to avoid shake, well that's all great but if *the bride* we'll say is walking she may cause the image to be blurred anyhow. Just my .02 to remember