Bruce Moore wrote:
Camera Shake.
I know that to avoid camera shake I need a shutter speed at least equal to my focal length. Because of the crop factor when mixing EFS Canon camera with full frame lens, I don't know whether I should match the lenses stated length eg 300 or the 480 because of the crop sensor. Any advice would be appreciated.
The "rule of thumb" is that we should use a shutter speed that's the reciprocal of the focal length with 35mm film cameras... But now with smaller sensor cameras we have to convert to the "perceived" lens focal length instead. In this case a 300mm lens will "act like" it's 480mm (so use 1/500, it's the closest). If you think about it, this makes sense. The camera's "crop factor" essentially "magnifies" the subject 1.6X. It also magnifies any camera movements by the same amount. (And, yes, as someone already noted above... it doesn't matter if the lens is EF/full frame/FX or EF-S/crop sensor/DX design... Focal length is focal length. 300mm is 300mm and you need to apply the same "adjustment" in either case.)
Also, when you go to make a print from the image or use it for any other purpose, it's magnified more than it would be from a camera with a larger sensor. For example, if you make an 8x12" from a "full frame" camera, without any cropping of the images itself, that's approx. and 8X magnification. The same from an APS-C camera like you are using makes for approx. 13X magnification. Once again, any camera shake blur would be magnified, too.
Finally, it's been noted that the higher resolution, more densely crowded camera sensors seem to be a bit more prone to camera shake blur. Canon put out a white paper about it around the time when they introduced the 18MP original 7D, noting that slightly faster shutter speeds might be needed to help insure as many sharp shots as possible. Cameras have only increased in resolution since then! 21MP and 24MP are now common in APS-C format cameras. Full frame cameras are as much as 46MP or 50MP.
All this makes it sound impossible to get a sharp shot... but it's not. In another sense, APS-C cameras work in your favor. Internal camera vibrations can cause blurry images, too. Those are usually from the "slap" of the mirror flipping up and the operation of the shutter itself. Those are smaller in an APS-C camera, so less prone to what can occur in larger format cameras. A full frame digital's larger mirror and shutter is likely to cause stronger vibration... and a medium format camera even more so. Back in the 1970s or 80s, Pentax 6x7 film cameras were widely recognized for this issue in the past. That's a very large mirror bouncing around in there! Later models addressed it with a mirror lockup mechanism. Just the opposite, "mirrorless" cameras largely solve the problem because they don't have mirrors at all... and many or most don't have a shutter either. No moving parts to cause internal vibrations.
However...
1. That's just an estimate. Everyone is different, so with good technique and care you might be able to hold a steady shot at slightly slower speeds, while someone else may need to use a slightly faster speed.
2. It's not a guarantee of a sharp, shake free shot. It's merely a guideline that we use to increase the odds of one.
3. There are other factors involved.... Does the lens have image stabilization? If so, with same good techniques you may be able to hand hold that lens at 1/250 or even 1/125. Possibly even 1/60 or slower. Can you use a tripod or a monopod or rest the camera and lens on something or even just lean against a stable object like a tree or a wall? Those also can help steady your shot.
4. Nothing you can do other than use a fast enough shutter speed can freeze subject movement. 1/500 is probably the minimum to freeze a person running... but would be too slow for a cheetah at full tilt and way too slow to freeze a hummingbird's wings. You can still get subject movement blur, though it will look different... only the subject or part of them will be blurry, while the rest of the image is sharp. (Note.... panning techniques take advantage of this... "dragging the shutter" with a somewhat slower speed while moving the camera along with the subject can blur the background, while hopefully getting the subject nice and sharp against it... but this takes practice and even then there can be more trashed shots than keepers.)
"Good technique" includes how you stand and hold the camera, as well as not "stabbing" at the shutter release button, but pressing it instead. It may also mean using a wired or wireless release to trip the camera's shutter, so that you don't need to touch the camera during exposure. The camera's self timer can be used instead sometimes, allowing a few seconds for any vibrations from you and/or the mirror mechanism to subside before the shutter is released. That usually won't work with moving subjects, though. Your own breathing and the wind can come in play, too, with really long telephotos. I usually use a lens hood, but sometimes in really gusty winds it can be a problem... especially the really large ones on big telephotos. Another trick, sometimes when I'm using a particularly long lens on a tripod, I'll even lay a beanbag on top the camera and lens, to minimize vibrations of various types. It also may help to add some weight hanging under the tripod to help stabilize it, too... some have a hood just for that purpose. A backpack hung on it might work.
At the other extreme is a "poor man's monopod"... Nothing more than a length of fairly heavy cord with a 1/4" x 20 bolt tied to one end, screwed into the mounting socket of the camera, with the other end of the dropped to the ground and stood on with one of your feet to make the cord taut. This actually works... and it can wad up small to fit in a pocket. (People watching you use it may think you're nuts... but who cares!
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