Question about camera shake

I have searched but came back empty handed. I have a question about the ss vs camera shake. I know that you are supposed to use the reciprocal of your focal length to reduce shake and include the crop factor. But is that because the lens length changes. I have a 70-200 and it is a non extending zoom so does that mean that I have to shoot at or above 1/320 at all times?

Not neccessarily.

The reciprocal x crop factor rule is just a starting point and as such would vary with the focal length at which you are shooting. However, since it is so easy to increase the focal length (zoom in) with a zoom lens, it might be safer to use a shutter speed which is the reciprocal of the longest focal length x crop factor.

This rule of thumb has many-many variables, including your physical condition (both health and tempory condition from running, etc,), your technical ability to hold a camera steady (breathing, gentle shutter release, etc.), your environment (wind, etc.), the weight and size of your lens and camera and many more. It can also be impacted by the adrenaline running through your body during exciting moments and the amount of caffine, nicotine or alcohol you consume.

I have found that this rule holds pretty true for me in the shorter focal lengths (100mm and under) but, when using long focal length lenses, I need to increase the shutter speed beyond the reciprocal of focal length x crop factor. That is why I really like IS equipped lenses in long focal lengths.

As an example, I can hand-hold my 70-200mm f/4L IS lens at 1/60 second and be assured of almost 100% sharp imagery when the IS is turned on and I am at 200mm. There is no way I could come close to this without IS. In fact, because of IS, I use the 70-200mm f/4L IS lens 3-4x more often than I ever used the non-IS version of that lens.

midnight_rider wrote in post #5830396
I have searched but came back empty handed. I have a question about the ss vs camera shake. I know that you are supposed to use the reciprocal of your focal length to reduce shake and include the crop factor. But is that because the lens length changes. I have a 70-200 and it is a non extending zoom so does that mean that I have to shoot at or above 1/320 at all times?

The 1/focal length rule-of-thumb has been accepted over many decades for the 35mm film format. If you are applying the rule-of-thumb to an APS-C format DSLR, you need to multiply the actual focal length you are using at the moment by the "crop factor". For example, if your 70-200 is dialed in at 120mm then you should start with 1/192 second (or faster) shutter speed [1/(120 x 1.6)].

As said above, a rule-of-thumb is for average people with average conditions in average situations. You may very well find that you can get away with much slower shutter speeds because you have trained yourself to act like a rock when holding a camera. On the other hand, you may need to double the results of the calculation to be even close to having your images looking like the camera was held steady.

And the rule is based not upon the absolute focal length, but by the angle of view seen by the lens...so that a certain percentage of the angle of view is what determines the real limit of the ability to hand hold at a certain speed. The fraction of the total frame height is constant, so shaking a hypothetical 1/100 of the frame height would hold true for a 20mm lens as it would for a 200mm lens.