Digital zoom versus optical zoom for minimising camera shake

Question

Here's the scenario: every so often our garden plays host to some small deer. Naturally, I try to take pictures of them. From inside the house, I can get a decent shot with full zoom on my camera. The difficulty is that the kids also like to see the deer and one particularly wriggly child needs to be lifted up to be able to see them. So sometimes I'm trying to take a picture one-handed with a wriggly child in the other arm. Not the best conditions for a steady shot!

My camera has enough resolution that I could take a photo with a lower zoom factor and then crop it later and still have enough detail for a decent photograph. So, given the above circumstances, which is going to provide me with the least blurred photograph: full zoom or least zoom with later cropping (which is what I mean by "digital zoom" in the title of the question)? Note that I'm only interested in the blur on the deer itself, I don't care about the rest, and (for the purposes of this question) I want to focus (ha ha) on blur from camera shake.

Also, due to having small child under one arm, in this circumstance I have the camera on "P" mode, letting it select the best aperture and shutter speed. I guess that this might make a difference.

Answer 1

Assuming you crop to the same area and print to the same size, the amount of camera-movement blur should be indistinguishable between the two cases. Using a shorter focal length will decrease the impact by exactly the amount you have to crop and enlarge.

So, it comes down to other factors. The most important (from the narrow viewpoint of camera-shake blur) may be that your zoom lens may allow a wider aperture at shorter focal lengths, which would let you speed up the shutter, reducing blur.

But in real use, I don't think that's necessarily going to make up for the decrease in resolution.

I think what I'd do is ask the kids to let you take turns taking pictures and holding them. They'll appreciate looking at the pictures, too.

Answer 2

Most cameras have a wider aperture possible at shorter focal lengths - and vice versa. So, when you are fully zoomed in, you are probably shooting at a narrower aperture, which means that your camera either cranks up the ISO, or slows down the shutter speed, or both to get the right exposure.

Therefore, zooming out and shooting with a wider aperture will certainly present you with a better ability to shoot with a faster shutter speed (given that ISO doesn't change, and your camera does move to a wider aperture).

What you may want to do (when your kids are not around) is to experiment with your camera settings. If your camera allows it, the best mode would be to shoot on ShutterSpeed priority mode. This means that you set the shutter speed (choose the slowest which allows you to take a non-blurry photo while moving about a bit) that will ensure motion freeze - typically 1/focal-length; and then let the camera decide on aperture and ISO (by setting the ISO on auto, if needed).

Like some of the others said, the question is not zoom. The question is shutter speed.

Answer 3

The cropped photograph might appear less blurry as you have a lower resolution. Technically, however, both pictures are equally blurry.

Go with the optical zoom to get the best resolution.

Answer 4

The previous answers got the basic point that the blur should be the same. There is another factor, which is the ability of the Image Stabilizer, if there is one, to cope with vibrations at different focal lengths. My guess is that, the IS will not be a factor, and the blur will be the same, but I may be wrong. You can only determine this with a controlled experiment.

Answer 5

Wow - most of these answers surprise me very much! I've done a lot of research on this and have found out that good camera makers are currently able to implement very effective Image Stabilizers in digital zooms. Therefore the difference is HUGE!!! If you really need a closer shot and don't have additional optical zoom (with IS) - just use the digital zoom! The result will be much better than crop it later with any desktop software on a personal computer.