Comments on: Time lapse 1: Snails

By: Yves Roumazeilles

Yves Roumazeilles — Fri, 17 Apr 2009 18:45:41 +0000

If the snail is really angry, the video will be great but don’t get too entangled in the passion of the moment and remember to move out its trajectory at the last second (or is it the last minute?)
🙂

By: Ted

Ted — Fri, 17 Apr 2009 17:58:41 +0000

Okay, I got your point. Manual focus + close aperture is the way to go when the subject moves around at roughly the same distance. I guess autofocus performs better if the subject moves along the optical axis, e.g. if the snail is angry and charging the photographer.

By: Yves Roumazeilles

Yves Roumazeilles — Fri, 17 Apr 2009 15:24:32 +0000

Autofocus is OK if you are sure that the focus will not jump from one image to the next. But it is usually very difficult to ensure. And at high spped its very unpleasant.

When the snail is moving from the bottom to the top, it must be tracked all the way without having images where the AF chooses the background to be more interesting. Since the AF has several sensors, uses a lot of intelligence to decide what is good and what is not. You may change focus shaprly from one image to the next and then get a snail focused, not-focused, focused-again at high speed. Nauseating…

It is easier to set a fixed focus and a close aperture (for large Depth-of-Field), or track the snail with very small manual increments.

Actually, a slow-moving subject like that is probably as difficult (or more) to track than a fast moving one. But some subjects (we’ll see some of them in the rest of the post series) are easier than others.

By: Ted

Ted — Fri, 17 Apr 2009 07:28:52 +0000

I’m not sure to understand the manual focus requirement. Don’t you want your snail to be in focus along the whole path across the field ? Fixed white balance and exposure are okay to avoid flickering.