distance of shots?

Shooting in macro mode, techniques, tips & tricks

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Joined: 07.02.2006 21:55

distance of shots?

Unread postby Anne » 07.02.2006 22:53

Dear members of forum,
We have used Helicon Focus to make pictures of micromoths (wingspan 12- 20 mm) since a few days, but the results were sometimes very depressing.
We use a Canon EOS 20D camera with a 60 mm Macro-objective. The most urgent question is at this moment: how do you determine the distance between two sequential shots; does it depend on the aperture of the lens, the depth of the body of the butterfly; the amount of available (flash)light? In short:is there a measure to calculate these distances in stead of moving the camera on the sledge(?) by trial and error?

Charles Krebs
Posts: 38
Joined: 06.04.2005 08:00

Unread postby Charles Krebs » 10.02.2006 07:47

It depends on the depth-of-field in each picture, which is a function of the aperture (f-stop) used to take the picture. You want to be sure that there is some "overlap" of the "in-focus" part for each image in the series. It is far better to have too many images rather than "out-of-focus" gaps in the series. You can always run every other image if you take too many. But if you spaced them too far apart, there is obviously no way the program can create a sharp section if it does not appear in any image.

There are mathematical formulas that can be used to calculate DOF, but I think it is far easier to do it by "eye" once you have some experience. You should first determine what aperture provides the sharpest results at the magnifications you will be using. If you are using the Canon MPE 60mm macro it is a superb lens, but avoid the smallest apertures when you are working at the higher magnifications (or else diffraction will seriously degrade resolution). Then you can use your depth-of-field preview, or better yet, do a few test shots to see what your DOF is. The number of images required will depend on the depth of your subject.

It is usually best to use a manual exposure and "lock" the white balance. You want the exposure and color balance to be the same for each shot in the "stack". Take great care that there is no subject motion while you are taking the series of images, and that the camera is moved in very smooth increments. In some cases it is actually easier to mount the camera rigidly, and move the subject back and forth instead. (If you do this, just be sure the lighting does not change on the subject).

With a little practice you should be fine. Good luck!

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