 Rob |
select focus in multiple images for increased DOF I have heard there is a way to incerase the depth of field by selecting the focus in multiple images. I wonder what this could mean. Is there a way for instance to make several exposures of the same(still) subject by focusing on the main subject in one exposure then shifting the focus to the background ( using the select focus wheel in the viewfinder without moving the camera) for a "double" exposure to put the background in focus too? (shooting each at one stop underexposed). I know all the usual ways of giving more DOF stopping down, distance from subject, lens etc. This would be for ECU shots . Any ideas? Thanks -Rob
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Michael H. Cothran |
Yes Rob, in essence only, you are correct, but your results will not be what you are striving for. It's a neat technique I use on occasion: that is, making multiple exposures (usually two) on a single sheet of film, or overlapping exposures in a digital camera, where I focus near on one, and far on the other (giving half the correct exposure to each). You will, indeed, end up with both near and far in focus, but the end result will appear like a really neat 'soft focus' image, since you have, in essence, sandwiched a 'sharp' image with an 'out-of-focus' image at both the near and far areas. The end results are quite pleasant, and very artsy, and a great way to get a near flower in focus, as well as the mountain range miles away. A point that most photographers have never paid attention to, and why your idea won't fly, has to do with the laws of optics. When you refocus your lens, the image size actually changes - the closer you focus, the larger the image becomes (even though it may go blurry). Thus when you focus near and far as multiple exposures, there will be parts in each image that will be larger and smaller than in the other, which, in effect, gives it the soft focus look, but where there is actually something near and far that is in focus. Try this technique - even though it is not the result you are looking for (which is optically impossible anyway), I think you'll like what you get, and may try more. To best use this technique, you need a near and a far subject on which you can focus. Good Luck Michael H. Cothran
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Rob |
Thanks-I thought what you are saying would be the case, I was wondering how getting near and far subjects in focus would be optically possible as I have never known of any way to do it with film cameras. I thought perhaps there was something different one could do with digital cameras that I didn't know about when I read of "selecting the focus in multiple images for increased depth of field" with a digital camera. Thank you for your time-Rob
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