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Nonsensical question about weird focusing


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#1 Wally Xie

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Posted 18 February 2011 - 08:16 PM

This might not make sense to anybody, but I was just playing around with the possibility of having one object closer to the camera that is focus, followed by a stretch of area that is not in focus, and then finally, another object that is in focus. No, I'm not talking about a rack focus -- in this image, two objects would simultaneously be in focus, with an area in the middle not be in focus. This goes against the normal laws of depth of field, so I presume this would take something special, perhaps a special lens, perhaps some FX, perhaps a combination of both. Anyhow is what I described possible?
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#2 Mathew Rudenberg

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Posted 18 February 2011 - 10:05 PM

This might not make sense to anybody, but I was just playing around with the possibility of having one object closer to the camera that is focus, followed by a stretch of area that is not in focus, and then finally, another object that is in focus. No, I'm not talking about a rack focus -- in this image, two objects would simultaneously be in focus, with an area in the middle not be in focus. This goes against the normal laws of depth of field, so I presume this would take something special, perhaps a special lens, perhaps some FX, perhaps a combination of both. Anyhow is what I described possible?


Try looking up tilt shift lenses or split-field diopters. Otherwise you could just blur part of the frame, in post or by schmearing vaseline on a clear filter in front of the lens.
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#3 Wally Xie

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Posted 18 February 2011 - 10:46 PM

Ah, cool. A split field diopter looks like something that'll do something similar to what I'm looking for. However, is there anything that can selectively cut out focus in the middle of a range? For example, say you got focus from 10 feet to infinity, and you want focus from 10-15 feet, and then focus from 22 feet to infinity, but then, no focus between 15 to 22 feet -- is that possible?
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#4 Mathew Rudenberg

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Posted 18 February 2011 - 11:19 PM

As far as I know it's impossible. You'd have to fake it with one of the techniques I mentioned.
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#5 Gabe Spangler

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Posted 19 February 2011 - 05:04 AM

The old split screen technique is always a possibility. Shoot a locked-off shot twice, once with the foreground subject in focus and then again with the background subject in focus, making sure they stay in their parts of the frame and do not overlap, then combine the two halves of the images in post. I suspect this was done in major film projects more because there was a conscious decision to have, seemingly, the whole image in focus, instead of racking between two characters, in low light situations that demanded a wider f-stop. But I also suspect it was at times a stylistic choice. Of course, anyone who knows what to look for can spot it immediately. Doesn't stop me from liking it if done well.
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#6 Wally Xie

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Posted 21 February 2011 - 12:57 AM

The old split screen technique is always a possibility. Shoot a locked-off shot twice, once with the foreground subject in focus and then again with the background subject in focus, making sure they stay in their parts of the frame and do not overlap, then combine the two halves of the images in post. I suspect this was done in major film projects more because there was a conscious decision to have, seemingly, the whole image in focus, instead of racking between two characters, in low light situations that demanded a wider f-stop. But I also suspect it was at times a stylistic choice. Of course, anyone who knows what to look for can spot it immediately. Doesn't stop me from liking it if done well.

Cool, thanks for your help Matthew and Gabe. Definitely will try the locked-in approach, and I'll also be looking at these split-field filters.
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