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DOF on a canon GL1


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#1 James Burns

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Posted 21 October 2007 - 01:18 AM

I just bought a Canon GL1 and i was wondering, is there any way to get the DOF effect with this thing?

Kind of like what this guy does at the end of this video:
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#2 Jonathan Bowerbank

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Posted 21 October 2007 - 01:38 AM

Well, it doesn't look great, but it works!

I wouldn't attach a zoom to it if I were to do it though, there's a good chance of it snapping off the camera if you don't have any support. But if you got a good set of SLR primes, I'd say it's worth it. You'll have to break a few screw-in filters to build it, so get the cheap-o's.
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#3 James Burns

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Posted 22 October 2007 - 12:54 AM

So i can't do it just using my GL1 only? I have to build the adapter?
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#4 Michael Nash

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Posted 24 October 2007 - 01:33 PM

So i can't do it just using my GL1 only? I have to build the adapter?


Did you watch the video? The adapter is what allows the shallow depth of field. That's why he built it, and that's what produces the look at the end.

Depth of field depends on three variables: focal length, aperture, and distance to subject. Long focal lengths, wide apertures (low f-stop), and a short distance to subject give you the shallowest depth of field. The problem with 1/3" chip cameras like the GL1 is that they use very short focal length lenses to be able to focus the image on such small chips. A 35mm-sized target can use longer focal lengths to frame the same sized image.
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#5 Chris Keth

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Posted 24 October 2007 - 05:36 PM

Another useful way to put what Michael said is that aperture and image magnification (which is determined by foc al length and subject distance) affect depth of field. That means that if you frame a person from the belt up at f4, the depth of field will be a constant. No matter if you do this on a 25mm lens at 4 feet or with a 50mm lens at 8 feet or a 100mm lens at 16 feet, the depth of field will be the same.

This also means that, contrary to popular belief, you can't use a longer lens and just back up and get shallower depth of field, assuming you framed up the same shot on the person.
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#6 Michael Nash

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Posted 24 October 2007 - 10:45 PM

This also means that, contrary to popular belief, you can't use a longer lens and just back up and get shallower depth of field, assuming you framed up the same shot on the person.


Well, sort of. It's true that the depth of field stays the same -- meaning that the area in focus stays the same. But with longer focal lengths the out-of-focus background gets magnified, and ends up looking softer (it's the same "softness", just magnified larger). So backing up and using a longer lens for the same frame size does make a soft BG look even softer. But if the BG is within the depth of field to begin with (as it often is with 1/3" chip cameras), you're outa luck.
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#7 Chris Keth

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Posted 24 October 2007 - 11:04 PM

Well, sort of. It's true that the depth of field stays the same -- meaning that the area in focus stays the same. But with longer focal lengths the out-of-focus background gets magnified, and ends up looking softer (it's the same "softness", just magnified larger). So backing up and using a longer lens for the same frame size does make a soft BG look even softer. But if the BG is within the depth of field to begin with (as it often is with 1/3" chip cameras), you're outa luck.


True. I gave the correct answer but your answer is probably more "right." I hadn't thought about that giving the illusion of softer focus.
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