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Old May 16th, 2006, 07:59 AM   #1
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getting closer depth of field with consumer MiniDV

what is the story on trying to get film-like depth of field on a consumer MiniDV camera?

i'd spend up to $100 if I knew I could solve this problem so i could easily blur the background in my videos.

are there lenses, filters...etc that will work?
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Old May 16th, 2006, 08:02 AM   #2
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This has been covered many times here and if you do a search on 'shallow depth of field' you are going to get a plethora of information on it.

The short and sweet answer is to move camera back, zoom in, open iris as much as possible.

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Old May 16th, 2006, 10:36 AM   #3
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For under $100, you can try a close-up or macro filter. They are often sold in kits of strengths +4, +2, and +1 combined. They make it impossible to focus completely on distant subjects so the background blurs but it is not dramatic. You can also make your own DOF/35mm adapter. Moving the camera far back and zooming in with an open iris works, but it narrows your field of view so much that it is rarely useful. I tried this a few times, but there is so little background behind the talent that it is hard to tell where they are. Imagine that an actor is on a street an you want to blur the background. With a narrow field of view, you may only see a bit of grey from a distant building in the background. The real solution is a 35mm adapter and you will need to buy at least one good lens and those cost more than $100.

Look in the "alternative imaging" forum.
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Old May 16th, 2006, 10:46 AM   #4
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Quote:
Originally Posted by Marcus Marchesseault
For under $100, you can try a close-up or macro filter. They are often sold in kits of strengths +4, +2, and +1 combined. They make it impossible to focus completely on distant subjects so the background blurs but it is not dramatic. You can also make your own DOF/35mm adapter. Moving the camera far back and zooming in with an open iris works, but it narrows your field of view so much that it is rarely useful. I tried this a few times, but there is so little background behind the talent that it is hard to tell where they are. Imagine that an actor is on a street an you want to blur the background. With a narrow field of view, you may only see a bit of grey from a distant building in the background. The real solution is a 35mm adapter and you will need to buy at least one good lens and those cost more than $100.

Look in the "alternative imaging" forum.
Agreed, it's mainly used for close up shots, but that's where I would want the most emphasis on DOF. On a wide shot, I would actually prefer to have more stuff in focus in order to orient the viewer as long as the background isn't too distracting.

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Old May 16th, 2006, 11:08 AM   #5
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At any given focus position on the focus ring, the same distance from the camera is targetted for being in focus. As you increase the focal length (zoom) any background object in the out of focus area is magnified so the softness becomes apparent. This, however, increases the size of the foreground image as well that we are trying to frame correctly, so we back the camera up away from the subject and zoom in with the iris wide open to get the effect you are looking for.

The farther away from your subject the camera is, the farther out you will be focusing, the sweet spot is somewhere in the middle, you want your talent just far enough from the camera that you are not at the far end of the focus and a large space between them and the background subjects.

If you prefer and have comfortable actors, you can keep the lens wide and put the camera right up to them...the backgrounds will stay smaller and out of focus as opposed to the leaves a block away being the same size as your actors' heads.

DV doesn't have the resolution to show subtleties that are small in the frame, so backgrounds often "Give away" the videoness of the image. Blurring them is one of the primary components of getting less amatuer looking video.

I don't say filmic, I say cinematic...if you want film, shoot film. Strive instead to work within the limitations of the DV format (I prefer shooting DV over film - you can get fabulous footage with care and it's alot cheaper to work with):

1 control your lighting to decrease the contrast range - Circular Polarizers are good for this
2 underexpose slightly
3 avoid pure whites (clipping kills them) in your frame
4 avoid reds (compression kills them) in your frame
5 push the background out of focus to hide the lack of resolution
6 tripod, stabilizer, dollies!
7 good sound
8 good story
9 good acting
10 good editing
11 break these rules as you see fit artistically...you can't fix these ones in post.
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Old May 16th, 2006, 11:45 AM   #6
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For a long time I was of the opinion that there was no difference between moving in and zooming out versus moving back and zooming in. Technically, the depth of field is the same for both approaches. What I neglected to understand is that while the depth of field is the same, the field of view is much tighter when zoomed in, which results in a perception of shallower depth of field, which is a good thing.

Don't forget, when you are at full wide you can usually have a F1.6 iris, but at full zoom, it's usually F2.8. Is the tighter field of view worth the increased depth of field from the tighter iris? I think everyone needs to test with their own gear and make up their own mind.
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Old May 16th, 2006, 05:56 PM   #7
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You can build your own 35mm adaptor for around $250 including the lens.
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Old May 16th, 2006, 06:33 PM   #8
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Not counting the lens, I spent $20 on mine...the 50mm Nikon lens used runs $25.

$3 plywood from scrap pile at Home Depot
$5 various screws and nuts
$10 Cheap Portable CD player to disassemble
$3 battery holder and switch from radio shack
$2 cheap matte black spray paint
$0 stray cereal box for hood
$0 clear/rumpled (not quite frosted) CD I had hanging around from stack 'o' blank CD's

used the diagrams on mediachance.com found the link on this board.
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