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Old June 25th, 2009, 11:42 AM   #1
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Maximizing depth of field without an adapter

I've read a lot of posts about adjusting the iris and using ND filters to increase/decrease depth of field, but I've never seen any mention of 'how much' the DOF is actually affected by these factors. I'm sure it varies from camera to camera, but is there a general consensus on this? If I bother to tweak these settings, will I really get much out of this technique? I am aware of, and use, the technique of putting some distance between the camera, subject, and background. In tight situations though, I would like to be able to maximize the 'look', while I'd like to minimize it in other situations.

In my own pseudo-tests, I've not seen a difference (using A Sony Z1), but I've not done any rigorous testing. Although I believe the hands-on approach is best in determining the value of a particular technique, I'm wondering also if there are specific conditions (that I'm missing) in which this technique would produce more drastic results...such as in different lighting conditions, zooms, distances (camera to subject to background), etcetera.

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Old June 25th, 2009, 11:58 AM   #2
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Tricky subject. Depth of field is affect mainly by iris and focal length - everything else considered. A place I like to go is Hyperfocal Distance and Depth of Field Calculator - DOFMaster - The have a tool there and some explanations of the subject that have been helpful to me.
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Old June 25th, 2009, 12:28 PM   #3
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Alec, if you can't get more distance between subject and background, iris is about the only thing you can use to minimixe depth of field. To this end, you can increase shutter speed (within reason - above about 1/250 the strobing effect becomes more pronounced) OR throw Neutral Density at it in order to force the iris more open, reducing depth of field.

You CAN also "cheat" with focus: Depth of Field is the amount of the field of view that is in focus: if your subject is 5 feet away from you and your DOF allows for 4 - 10 feet to be "in focus", try focusing CLOSER than your subject with the intent of "catching" your subject at the VERY END of the "in focus" field.
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Old June 25th, 2009, 03:52 PM   #4
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Thanks for the link Gene. Good info there.

Good trick Shaun. I'm not sure I'd want to overuse for effect, but I'm often estimating the midpoint between subjects at different distances to achieve similar sharpness between them (as long as both are still acceptably clear).

Good advice.

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Old June 27th, 2009, 09:20 PM   #5
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There are ways you can achieve shallow depth of field without an adaptor, if you understand and combine the following principles:

1. Iris. Open your iris as wide as possible for shallowest depth of field.
2. Lens focal length. Longer lenses will give you shallower depth of field than wide ones.
3. Lens to subject distance. The closer your subject is to your lens, the shallower your depth of field. If your lens has a macro mode, you'll be able to get very close to your subject, yielding extremely shallow depth of field.
4. Subject to background distance. The more separation you have, the shallower your apparent depth of field.
5. Imager size. The bigger your CCD or CMOS chip, the shallower your depth of field.

In conclusion, try using a camera with a big imager, use a long lens, and keep your subject as close as possible to the camera. Open your iris up wide open, and use neutral density filters or a faster shutter speed to obtain correct exposure. In many situations you can achieve very shallow depth of field shots that mimics adaptors very well.
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Old June 28th, 2009, 02:01 PM   #6
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Alec,

For most people the problem with achieving a film-like depth of field is related to the fact that on consumer, prosumer, and even some professional level camcorders, the size of the IMAGING CHIP is relatively small.

Based on the physics of how light and lenses work, the smaller the area the lens focuses it's light upon, the deeper the depth of field will be - all other things being equal.

So the smaller your cameras imaging chip or chips, the HARDER it will be to create a shallow depth of field.

If you shoot a play, however, from a position at the back of a theatre in relatively dim light, you'll notice that even the smallest chip camera can achieve a relatively narrow depth of field. (and drive you nuts trying to keep people upstage and downstage both in focus!)

Cameras with larger chips have a much easier time. This is one reason people are so encouraged by the new DSLRs that shoot video with a full 35mm image size. Their image geometry is virtually identical to 35mm movie cameras. They just cost a whole LOT less.

FWIW.
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Old June 28th, 2009, 02:24 PM   #7
 
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Quote:
Originally Posted by Warren Kawamoto View Post
There are ways you can achieve shallow depth of field without an adaptor, if you understand and combine the following principles:

1. Iris. Open your iris as wide as possible for shallowest depth of field.
2. Lens focal length. Longer lenses will give you shallower depth of field than wide ones.
3. Lens to subject distance. The closer your subject is to your lens, the shallower your depth of field. If your lens has a macro mode, you'll be able to get very close to your subject, yielding extremely shallow depth of field.
4. Subject to background distance. The more separation you have, the shallower your apparent depth of field.
5. Imager size. The bigger your CCD or CMOS chip, the shallower your depth of field.

In conclusion, try using a camera with a big imager, use a long lens, and keep your subject as close as possible to the camera. Open your iris up wide open, and use neutral density filters or a faster shutter speed to obtain correct exposure. In many situations you can achieve very shallow depth of field shots that mimics adaptors very well.
Truth be known, imager size is related to lens diameter, which is related to maximum aperture of the lens. In the end, it is ONLY maximum aperture and subject distance that affect DOF. The fact that zoom lenses appear to create shallower DOF is an optical illusion based on the zoom factor of a smaller portion of the original image. If one keeps the object size(within a given image) constant, then, when zooming in(ostensibly to decrease DOF)then one must move away from the subject to maintain a constant object size, and the DOF is appropriately decreased back to the original(unzoomed) value.
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Old June 28th, 2009, 05:51 PM   #8
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Originally Posted by Bill Ravens View Post
Truth be known, imager size is related to lens diameter, which is related to maximum aperture of the lens. In the end, it is ONLY maximum aperture and subject distance that affect DOF. The fact that zoom lenses appear to create shallower DOF is an optical illusion based on the zoom factor of a smaller portion of the original image. If one keeps the object size(within a given image) constant, then, when zooming in(ostensibly to decrease DOF)then one must move away from the subject to maintain a constant object size, and the DOF is appropriately decreased back to the original(unzoomed) value.
Bill's correct in pure theory - however, in practical terms, it can easily be argued that what effectively limits the camera/camcorder to a particular size aperture, IS the size of the imaging chip. You don't find large maximum aperture opto/mechanics feeding small chips because it simply makes little sense to do so.

And when it comes to parts costing, clearly, making a larger sized and attendantly greater pixel density chips - while simultaneously keeping them affordable - is where camcorder manufacturers face the biggest challenge.

Particularly with traditional "3-chip" imaging block designs where the manufacturer must pay for chip size and sophistication 3 times over.

So while Bill makes a valid point, I'd argue that what lets you USE the larger aperture effectively and therefore achieve a functionally shallower depth of field at a given distance and f-stop, at least in large part, today's larger, more efficient, and faster sensors.

As RED heralded and now Canon is making super affordable - larger sensor video shooting provides real-world benefits in achieving filmic depth of field that are pretty amazing.

Which benefits all of us in the long run.

Interesting times we live in.
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Old June 28th, 2009, 06:28 PM   #9
 
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Originally Posted by Bill Davis View Post

So while Bill makes a valid point, I'd argue that what lets you USE the larger aperture effectively and therefore achieve a functionally shallower depth of field at a given distance and f-stop, at least in large part, today's larger, more efficient, and faster sensors.
I think the question is, "what came first, the chicken or the egg", or in this case, the sensor size or the lens to match...LOL A little humorous, but, you make a point, Bill. Indeed, the modern DSLR, with a full 35mm sensor, and the matching lenses, provide DOF to rival Cinemascope. Now, if only the DSLR can match the full functionality of a film camera. The day is coming.
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Old June 28th, 2009, 09:52 PM   #10
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I'm not so sure about DSLR's being used primarily for video, but I am excited about systems of lenses developed for [D]SLR's, and in the large sensors developed over the laast couple of years. I think Sony buying the Minolta assets was a great move. Wouldn't it be cool if they made a video camera that used alpha lenses? Think of the economics, those are nice lenses and wouldn't cost a fortune as cost are spread out.
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Old June 28th, 2009, 10:17 PM   #11
 
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The point of convergence is nearly upon us. I would like to refer to the attached article by the esteemed Michael Reichman...
Video DSLRs vs Camcorders
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