1/4 vs 1/3 dof at DVinfo.net

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Canon GL Series DV Camcorders
Canon GL2, GL1 and PAL versions XM2, XM1.


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Old July 25th, 2004, 12:09 AM   #1
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1/4 vs 1/3 dof

Hey, i wondering how the depth of field on the gl2's 1/4 inch chip compares to some 1/3 inchers like the dvx and xl1. I know none of them are great but is there a significant difference between them?
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Old July 25th, 2004, 02:38 AM   #2
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With regard to what? Throwing Focus? I use the XM2 and I can get some amazing thrown focus .. but maybe you are wanting a far more scientific response from people here? Anything specific you are thinking of? It was the "I know none of them are great but is there a significant difference between them?" . . that "threw" me of Focus!

I recently asked a question about CCD sizes, and I got back this great link - thanks Luis - have you read it? Might give you some clues .. don't know: http://www.edmundoptics.com/TechSupp...icleid=290#4.3

Grazie
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Old July 25th, 2004, 02:52 AM   #3
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Thanks . .you got me thinking too!

Here yah goes! . . ..

Our Own Jeff Donald's "The Ultimate Depth-of-Field Skinny" article

http://www.dvinfo.net/articles/optics/dofskinny.php

. . and . .

http://www.belgiumdigital.be/Tips_&_...difference.htm

and . . .

http://home.comcast.net/~jonsachs/DOF.htm


Grazie
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Old July 25th, 2004, 11:47 AM   #4
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"thanks Luis"

Hey, you're welcome.



EDITED TO DELETE A BUNCH OF STUPID QUESTIONS:

Thanks for the link to Jeff's article,
I hadn't seen that before and it answered every question
I had posted.

I guess we're even now Graham
:)

-Luis
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Old July 25th, 2004, 11:55 AM   #5
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"Now perhaps you can clear something up for me." - er . .nope!. . PASS!

ROBIN? Where Are you? At Pinewood again. .. looking at another launch? . . .;-)

Sorry matey, I really haven't a clue .. Don't you just love the technical "Circle of Confusion" . . yeah, right!

Grazie
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Old July 25th, 2004, 12:00 PM   #6
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To be honest, I've simply given up on trying to understand
'circles of confusion.' Although I do think it is a aptly named
thing.

Jeff's article did help explain the difference between target areas however.

I'll have to reread it a few times, but the answer is in there.
Just hasn't clicked yet.

-Luis
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Old July 25th, 2004, 12:14 PM   #7
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Sorry if my question was unclear i was just asking if anyone had seen a tangible difference in depth of field between cameras with 1/4" ccd's and camera with 1/3" inch ccd's. I've heard the dof is more shallow on the 1/3 inch chips, but has anyone actually seen this? I of course would be going for a more "film" look with the backround out of focus. I know and use all the tricks to make this happen i was just wondering if the size of the ccd's actually had an effect. Thanks a lot
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Old July 25th, 2004, 12:28 PM   #8
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Luis (looks like you edited your post...but I decided, since I had already written it, to post answer to your now vanished question :,)

There are a couple of issues relative to the Depth of field relationship between format sizes using the same focal length lens. The first, and main one is this. Say you use a 100mm lens to shoot a portrait on your 6x7 camera. You're at f 5.6 and you see a modest amount of blurring in the background.

Now if you were able to switch bodies to a 35mm, but kept your tripod and lens at the same spot, you would find that the DOF is identical...everything is identical, except the framing, as you have essentially just cropped the image by placing a smaller piece of film behind the lens.

But what if you decided you wanted to get the same framing with the 35mm camera, and the same lens -- you'd have to move the camera back-- and in the process, you would change the relationship between the camera-subject distance, and the subject - background distance. In this case, if you compared the 35mm to the original 6x7 image, you would see greater, or less shallow depth of field in the 35mm image....

The second issue is this...similar situation...with either the cameras at two different points of view, but essentially the same framing, or using the same point of view with different lenses. You have a 6x7 image which is capable of resolving much more detail than the 35mm.... and thus exposes the fall-off of sharpness more quickly than does the lower resolution 35mm image...this is the same principal that allows the mini35 adapter to create shallow depth of field on the xl1s...using equivalent field of view lens to produce a larger (and thus higher resolution) image on a ground glass (and thus shallower depth of field) and then photographing that projected image with the xl1s.

Ryan-- the above also applies to your question, but the short answer is yes...there is a difference in DOF between a 1/4 and 1/3" chip. It is not a huge difference, but it's there. Although, I've found that in practice, I can get almost equivalent DOF looks with the gl2 and xl1s, as I feel more comfortable shooting wide open with the gl2, than I do with the xl1s.

Barry
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Old July 25th, 2004, 12:30 PM   #9
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I suspect that you would like to see a shallow depth of field on wider shots. Certainly a 1/4inch CCD will give you a narrow depth of field if you zoom in enough. The "film" look you mention is when you can get differential focus on wide shots and you're only going to get anything near that on something like the P+S Technik Mini35 setup which produces an image from 35mm lenses (lenses designed for 35mm cameras, not 35mm focal length) on a ground glass screen at a size large enough to imitate the film gate in a 35mm camera. This becomes a virtual CCD that is shot by a DV camera. I don't think that the difference between 1/4, 1/4 CCDs would be noticeable at all. Even the chips in a Digibeta will not give such narrow depth of field.
It's a shame that we can't get it on our cameras, but it's down to the laws of physics I'm afraid...

Robin
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Old July 25th, 2004, 01:03 PM   #10
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Barry,

Thank you for the clear answer.
That made a lot of sense.


Sorry about editing my post...
In the future I'll leave them alone for the consistency of the thread.
I just didn't want to hijack the thread in a different direction.

-Luis
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