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Old January 26th, 2003, 03:15 AM   #1
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CCD size vs. depth of field

Now from what I understand, the bigger the CCD the shallower depth of field can be achieved, right?

My question is how much of a difference of a DOF there will be?
Say between the XL1 with 1/3" CCDs and something with either 1/2" or 2/3" chips?
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Old January 26th, 2003, 07:41 AM   #2
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I've looked up a few common chip sizes and I'll list some important details.

1/4 inch CCD. 3.2mm X 2.4mm. 4.0mm diag. Focal length mag. 11.3X


1/3.6 inch CCD. 4.0mm X 3.0mm. 5.0mm diag. Focal length mag. 9.0X


1/3 inch CCD. 4.8mm X 3.6mm. 6.0mm diag. Focal length mag. 7.5X


1/2 inch CCD. 6.4mm X 4.8mm. 8.0mm diag. Focal length mag. 5.6X


2/3 inch CCD. 8.8mm X 6.6mm. 11.0mm diag. Focal length mag. 4.1X


35mm Film. 36.0mm X24.0mm. 43.3mm diag. Focal length mag. 1.0X


Because I couldn't get the proper spacing due to software limitations let me explain the numbers. The first set is the common size of the CCD chip. Next is the width and height of the chip. The diagonal measurement is next and the focal length magnification factor is last.

The aspect ratio (height to width) is 4:3, except for the 35mm film, which 3:2. The diagonal is listed for two reasons. A rough equivalent to the normal focal length is derived from the diagonal (35mm film is 43.3mm diag. 50mm lens is considered normal). Some people use the diagonal to derive the focal length magnification. The 7.2 magnification factor used by Canon (for use of EOS lenses with EF adapter) is obtained by dividing 43.3 by 6.0 (the diagonal of film divided by diagonal of 1/3 inch chip). My materials list the Focal length magnification using the widths (long dimension) hence the slightly different numbers.

Since we are not changing any of the components of the DOF formula, the DOF can be calculated as a percentage of the different focal length magnifications.

The DOF on 1/3 inch CCD's is 7.5X the DOF of 35mm film. DOF is 25% greater with 1/3 inch CCD's vs. 1/2 inch CCD's. A 2/3 inch chip has 27% less DOF than a 1/2 inch chip.

You can get real world measurements by using a DOF calculator They are set up to show 35mm film DOF so the distance will need to be increased by the appropriate percentages derived by the information above.
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Old January 26th, 2003, 01:33 PM   #3
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Jeff:

Not faulting the math, but confused about something--I was always under the impression that 2/3" video and 16mm were approximately the same in terms of field of view at a given focal length, and that they were both roughly half of 35mm (2/3" video being more like 2.2x magnification and 16mm 2x). Obviously this doesn't agree with your table...help?
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Old January 26th, 2003, 03:48 PM   #4
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I don't know about the math, there may be a typo there. But, the basic physics is the same. The bigger the chip (or negative) the shallower the depth of field. I believe a 2/3" chip and 16mm film is close, though not exact. Some people consider a 50mm focal length to be "normal" in 35mm, and it's 25mm in 16mm, and roughly the same for 2/3", give or take a mm or two.
Practically speaking, there is quite a big difference between the depth of field you get with 1/2" and 2/3" chips. Not as big as the jump for 16mm to 35mm, or from 1/3" to 2/3", of course, but it's more difficult to get shallower depth of field with 1/2" chips. Even with the newer 2/3" chip cameras like the DSR500/570, it's difficult under long shot conditions, because the cameras are so light sensitive you're usually stopped down quite a bit. I always shoot at a -3db with the DSR500 and have only taken it off that setting one time for a night exterior shot.
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Old January 26th, 2003, 04:34 PM   #5
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Charles,

Do you have the dimensions for Super 16, Academy 35 and Super 35? I used 35mm still film as the basis for the factors. I believe 35mm motion picture film varies from still film and is the cause of the confusion.

Bill,

Thanks for catching the typo. That'll teach me to write these things before my first cup of coffee.

Jeff
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Old January 26th, 2003, 05:03 PM   #6
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Re: "That'll teach me to write these things before my first cup of coffee."

Yeah, but Bill has a new coffee maker, for that better cup of coffee. That's why he keeps on humming. He only paid $160 US for it.

I've read that 1/6" CCDs almost gives a 3D look, so what kind of look would a cam with mega pixel 1/8" CCDs give you? 3D?
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Old January 26th, 2003, 06:41 PM   #7
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sorry about the inches...
Super 16: .486x.295
Full ap 35: .980x.735
35mm 1.85 ap: .825x.446
Super 35 (2:40:1): .945x.394 (extracted)
Anamorphic projection ap: .825x.690
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Old January 26th, 2003, 07:13 PM   #8
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I used the long dimension to calculate the magnification factors. On 35mm still film its 36mm or 1.47 inches. Big difference between 1.47 inches and .945 inches on Super 35. I'll add the film sizes to the chart in a couple of days. I'm going to be out for a couple of days for surgery on my shoulder. Too many years of carrying Betacams, tripods, light kits etc.
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Old January 26th, 2003, 11:26 PM   #9
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Great info. Thanks Jeff et. all!
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Old February 8th, 2003, 04:42 PM   #10
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Just a friendly reminder that while shallow DOF is part and parcel
to the Pro Look, it is not the entire affair.Long before long lenses even showed up,filmmakers were doing just fine with what they were dealt at the time,which included mostly wide shots done with limited focal length lenses.A recent example of that "old school" stuff was brilliantly executed by Owen Roizman ASC for "Wyatt Earp".If you haven't seen it in a while,watch it again-it is well worth it.

If I heard as much about composition on some of these boards as I did about shallow DOF,I would be greatly heartened.We would also see way more examples of fine cinematography on the various short film websites than we are seeing now.

Shallow DOF is a subject second only to the "film look" in terms of the frequency that it is discussed.

But composition should be number one among these three,because without it,we are nowhere.I believe it is the most important aspect of any production as far as acquisition is concerned.You may not always have what you want to shoot on,and you may not always have super long lenses......


But,you will always have that little "window on the world" to work with....
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Old February 9th, 2003, 06:31 PM   #11
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Just to support what "skyy" says in a more recent example, I hope you will all take a good look at "Signs," now that it is available on dvd. Tak Fujimoto's lighting and compositions are fabulous, and, surprise! Deep focus. That's right. For almost the entire movie there are no blurry backgrounds. But still, the DP is able to separate the people from the backgrounds (when he wants to). How does he do it? Rent the movie and find out.

Of all the things first time film makers should worry about, depth of field is way down the list.
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Old February 9th, 2003, 07:03 PM   #12
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If i throw this into the mix i have found using the sony pd150 is almost the same in operation as super 8mm when it comes to DOF and so on. I can imagine it must be similar in size.

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Old February 9th, 2003, 07:08 PM   #13
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Composition is extremely important. But unless the camera operator has prior education or experience, appropriate composition is going to take time. It's not something learned by books or forums (which I presume is why it is not discussed much). Composition many times goes unnoticed (an indication of good composition). The scene looks so natural it doesn't call attention to itself. Teaching natural elements of style and composition is tough.

DOF on the other had is more easily seen and noticed by novices. The results, good, bad and mediocre are easy to see. It is also easy to discuss and to teach. Basically use small numerical F/number for a shallow DOF and large numerical F/numbers for large DOF. Try teaching composition in one sentence.
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Old February 9th, 2003, 09:09 PM   #14
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<<<-- Originally posted by Jeff Donald :
DOF on the other had is more easily seen and noticed by novices. The results, good, bad and mediocre are easy to see. It is also easy to discuss and to teach. Basically use small numerical F/number for a shallow DOF and large numerical F/numbers for large DOF. Try teaching composition in one sentence. -->>>

It may be "easy to teach," but in the real world it is not easy to control with small chip dv cameras. So much time and effort is seen in posts to this and other forums trying to achieve narrow depth of field with these cameras, and it ain't gonna happen. Its laws of physics. So rather than bang your head talking about $7000.00 solutions on a $3000.00 camera to reduce depth of field, maybe time would be better spent studying a film like "Signs" and seeing how deep focus can work to the filmmaker's advantage.

Yes, composition takes time to learn. So does lighting, so does editing. So what else is new? Read my signature.
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Old February 9th, 2003, 10:04 PM   #15
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Shallow DOF can happen with small chip cameras.
I'm sorry,but,while I appreciate what larger chip cams can have to do with shallow DOF,it is not the entire affair.

A nice healthy zoom lens ratio has more to do with it.Anything from 16x and above will do.

As does the distance between your cam and your subject and also the difference between your subject and the background.

The above,(besides the other things that have been brought up already) is basically it.

And I am not going to explain it here for the umpteenth time because there is some else whose text is more timeless.

Pick up "Cinematography" by Malkiewicz.He will explain all that you need to know.

I can get "shallow" with my humble little Sharp Hi 8.
Or any other instrument,for that matter.....


Quit obsessing about chips and whatnot...

....obsess about *knowledge* instead....
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