DOF and Sensor Size

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Archive 2005 · DOF and Sensor Size

Jeff Donald
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p.8 #1 · DOF and Sensor Size

And your doctorate was in what? Optical engineering? I'll take the word of someone trained by Canon on the characteristics of a Canon lens over some link to a self proclaimed photography guru's web page.

This what I've kown all along, and the Canon Tech just confirmed that for me.

I have a Masters of Science in Photography and a Masters of Science in Education. I have completed approximately 25 hours towards by doctorate in education.

I've reviewed approximately 12 college text books I teach from and The Optical Society of America Handbook of Optics, second edition volume 1. Nearly every source referred to Applied Photographic Optics, third edition, by Sidney Ray as the source for there information on Depth of Field and Circle of Confusion. Both books are available from Amazon, for those interested.

I reproduced the pertinent page, 217, from Ray's book. You can also view the page if you log into you Amazon account. I quote "Depth of field is therefore determined by the geometry of the taking, enlarging and viewing conditions related to the circle of confusion standard adopted (Figure 22.3)."

If this isn't a good enough authority to conclude that enlarging and viewing are essential to determining DOF then I'm at a loss. nsbca and others are wasting their time and should be writing the next college text on the subject as it will revolutionize optics and photography.

Applied Photographic Optics, Third Edition read page 217

Handbook of Optics, V1, second edition

Edited by Jeff Donald on Aug 15, 2005 at 05:17 PM GMT (Reason: fixed link)

Edited by Jeff Donald on Aug 15, 2005 at 05:31 PM GMT (Reason: fixed link)

Aug 15, 2005 at 09:14 PM

Jeff Donald
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p.8 #2 · DOF and Sensor Size

page 217

Aug 15, 2005 at 09:14 PM

nsbca
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p.8 #3 · DOF and Sensor Size

slin100 wrote:
A picture, or in this case two, will be worth the thousands of words thrown around so far. Can someone with two different format cameras do this? I can simulate this with my single DSLR, but I suspect someone will cry foul.

When my 1Ds Mark II comes in next week I will be glad to do this.

Aug 15, 2005 at 11:13 PM

nsbca
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p.8 #4 · DOF and Sensor Size

Jeff Donald wrote:
And your doctorate was in what? Optical engineering? I'll take the word of someone trained by Canon on the characteristics of a Canon lens over some link to a self proclaimed photography guru's web page.

This what I've kown all along, and the Canon Tech just confirmed that for me.

I have a Masters of Science in Photography and a Masters of Science in Education. I have completed approximately 25 hours towards by doctorate in education.

I've reviewed approximately 12 college text books I teach from and The Optical Society of America Handbook of Optics, second edition volume 1. Nearly every source referred to Applied Photographic Optics, third edition, by Sidney Ray as the source for there information on Depth of Field and Circle of Confusion. Both books are available from Amazon, for those interested.

I reproduced the pertinent page, 217, from Ray's book. You can also view the page if you log into you Amazon account. I quote "Depth of field is therefore determined by the geometry of the taking, enlarging and viewing conditions related to the circle of confusion standard adopted (Figure 22.3)."

If this isn't a good enough authority to conclude that enlarging and viewing are essential to determining DOF then I'm at a loss. nsbca and others are wasting their time and should be writing the next college text on the subject as it will revolutionize optics and photography.

Applied Photographic Optics, Third Edition read page 217

Handbook of Optics, V1, second edition

That's pretty. I like that.

The above calculations are 100% correct if all thing given - focal length, aperture diameter, distance from subject and (your 8x10) size of print and viewing distance from print remain the same. If the sensor size changes under these conditions the image will indeed change and the percieved DOF will also change. I have no problem with that whatsoever.

In the practical world the 8x10 standard is non-existant. Use all the forementioned conditions, but change the 8x10 to 100% enlargement. What happens?

In the real world how many people buy a 1Ds Mark II to print at 8x10? Few. You can do that quite well and for a few thousand less with a 300D.

Let's go through a real life scenario. I have a FF 1Ds. I shoot a picture crop and enlarge the image to say 54x24. Nothing hard about that is there? Can I do that with my 300D? Not very well. If I wanted the same aspect ratio I would print the image from the 300D at 34x15. That would give me a very close DOF (+/-) and the print would be close to the same in clarity and sharpness.

The truth is that you will not print as large an image from a 300D as you can from a 1Ds.

On paper, with the 8x10 standard in place (all other variables staying the same) the DOF will change if the sensor size changes. In the practical world it remains a constant.

Aug 15, 2005 at 11:46 PM

Tom_W
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p.8 #5 · DOF and Sensor Size

Hark - I hear a new song....

Aug 15, 2005 at 11:59 PM

jasin
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p.8 #6 · DOF and Sensor Size

Just GIVE IT UP!
Sheesh this is a 'I am right you a wrong' forum.
You guys use the same gear obviously have the same interests but quite obviously just hate each other.
Back to the lounge for me!
Cheers,
Jasin.

Aug 16, 2005 at 12:01 AM

nsbca
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p.8 #7 · DOF and Sensor Size

10DFT wrote:
Hark - I hear a new song....

You don't hear anything different then what I have been saying all along. I am going to print larger with a 1Ds Mark II then I would if I was using a 1D Mark II It is that simple. If I crop my 1Ds Mark II image by a factor of 1.3 I have the EXACT same image, give or take a few pixels.

Aug 16, 2005 at 12:06 AM

AJSJones
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p.8 #8 · DOF and Sensor Size

nsbca wrote:
Let's go through a real life scenario. I have a FF 1Ds. I shoot a picture crop and enlarge the image to say 54x24. Nothing hard about that is there? Can I do that with my 300D? Not very well. If I wanted the same aspect ratio I would print the image from the 300D at 34x15. That would give me a very close DOF (+/-) and the print would be close to the same in clarity and sharpness.
1) Yes, I think you have just said that the DoF remains the same if the magnification ratio is the same.
On paper, with the 8x10 standard in place (all other variables staying the same) the DOF will change if the sensor size changes.
2) Yes. And that's why you can't use the DoF scales unmodified - the answer to the original question on page1
In the practical world it remains a constant.
3) Yes, if you print your 1dDs images bigger than your 300D, 350D, 10D etc images by the 1.6 factor. (see 1) above)
It becomes a variable if you don't use the 1.6 factor. (see 2) above )

We are agreed.

Aug 16, 2005 at 12:08 AM

nsbca
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p.8 #9 · DOF and Sensor Size

AJSJones wrote:
We are agreed.

That wasn't hard.

Aug 16, 2005 at 12:25 AM

slin100
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p.8 #10 · DOF and Sensor Size

nsbca wrote:
slin100 wrote:
A picture, or in this case two, will be worth the thousands of words thrown around so far. Can someone with two different format cameras do this? I can simulate this with my single DSLR, but I suspect someone will cry foul.

When my 1Ds Mark II comes in next week I will be glad to do this.

There's no need for you to do the test any more now that you said the following (bold text my emphasis):
nsbca wrote:
The above calculations are 100% correct if all thing given - focal length, aperture diameter, distance from subject and (your 8x10) size of print and viewing distance from print remain the same. If the sensor size changes under these conditions the image will indeed change and the percieved DOF will also change. I have no problem with that whatsoever.

That convinces we that we actually are in agreement with respect to fundamentals.

I think we still differ on other details (e.g. the validity of the DOF scales for different print sizes), but that's a minor quibble.

Whew! What a ride it's been.

Aug 16, 2005 at 12:26 AM

AJSJones
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p.8 #11 · DOF and Sensor Size

I was looking for the smiley that has folks drinking beer and cheering :beer

Anyway you know what I mean....

Aug 16, 2005 at 12:28 AM

jdaily
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p.8 #12 · DOF and Sensor Size

Some of you guys are (no disrespect intended) really thick.

Wow. I'm a little skeptical you can state that with respect.

"Respectfully, boss, you're a jackass."

Aug 16, 2005 at 01:51 AM

Imagemaster
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p.8 #13 · DOF and Sensor Size

Jeff Donald wrote:

DOF didn't really exist until there was photography (capturing a 3 dimensional world on a 2 dimensional medium). Try to find a 16th Century painting that displays DOF. DOF is an optical phenomenon that can be described mathematically, but it is hardly a "law of physics" as some have claimed.

Perhaps not under this definition that we have today, but this "optical phenomenon" as you put it, has been around for as long as creatures on this planet have had eyesight. Perhaps instead of "depth-of-field", you would prefer to call it "depth-of-focus" or "depth perception".

Hold your finger four inches in front of your face and see if you can focus on it and something 100 feet away at the same time. If you can't, it is because the depth-of-field is too great for your eyes optics to handle. People with poor depth perception are looking at a shallower depth-of-field than those with good depth perception.

This optical phenomenon is older than mankind.

Aug 16, 2005 at 02:42 AM

Hrow
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p.8 #14 · DOF and Sensor Size

My God, is this thing still going?

Aug 16, 2005 at 02:51 AM

Jeff Donald
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p.8 #15 · DOF and Sensor Size

Hold your finger four inches in front of your face and see if you can focus on it and something 100 feet away at the same time. If you can't, it is because the depth-of-field is too great for your eyes optics to handle.

I think you're talking minimum focus distance not DOF. My 50 mm at f/16 can't focus on something 4 inches in front of it and have an object 100 feet away in focus. However my eyes can focus on an object about 12 inches from my face and 100 feet at the same time. Prior to Lippershey and Galileo DOF was not known. It requires optical lenses to perform the phenomenon. I think you're confusing depth perception, which requires stereo viewing, with DOF.

Aug 16, 2005 at 02:58 AM

jdaily
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p.8 #16 · DOF and Sensor Size

Jeff Donald wrote:
However my eyes can focus on an object about 12 inches from my face and 100 feet at the same time.

I don't disagree with anything you've said about DoF to this point, but can you clarify this statement?

Perhaps it's just my eyeglasses that are distorting the world in ways that my eyes wouldn't if they weren't astigmatic, but if I close one eye and focus on my finger at arm's length, then switch focus to an object about 3 times as far away (box of Ilford Galerie paper), I can see the text come into focus. Conversely, if I focus on the text, then on my finger (again with one eye closed) my finger appears to become sharper and there's no way I can read the text.

Thus, it would appear that just one eye is unable to focus both on the text and my finger.

If I use both eyes, the stereo vision issue comes into play, and objects at a closer distance clearly go double. However, holding up something with text and looking at it (while leaving my eyes focused on the box of paper), the text not only is doubled, but a single copy looks blurry.

Aug 16, 2005 at 03:50 AM

nsbca
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p.8 #17 · DOF and Sensor Size

Jeff Donald wrote:
However my eyes can focus on an object about 12 inches from my face and 100 feet at the same time.

Not possible. There is a transition as your eyes refocus.

Aug 16, 2005 at 04:02 AM

rcmanoj
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p.8 #18 · DOF and Sensor Size

my 2 cents.

"DoF is controlled by four factors;the actual "f-stop" at which the picture is taken, the focal length of the length being used,the size of the subject being photograped, and the distance between camera and the subject"
------------------ John Shaw

If all the parameters except focal length are same, then a 50mm lens on a camera which has 1.6 crop factor produces exact same FoV as a 80mm lens on a FF body.So here only difference is the focal length of the lens being used.
Now as per the above definition , longer the focal length, narrower the DoF.

Does it make any sense

Edited by rcmanoj on Aug 16, 2005 at 04:39 AM GMT

Aug 16, 2005 at 04:20 AM

jdaily
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p.8 #19 · DOF and Sensor Size

I'm going to start a pool on when this thread will finally die. However, while it's still alive...

What in the world does the size of the subject being photographed have to do with the depth of field? And as much as I admire Mr. Shaw, he seems to be making the same oversight that has contributed to much of the controversy in this thread: the relationship between circle of confusion, film size, and print size.

Anyway, setting that aside, yes, Manoj, that's why crop cameras have a larger depth of field when the field of view is otherwise identical.

Aug 16, 2005 at 04:36 AM

nsbca
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p.8 #20 · DOF and Sensor Size

rcmanoj wrote:
my 2 cents.

rcmanoj wrote:

If all the parameters except focal length are same, then a 50mm lens on a camera which has 1.6 crop factor produces exact same FoV as a 80mm lens on a FF body.So here only difference is the focal length of the lens being used.

Actaully if you are going on that track it would be closer to a 63mm lens and there would be more different about the resultng image then just saying what focal length you used. The light from a 50mm and a 63mm lens travel at different angles and thus would affect the aestetics of the image. And then again that furmula only works if both images are printed and viewed the same size and from the same distance.

Aug 16, 2005 at 04:39 AM

rcmanoj
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p.8 #21 · DOF and Sensor Size

jdaily wrote:
I'm going to start a pool on when this thread will finally die. However, while it's still alive...

Only after everyone owns a FF camera

Aug 16, 2005 at 04:42 AM

jdaily
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p.8 #22 · DOF and Sensor Size

63mm? 50 * 1.6 = 80. Where did 63 come from?

Aug 16, 2005 at 04:43 AM

nsbca
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p.8 #23 · DOF and Sensor Size

jdaily wrote:
63mm? 50 * 1.6 = 80. Where did 63 come from?

That's not how the DOF formula works.

A FF sensor is not 1.6 times larger then a 1.6 crop sensor in area. The full frame is more then twice as large, so applying the 1.6 directly to the lens will not get you the correct FOV.

Edited by nsbca on Aug 15, 2005 at 10:54 PM GMT

Aug 16, 2005 at 04:44 AM

rcmanoj
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p.8 #24 · DOF and Sensor Size

rcmanoj wrote:

The size of the subject? Where did that come from

From "Landscape photography" by John Shaw.

Did I get a bad "copy" of the book

Aug 16, 2005 at 04:46 AM

jdaily
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p.8 #25 · DOF and Sensor Size

I have 3 of his books, and only in "Landscape Photography" does he make that statement. I think he was trying to say image size, because image size pops up again (rather obscurely) about 5 paragraphs later. Or...

In "Closeups in Nature", he says this:

If the image size and the aperture remain the same, all focal-length lenses give the same depth of field...If you photograph a subject at life-size with a 50mm lens and then move back and photograph it again at life-size with a 200mm lens at the same f-stop, the depth of field will be the same.

Perhaps that's where he was headed with "size of the subject" in "Landscape Photography".

Aug 16, 2005 at 04:59 AM


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