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Thread started 10 Feb 2013 (Sunday) 16:55
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Why does FF yield shallower DOF?

 
Charlie
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Feb 12, 2013 10:00 |  #136

Canon_Lover wrote in post #15601565 (external link)
Like I said. You guys are going off topic here. Print size and viewing distance have nothing to do with the full frame vs. crop question. That is entirely something of resolution. Since a crop sensor "may" have more MP density, then your assumptions of another topic would be correct. In the case of the d800 and a 15mp crop camera, there is no difference in COC, when every other factor is equal and the d800 is cropped to 15mp in post.

I got to agree with this. While statements of print sizes and perceived DOF are true, it's veering offtopic BADLY and this topic takes a bit of understanding before you can tackle that one. It's sending mixed signals IMO. Large print vs small print is no longer apples to apples comparisons... might as well be comparing color depth and resolution at that point.


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Feb 12, 2013 10:09 |  #137

TSchrief wrote in post #15595568 (external link)
The only DOF that can possibly matter is the body/lens/aperture and focal distance you are working with right now. Very few of us shoot two cameras simultaneously. I would guess ZERO. What is happening to a camera/lens system you are not using will have very little impact on the photo you are currently taking.

I don't shoot with two cameras simultaneously, but I do have two cameras with me almost all of the time. As soon as a subject appears, I assess the situation and try to envision the type of image I want to make at that time. Then I make a decision as to whether I want more DOF, or shallower DOF. I then switch bodies (rather than switching lenses) to best achieve the look I am going for.

The above, of course, applies only to situations in which I can "work the subject" and change my position so as to frame an image the same way with a FF body and a 1.6 crop.

The difference in DOF between FF and crop is not irrelevant at all - rather, it is a factor that I take into consideration every day I shoot.


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Feb 12, 2013 11:30 |  #138

Charlie wrote in post #15601760 (external link)
I got to agree with this. While statements of print sizes and perceived DOF are true, it's veering offtopic BADLY and this topic takes a bit of understanding before you can tackle that one. It's sending mixed signals IMO. Large print vs small print is no longer apples to apples comparisons... might as well be comparing color depth and resolution at that point.

It's not "Large print vs small print," it's "lesser enlargement vs more enlargement," which is definitely a factor any time one is discussing differences in depth of field between two formats that will require different degrees of enlargement to a common final display size. The 15x22 format requires ~1.6x the enlargement of the 24x36mm format to reach the same final display size.

No discussion of depth of field is accurate or complete without a common premise of the degree of enlargement to the final display size. Unfortunately, that common premise is so old that most people today don't even seem to know that it exists and what it means.


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Feb 12, 2013 12:25 |  #139
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JeffreyG wrote in post #15601372 (external link)
The example I give when tutoring my kids in significant figures is thus:

I have a circle with a radius of about 3 inches. What is the best answer for the area of this circle:
A - 28.27431 square inches
B - 27 square inches
C - 30 square inches

The best answer is C, becuase it (which can be written as 3 x 10) does not imply any more knowledge of the radius than we have.

Please, allow me to add to the confusion. If the circle measured 3.00 inches, the area would be correctly reported as 28.3 square inches. A similar bit of confusion has take over this thread.


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Feb 12, 2013 12:35 |  #140

TSchrief wrote in post #15602259 (external link)
Please, allow me to add to the confusion. If the circle measured 3.00 inches, the area would be correctly reported as 28.3 square inches. A similar bit of confusion has take over this thread.

I am sorry but it is a test, you don't get to add your own answers. :lol:


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Feb 12, 2013 12:35 as a reply to  @ TSchrief's post |  #141

You missed the point of the exercise. A circle with radius 3 can be anywhere from 2.50 to 3.49. When you answer 28.3 you imply you know the radius with much more accuracy than you do. You cannot assume the radius is 3.00.


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Feb 12, 2013 12:36 |  #142

TSchrief wrote in post #15602259 (external link)
Please, allow me to add to the confusion. If the circle measured 3.00 inches, the area would be correctly reported as 28.3 square inches. A similar bit of confusion has take over this thread.

He said "about 3 inches." Any answer that implies any greater precision than suggested by the word "about" is misleading.

And that is the problem in this discussion--people are presuming decimal-point precision for a concept based on "about."


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Feb 12, 2013 12:43 |  #143

TSchrief wrote in post #15602259 (external link)
Please, allow me to add to the confusion. If the circle measured 3.00 inches, the area would be correctly reported as 28.3 square inches. A similar bit of confusion has take over this thread.

How do you know that is correct? You don't have enough information to say that the correct answer for the area is 28.3

You just failed the test that question was for.




  
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Feb 12, 2013 12:48 as a reply to  @ sandpiper's post |  #144

Darn it!...Measure that radius more accurately.:lol:


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Feb 12, 2013 18:40 |  #145
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RDKirk wrote in post #15602299 (external link)
He said "about 3 inches." Any answer that implies any greater precision than suggested by the word "about" is misleading.

And that is the problem in this discussion--people are presuming decimal-point precision for a concept based on "about."

sandpiper wrote in post #15602321 (external link)
How do you know that is correct? You don't have enough information to say that the correct answer for the area is 28.3

You just failed the test that question was for.

28.3 is correct. Google "significant figures'. 3.00 is HUGELY different than 3. It is 100 times more precise, to be exact.


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Feb 12, 2013 18:45 |  #146

TSchrief wrote in post #15603542 (external link)
28.3 is correct. Google "significant figures'. 3.00 is HUGELY different than 3. It is 100 times more precise, to be exact.

And where did you invent 3.00 from? Google that if you can.


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Feb 12, 2013 18:56 |  #147

TSchrief wrote in post #15603542 (external link)
28.3 is correct. Google "significant figures'. 3.00 is HUGELY different than 3. It is 100 times more precise, to be exact.

He didn't say "3.00," he said "about 3 inches."

This is the same thing you did before--invent an argument by inventing the point you're arguing against. That's called a "knocking down a strawman."


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Feb 12, 2013 19:04 |  #148

SkipD wrote in post #15599477 (external link)
The depth of field WILL change when using different format cameras when both have the same focal length lens, same camera-subject distance, and same aperture settings. The reason is a point that most folks checking into this thread (and most similar threads) are totally missing is that depth of field is not analyzed at the film/sensor plane inside the camera.

ALL depth of field analysis is done with a standard-sized print which is viewed at a standard distance (the size and distance are defined by the person creating the formula for the calculation). Thus, the different sized in-camera images from different format cameras (format refers to the size of the film frame or sensor in a camera) must be enlarged (magnified) by different amounts to fill the same standard print. If two different format cameras were used to make test shots with the same subject distance, same focal length, and same aperture, the IN-CAMERA blurs for out-of-focus points would be the same. After printing the images, though, the same blurs would be larger from the smaller format camera as compared to the ones from the larger format camera. There is a difference.



While I am clear what you are saying, you did not read my entire sentence, even though you highlighted it.

EDIT: your speaking of an untouched (uncropped) version of both then? If so it is irrelevant because it was not 2nd question the OP asked, which your scrutinizing my answer to.


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Feb 12, 2013 19:11 |  #149

TSchrief wrote in post #15603542 (external link)
28.3 is correct. Google "significant figures'. 3.00 is HUGELY different than 3. It is 100 times more precise, to be exact.

Yes, but the radius isn't 3.00 inches (or 3 inches) it is "about 3 inches". It may be 2.8" or 3.2" we don't know. I don't agree that it is "100 times more precise" either. Mathematically "3" and "3.00" are exactly the same, but it may be assumed that "3" is rounded off whereas "3.00" is less likely to be.

Once again though, somebody has asked a question and you have invented your own question and answered that instead. Then used THAT answer to tell everybody they got the answer to the ACTUAL question wrong.

Your answers are correct, but only to the questions that you have invented, they don't apply to the real questions under discussion. Nobody posed the question "what is the area of a circle with radius 3.00 inches"?

I have to assume that you are just trolling (and have been assuming that now for some time).




  
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Why does FF yield shallower DOF?
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