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03-16-2016, 02:43 PM - 1 Like   #61
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QuoteOriginally posted by 2351HD Quote
How on earth will you see less depth of field. It's the same lens, same aperture on the same sensor. It won't change one bit.

Where you people get this rubbish from is beyond me.

This is out of control.
If it makes you feel better, you're not the first to be incredulous re this, happens al the time, and probably the majority of people (to some degree) doubt it at first... But it's true. Cropping (and enlarging the crop) changes the DOF. You can test this yourself with one camera, and there are several good examples out there on the fora.

03-16-2016, 03:13 PM   #62
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QuoteOriginally posted by jsherman999 Quote
Cropping (and enlarging the crop) changes the DOF
If the image has already been taken, how can this be so?
03-16-2016, 03:21 PM   #63
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QuoteOriginally posted by rawr Quote
If the image has already been taken, how can this be so?
That's right. DOF is created at the time of capture, not after.
03-16-2016, 03:23 PM   #64
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QuoteOriginally posted by rawr Quote
If the image has already been taken, how can this be so?
Did you read my last post?

Because everything is about perception. And this does change with moving closer or farther away and its equivalent of enlarging after cutting it down/cropping.

03-16-2016, 03:23 PM   #65
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QuoteOriginally posted by rawr Quote
If the image has already been taken, how can this be so?
DoF also depends on print/viewing size. If you crop and enlarge-> you're changing the size this cropped area is being viewed.

An example I've posted before: https://www.pentaxforums.com/forums/169-pentax-full-frame/240468-dof-ffs-aps-...ml#post2553553
03-16-2016, 03:28 PM   #66
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QuoteOriginally posted by 2351HD Quote
That's right. DOF is created at the time of capture, not after.
Wrong, actually. DOF is a perceptual measure, and your ability to perceive areas as acceptably in focus or not changes depending on the enlargement of the image. Thus, when you crop an image, and enlarge the crop to the match the same viewing size as the uncropped version, the DOF of the image will be 'less' in that some areas which you perceived to be acceptably in focus in the uncropped image will no longer be so.

An example of a decent demonstration of this is here: DOF and cropping/enlargement: Open Talk Forum: Digital Photography Review

Of course, this point is not terribly practical, since most would agree that the change in image composition when cropping is MUCH more apparent than the different DOF and renders close comparison between the cropped vs. uncropped images rather difficult!
03-16-2016, 03:29 PM   #67
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You may be able to change the way in which you perceive the depth of field by viewing the image at a shorter or greater distance, or by viewing it a little larger. BUT you haven't changed a thing by cropping it. It's the same image.
03-16-2016, 03:35 PM - 3 Likes   #68
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QuoteOriginally posted by 2351HD Quote
You may be able to change the way in which you perceive the depth of field by viewing the image at a shorter or greater distance, or by viewing it a little larger. BUT you haven't changed a thing by cropping it. It's the same image.
In a certain way, yes, you have not changed to image. But DoF is not a direct property of an image.
It's a result of your perception only.
That is why anybody seriously discussing absolute DoF measures also MUST state that this applies only at a certain viewing distance and at a certain definition of "acceptably sharp".
Without these perception related parameters there is just no way to measure "DoF"

edit:
To an eagle the DoF of the same image is much smaller than it's to you. And the eagle will think the image is much more noisy than you think.

03-16-2016, 03:36 PM   #69
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QuoteOriginally posted by 2351HD Quote
You may be able to change the way in which you perceive the depth of field by viewing the image at a shorter or greater distance, or by viewing it a little larger. BUT you haven't changed a thing by cropping it. It's the same image.
Ah, but you HAVE changed your perception of the image, and since DOF is a perceptual measure it is also changed. The fundamental thing is to realize that DOF is defined in terms of perception of acceptably sharp or 'in focus' areas, thus if your perception of these areas changes (such as by cropping/enlarging), so does DOF.
03-16-2016, 03:37 PM   #70
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QuoteOriginally posted by 2351HD Quote
How on earth will you see less depth of field. It's the same lens, same aperture on the same sensor. It won't change one bit.

Where you people get this rubbish from is beyond me.

This is out of control.
Yup. It does not change.
People have no idea what they are taking about, or do not know what you are talking about and are easily confused.

You will hear all these people shut up pretty quick when they buy their magical FF cameras and realize they tossed $1800 on something that does not work the way they think it will.
Their loss.

I mean it isn't difficult It is basic 5th grade physics


---------- Post added 03-16-16 at 06:40 PM ----------

QuoteOriginally posted by 2351HD Quote
You may be able to change the way in which you perceive the depth of field by viewing the image at a shorter or greater distance, or by viewing it a little larger. BUT you haven't changed a thing by cropping it. It's the same image.
Yup.
Light comes out of the lens obeying physical laws. The object and size of object (sensor) on which it falls does not change those laws.

It is only what changes after capture, or before light falls onto the object (sensor) that changes DOF.
(slight variance of pixel density and technical details of per-pixel capture not withstanding course)

Last edited by amoringello; 03-16-2016 at 03:44 PM.
03-16-2016, 04:05 PM - 2 Likes   #71
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QuoteOriginally posted by amoringello Quote
I mean it isn't difficult It is basic 5th grade physics
You are right, it is not terribly difficult, but it does require a little bit of reading to understand how DOF is defined. If you read the following two links which explain how to use equations to estimate DOF, you will see that one of the variables in any of the equations for DOF is 'c' which represents the size of the circle of confusion which in turn varies with image format (assuming the same viewing size). When you crop an image, you are changing the image format being used to capture or represent the image, so DOF changes because 'c' changes.

https://en.wikipedia.org/wiki/Depth_of_field#DOF_formulae

https://en.wikipedia.org/wiki/Circle_of_confusion#Circle_of_confusion_diamet...in_photography
03-16-2016, 04:11 PM   #72
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QuoteOriginally posted by crussellsprout Quote
DOF is a perceptual measure
And I guess focus is perceptual too ... since an image can look more in focus if you stand 5 metres away, rather than looking at it 30 cms from your computer screen.

Time to throw away my LensAlign focus tester. Just need to make sure everyone stands a long distance away from anything I display or print.
03-16-2016, 04:26 PM - 1 Like   #73
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QuoteOriginally posted by rawr Quote
And I guess focus is perceptual too ... since an image can look more in focus if you stand 5 metres away, rather than looking at it 30 cms from your computer screen..
Critical focus? As in the placement of the plane of focus? No, that's not perceptual.

"Acceptably in-focus/sharp" is what DoF is measuring and this is very much perceptual, made into some handy numbers after we've agreed on some assumptions about viewing distance, eyesight, print size, etc. and what circle of confusion we're willing to accept as 'acceptably sharp'.

How do you define DoF? The same as the wikipedia links above? If not, I'd love to hear your definition, and please be as precise as possible.
03-16-2016, 04:53 PM   #74
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Wouldn't the chroma (colour) noise be better on the K1 just because it's a better sensor all other things being equal?

Randy
03-16-2016, 05:12 PM   #75
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QuoteOriginally posted by crussellsprout Quote
When you crop an image, you are changing the image format being used to capture or represent the image, so DOF changes because 'c' changes.
This comment shows that you are not understanding the most basic concept of the issue.

You are exactly correct... but with that it has no bearing on the initial post.
If you change things, things change. Pretty much a no-brainer!

Stop making it out to be more complex than it is. We're not cropping. we're not enlarging.
I have no idea where the concept of enlarging or cropping ever came in, except that FF zealots want to bring in "equivalence" to try to prove a point but they forget that it requires that some aspect needs to change. And that will of course change the results.
But AGAIN, that has NO relevance to the initial post.

Last edited by amoringello; 03-16-2016 at 05:20 PM.
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