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04-02-2014, 09:23 PM   #76
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Jsherman has already expertly put this to bed with his excellent selection of images at different crop factors.


These images show categorically that depth of field dos not alter as crop alters, the depth of field remains exactly the same in absolute terms. But are we talking absolute depth in millimetres/inches, or are we talking depth within the image when we speak of depth of field?


The depth of perceived focus in the image does change, yes thats a made up term.


The in-focus areas appear to be shallower and the out of focus areas appear to grow when moving up towards FF.


Whats happening is the depth of acceptable focus - DOF, stays exactly the same, but due to crop factor, the perceived amount of surrounding "out of focus areas" either increases or reduces with changes in crop factor.


A FF image will natively display images with greater out of focus areas than an APS-C image would display with the same lens at the same focussing distance.


This can be emulated quite easily by cropping an image, if you take an image with shallow depth of field, and crop everything away that's out of focus, have you just altered the DOF characteristics of either the lens or the sensor?


No you haven't. But the "appearance" of the DOF in the image does however change. And isn't this what we really want.

04-03-2014, 03:40 AM - 1 Like   #77
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QuoteOriginally posted by jsherman999 Quote
You want to talk about noise? I thought you were trying to keep it to DOF only - you've made claims like that several times in this thread, should I quote you?
WTF? You're not even making sense.
Your totally bizarre set of lies, and changing of stories and typical trolling action is all fun and games, but quite honestly doing a disservice to this website.

Someone might actually come to this thread for help.
Hopefully they will not have to read through all of the idiocracy which you have filled within it.

Go stick your head in the ground if you must, but keep your false claims, convoluted logic and improper conclusions to yourself.
They are not helping anyone and it not fair to those looking for actual information.



---------- Post added 04-03-14 at 06:44 AM ----------

QuoteOriginally posted by Imageman Quote
Whats happening is the depth of acceptable focus - DOF, stays exactly the same, but due to crop factor, the perceived amount of surrounding "out of focus areas" either increases or reduces with changes in crop factor.


A FF image will natively display images with greater out of focus areas than an APS-C image would display with the same lens at the same focussing distance.
Although a bit of a backwards way to think about, it is mostly correct... only exception is that DOF is "Depth of Field" or "Depth of Focus", not "Depth of Out-Of-Focus". That would be DOOOF. Maybe a more fun thing to say, but it is not really the same thing and not interchangeable. But that way of looking at things certainly explains some of the arguments.

The Out Of Focus area is greater on a larger sensor because a greater area of the image circle is captured. But the actual In-Focus (i.e DOF) area remains the same, as does the image circle itself.

Last edited by amoringello; 04-03-2014 at 04:18 AM.
04-03-2014, 05:05 AM   #78
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QuoteOriginally posted by amoringello Quote
Although a bit of a backwards way to think about, it is mostly correct... only exception is that DOF is "Depth of Field" or "Depth of Focus", not "Depth of Out-Of-Focus". That would be DOOOF.
Please, lets not introduce "Depth of Focus" into this, it's not the same as Depth of Field. Abuse of terminology is why this thread exists in the first place.

QuoteOriginally posted by amoringello Quote
The Out Of Focus area is greater on a larger sensor because a greater area of the image circle is captured. But the actual In-Focus (i.e DOF) area remains the same, as does the image circle itself.
Hang on here, are you guys (not just you specifically) using the word 'area' here to refer an actual area that can be measured in mm^2?
04-03-2014, 05:29 AM   #79
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QuoteOriginally posted by Imageman Quote
Jsherman has already expertly put this to bed with his excellent selection of images at different crop factors.


These images show categorically that depth of field dos not alter as crop alters, the depth of field remains exactly the same in absolute terms. But are we talking absolute depth in millimetres/inches, or are we talking depth within the image when we speak of depth of field?


The depth of perceived focus in the image does change, yes thats a made up term.


The in-focus areas appear to be shallower and the out of focus areas appear to grow when moving up towards FF.


Whats happening is the depth of acceptable focus - DOF, stays exactly the same, but due to crop factor, the perceived amount of surrounding "out of focus areas" either increases or reduces with changes in crop factor.


A FF image will natively display images with greater out of focus areas than an APS-C image would display with the same lens at the same focussing distance.


This can be emulated quite easily by cropping an image, if you take an image with shallow depth of field, and crop everything away that's out of focus, have you just altered the DOF characteristics of either the lens or the sensor?


No you haven't. But the "appearance" of the DOF in the image does however change. And isn't this what we really want.
But this has nothing to do with depth of field. This is a compositional issue only.

Go back to a post I made a few days ago. The real issue with FF and cropped sensors is due to the change in magnification of foreground to background, when you change lenses to get the equal field of view while shooting from the same position. The shorter lens on the crop sensor has reduced background magnification compared to the FF arrangement, so the out of focus background is made up of smaller out of focus blobs,

The real issue is you can get the same basic results but you need to move the subject closer to the background by the crop factor, when using a shorter focal length on a cropped sensor.

The whole issue is one of understanding not APS-C vs FF itself

04-03-2014, 05:49 AM   #80
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QuoteOriginally posted by BrianR Quote
Please, lets not introduce "Depth of Focus" into this, it's not the same as Depth of Field. Abuse of terminology is why this thread exists in the first place.

Sure Depth of Field and Depth of Focus are not quite identical, but until you get into variations of where the sensor sits relative to the focal plane inside the camera. If your film/sensor plane is flat, parallel and stable (which I hope it is until you get to a bellows or similar body), it really has little or no bearing on the outcome or the discussion here-in.
I suppose tilt-shift lenses also cause similar discrepancies. So fair enough! Thank for pointing that out.

QuoteOriginally posted by BrianR Quote
Hang on here, are you guys (not just you specifically) using the word 'area' here to refer an actual area that can be measured in mm^2?
If your talking about the image circle itself, sure. The total geometric area (HxW) will remain constant.
Since the image circle is capturing a two dimensional representation of a three dimensional world, you can think of it that way. Generally one direction (let say height, for a typical landscape) will be an indication of the depth into the 3-d space. Thus "depth" of field. This Depth of Field does not change regardless of the total geometric area captured by a different sized sensor.

---------- Post added 04-03-14 at 08:54 AM ----------

QuoteOriginally posted by Lowell Goudge Quote
The real issue is you can get the same basic results but you need to move the subject closer to the background by the crop factor, when using a shorter focal length on a cropped sensor.

The whole issue is one of understanding not APS-C vs FF itself
And by adjusting one of the other primary properties of DOF to balance out, you get the same image.
You cannot change a single primary property of DOF (distance) and say that the sensor is "at fault".

FF v.s. APC has no bearing on what is happening to the light.
What I find ridiculous is the fact that some believe or are trying to pass on the idea that the size of the sensor changes how light behaves.

Last edited by amoringello; 04-03-2014 at 05:59 AM.
04-03-2014, 06:53 AM   #81
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No one is saying that the size of the sensor changes how light behaves.... or certainly not jsherman, who understands what is going on.
04-03-2014, 07:15 AM   #82
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QuoteOriginally posted by ElJamoquio Quote
No one is saying that the size of the sensor changes how light behaves.... or certainly not jsherman, who understands what is going on.
I've come to the conclusion amoringello has a reading-comprehension issue. He hasn't fully followed everything I've written, and can't come up with any factual refutation of anything. It's like he tunes out half way through a post he's reading and answers what he thinks it's saying, probably based on past arguments he's had on the subject. It becomes a wasted (or one-sided) effort to engage folks in good faith like that. (You would think I'd learn my lesson )
04-03-2014, 07:25 AM   #83
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QuoteOriginally posted by ElJamoquio Quote
No one is saying that the size of the sensor changes how light behaves.... or certainly not jsherman, who understands what is going on.
So what behavior is changing, if not light?
Last I checked, sensors in most common cameras collect light. There are not a lot of options.

04-03-2014, 07:28 AM   #84
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OMG,


This thread began by talking about Depth of Field, and I answered that.


I was talking about the depth of the area in the image that is in acceptable focus, and im being told that im not talking about the Depth of Field.


The depth in the image of the acceptably sharp area has always been called "Depth of Field" and has been since I cut my teeth developing printing and enlarging in 1966 and since I began as a photographer in 1958.


Has something changed since then? Wikipedia has Depth of Field as:-


"depth of field (DOF) is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image"


No thats my understanding of what Depth of Field means as well, and its what im talking about, and its what I thought this thread was about, - the distance in the image between nearest and farthest objects that appear to be acceptably sharp.


Does Wikipedia need to be corrected now, as well as all the past publications and instructionals on photography that cover this topic.


I also spoke of the areas in the image that are not in focus, which I called "out of focus areas", I called them "out of focus areas" because they are areas that are out of focus. I thought that was a reasonable name for them. It appears I was wrong on that as well.


Am I not speaking English? Is Depth of Field no longer the correct name for the area within the image which is acceptably sharp?


I wish these terms would stay the same.


Maybe someone would like to define this new term "Depth of Field" for me, because I clearly don't have a clue anymore what it means.


Or you guys haven't read what I wrote properly.


Are we talking about the area that appears to be in focus in an image or are we not.
04-03-2014, 07:39 AM   #85
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04-03-2014, 07:42 AM   #86
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Imageman, you're 100% correct in your prior posting...
QuoteQuote:
Whats happening is the depth of acceptable focus - DOF, stays exactly the same, but due to crop factor, the perceived amount of surrounding "out of focus areas" either increases or reduces with changes in crop factor.
But just because a larger out of focus area is captured by the larger sensor, you cannot infer that the in focus area changes or is necessarily perceived that way.

Last edited by amoringello; 04-03-2014 at 07:54 AM.
04-03-2014, 07:42 AM   #87
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QuoteOriginally posted by Lowell Goudge Quote
But this has nothing to do with depth of field. This is a compositional issue only.
There's a sub-issue in this thread that that was addressing - the question of whether or not cropping, and enlarging the crop affects the DOF in the image, or the percentage of picture height in 'acceptable focus' in the resulting image. And it does. No one is saying anything in the original image itself is changing, no linear measurements change between the focal plane and the range of acceptable focus or the range of acceptable focus (near & far) and the lens position. That can't change because of a crop, and no-one ever claims that it does. This is where some folks get all wound up, they don't actually understand what is being said, and when hey finally do they don't understand why it's important to say.

The reason it's important to point this out is that cropping and enlarging crops change several important things in the resulting image - and you as a photographer benefit from knowing that. Two other important things that change are image noise and DR** - and these facts also whip some people up into a frenzy, because they think you're saying that the sensor technology somehow changes with a crop, that there's somehow less DR or more noise coming off the sensor, which of course isn't what anyone is saying, ever. Cropping and enlarging that crop is what changes the image DR and noise, and DOF is affected the same way - with regard to noise and DR it's almost to the exact proportions if you had shot the scene with a crop camera in the first place, as long as the sensor efficiency are similar between the sensors of different sizes. (example: cropping a D800 shot 1.5x gives you almost exactly the same image a K5 would have taken natively with regard to DR & noise, and exactly the same DOF for the resulting cropped FOV - ie the image DOF would have been changed by the crop.)


This is a real issue that confuses people, and it actually helps you to know how exactly cropping is going to affect your resulting image, to keep you from being unpleasantly surprised later.. or to help you simulate something you can't do because you don't have the exact correct lens for the situation. It also can help you decide if buying a higher-MP FF camera and using your aps-c lenses on it in crop mode is going to be something that's acceptable to you until you get FF-capable lenses, or if that would be a waste of your money. (For example.)

** There are folks who think that all benefits a FF sensor can bring are retained when they crop - that the FF sensor still somehow always gives them the same noise and DR advantage (and even the same image DOF) when they crop the FF image and enlarge it to the same display size as the uncropped image. These folks would have benefited from this discussion before hitting 'add to cart' on that FF purchase, methinks


QuoteQuote:
The real issue is you can get the same basic results but you need to move the subject closer to the background by the crop factor, when using a shorter focal length on a cropped sensor.
You usually can, you simply have less options available with FOV/DOF combinations as your sensor size decreases - near the high-aperture end. In some cases, your options run out and you need to move & change perspective to get the desired DOF for that FOV... which probably isn't a big deal 90% of the time. In this example I wouldn't have had the option to move much.


QuoteQuote:
The whole issue is one of understanding not APS-C vs FF itself
Exactly. See my aps-c vs. 1/2.3'' example a few posts back - FF vs aps-c is just the idée de la journée, always.

.

Last edited by jsherman999; 04-03-2014 at 08:18 AM.
04-03-2014, 08:23 AM   #88
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QuoteOriginally posted by jsherman999 Quote
There's a sub-issue in this thread that that was addressing - the question of whether or not cropping, and enlarging the crop affects the DOF in the image, or the percentage of picture height in 'acceptable focus' in the resulting image. And it does. No one is saying anything in the original image itself is changing, no linear measurements change between the focal plane and the range of acceptable focus or the range of acceptable focus (near & far) and the lens position. That can't change because of a crop, and no-one ever claims that it does. This is where some folks get all wound up, they don't actually understand what is being said, and when hey finally do they don't understand why it's important to say.
And with that much we are in agreement.
But then you again go off into all this other stuff that has nothing to do with DOF.
Not that I necessarily disagree with any of it either, but it really is not related to the issue.
04-03-2014, 10:04 AM   #89
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04-03-2014, 10:07 AM   #90
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This has been answered many times by Jshermans excellent posts.


The depth of field does not alter as the sensor size alters.


What does alter is the amount of out of focus image shown around the in focus area.


Whats really going on?


well lets say that the image circle from a FF lens is 40mm in diameter, and the in focus area is just the central 5mm of that 40mm area, then a full frame sensor would show massive amounts of out of focus detail surrounding a 5mm in focus area, thats because theres 10mm out of focus are above and 10 mm out of focus area below the 5mm in focus area.


That's just 20% of the image is in focus.


Put that same lens on an APS-C sensor, and the stats are the same, the in focus area is still 5mm the image circle cast by the lens is still 40mm in diameter, Nothing has changed.


However the sensor only sees a smaller area in the middle of that 40mm image, this time, the visible out of focus areas are 5mm above and 5mm below the in focus area, the rest of the out of focus area that the FF sensor recorded are outside the smaller sensor and are not recorded.


On this sensor 33% of the image is in focus.


It appears that the depth of field has increased on the APS-C sensor but it hasn't, its entirely due to cropping.


Put that same lens on a 4/3 sensor and the in focus area (DOF) expands to fill 38% of the frame.


This is not a real change to the Depth of Field, its a perceived change due to the sensor size magnifying the central portion of the image cast by the lens. "cropping" it.


If you could fit this lens onto a point and shoot sensor, the central in focus area would occupy 85% of the image.


On a mobile phone sensor, the sensor would be entirely within the in focus area, and the in focus area would occupy 100% of the image.


And here is the issue.


The real depth of field cast by the lens doesn't change, the definition of depth of field is:-
depth of field (DOF) is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image.


The definition doesnt care how much of the image if any is out of focus beyond this distance.


But the visible depth of field in the image does appear to change.


How else would you have 80% of the image out of focus on FF when the same image is 100% in focus in the smallest sensor.


This is not a compositional change, it is not a Depth of Field change, its a magnification change that alters the perceived depth of field.


It appears to be a real depth of field change, and compositionally it affects the image dramatically. And so must be treated artistically as a depth of field change.
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