Depth of field (DOF) does NOT change with sensor size

[WayneF]

@WayneF

Ok, your first post in this thread lost me. I am way to dense or you packed in to much info into a a short post. (I hope the latter more then the former).
I got lost when you jumped between the CoC and enlargement of the crop sensor. Any chance for a breakdown for dummies?

Tim

Hi Tim. I think I understand the question, but not fully sure what precise point the question is about. I do wish I knew which sentence needs clarification, but will try again as follows:

OK, just to have a number, here speaking of a full frame 35 mm film frame, with classic CoC of 0.03 mm diameter. That hypothetical 0.03mm standard is from the lens, and presumed present on the sensor image (not yet enlarged). We compute Depth of Field distance limits using that CoC diameter, and the lens parameters (focal length and aperture and focus distance), and the required sensor size enlargement to 8x10 inches (8x10 inches was just an arbitrary choice for DOF calculations many decades ago, it had to have a number too).

That 0.03mm CoC was historically tested and declared to be the maximum limit (when on the full frame sensor) of what how much out-of-focus blur diameter can still be enlarged (by our sensor size enlargement) to still be acceptable when enlarged (larger diameter should be generally perceptible to our eye, but we say our eye cannot perceive less than 0.03 mm size when it is enlarged that much).

Because when we enlarge the sensor image to print an 8x10 inch print, that enlargement also increases the blur size, and the 0.03 mm diameter limit, to something larger (this full frame enlargement is near 9x larger), which then the previous 0.03 mm becomes about the size that our normal eye vision can probably detect as blur being present. Seeing that blur becomes objectionable, which is why we defined that 0.03 mm maximum size. If we instead had a smaller sensor, then there would have been an appropriate smaller CoC. The blur can grow larger of course, further out of focus, but it becomes unacceptable if it does.

Depth of Field computes the distance limits where this viewing enlargement increases the 0.03 mm CoC limit diameter to be large enough for our eye to perceive its presence.

If the distance is within the DOF limit distances, it means the blur there is less than 0.03mm on the sensor. If outside the limits, the blur is worse. Of course, at any reasonable distance, there would really be no practical difference between one inch inside and one inch outside, it changes gradually across the boundary, but the math computes the precise hard boundary line.

I hope that was the question.

 

[Ysarex]

@Tim, this might help:

Next a smaller aperture:

Next closer focus:

Joe

 

[Tim Tucker 2]

@WayneF

Ok, your first post in this thread lost me. I am way to dense or you packed in to much info into a a short post. (I hope the latter more then the former).
I got lost when you jumped between the CoC and enlargement of the crop sensor. Any chance for a breakdown for dummies?

Tim

I'm not disagreeing with Wayne here, just using different words.

We asked the question as photographers about the limits of perceived sharpness ages ago. So they got a 10"x 8" print and asked, "how big does a dot have to be before it begins to look like a blur." What they were asking is how out of focus, or how blurred does a single point of focus have to be before we notice it as being out of focus on a 10"x 8" print.

When we had the answer it was a simple maths question to work out how big that dot had to be on the sensor to produce that dot on the finished print, basically divided it by the magnification factor. This is the circle of confusion size or CoC on the sensor. The constant is the size of this dot on a 10"x 8" print, it varies by sensor size because of the enlargement needed on smaller sensors to make a 10"x 8" print.

 

[WayneF]

I like this picture of CoC from Wikipedia. Focus is S1. Blur C at distance S2 on left is CoC on sensor at c on right.

 

[Christie Photo]

I confess I haven't CLOSELY read through all of the above, but I don't recall a single mention of a "normal lens."

I wonder if that's what causing all the confusion.

Those of us who used a variety of film cameras (old guys), know the normal focal length of a lens changes with the format of the camera. AND since the vast majority of the camera market was not (and still isn't) the pros, most discussion about lenses refereed to 35mm cameras. Oddly, it still does... at least a bit. Thus the terms "full frame" and "crop sensor." These terms are relative to 35mm photography. One sensor is simply a different "format" than the other.

A normal lens is one that approximates what we usually see with our eyes. The focal length of a normal lens differs from format to format. I seldom hear the term used anymore.

A normal lens for a 35mm camera is something like 47mm (most cameras were equipped with a 50mm or 55mm. A normal lens for a square format 12o camera (6x6) is about 80mm. And a normal lens for a 4x5 camera is about 6" (150mm).

So could this be contributing to the debate? Hmmm.

-Pete

 

[WayneF]

So could this be contributing to the debate? Hmmm.

Yes, it is nothing new, it was indeed the same thing with film cameras. We called the difference Film Format then, instead of Crop Factor.

Different sensor sizes or film sizes do have different "normal" lenses (with their focal length more or less considered approximately equal to the sensor or film diagonal dimension), but not sure that "normal" otherwise really relates here, other than DOF does depend on focal length (as one factor), .

The "normal" focal length means they all give about the same normal photo view, about like we remember our eye saw, as you said. But yes, to do that, the tiny sensors do have very short lenses, and larger sensors have longer lenses.

Zoom lenses are about universal now, and do strongly affect the field of view, so "normal" has lost much meaning today. The "regular" zooms should have one setting that could be called Normal, but we may not be aware of it today.

And another difference in this era is that the usual Equivalent Lens discussion is about DSLR with two bodies of two sensor sizes (full frame and cropped) which can both accept the same interchangeable lens. The different sensor size then causes the questions when using the same lens on both sensors. The Equivalent questions can get funny until they realize that a 50 mm lens is always 50 mm on any sensor, only the field of view changes with the sensor size. But the Equivalent lens is mounted on the other full frame camera, if we are used to thinking in those terms.

Normal lens is more a moot point for compacts and phones, because they don't have interchangeable lenses. There is no choice about lenses, other than the one built into the camera, so the camera simply does what it does. Compacts have zooms, and phones seem a bit wide. Many film cameras also did not have interchangeable lenses. Those that did then generally could not accept lenses for other frame sizes, so the question didn't arise that often (OK, view cameras could be an exception).

 

[bhop]

Technically speaking, maybe not, but visually yes. IMO photography is based on visuals, not charts and numbers.

 

[Ysarex]

Tim, Petrochemist, Braineack, Wayne, Derrel, et al. It looks like we're all wrong after all.

Here's a new one making the rounds and the evidence against us is just too overwhelming:



Joe

 

[bhop]

Tim, Petrochemist, Braineack, Wayne, Derrel, et al. It looks like we're all wrong after all.

Here's a new making the rounds and the evidence against us is just too overwhelming:



Joe

Darn it!

 

[donny1963]

every lens made on earth craps out the same light same bokah same everything regardless of what sensor it is used on.
a 50 mm lens will output the same thing on a crop sensor vs a full frame or med format camera..
same everything nothing changes.. except the CROP!!!!! smaller sensors that same lens will zoom in a bit according to the crop, but WILL NOT CHANGE THE DOF!!!!
the only time the DOF will change is if you step back to get the same focal length on the crop sensor vs you doing it on a full frame sensor that is the only way DOF WILL CHANGE,
you would have to change your distance to the subject that would change the DOF but it's not the Sensor that changes it, if your in the same exact position taking the shot on larger sensors vs smaller sensors the DOF WILL NOT CHANGE!!!
that is an undeniable fact period!!!!
now matter how you slice it... SORRY, but many people are under the illusion that DOF changes but, fact is it doesn't just like larger sensors do not gather more light then crop sensors.
this is another misconception fallacy that people think larger sensors gather more light, NO they don't, they are not solar panels they don't work the same as solar panels..
OMG!!!!!!!!!!!!!!!!!!!!!!!!

So I take it you couldn't be bothered to go test it yourself?


Would you believe B&H?

Depth of Field, Part III: The Myths

they even show the math and examples... [there's also a video, but the girl doesn't just tell and actually explains things, so you might not be able to follow along.]

and just because I know you won't be bothered to actually click the link and learn:

borrowed from the above link.

So, at 5.9' and an aperture of f/2.8, there is a 2.9" difference in the total DOF for the two different sensors (almost 1.5" on the near and far side). The APS-C camera has a shorter DOF when using the same lens at the same aperture and distance.

not shockingly [for us, not you], the 50mm Crop vs FF shot, the DOF is completely different and the crop sensor has much better background blur as result. You can clearly see the crop sensor shot is NOT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! the same image as the FF just cropped in -- you can see the crop sensor is doing a better job of blurring out the metal fence posts here.

what are you trying to imply that i would not be able to follow?
really?

also this does not disprove that DOF does not change when you take the same shot with the same lens and same distance using both a crop sensor camera and then full frame or even medium format, ..
DOF does not change, the crop changes, but not the DOF the DOF is exactly the same a 50 mm lens craps out the same amount of DOF on both a crop sensor camera and a full frame camera, the only thing that changes is the crop of course, but the lens still works the same way as far as DOF goes.. Period & FACT!!!!!!!

 

[Ysarex]

every lens made on earth craps out the same light same bokah same everything regardless of what sensor it is used on.
a 50 mm lens will output the same thing on a crop sensor vs a full frame or med format camera..
same everything nothing changes.. except the CROP!!!!! smaller sensors that same lens will zoom in a bit according to the crop, but WILL NOT CHANGE THE DOF!!!!
the only time the DOF will change is if you step back to get the same focal length on the crop sensor vs you doing it on a full frame sensor that is the only way DOF WILL CHANGE,
you would have to change your distance to the subject that would change the DOF but it's not the Sensor that changes it, if your in the same exact position taking the shot on larger sensors vs smaller sensors the DOF WILL NOT CHANGE!!!
that is an undeniable fact period!!!!
now matter how you slice it... SORRY, but many people are under the illusion that DOF changes but, fact is it doesn't just like larger sensors do not gather more light then crop sensors.
this is another misconception fallacy that people think larger sensors gather more light, NO they don't, they are not solar panels they don't work the same as solar panels..
OMG!!!!!!!!!!!!!!!!!!!!!!!!

So I take it you couldn't be bothered to go test it yourself?


Would you believe B&H?

Depth of Field, Part III: The Myths

they even show the math and examples... [there's also a video, but the girl doesn't just tell and actually explains things, so you might not be able to follow along.]

and just because I know you won't be bothered to actually click the link and learn:

borrowed from the above link.

So, at 5.9' and an aperture of f/2.8, there is a 2.9" difference in the total DOF for the two different sensors (almost 1.5" on the near and far side). The APS-C camera has a shorter DOF when using the same lens at the same aperture and distance.

not shockingly [for us, not you], the 50mm Crop vs FF shot, the DOF is completely different and the crop sensor has much better background blur as result. You can clearly see the crop sensor shot is NOT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! the same image as the FF just cropped in -- you can see the crop sensor is doing a better job of blurring out the metal fence posts here.

what are you trying to imply that i would not be able to follow?
really?

also this does not disprove that DOF does not change when you take the same shot with the same lens and same distance using both a crop sensor camera and then full frame or even medium format, ..
DOF does not change, the crop changes, but not the DOF the DOF is exactly the same a 50 mm lens craps out the same amount of DOF on both a crop sensor camera and a full frame camera, the only thing that changes is the crop of course, but the lens still works the same way as far as DOF goes.. Period & FACT!!!!!!!

This does prove you're wrong. Go ahead and post a link to any DOF calculator that proves you're right. You can't because you're proven wrong.

Joe

 

[donny1963]

Tim, Petrochemist, Braineack, Wayne, Derrel, et al. It looks like we're all wrong after all.

Here's a new one making the rounds and the evidence against us is just too overwhelming:



Joe

there you go that proves what i said, if your standing in the exact same place, feet glued to the floor using the same lens it won't matter if your shooting with a crop sensor full frame or even medium format Sensor size has nothing to do with DOF NOTHING!!!!
it doesn't not change it a bit, your just recording the same exact thing on a larger recording sensor that is it..
people get confused saying the DOF changes using full frame vs crop sensor because they are re-positioning them self to get the same composition of the shot.
so naturally the DOF will change if you change your distance because on smaller crop sensors vs larger sensors, they have to move further back to get the same fame shot so they are getting a different DOF But it has nothing to do with the sensor at all where the DOF changes only because they are a different distance.....

 

[donny1963]

every lens made on earth craps out the same light same bokah same everything regardless of what sensor it is used on.
a 50 mm lens will output the same thing on a crop sensor vs a full frame or med format camera..
same everything nothing changes.. except the CROP!!!!! smaller sensors that same lens will zoom in a bit according to the crop, but WILL NOT CHANGE THE DOF!!!!
the only time the DOF will change is if you step back to get the same focal length on the crop sensor vs you doing it on a full frame sensor that is the only way DOF WILL CHANGE,
you would have to change your distance to the subject that would change the DOF but it's not the Sensor that changes it, if your in the same exact position taking the shot on larger sensors vs smaller sensors the DOF WILL NOT CHANGE!!!
that is an undeniable fact period!!!!
now matter how you slice it... SORRY, but many people are under the illusion that DOF changes but, fact is it doesn't just like larger sensors do not gather more light then crop sensors.
this is another misconception fallacy that people think larger sensors gather more light, NO they don't, they are not solar panels they don't work the same as solar panels..
OMG!!!!!!!!!!!!!!!!!!!!!!!!

So I take it you couldn't be bothered to go test it yourself?


Would you believe B&H?

Depth of Field, Part III: The Myths

they even show the math and examples... [there's also a video, but the girl doesn't just tell and actually explains things, so you might not be able to follow along.]

and just because I know you won't be bothered to actually click the link and learn:

borrowed from the above link.

So, at 5.9' and an aperture of f/2.8, there is a 2.9" difference in the total DOF for the two different sensors (almost 1.5" on the near and far side). The APS-C camera has a shorter DOF when using the same lens at the same aperture and distance.

not shockingly [for us, not you], the 50mm Crop vs FF shot, the DOF is completely different and the crop sensor has much better background blur as result. You can clearly see the crop sensor shot is NOT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! the same image as the FF just cropped in -- you can see the crop sensor is doing a better job of blurring out the metal fence posts here.

what are you trying to imply that i would not be able to follow?
really?

also this does not disprove that DOF does not change when you take the same shot with the same lens and same distance using both a crop sensor camera and then full frame or even medium format, ..
DOF does not change, the crop changes, but not the DOF the DOF is exactly the same a 50 mm lens craps out the same amount of DOF on both a crop sensor camera and a full frame camera, the only thing that changes is the crop of course, but the lens still works the same way as far as DOF goes.. Period & FACT!!!!!!!

This does prove you're wrong. Go ahead and post a link to any DOF calculator that proves you're right. You can't because you're proven wrong.

View attachment 166131
Joe

your video you just posted proves what i sand and disproves what you said lol

 

[donny1963]

Technically speaking, maybe not, but visually yes. IMO photography is based on visuals, not charts and numbers.

Technically and visually, what i said was 100% correct how could the sensor size have anything to do with changing DOF Except for some one who would step a few feet back to get the same shot as they got with the full frame, while uing crop sensor. that is the only reason DOF changes has nothing to do with the sensor size..
Sensor size will not change anything..

 

[Ysarex]

Tim, Petrochemist, Braineack, Wayne, Derrel, et al. It looks like we're all wrong after all.

Here's a new one making the rounds and the evidence against us is just too overwhelming:



Joe

there you go that proves what i said, if your standing in the exact same place, feet glued to the floor using the same lens it won't matter if your shooting with a crop sensor full frame or even medium format Sensor size has nothing to do with DOF NOTHING!!!!
it doesn't not change it a bit, your just recording the same exact thing on a larger recording sensor that is it..
people get confused saying the DOF changes using full frame vs crop sensor because they are re-positioning them self to get the same composition of the shot.
so naturally the DOF will change if you change your distance because on smaller crop sensors vs larger sensors, they have to move further back to get the same fame shot so they are getting a different DOF But it has nothing to do with the sensor at all where the DOF changes only because they are a different distance.....

So you didn't actually look at the DOF examples I posted?! Here I'll post it again:

Notice the subject distance for both cameras. It's 10 feet for both -- no distance change. Same f/stop for both and same lens focal length for both. The only change is the sensor size from FF to crop and the DOF changes.

You are proven wrong by your own criteria.

Joe