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

[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!!!!!!!!!!!!!!!!!!!!!!!!

 

[Ysarex]

The amount of blur on the sensor doesn't change, but AFAIK no one actually views their pictures directly on the sensor. When you output images from small sensors you magnify them more so even without changing position or focal length DOF will change.
It also changes depending on how the images are viewed so the simplistic calculators that use a fixed circle of confusion for each sensor are not a great deal of help if they're not set up using the conditions your prints are viewed at. Pixel peepers need much sharper images (smaller coc) than those downsizing for the web or making the old 6x4 size prints.

the dept of field doesn't change, how ever the crop does change, that's the only thing the DOF does not change at all.. unless you use a different lens..

Wrong.

Proof:

View attachment 166045

Joe

Donny

First of all your comparing Digital to actual film..

Digital/film makes no difference and after all it was you who started this thread with "If you take a 50mm lens and attach it to a Crop sensor camera then also that saame lens then attach it to a Full Frame or Even Medium format camera..."

full frame or med format vs crop sensor doesn't matter DOF will not change.. Just because of Sensor Size..

Wrong.

Proof:

Joe

NOPE!!!!!!!

 

[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!!!!!!!!!!!!!!!!!!!!!!!!

If you repeat wrong and add a bunch of !!!!!!!!!!!!!!!!!! you have wrong!!!!!!!!!!!!!

Proof:

Joe

 

[smoke665]

Here we go again

 

[Ysarex]

Here we go again
View attachment 166048

This should be a pretty short one. It is regrettably worth the effort because Mr. Apophasis and Donny are not the only proponents of this fallacy and so getting the public record straight has value for novices who might otherwise stumble upon the nonsense and be persuaded.

Joe

 

[Tim Tucker 2]

Slow down, chill out and reflect, rather than jump to conclusions - observe.

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

So focal length changes with camera position? I'm sure you don't mean this, but the just same in the video TAP spews out a misconception and expects you to accept it as fact without thinking.

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!!!

No, changing your distance to the subject changes your point of focus.

that is an undeniable fact period!!!!

Or misunderstanding presented as fact for Youtube traffic? Don't forget the amount of hysterical laughter in the video, it's relevant. Especially the bit about equalising fov by changing camera position...

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 what did the photo look like? I mean have you actually used this to understand and take an image, communicate a thought through the taking of an image? Has it ever even influenced how you focus, compose or expose an image? Is it actually possible to use any of this to create an image? Have you ever seen this in an image, tried to confirm this by taking images?

TAP creates confusion and mis-understanding. None of what he spews makes any sense at all, and above it all is the voice that says "believe me without question, it is truth!" The whole history of photography and the relevance of the images has not suddenly collapsed because of his revelations. That so many images have been taken that are relevant and thought provoking in the pre-TAP era and continue to be taken by those who consider him a blithering idiot kinda indicates his relevance...

 

[WayneF]

That was a really dumb video, which was totally incompetent to discuss its subject. It was embarrassing to watch, I couldn't make it past half way. No redeeming merit whatsoever. My concern is that some newbie will see it and suffer a setback with wrong information.

It is true that the image that a lens does output does not depend on the sensor. A lens does what it does. But we don't view that direct lens image, and that is simply NOT what Depth of Field is.

Depth of field is about viewing enlargement, how much we enlarge that lens image until we can actually see that focus blur that the lens might do. We enlarge the original small sensor size or film size into a larger view that we can actually see, to be able to see and judge the focus blur.

Depth of Field is computed from Circle of Confusion (CoC), which is the diameter of that blur spot from the lens. In practice, DOF specifies the term CoC as an acceptable maximum limit of that diameter. The blur diameter is of course seen better when we enlarge it, and which is even overlooked if kept too tiny to see. Depth of Field is about seeing the blur.

CoC is numerically computed as a divisor of the sensor diagonal (typically CoC = diagonal/1442 or sometimes /1500). Because, the smaller the sensor, the more its image has to be enlarged to view it. And the more we enlarge it, the better the blur shows up, and becomes more objectionable (and we don't like objectionable). The lens does what it does, but Depth of Field is about the enlargement we use to view it. We see detail better in greater enlargement sizes. The blur spot is much larger on the enlarged print or monitor than it was coming out of the lens. And thus more objectionable, so enlargement of the small sensor is a very important criteria.

And in fact, the standard Depth of Field is computed from the enlargement of that small sensor size to (by standard definition) to an 8x10 inch print viewed at 10 inches. Numbers vary slightly, depending on source, but for example, full frame 35 mm cameras typically use CoC of 0.03 mm (43.267 mm diagonal / 1442 = 0.03 mm CoC), that being the maximum acceptable blur spot size from the lens onto the sensor, which when then enlarged to standard 8x10 inch print size, becomes about the limit of what the human eye can see, which is when larger becomes important.

Specifically, DOF computes limits at the distances where the blur diameter exceeds this CoC limit, meaning when it could be seen by eye when sensor size is enlarged to 8x10. The lens focuses at only one distance, and it does what it does elsewhere, which becomes blur when enlarged enough that we can see it, but is not considered blur if we can't see it. Coc, and thus Depth of Field depends on enlargement, which of course depends on sensor size. If viewing smaller than 8x10 inch inch size, then DOF will be better than computed, which is not often a problem. But if viewing larger than 8x10, DOF will be worse than computed.

Smaller sensors (a few mm size) have to be enlarged much more to reach an 8x10 inch print, so their allowable CoC that we must compute with is much smaller. (Fortunately, their cropped field of view has to use a much shorter lens, which is less magnification from the lens, which more than compensates in the DOF formula.) The computational tool is that their sensor diagonal is much smaller, so diagonal / 1442 is much smaller CoC, for that reason. Every existing DOF calculator is computing this enlargement of CoC, which depends on Sensor size.

Depth of Field is a very worthy subject to discuss, but try to forget that embarrassing video. Try to forget you ever heard of it. Apparently just some guy seeking Youtube views with ridiculous claims. A lack of understanding, blatantly wrong.

 

[Derrel]

The Angry Photographer's videos are for entertainment purposes only, and no valid technical information should be be expected from them. Users should watch his videos at their own risk. Opinions expressed in TAP videos are the property of The Angry Photographer, and do not necessarily reflect the opinions of people who actually understand photography fundamentals.

 

[WayneF]

I suppose I've lead a sheltered life, as I had never heard of him. Some people must have strange notions about what they think is funny, but I think we should try to help the newbies to understand photography.

 

[Dave442]

Great point bringing up CoC. The DOF estimations and F-stops make are great developments that allow photographer to focus more on the art of photograpy.

Any discussions about the physics of DOF or Total light gathered have to include all the variables used in said calculations (such as CoC, actual aperture diameter, etc).

 

[Overread]

First, great post Wayne and thanks for giving a far more detailed reply

I suppose I've lead a sheltered life, as I had never heard of him. Some people must have strange notions about what they think is funny, but I think we should try to help the newbies to understand photography.

Every market has them. Though I don't tend to lurk enough photography youtube pages to know them, but in the Computer game world there are some that can rise to have quite large and extensive fanbases. Some are very snide and hostile with their commentary, whilst others are clearly playing and acting it up and their attitude is more jovial and less hostile. However the core element is the same in that their videos tend to point out problems (real, imagined or based on personal interpretation) and then deride and insult other groups.

Those watching get entertainment and some a sense of superiority because they are agreeing with (or being ledby) the the video host in being superior to those who are being insulted in the video.

Of course those making the videos often realise that they can get a huge market by publishing "bad news" or extreme viewpoints (good old Ken Rockwell was very much like this, only his views were more just personal preferences and often presented as such. Ergo he was extreme, but rather tame and not confrontational/hostile. Heck when he became popular many other reviewers poked the joke back such as commenting on how they used a tripod even if Ken God Rockwell didn't

 

[Braineack]

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.

 

[WayneF]

Of course those making the videos often realise that they can get a huge market by publishing "bad news" or extreme viewpoints (good old Ken Rockwell was very much like this, only his views were more just personal preferences and often presented as such. Ergo he was extreme, but rather tame and not confrontational/hostile. Heck when he became popular many other reviewers poked the joke back such as commenting on how they used a tripod even if Ken God Rockwell didn't

Thanks. Maybe it was just to make noise to get views, but I did get the very strong impression this DOF guy just cannot see past his own faulty conclusion. His video seems an excellent case of "When everyone else is wrong, it may be time to reconsider your own opinion".

To me, Ken Rockwell seems a pretty good source of information. He doesn't have the smart aleck approach, he's just telling how it is. He does have an impressive background and knowledge, always knows what he's talking about. And it's not just talk. Lighting for example, it's clear he has been there, done that, and a lot of that. If it is just a show, then he fools me. But there has been an non-mainstream opinion now and then. He always explains those opinions clearly, and I'd say accurately and reasonably. For example tripods...

Just Say No (Rockwell)

Don't use a tripod if you can help it. Having to carry one is a pain and thus cripples creativity. See Digital Killed My Tripod.

Only use a tripod for still subjects either at night or when you need long shutter speeds of about 1/60 or slower.

It's a common misconception among photo teachers and amateurs that tripods are good, although no one really knows why. I guess some people just associate tripods with serious photography.

Nah, no one needs a tripod unless the shutter speed is long. Today VR and IS lenses also help obsolete them. Long shutter speeds only happen at night, or if you are at f/22 for a lot of depth of field.

Perhaps no one reads more than the first line, but I don't find any fault with it. It is exactly what I do, and did long before I ever read Rockwell.

He says use them when needed, but don't carry them around 24/7. And mighty few of us do more.
I think it could compare to "don't use flash from the far row of grandstand or auditorium".

 

[n614cd]

@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

 

[Ysarex]

@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

Since you asked I'll let Wayne get back to you, but, since I have this handy, here's the graphic that goes with the answer.

Joe