depth of field of APS C Sensor

[bags27]

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3 minutes ago, ramarren said:

Play around with the DoF calculator here: http://www.dofmaster.com/dofjs.html Pick and compare any FF and any APS-C camera. The differences become readily apparent. 

For a little more graphic approach, this one works reasonably well too: https://dofsimulator.net/en/

Essentially, a 35mm lens on the Leica CL nets the same FoV as a 50mm lens on FF. The DoF of a lens on the APS-C format, at any given distance and aperture, is approximately one stop more than a lens with similar field of view at the same distance and f/number setting on FF. 

Thanks, as always, for your help. Despite my appreciation of Mandler lenses, I'm completely besotted by some of the images coming out of the 35 f/1.4 FLE, and I'm trying to talk myself out of it. This isn't helping!

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[jaapv]

1 hour ago, lct said:

CoC is just a factor of DoF. Nothing new under the sun.

A very scientific definition...🙄

[lct]

3 minutes ago, jaapv said:

A very scientific definition...🙄

Just a true one AFAIK. Do you know of any other one? Just curious.

[jaapv]

Yes. I  do.

Quote

a circular spot on a film, resulting from the degree to which a pencil of light reflected from the field of view is focused in front of or behind the film, or from aberration of the lens, or from both.

 

[thomasstellwag]

a 35mm  1.4 is a 35mm 1.4 independant, what you hang behind it - you may even take your coffe cup, just no card slot in it, so no proof

deep of field is a function of lens data (incl aperture value) and distance to the subject, independant what you hang behind your lens...see above

imo  the confusion with crop factor comes from that:   on a APSC sensor you get the same angle of view with a 35mm lens, as with a 52mm lens on a FF sensor. Do as well not get confused with 35mm lense for APSC, they will just vignet on FF sensors, but still be 35mm.

if you start now to get the "same"  image on smaller sensors, you have to go back with the lens (distance to subject varyies), thus the bigger DOF is made, not by any  crop factors - this is marketing language.

For those, who still do not believe in that:  imagine on your FF sensor,  the same lens, the same distance to subject and you put a matte board with APSC cut onto your sensor. Do you really think  the viewable part of the image changes?

[01af]

vor 3 Stunden schrieb ramarren:

The depth-of-field of a lens on the APS-C format, at any given distance and aperture, is approximately one stop more than a lens with similar field of view at the same distance and f-number setting on 35-mm format. 

Yes. But it is approximately one stop less than the very same lens at the same distance and f-number setting on 35-mm format. Which is what we are discussing here.

.

vor 23 Minuten schrieb thomasstellwag:

Depth-of-field is a function of lens data (incl. aperture value) and distance to the subject, independent what you hang behind your lens ...

That's a common misconception.

[FlashGordonPhotography]

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I predict this thread will go for several more pages and that most will leave more confused than before they entered.... Anyone prepared to bet against me?

Gordon

[01af]

vor 6 Minuten schrieb FlashGordonPhotography:

Anyone prepared to bet against me?

No!

[bags27]

i should have posed the question as a true or false.....😃

[Ecaton]

vor 5 Stunden schrieb FlashGordonPhotography:

I predict this thread will go for several more pages and that most will leave more confused than before they entered.... Anyone prepared to bet against me?

Gordon

And this is why I suggested to go for chips and beer 😄. 

[ramarren]

On 9/17/2019 at 4:34 PM, bags27 said:

I'm sure this has been discussed many times on this site, so forgive the duplication: my only excuse is laziness.

What is the DoF of a wide open  L 35 f/1.4 (Sigma makes one) or an M f/1.4 on the APS C sensor? IIRC wide open it's something like the equivalent of a 50 f/2.3. Is it the same as that of the TL 35 f/1.4? Or, is the TL lens somehow fixed so that its DoF is equal to a "true" 50mm f/1.4 lens?

Quote

The depth-of-field of a lens on the APS-C format, at any given distance and aperture, is approximately one stop more than a lens with similar field of view at the same distance and f-number setting on 35-mm format. 

8 hours ago, 01af said:

Yes. But it is approximately one stop less than the very same lens at the same distance and f-number setting on 35-mm format. Which is what we are discussing here.

Okay. Perhaps I misunderstood the question. Reading from the first post quoted above... 

As far as I can read it, the question is whether the DoF of a wide open 35mm f/1.4 lens is the same as the DoF of two other wide open 35mm f/1.4 lenses, all on the APS-C sensor.

Answer to the first two questions: The DoF will be exactly the same for all three lenses on the APS-C sensor, just like it would be the same if all three lenses were put in front of an FF sensor. Because each of the three lenses has a focal length of 35mm and a maximum aperture of f/1.4. The answer to the third question is "No." The part of the post that has been stricken through is irrelevant ...  

G

Edited September 19, 2019 by ramarren

[jaapv]

Yes Godfrey, but as the subject distance will be different on the different sensor sizes to achieve the same framing, the DOF will be different. Alternately, if you keep the same subject distance you will have to crop and enlarge  to keep the framing, which influences DOF.

And this introduces the subject of perspective into the thread which will confuse it even more.

[jaapv]

10 hours ago, FlashGordonPhotography said:

I predict this thread will go for several more pages and that most will leave more confused than before they entered.... Anyone prepared to bet against me?

Gordon

On average we have this thread every three years and two months. The content never varies.

[ramarren]

6 hours ago, jaapv said:

Yes Godfrey, but as the subject distance will be different on the different sensor sizes to achieve the same framing, the DOF will be different. Alternately, if you keep the same subject distance you will have to crop and enlarge  to keep the framing, which influences DOF.

And this introduces the subject of perspective into the thread which will confuse it even more.

The statement by 01af that I was responding to said, "...the very same lens at the same distance and f-number setting..."  

You can't have it all different ways at the same time. Either you're talking about the same lens at the same subject distances, or your talking about the same field of view using different lenses at the same subject distance, or your talking about the difference in DoF given different subject distances with the same lens on two different formats. They're mutually exclusive comparisons. 

The bottom line is that a lens's imaging characteristics are going to be the same at the same focus distance and aperture setting modulo the amount of the scene you will see based on different formats. If you change the focus distance to accommodate the different FOV for a smaller or larger format, then depth of field AND perspective will differ between photos made with the same lens. 

How the DOF for ALL these situations will vary can be calculated easily with the DOF calculators I posted links to earlier. How the perspective will vary and what the difference in FoV will be can also be previewed with other tools.. 

But ... How a specific lens images on a specific format is best learned simply by putting them together and going out to make photographs with the setup. All these previsualizations and calculations don't tell you anywhere near as much about what the look of a particular lens is going to be in the situations that you want to use it in compared to just using it and looking at your results. 

There's a reason I have the 1972 Summilux 35mm f/1.4 v2 in M-mount and haven't replaced it with a Sigma L 30mm or APO-Summilux-TL 35mm, or anything else.  

What this thread has inspired me to do is to take the Voigtländer 10mm off the CL for the first time in a couple of months and fit my 'Lux 35 for a time. Time to give another meme a chance to surface, eh?   

[frithjof.b]

On 9/18/2019 at 3:59 PM, 01af said:

Depth-of-field is proportional to the linear sensor size. The smaller the sensor, the narrower depth-of-field will be.

Are you claiming that depending on which size of paper I put behind the lens, the optical properties of the lens will change?

The DOF depends one the focal length, the aperture, CoC .

The problem with the DOF calculators are that they are using simplified geometric optics (a flat ideal lens), and then people make some assumption of the CoC. The pixel distance can be used for the theoretical minimal DOF given a sensor lens combination (the sensor size is usually irrelevant) However, it make a different, if you print the 24MP image as 90x60 poster or look at it on a smartphone. The output media finally defines the relevant CoC and there size matters! 

The biggest problem are all these strange crop factors people are using and confusing. A 35mm lens remains a 35mm lens on a MFT, an APSC a 35mm or a MF sensor. A f2 aperture is defined by the focal length and a useful concept for light gathering independent of the recording format. Only your personal angle of view is changing nothing else. Once people understand that it becomes very easy. I never understood the crop factor concept.

 

 

[jaapv]

55 minutes ago, frithjof.b said:

Are you claiming that depending on which size of paper I put behind the lens, the optical properties of the lens will change?

The DOF depends one the focal length, the aperture, CoC .

The problem with the DOF calculators are that they are using simplified geometric optics (a flat ideal lens), and then people make some assumption of the CoC. The pixel distance can be used for the theoretical minimal DOF given a sensor lens combination (the sensor size is usually irrelevant) However, it make a different, if you print the 24MP image as 90x60 poster or look at it on a smartphone. The output media finally defines the relevant CoC and there size matters! 

The biggest problem are all these strange crop factors people are using and confusing. A 35mm lens remains a 35mm lens on a MFT, an APSC a 35mm or a MF sensor. A f2 aperture is defined by the focal length and a useful concept for light gathering independent of the recording format. Only your personal angle of view is changing nothing else. Once people understand that it becomes very easy. I never understood the crop factor concept.

 

 

No. O1AF assumed that the image framing would remain the same. To do that he would either need to change position or change focal length. 

[UliWer]

The confusion starts when people do not explain what exactly they are comparing, when they state that DOF is smaller or deeper with different sensor sizes.

If you compare DOF (at the same distance and same f-stop) of a lens with 35mm on APS-C and 24*36mm "full-format" - the DOF with APSC will be smaller, though the angle of view you get in both case will be very different.

If you compare DOF (at the same distance and f-stop) of a lens with 35mm on APSC with a lens which gives the same angle of view on "full-format" (i.e. a lens of 52,5mm) - the DOF with APSC  will be deeper. In #2 it has already been said, that the DOF of a 1.4/35mm on APSC will equal the DOF you'll get from a 2.1/52 on "full format", which of course is more than you'd see from a 1.4/52mm lens. But the lens of course keeps its opening of 1:1.4 and you don't get the exposure of a lens with 1:2.1. 

[01af]

vor 3 Stunden schrieb frithjof.b:

Are you claiming that depending on which size of paper I put behind the lens, the optical properties of the lens will change?

Of course I don't.

Are you claiming depth-of-field was a property of the lens?

.

vor 3 Stunden schrieb frithjof.b:

The depth-of-field depends on the focal length, the aperture, and the circle-of-confusion.

... and the distance. And a few more factors. What do you think is the circle-of-confusion, and what does it depend upon?

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Hallo,

Look here: Leica L-Mount

[lct]

49 minutes ago, 01af said:

What do you think is the circle-of-confusion, and what does it depend upon?

+1

[ramarren]

The "circle of confusion" is a subject of myth and silliness. 

The image of a point (call it a solid white dot that is 0.001 inch in size) becomes smaller and better defined as the focus is racked from infinity to the subject plane, then grows and becomes less well-defined as the focus is racked further (closer) than the subject plane. If you were to look at the image of the point with a high powered magnifier as this process occurs, you'd see a hard circular area that stays solid white surrounded by a slightly grayish annulus that grows and shrinks as the focus racks from infinity, through the critical point of focus, and grows again as the focus setting gets too close. 

Remember that depth of field (DoF) is simply a calculated range of acceptable perceived sharpness at a given focus setting and aperture, based upon a reference for "what is considered sharp" at a specific image magnification and viewing distance. It's not the property of a lens, it's a property of a complete imaging system including the lens, the magnification, plus the reference standards for "what is sharp" and "at what magnification". The calculation of DoF includes focus distance, the CoC, the end-result magnification reference and viewing distance, the physical size of the lens opening, and so forth. 

The legendary Circle of Confusion is simply a reference size of how large that grayish annulus can be and still allow us to call the point sharp rather than blurry. If we pick a large CoC (because the image is going to be viewed from a substantial distance where the acuity of our eyes is such that we wouldn't be able to distinguish the specific defocus amount very well), the effective DoF calculation becomes more generous and we consider the in-focus zone to be larger. If we pick a small CoC (because we're going to be looking at the image close up and maybe with magnification so we can see the defocus of the point easily), the effective DoF calculation becomes less generous and we consider the in-focus zone to be smaller. 

That's really all the circle of confusion is, other than a term upon which reams of silliness has been written attempting to define and understand it: A reference based on the imaging of a point for how much blur is acceptable allowing the point to be considered sharp.  

Edited September 20, 2019 by ramarren