DOF where is it?

[Symeon]

Has anyone using an M8 ever gone to the trouble to calculate a proper Depth of Field table for any Leica lens, like we used to do in the old days? I mean, do the numbers on our lenses (giving you an idea of the Dof at a given aperture) mean the same thing on the M8? Or has the x1.3 digital factor changed everything?
Regards.😕

 

[Ororaro]

Look, DOF changes as soon as you move. But regardless of the sensor, the markings on the lens are correct. Always correct.

The M8 1.3x factor and changed DOF only depends if you MOVE to get the SAME COMPOSITION as with a 1.0 sensor (film)

I will not go deeper into this but anyone who thinks dof changes as soon as a sensor changes is deeply wrong.

The final word is: No matter how and where you focus, the DOF marks on a lens STAY the same and they are accurate, no matter what.

 

[OldNick]

The DOF scale on the lens is correct regardless of the sensor format. All that really changes is that the sensor only captures a smaller percentage of the image created by the lens than that captured by the film format for which the lens was originally intended.

Jim N.

 

[JeremyLangford]

The DOF scale on the lens is correct regardless of the sensor format. All that really changes is that the sensor only captures a smaller percentage of the image created by the lens than that captured by the film format for which the lens was originally intended.

Jim N.

which means that you generally have to stand farther away from the subject, which increases the DOF. And if you don't want to stand farther away from the subject, then you have to get a 1.3x wider lens to compensate, which will increases the DOF.

 

[Michiel Fokkema]

Look, DOF changes as soon as you move. But regardless of the sensor, the markings on the lens are correct. Always correct.

The M8 1.3x factor and changed DOF only depends if you MOVE to get the SAME COMPOSITION as with a 1.0 sensor (film)

I will not go deeper into this but anyone who thinks dof changes as soon as a sensor changes is deeply wrong.

The final word is: No matter how and where you focus, the DOF marks on a lens STAY the same and they are accurate, no matter what.

Are you sure?
My MF 50 has a different DOF than a 50 on a 35 camera because of the different circle of confusion. Doesn't the same apply for sensors?

Cheers,

Michiel fokkema

 

[Bryce]

And you guys poke fun at Ken Rockwell?!?!?!???!
Circles of confusion will be magnified in size 1.3x along with the rest of the image, compared to 35mm film. Your DOF scale will be somewhat more optimistic on a cropped sensor camera than it is on film.

 

[mfunnell]

http://doug.kerr.home.att.net/pumpkin/Depth_of_Field.pdf

http://en.wikipedia.org/wiki/Depth_of_field

...Mike

 

[Ororaro]

Are you sure?
My MF 50 has a different DOF than a 50 on a 35 camera because of the different circle of confusion. Doesn't the same apply for sensors?

Cheers,

Michiel fokkema

Of course I am sure!

 

[Ororaro]

Fred, you're running around the subject here. You are now saying that the real answer is not really useful in the real world?

The original question was simple: Are the dof marks on a lens accurate when used on a M8? The answer to that is a very simple Yes. Can't you just agree on this?

 

[bottley1]

Depth of field is directly proportional to the diameter of the circle of confusion, the f-number and the square of the focused distance, and inversely proportional to the square of the focal length of the lens, viz:

dof = (2 x u x u x N x c) / f x f, where u is the focused distance, N is the effective aperture, c is the circle of confusion, and f is the focal length.

Nothing to do with film or sensor size, or more correctly, film or sensor diagonal dimension.

 

[tomasis]

I think here are some misunderstandings though you all are not wrong.

If you want to get same dof at the same FOV so one has to always to compensate about a stop on smaller sensor. M8 with 35mm lens gets about 50 mm fov of film but you have to use dof marks from 35mm, not 50mm as you do with film. So dof are not same if you use both 35 and 50mm lenses on different bodies to get same 50mm fov.

 

[bottley1]

Sorry you are wrong tomasis. The depth of field of a 35mm (or any lens for that matter) will be the same irrespective of camera used, all other things being equal. A 35mm lens on a leica M8 is still a 35mm lens, the dof marking being valid for all film or sensor formats. The fact that a lens may behave differently (i.e. will have a lesser or greater field-of-view) is not the issue. If you change your object distance, to compensate for a higher magnification (say when using a 35mm lens on a M8, giving an effective approx. 50mm f-o-v), the markings will still be valid for that distance.

 

[tomasis]

bottley, you miss my point. I was talking about FOV. I agree what it comes through lens, everything is same (dof markings identical to every lens) But one gets cropped images on cropped sensor. You don't get pictures of 35 mm fov on M8 with 35mm lens but approx. 50mm fov though it was used with 35mm lens.

I have looked at my 35 and 50 mm lenses and I could see that distance between f16 is far greater on 35mm lens dof markings compared to 50mm. This explains for me. As Jaapv said somewhere, that the lens gets more enlarged image, the thinner dof gets. More important, I don't get same impression of dof by looking on images taken with both rd1 and film camera with the same lens though dof is identical on film and sensor.

Let me ask you which lens and aperture do I need for Rd-1 with 1.5x cropped sensor to get exactly same DOF and distance with film camera with 50mm at aperture F2?

Let us assume if I mount 50mm on Rd1 so it gets 75 mm fov. To get same image of 50mm with film camera, I have to go a few steps back so more further the object comes away from lens, dof gets deeper. You have to use a stop larger apeture to compensate that deeper dof. If my intention is to shoot images of fov fiilm 50mm, why I have to go through troubles of going a steeps back and carry larger lens to have extra stop to compensate. You can use a bit wider lens instead but you have to compensate by extra stop of larger apeture too.

 

[Benjamin Marks]

I think I see what is happening and think it might shorten the thread if you all state your assumptions. A couple of things seem right:

1) markings on the lens are correct, regardless of the medium of capture. If this were not true, then you could change the optical nature of the lens by inserting a cardboard mask over a portion of the film/sensor. This seems an obvious counterfactual. Note that this says nothing about comparisons of lenses of different focal lengths, which of course have different optical qualities.

2) perception of DOF will change somewhat with print size. If you don't think this is right, come on over and see some of my contact sheets. Circle of confusion is otherwise a red herring in this debate.

3) FOV changes when you sneaker-zoom (that is, move you position relative to the subject to compensate for a crop factor). Of course then you have to re-focus, and that _will_ change your depth of focus.

I like to think of a lens casting light on a sensor as the same as a flashlight shining on a wall. Your "format" is just the size of the rectangle you are carving out of the circle of light on the wall. If you don't move the wall or the flashlight, nothing else about the image (except the crop) will change.

Hopefully,

Ben Marks

 

[Benjamin Marks]

I think I see what is happening and think it might shorten the thread if you all state your assumptions. A couple of things seem right:

1) markings on the lens are correct, regardless of the medium of capture. If this were not true, then you could change the optical nature of the lens by inserting a cardboard mask over a portion of the film/sensor. This seems an obvious counterfactual. Note that this says nothing about comparisons of lenses of different focal lengths, which of course have different optical qualities.

2) perception of DOF will change somewhat with print size. If you don't think this is right, come on over and see some of my contact sheets. Circle of confusion is otherwise a red herring in this debate.

3) FOV changes when you sneaker-zoom (that is, move you position relative to the subject to compensate for a crop factor). Of course then you have to re-focus, and that _will_ change your depth of focus.

I like to think of a lens casting light on a sensor as the same as a flashlight shining on a wall. Your "format" is just the size of the rectangle you are carving out of the circle of light on the wall. If you don't move the wall or the flashlight, nothing else about the image (except the crop) will change.

Hopefully,

Ben Marks

 

[Benjamin Marks]

I think I see what is happening and think it might shorten the thread if you all state your assumptions. A couple of things seem right:

1) markings on the lens are correct, regardless of the medium of capture. If this were not true, then you could change the optical nature of the lens by inserting a cardboard mask over a portion of the film/sensor. This seems an obvious counterfactual. Note that this says nothing about comparisons of lenses of different focal lengths, which of course have different optical qualities.

2) perception of DOF will change somewhat with print size. If you don't think this is right, come on over and see some of my contact sheets. Circle of confusion is otherwise a red herring in this debate.

3) FOV changes when you sneaker-zoom (that is, move your position relative to the subject to compensate for a crop factor). Of course then you have to re-focus, and that _will_ change your depth of focus.

I like to think of a lens casting light on a sensor as the same as a flashlight shining on a wall. Your "format" is just the size of the rectangle you are carving out of the circle of light on the wall. If you don't move the wall or the flashlight, nothing else about the image (except the crop) will change.

Hopefully,

Ben Marks

 

[tomasis]

benjamin, you did managed very well to shorten thread 😉

 

[Benjamin Marks]

Note: the very first words of the explanation in that article are: "For an equivalent field of view." So: if you were to test the assumptions in this article with four different cameras each with a 50mm lens (assume an APS digicam, a 35mm camera, a 6x6 MF camera and an 4x5 field camera), you would have to have each camera in a different position to hold the field of view constant. This will mean, in turn, that the lens-to-focal-plane distance will be different for each set up. So of course the depth of focus will be different in each of these situations. But this is not a function of the sensor/film size, it's a function of moving your rig around and changing the relationship between the lens and the sensor/film plane.

Ben Marks

 

[bottley1]

thanks ben....so common sense at last

 

[Ororaro]

Well, you're wrong. What you're saying is the same as seeing depth of field increase in a 4x6 print by just cutting 1 inch off each side.