Depth of field on M8 vs MP... Sorry for being thick!

Mister E said:
This is incorrect. DoF doesn't change based on sensor size, but the working distance for a given focal length to get the same perspective does. For a 1.5x sensor you would have to stand 1.5x further away to achieve the same framing. Because you are 1.5x further away you will have MORE depth of field. This has nothing to do with the magnification for prints, etc. The hyperfocal markings on the lens still apply to crop sensors because of this. A 50/1.4 Lux has the same DoF at 10' on the M8, M9 and m4/3.

Makten needs to show up in here. He is DoF explainer number one fan.
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Actually, I am perfectly right. You are simply adding arbitrary condition such as equal field of view. This is just about the DoF scales on a 35mm lens. Step back and the same adjustment would have to be made.
 
Finder said:
Actually, I am perfectly right. You are simply adding arbitrary condition such as equal field of view. This is just about the DoF scales on a 35mm lens. Step back and the same adjustment would have to be made.
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The DoF scales do not change accuracy when sensor size chances. If you mount a 21/4 on an M8 and set it to the f/8 markings and stop the lens to f/8 and then mount it on an M9 you will see LESS in focus because of the larger sensor and wider view, but the same 10'-Infinity will be in sharpish focus. We all know that f/8 and the f/8 hyper-focal markings do not give a satisfactory level of sharpness.
 
Depth of field is predicated on the limit of resolution of human vision, while viewing an enlargement of a photographic image at a specific distance from the viewer. Without these assumptions of acceptable resolution, only at the exact focus plane would we expect adequate focus, and therefore all DOF scales would be invalid, and would render this entire discussion moot.

This acceptable circle of confusion is what is refered to by manufacturer-specific figures of fractions of millimeters, as stated by others above. However, we must remember that those figures are only valid for the conditions under which the manufacturer stated them, for a specific enlargement factor (from camera to finished print, NOT crop factor).

Therefore, if you start performing comparisons where prints are cropped to match another print's field of view, the comparison is no longer valid. You have to use the same enlargement factor that the manufacturer assumed for his lens markings.

In practice, most photographers choose to mount a specific lens on a camera body for its angle of view. So comparisons of DOF between two camera formats using the same focal length and lens aperture for the same angle of view become entirely valid -- in practice. In theory, I could inform Aunt Mildred that she will be cropped out of the family portrait because some bloke on the internet says I have to use the same camera-to-subject distance; but in practice that's not how real photographers take real pictures with real cameras using real lenses. Which is why maintaining equivalent angles of view is entirely appriopriate. I'm sure the OP is interested in this for practical considerations, not merely theory. "If I want to include Aunt Mildred in the family portrait, what does that do to my DOF?" becomes an entirely practical and appropriate question.

~Joe
 
Frankie said:
Try this:

http://www.dofmaster.com/dofjs.html

Select Leica M8/8.2 and lens focal length...
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From this resource, if using a 35mm focal length lens:

M8 @ f4 focused at 10' will have a DoF 4.77' (8.15'~12.9');
M7 @ f4 focused at 10' will have a DoF 6.47' (7.72'~14.2').

M8 @ f8 focused at 10' will have a DoF 11.42' (6.88'~18.3');
M7 @ f8 focused at 10' will have a DoF 18.10' (6.29'~24.4').

Infer what you will.
 
Mister E said:
Your display size and magnification is completely irrelevant.
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No it's not. Display size and viewing distance are an integral part of the definition of the DOF word and metric, on which the DOF scales on your lenses are based.

For example (from http://www.ronbigelow.com/articles/depth-of-field-1/depth-of-field-1.htm)

How can things like print size and viewing distance affect DOF when these DOF devices don't even consider them? The answer is rather simple. The people who created these devices, as well as the people that manufacture cameras and lenses, make assumptions when they evaluate DOF. A typical assumption for a full-frame digital camera or a 35mm film camera is that the photographer will make an 8"x 10" inch print that will be viewed at about 12".
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Of course you can define your own language and metrics. But then discussions become really difficult. In that spirit, this is my last post to this thread.

Cheers,

Roland.
 
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Frankie said:
From this resource, if using a 35mm focal length lens:

M8 @ f4 focused at 10' will have a DoF 4.77' (8.15'~12.9');
M7 @ f4 focused at 10' will have a DoF 6.47' (7.72'~14.2').

M8 @ f8 focused at 10' will have a DoF 11.42' (6.88'~18.3');
M7 @ f8 focused at 10' will have a DoF 18.10' (6.29'~24.4').

Infer what you will.
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Is that a 35mm FoV or a 35mm lens?
 
Note from Leica on M8 DOF = FF 24x36

Note from Leica on M8 DOF = FF 24x36

Roland, all:

It's on page 87 of the M8 owner's manual:

"The extension factor
The nominal focal lengths of Leica M lenses are based
on the 35mm-format, i.e. on a film format of
24x36mm. In comparison, with its 18x27mm, the
sensor in the LEICA M8 is somewhat smaller though –
by a factor of 0.75. Therefore, when used on the
LEICA M8, these lenses have angles of view corresponding
to lenses with focal lengths that are longer
by a factor of 1.33 (1.33 = reciprocal of 0.75). This
has the respective effects on their perspective, but
not on their depth of field, which, with the LEICA M8,
can also be read directly off the lens (see the lens
instructions for more details).
The bright-line frame in the viewfinder of the LEICA M8
of course always shows the “correct” field of view for
this camera, i.e. it takes account of the increased
focal length. You can therefore compose your pictures
in the normal way, just as for other cameras in the
Leica M series (see also “The bright-line view- and
rangefinder “, p. 102)."

ferider said:
Can we see the Leica quote, Ted ?

It's very simple really:

1) take a "bokeh shot" with background lights on film; scan in; print it on 5x7.
2) take the scan into Photoshop; crop it by factor 1.3; enlarge it and print it out on 5x7.

The OOF circles of 2) will be 1.3x larger than 1). Less DOF in the cropped picture.

2) is equivalent to taking the same picture as 1) on the M8, at the same focus distance.. Ergo, the DOF marks on the lens mean something different for MP vs. M8.

DOF is defined for fixed print size and viewing distance.

Here is a longer explanation (scroll towards the end):

http://www.luminous-landscape.com/essays/Leica-M8-Perspective.shtml

Roland.
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What camera, lens, aperture?

What camera, lens, aperture?

You may not realize it, but the smaller sensor is more diffraction limited than the larger sensor, (given same pixel pitches, sensor pattern design) so let's get on with my 2nd favorite topic today, what were the apertures and cameras used?

Finder said:
Well guys. I win. Here is an image photographed with the same lens, same aperture, at the same distance. The only difference is sensor size. the image on the left has more depth of field than the image on the right.

http://www.rangefinderforum.com/photopost/uploads/3853/dof.jpg
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Finder said:
Jeff, "object size occupying the same portion of the frame" is not having the same magnification. You are simply fixing field of view, which is not what we are talking about.

You "expert" source that DoF scales are wrong is wrong. DoF scales is only a guide. You can change the criteria for sharpness if you are not satisfied with it. However, it still does not change what DoF is nor the conditions that affect it. Having zone focused with modern cameras, their DoF scales are very good.
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Hey, you're the one who said focal length affects DOF. And, you're wrong...http://www.luminous-landscape.com/tutorials/dof2.shtml

And, obviously, DOF scales are only a guide. Duh. But, they are worse of a guide now than they were when established long ago. If you don't understand that, there's no point arguing with you.

Jeff
 
I haven't read all the answers here so my apologies if I repeat what someone has already said.

There are two answers. The first is purely scientific and the second is real world.

First is that the lens has not changed. It is the sensor that has changed. DOF is not affected by a sensor. It a property of the lens and not of a sensor. Therefore changing sensor has no effect on DOF. This is true and unarguable.

The second and real world answer depends on how you phrase your question.
If you mean "does the DOF change for the same subject area?" then yes it does. If you mean "does the DOF change for the cropped area caused by the reduced sensor size?" then no it doesn't.
The reason is simple to answer. The basics of DOF are that the nearer you are to the subject, then the shorter the DOF and the further you are from the subject then the greater the DOF.
Well with a smaller sensor and using the "same subject area", then you need to be further from the subject to get it all in. That means you get greater DOF. The DOF scale on the lens is still correct and you don't need to compensate because of smaller sensor. The compensation is automatic as a result of changing distance from the subject which will give you a new reading from your DOF scale.
If you stay the same distance from subject then nothing has changed and DOF will remain the same but you will get a smaller subject area on the sensor.

There is a third answer which is dependant on how sharply a sensor is capable of recording the subject but that is not factored into lens DOF scales as far as I know.

Leicas statement that there is no compensation required is true as far as I'm comcerned.

Finally, what this means is that with your M8 you will tend to be able to use a slightly wider aperture and benefit from increased shutter speed compared to your MP if you are working the same way and looking for the same DOF as you normally do on your MP. You will tend to be a little further from your subjects. I am of course assuming you are using the same lens.
 
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Finder said:
Well guys. I win. Here is an image photographed with the same lens, same aperture, at the same distance. The only difference is sensor size. the image on the left has more depth of field than the image on the right.

http://www.rangefinderforum.com/photopost/uploads/3853/dof.jpg
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No you don't win because you have completely failed to take into account that different sensors produce different sharpness due to AA filters. So an M9 is claimed to be super sharp. An M8 isn't. That super sharpness will affect apparent DOF. But being scientifically challenged you have made a false assumption that it is a DOF issue. It's not. We live and learn. Well some of us do.
 
Andy Kibber said:
I was wandering in the darkness on this subject until I recently saw the light. Ferider says it right in post #6.

If you don't believe that a 50mm lens at f/2 focused at 1 meter has different DOF on an M9 vs. M8 vs. EP-1, just trot over to http://www.dofmaster.com/dofjs.html, input the data and see for yourself.
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That site is highly misleading. It changes the CoC to suit the sensor size which is what you lot seem to think is correct and the reason that DOF is reduced.
But what you have not figured out is that the CoC it uses is the one that a lens would need to be able to produce to give the same resolution and DOF as a lens designed for Full Frame. Unfortunately just throwing a new CoC into a dumb online calculator does not change the design specification of the actual lens being used and which was designed to produce a CoC to suit a FF format.
To put it simply for you, you have interpreted the dumb online calculator incorrectly. i.e. The blind leading the blind.
 
All these DOF threads should be merged into one mammoth thread if confusion ..... a 50mm lens at f2 has the same DOF whatever it projects the image onto, then use reason from there
 
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