Hyperfocal with Leica M8

[lars_bergquist]

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Bill Parsons, the CV15 is dead easy to use. Set it to f:8 and 2 meters, and you are home free, with d.o.f. from 1 meter to infinity. See above for the reasoning. Maximum definition is of course had only by exact focusing to distance, and there are no markings between 2m and infinity. But halfway between 2m and infinity is 4 meters.

 

The old man again

[@bumac]

It should work. CV15 on M8 without filter or coding.

 

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[lars_bergquist]

Reading the previous postings carefully, I want to say that my judgment that most of the "facts" posted were wrong, does NOT apply to the signature Johiratnam, or to Andy Piper. Both got it right, as far as they went (Andy went pretty far).

 

There are few areas where so much confusion and superstition reign as in the matter of depth of field. Possibly with the exception of film development, which is history. We have got to be grateful for any glimmer of clarity.

 

The old man from the Age of Medium Format

[jaapv]

This has been a very confused debate. Most "facts" cited are plain wrong. I will not cite individual posters, for reasons of space.

 

First, cropping does neither increase nor decrease d.o.f. Saying that "a 35mm lens on the M8 is equivalent to a 50mm lens on film" refers to angle of acceptance (field) only. Cropping does not change the focal length of the lens. Magnification (print size divided by sensor size) does affect what looks sharp or not in the print. See below for the reasoning.

 

The d.o.f. tables and scales have been unchanged since the 1920's. They are based on a circle of confusion of 1/30th of a millimeter (.033mm). The choice of that measure was based on the assumption that the 24x36mm neg would be enlarged at most 3x, so that the print could compete with the then-popular contact prints from 6x9cm roll film (a.k.a. 120).

—This measure went totally obsolete already during the 1930's, as photographers started to make large prints. Leitz however did never dare change their tables and scales, seemingly fearing that stupid customers would believe that shrinking d.o.f. meant that lenses had gotten less good! Leica cameras, as we know, are used by idiots (NOTE! NOTE! Sarcasm!)

 

So very long ago, knowledgeable photographers started following the practice mentioned in this thread, setting their lenses to one stop wider on the scales, than the one actually used. I.e. aperture 8 set, read depth of field at 5.6 on the scale. This was adequate for a 5x7" print from film. The smaller sensor of the M8 means that the magnification factor (print size for print size) goes up however. So, we do need to stop down even more. To repeat, not because optical science has changed in the digital world, but simply because of increased magnification.

—For this is a fact: d.o.f. varies with two factors only: aperture and magnification. Tele lenses have less d.o.f. than wide angles, not because of the focal length per se, but because they magnify the subject more than wide lenses do. A smaller "sensor" such as 18x24mm on film, or 18x27mm in the M8, tends to decrease the d.o.f. in the print (apertures being equal) because it necessitates a higher degree of magnification (print size being equal). So, existing fuzziness is enlarged more. So, fuzziness has to be decreased.

 

Already before the switch to the M8 I read my aperture scales at TWO f-stops wider than the set aperture. I.e. if f:8 is set, read at f:4. This does effectively halve the permissible circle of confusion to 1/60th of a mm. Now this means of course that both zone focusing and hyperfocal focusing cannot in practice be used with lenses longer than 35mm. That is a fact of life. But this is all the d.o.f. in town ...

 

A permitted c.o.c. of 1/50th (.02mm) would probably have been adequate, but this cannot be conveniently read off the d.o.f. scales.

 

The old man from the Age of Box Cameras

 

An excellent explanation, Lars. However, one thing HAS changed with the advent of sensor photography, the technical nature of the capture medium. On film there is a thickness, which means film has its own built-in DOF as it were. A sensor behaves like an infinitely thin plane. For that reason DOF is more defined on a sensor than on film, giving the impression of a more narrow DOF.

 

The photograph in th OP seems to be generally blurred, so I wonder whether that is not either motion blur or an out of tolerance adapter.

[Peter Branch]

For the same Depth of Field, which is closely related to the hyperfocal distance, the physical diameter of the diaphragm has to be the same using a lens that gives the same Field of View. Thus with an M8 where a 35 mm lens has the same Field of View as a 50 mm on film you get more Depth of Field at the same numerical aperture with the M8 – as others have pointed out. To get the same physical diameter one needs to open up the 35mm lens by the ratio of 50/35 = 1.43 which is almost exactly one stop. So using the example of the 50mm on Film and the 35mm on an M8 you will get the same Depth of Field at f/5.6 on the M8 and f/8 on film.

 

Thus the hyperfocal distance, for a given numerical aperture and the same Field of View, with the M8 moves to a closer focusing distance, which is exactly what the marks on the 35mm lens used in this example do. Leica are absolutely right on this point.

 

This is not to say that when viewing digital pictures on a screen at 100% that the old standards for Circle of Confusion still apply – they probably don’t, but that is a separate issue.

[Jamie Roberts]

EDIT:

 

OK--I'm now confused enough to say I'm wrong on DOF and cropped bodies (though I now have to think through why I see what I see, as opposed to what Andy and Lars tell me).

 

BTW--I never had any disagreement with the hyperfocal markings being off by a stop or more.

 

Poor Bill: your CV 15 should be in focus anyway at 5,6 to 8. If it isn't it's still defective

 

I need more coffee.

 

What I see on my cropped and uncropped bodies is more DOF with the cropped body if I adjust for the crop with my feet with the same lens. For instance, the 50 1.2L seems to have more DOF on the 1d3 than 5d.

 

I see absolutely no "magnification factor" in the crop itself.

 

Why?

[2Bébèrt]

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I 'carefully' read the http://www.luminous-landscape.com/essays/Leica-M8-Perspective.shtml aticle and now I am almost convinced on the DOF subject.

Just turn your focus-scale 1 stop less than your lightmeter readout. So the Hyperfocal length gets less, as I already thought, by factor 1.33. Further fieldtesting will get me on the right path.

 

by the way, just recieved the 2 free UV/IR filters in less than 2 weeks.

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[adan]

Aha!

 

Jamie, you likely DO see more apparent DOF if you "adjust for the crop with your feet". One factor in the DOF equation (literal and conceptual) is DISTANCE, so if you change the distance, you are changing TWO variables at once (distance and crop). When you do that the scientific method breaks down.

 

Sort of as if you tested one of your profiles on RAW converter A, and a different profile on RAW converter B - there's no way to know if any differences you see are because the profiles are different - or because the converters are different. You've eliminated your control mechanism.

 

Consider - if you shoot a landscape, where the subject matter is, say, from 100 meters away out to infinity, you likely have enough DOF even at f/1.2 for it all to be sharp, so the DOF may be including things miles apart. Whereas at 1 meter the DOF @ 1.2 may be only a couple of cms. What you are seeing, when you adjust your position to account for the cropping difference between the 5D and 1D3, is just a smaller distance change along that curve from infinity to minimum focus, with smaller, but still visible effects.

 

This is one reason (I believe) why I often have more luck with focusing my 135 f/4 for a given framing than a 90 f/2. Aperture certainly plays a role - but so does moving back from 2 meters to 3 meters, or 4 meters to 6 meters. The small differences in internal subject distances (the difference between getting the eyes in focus, or the tip of the nose, or the ears) become smaller and less significant relative to the camera-to-subject distance.

 

I think if you try, with your 1D3, what the original poster tried: put on a wide lens, stop down, and then set infinity on the right-hand DOF marking on the lens for that aperture - then you will find that subjects at the extremes of the supposed DOF implied by the markings are not actually rendered sharp, whereas with the 5D (same lens, same position, same aperture, same focus setting) those same parts of the subject will look sharper (and also smaller) if you view the whole frame at the same size - say the width of your monitor (not 100% pixels!).

[Olsen]

Bill-Something must be wrong with your 15 or adapter. This lens is basically always in focus. At f5.6 and turned to infinity everything but your shoes should be in focus (and really sharp in my experience) check that thing out....B

 

Bill,

 

I agree with this. My VC 15 has a deep DOF from 5,6 and is focused 'like hell'. So, what is the problem with yours? Even though the VC 15 is mounted on the M8 it still a 15 mm focal length lense. The M8 sensor utilizes only the inner part of the lense circle. The DOF should still be something like a 15 mm lense, - with the exception of factors mentioned in Puts' article. Which amounts to one aparture step, or so. Have your 15 VC checked.

[teehas53]

As soon as Leica makes a 15mm f1.4...

 

Good one, Bill, I laughed involuntarily! I appreciate the spirit of it though.

 

Seriously, if it were even practical from a manufacturing standpoint, the vast majority of us would TRULY have to mortgage the farm to afford one. Also, it'd be pretty huge (look at a 21/2.8 and extrapolate.) So much for the small, unobtrusive "street camera... "

 

I have to agree with others, it sounds like your CV 15 is on the fritz. Mine makes really good images, and I haven't had trouble getting it sharp even at fairly wide apertures. I'd contact Stephen Gandy at CameraQuest about having it looked at.

 

T

[sean_reid]

Bert, I have noticed results like you show, when using my only CV lens, the 15mm. I use this with John Milich's ltm adapter and his hood.

 

I find that unless I stop down to f11 or more, my pictures show a lack of focus.

 

This is the second lens I have gotten, and it produces a satisfactory image at f11. I don't, however, think the image is as good as I expect to see from Leica glass.

 

I would expect that the 1.3 multiplier would narrow the DOF of the lens, and have been setting the focus point accordingly. As it happens, the images look terrible to me unless I go to f11.

 

Hi Bill,

 

The lens is actually very sharp at F/4 if it's focused at the right distance. That "if" is the important thing. Few lenses do their best at F/11.

 

Cheers,

 

Sean

[sean_reid]

Jamie, my dof calculation was as follows:

 

My 35mm becomes a 47mm (or so). That's a longer lens. A 47 has a narrower dof than a 35, other things being equal.

 

If I get you, you're saying that my 47 is really as 35 and enjoys the 35's dof.

 

Which is the operative process?

 

 

 

As to the CV15, I've tried with and without a tripod. It's definitely NOT Leica glass (not a surprise at 10% of the cost). Perhaps I don't have the screw mount tight enuf. At f11, I can get a satisfactory image. At 5.6 or 8, I don't like what I get. This may be due to the fact that the out-of-focus part of the image sucks.

 

If you look at the image above, the grass in the background, where the pieces of grass in the foreground are in focus, doesn't resemble the background images I have come to expect from Leica glass.

 

I need a wide lens. Not finding a WATE to my specifications, I bot the CV15. As soon as Leica makes a 15mm f1.4, I'm giving the CV15 away (don't all shout at once; the candidate has been chosen) or selling it. If they goof off too long, I'll go for the Zeiss.

 

Hi Bill,

 

The Zeiss 15? It's not RF coupled either so you'll be back where you started. Maybe the Zeiss 18? I'm still very surprised that you're so unhappy with the CV 15.

 

Cheers,

 

Sean

[sean_reid]

I've posted this before in similar discussions but the *only* way to know how much DOF each of one's lenses will give (at various apertures and various distances) is to actually spend some time testing and making prints. The rest is all hypothetical and depends on various assumptions. There are too many variables.

 

Test and trust the eyeballs.

 

Cheers,

 

Sean

[ho_co]

I've posted this before in similar discussions but the *only* way to know how much DOF each of one's lenses will give (at various apertures and various distances) is to actually spend some time testing and making prints. The rest is all hypothetical and depends on various assumptions.

Correct. That's why I said above that we all know there is no such thing as accurate calculation of depth of field.

 

 

And Lars is correct as usual, but ignores the improvement in precision offered by Peter Karbe's method of applying the crop factor to both the aperture and the focal length.

 

There's nothing wrong with doing as Lars and Andy suggest, and setting a different f/stop from the one whose scale value we read. We've done that for years.

 

But consider this: Peter Karbe is Leica's Director of Lens Development, and came up with a serious illustration of the concept of applying the crop factor to the aperture, shown in LFI 3/2006. If you differ with me, read his explanation. He points out that the reason for doing this is that an identical light flux will render identical depth of field. And he says that the 6.3-25.2 mm, f/2.8-4.9 lens of the D-Lux 2 becomes the 35mm equivalent of a 35-135 mm, f/16-26 lens. (BTW, he also uses a fascinatingly different way to define depth of field from the one we're used to. The article is a real must for anyone curious about photography.)

 

Back to the topic: Saying that the 6.3-25.2 mm, f/2.8-4.9 lens of the D-Lux 2 becomes the 35mm equivalent of a 35-135 mm, f/16-26 lens is much more exact than saying, "Well, it has the equivalent fov of a 35-135 mm lens, but with more dof because of the small sensor."

 

The same concept is used in the article "Lens Equivalents" that I cited above at LuLa, by Charles Sidney Johnson Jr and Nathan Myrvhold.

 

I know this gives many people trouble, but it soon becomes pretty obvious when you read up on it. I suggest you start with the LFI article, as I've now said three times.

 

We all know that a 50/2 remains a 50/2 whether it's on a bellows or an extender or a larger- or smaller-format camera.

 

But some had a hard time understanding what it meant to say that the 50mm focal length becomes 'equivalent' to a 67mm focal length on the M8 in terms of field of view. That's pretty much behind us now.

 

Many more people have a difficult time seeing that an f/2 lens on the M8 has the identical depth of field of an f / (2 * 4 / 3) = f/2.7 lens used on a full-frame 35mm camera. The exposure doesn't change, because it's still an f/2 lens. And the focal length doesn't change doesn't change, because it's still a 50 mm. But it becomes the equivalent of a 67 mm f/2.7 in pictorial effect.

 

Now Lars, read the LFI article first. Then notice that this concept is assumed with no rigmarole at Luminous landscape.

 

(Note: this is not the M8 perspective article, but the Equivalent Lenses article.)

 

Nothing you've said is wrong. My point is that we can be more specific and save the time of explaining "set one aperture but read the scale from another one" by applying this rule.

 

You're also correct, as I pointed out, and as every article on depth of field does, that these lenses are engraved with markings set for a larger circle of confusion than we would use today. Remember the Zeiss lenses for Contax II and IIa? They showed twice the depth of field of Leica lenses of the day--advertising?

 

And now, of course, digital has completely changed the nature of depth of field because there is no film thickness to hold slightly de-focused light rays. As Sean said, only your own tests with your own criteria can define what you are happy with in terms of the effect of field. In fact, many current AF lenses from Nikon, for example, don't even have a depth-of-field scale. Part of the reason for that, as I said above, is that the sensor has no depth. No optical formulae have changed. Simply the medium onto which the image is projected has changed, as pointed out in LFI 6/2007, pp 42-53.

 

Respectfully, but correct!

 

--HC

 

Oh, grammatically: There is no such thing as "a hyperfocal." The correct term is "hyperfocal distance," part of the ISV (international scientific vocabulary), and defined by Merriam Webster as: "hyperfocal distance: the nearest distance upon which a photographic lens may be focused to produce satisfactory definition at infinity."

 

You can set your lens to its hyperfocal distance, but you cannot set it to its hyperfocal, because that doesn't exist.

[gmaurizio]

 

Remember: a 50/2 remains a 50/2 whether it's on a bellows or an extender or a larger- or smaller-format camera. We all know that.

 

--HC

 

I have a comment regarding the statement above. When you use a bellows, you must correct the exposure because the longer light path generates a loss inside the bellows. This was true in Large format, and it is still true in digital.

[Jamie Roberts]

{snipped}Many more people have a difficult time seeing that an f/2 lens on the M8 has the identical depth of field of an f / (2 * 4 / 3) = f/2.7 lens used on a full-frame 35mm camera. The exposure doesn't change, because it's still an f/2 lens. And the focal length doesn't change doesn't change, because it's still a 50 mm. But it becomes the equivalent of a 67 mm f/2.7 in pictorial effect.

{snipped}

 

Howard, the LuLa article is exactly the article I was thinking of pointing out as well. I haven't seen the LFI one, but I'll try to dig it up.

 

And thank you for essentially supporting what I was saying: the crop factor plays a role in the effective depth of field, or at least it appears to. And for a given f stop, the "equivalence" creates greater--not less--depth of field with the same lens. At least, I think that's what those articles say (well, in addition to talking about sensor diffraction limits beyond lens diffraction limits!)

 

That the traditional hyperfocal distance marks are off by a stop (or more) is also true. But the two are not related, as far as I can see.

 

(BTW--Andy--I also agree that distance plays a key role, but again that's relative when you talk equivalence, I think. IOW, when I correct with my feet for a the crop, it's true I'm moving backwards, and thus gaining DOF, but not by enough to account for the difference I'm seeing, usually...)

 

Now I'm still willing to admit that I have this backwards, but again, this article corresponds to what I see when shoot.

 

Practically--Sean, as usual, is right And the CV 15 should still be easy to focus on the M8!

[hofrench]

Thank you, Lars, for introducing some much needed lucidity to the conversation.

DOF has no relation to crop factor.

Bill, I think you've got a bad unit. The Heliar 15 is a very fine lens, and with a careful prior calculation of the scene, stopping down to f/5 is in my experience almost impossible to produce an out of focus image:

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[nryn]

Everyone,

 

I did some tests yesterday using my CV 15 (on a self-coded Milich LTM adapter), the m8 on a tripod, shooting an outdoor scene with a number of elements in varying distances between foreground and background. I was a little surprised at the results.

 

Basically, focus was best at:

f8 with the infinity mark of the focus ring at 4.5

f6.3 with the infinity mark of the focus ring at 4.5

f5.6 with the infinity mark of the focus ring at less than 4.5

 

The images produced by the above settings are pretty indistinguishable from each other.

 

Other combinations I tried: (aperture/infinity mark focus setting):

6.3/8

6.3/6.3

6.3/4.5

6.3/less than 4.5

5.6/less than 4.5

5.6/4.5

5.6/6.3

5.6/8

8/11

8/8

8/5.6

8/4.5

5.6/16

6.5/16

8/16

5.6/11

 

The last four were, unsurprisingly, the worst.

 

My test was not scientific (the focus ring has no detents, so discrete settings were not possible), and I'm not going to bother posting images because last time someone did this the discussion turned to critiquing the methodology (but actually I'm not going to post images because I'm leaving for two weeks in a few hours ). I should also mention that I forgot (and always forget) to set the wate focal length to 16 when turning on the camera (my LCD is usually covered). Also, I had no IR filter for these shots (though I do have the jlm filter adapter).

 

One question came to mind: when installing an LTM adapter, is it possible to tighten too much? Would that throw off focus? Some earlier responses suggest it might. My corner performance on the CV15 is pretty poor by my standards, and I have much less stringent standards than most on this board, probably. That said, I have taken images with this lens which were amazingly sharp, though I think those images were taken in bracketed sequences. Perhaps my lack of using the WATE settings threw off the focus in the corners?

 

Some of my better CV 15 images:

 

Blue Mosque Courtyard

 

Berliner Dom Interior

 

Blue Mosque Interior

[gmaurizio]

Just a point to remember. When focusing at infinity setting, the minimum detail your digital capture will reveal are elements of the subject space whose physical dimensions are larger than the lens focal length divided by the F-number. Using a 15mm lens (it does not matter if it is film or digital) at F8 will render anything larger than 2mm IN THE SUBJECT!

This recipe was used a lot in the old days of 4x5 and 8x10. It is still used in Real Estate pictures of large mansions with interesting foregrounds and a nice scenery around.

When testing for DOF, this must be taken into account.

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Hallo,

Look here: Leica M

[lars_bergquist]

For the same Depth of Field, which is closely related to the hyperfocal distance, the physical diameter of the diaphragm has to be the same using a lens that gives the same Field of View. Thus with an M8 where a 35 mm lens has the same Field of View as a 50 mm on film you get more Depth of Field at the same numerical aperture with the M8 – as others have pointed out. To get the same physical diameter one needs to open up the 35mm lens by the ratio of 50/35 = 1.43 which is almost exactly one stop. So using the example of the 50mm on Film and the 35mm on an M8 you will get the same Depth of Field at f/5.6 on the M8 and f/8 on film.

-------------------.

This is not correct. Rays from a point in the subject form a cone with the basis = the aperture (strictly, its projection on the main optical plane) and its apex on the plane of best focus, hopefully on the sensor. So the rays converge in front of the focal plane, and diverge behind it. Depth of field depends on how fast they converge and diverge. This is given by the apex angle of the cone. This is *exclusively* dependent on a) the diameter of the cone's base, i.e. the diaphragm opening, and the distance from this base to the sensor/apex. Simple geometry. The size of the sensor has absolutely nothing to do with this. It cannot change the cone's geometry. Ergo, sensor size does not affect d.o.f. Q.E.D. Sorry, I can't make it simpler than that, because it isn't simpler!

 

The old man from the Age of Euclidean Geometry