Is my lens calibration off?

[Ulophot]

After taking a few photos last week with my Mamiya 645, I found on examining the negatives that after using the focus collar to set hyperfocal distance with infinity aligned to a stop more open than I was using, distant objects were still quite soft. That led to testing my four lenses yesterday with results today.

Let me say that I am well aware that lens scales are optimistic, based on minimal enlargement, and may be variably accurate as to distance indication.

With tripod solid, mirror lock-up, and 1/250 or 1/500, I took in a scene with signs at varying distances and a road and trees perhaps quarter-mile distant. For each of my three most used lenses, I made four exposures: 2 at f16 and 2 at f/11, the first two with infinity aligned with 11 and then 8, the next two at 8 and then 5.6, thus doing in a different way what those who know do, i.e., closing down 1-2 stops after using whatever guide for DOF. The guides, including the lens scales, are based on minimal enlargement to render apparent adequate sharpness of DOF at the boundaries. My lenses are all Mamiya.

My 80 appears good, in that Inf looks respectably sharp even with an extra 1 stop "leeway." The 55 and 110 do not look sharp at Inf even with 2 stops "surplus", though they are very sharp in the nearer distances. I also tested the 55, the 110, and my 150 for infinity when actually focused on Inf. In each case objects at Inf look sharp and well-defined.

I checked my lenses scales against an online DOF calculator that uses d/1500 for CoC. At f/16, the hyperfocal distance (H) for the 55 is 14'. At f/8, my scale put H at about 17-18 ft, so at least that neg should be sharp. H for the 100 at f/16 on the calc is 55'; on my lens at f/8, it's maybe 70'.

I don't know enough about optics to judge these results. So, I am wondering whether the 55 and 110 (which was recently serviced by itself by a reputable place) need to be calibrated on camera for mount adjustment, or what.

 

[snusmumriken]

Sounds like you might find it helpful to read Harold Maerklinger’s book The Ins and Outs of Focus. You can download it free here. A consequence of his reasoning - I think - is that you can’t judge lens performance at infinity except with the lens set at infinity. The whole concept of hyperfocal focusing gets turned inside-out in the book.

 

[koraks]

hyperfocal distance

An overrated construct that IMO nobody should rely on except maybe when using 35mm cameras in street photography.

I'd suggest just checking if the film plane and ground glass focus agrees. You'll likely only need one lens to test with, since this is mostly about ground glass and mirror alignment. If this test shows no problem, then the whole "hyperfocal" business will work as intended and any limitations you'll experience are due to the physical limitations inherent to it (which are very significant indeed).

 

[BMbikerider]

Being an medium format SLR why on earth are you trying to use the scale focussing even to get the Hyperfocal distance?
If you are after absolutely critical sharpness then the hyperfocal distance is a waste of time. It is all down to what is or was known as the 'circle of confusion' The dead centre of the circle can be taken to mean as sharp as possible, then the further you get from the point in the centre, the less sharp it will appear. that is a fact of science you cannot avoid or change pas a certain point.
On all lenses, the hyperfocal distance can be changed by using a smaller aperture, but there reaches a point where closing it down further will also affect the apparent sharpness will change by light dispersion caused by the edges of the diaphragm blades trying to deflect the rays of light.

Are you expecting just too much.

As Koraks says above, hyperfocal focussing is the realm of the 35mm camera.

 

[Ulophot]

Thanks to all. I do have Merklinger's book, which I got for LF work, though I abandoned trying to use his approach in the field, and his math is out of my (little) league. My camera is a field camera without even detents for lens board vertical, so tilting 2.5 degrees, never mind about figuring out J with my poor geometric skills, was not going anywhere, and I adopted a different method of determining tilt/swing.

I am aware of diffraction limiting, which is why I chose the apertures I did. This is a factor that I have tested more on my 4x5, with which I am more likely to consider a very small aperture when shooting a scene or still life. My primary interest is portraiture, and I'm not one looking for skin pores, so ultimate sharpness is not my concern.

Back to the 645, I find it interesting that my 80 should produce a better result than either my 55 or 110 in my test, but perhaps there is another factor at work. Generally I have found the Mamiya lenses very sharp.

 

[Alan Edward Klein]

Sounds like you might find it helpful to read Harold Maerklinger’s book The Ins and Outs of Focus. You can download it free here. A consequence of his reasoning - I think - is that you can’t judge lens performance at infinity except with the lens set at infinity. The whole concept of hyperfocal focusing gets turned inside-out in the book.

Without reading a whole book, can you sum up his theory about hyperfocal focusing that is different?

 

[Alan Edward Klein]

An overrated construct that IMO nobody should rely on except maybe when using 35mm cameras in street photography.

I'd suggest just checking if the film plane and ground glass focus agrees. You'll likely only need one lens to test with, since this is mostly about ground glass and mirror alignment. If this test shows no problem, then the whole "hyperfocal" business will work as intended and any limitations you'll experience are due to the physical limitations inherent to it (which are very significant indeed).

I use hyperfocal and more often DOF tables all the time with medium format. Often, I'll calculate the DOF required and then add one stop for good measure. I do agree that lens scales and calculations are not exact. Hence the adding of an extra stop.

 

[BrianShaw]

Without reading a whole book, can you sum up his theory about hyperfocal focusing that is different?

Read just Chapters 4 and 11; about 5 pages...

 

[250swb]

There is only ever one thing or plane truly in focus, the DOF scale tells you how much else will be tolerably sharp depending on aperture. But using hyperfocal focusing you move the focus way off from whatever was important to something else and hope tolerable sharpness overall is err, tolerable. The rules don't change for landscape so you have to ask yourself if you'd use hyperfocal focusing for making a studio portrait? No, I doubt you would, so think of landscape photography as making portraits of the landscape and leave hyperfocal focusing for 35mm street photography where pro rata DOF is much greater, and even then relying on it is dubious as a practice. It's only something to have in the armoury, not to rely on.

 

[snusmumriken]

Without reading a whole book, can you sum up his theory about hyperfocal focusing that is different?

What @BrianShaw said. You’ll find that it is written in a very reader-friendly fashion.

But briefly, the hyperfocal method is based on how much fuzziness is acceptable at the film plane. Maerklinger’s approach starts instead outside the camera, asking what size objects or features in the scene you want to be able to distinguish. The two approaches are not contradictory: neither is theoretically wrong. But they do lead to different practical conclusions.

 

[Ulophot]

An overrated construct that IMO nobody should rely on except maybe when using 35mm cameras in street photography.

I'd suggest just checking if the film plane and ground glass focus agrees. You'll likely only need one lens to test with, since this is mostly about ground glass and mirror alignment. If this test shows no problem, then the whole "hyperfocal" business will work as intended and any limitations you'll experience are due to the physical limitations inherent to it (which are very significant indeed).

Regarding this test, if I choose closest possible focus at f/2.8 for the 55, to minimimze DOF, setting up a ruler test (angled rule scale to see where focus actually falls on neg in comparison to distanced in focus on the finder), is this sufficient, or this there more involved?
Thanks.

 

[John Koehrer]

The first thing I would do is check what Koraks suggested in the third post then trying to
find a problem with anything else.
Check GG against lens focus & go from there.

 

[Dustin McAmera]

If you have, or can borrow, a second SLR with a lens you trust, you can check infinity focus with each lens against what the lens scale shows, with this method shown at Rick Oleson's site.
http://rick_oleson.tripod.com/index-123.html

 

[Sirius Glass]

Sounds like you might find it helpful to read Harold Maerklinger’s book The Ins and Outs of Focus. You can download it free here. A consequence of his reasoning - I think - is that you can’t judge lens performance at infinity except with the lens set at infinity. The whole concept of hyperfocal focusing gets turned inside-out in the book.

For a given f/stop set the infinity sign at that f/stop and the in focus range will be at the maximum for that f/stop.

 

[BrianShaw]

For a given f/stop set the infinity sign at that f/stop and the in focus range will be at the maximum for that f/stop.

You might want to skim Merklinger's book for a bit of a different approach.

 

[Sirius Glass]

You might want to skim Merklinger's book for a bit of a different approach.

On my list of things to do.

 

[Sirius Glass]

You might want to skim Merklinger's book for a bit of a different approach.

On my list of things to do.

I just ordered it. Thank you for reminding me to do that.

 

[reddesert]

I'm not sure exactly what you (the OP) are trying to test. However, it seems that you found when you scale-focused each lens at infinity, that infinity was acceptably sharp. So we know the lenses are fine and the focusing scale is correctly calibrated at infinity.

Next, you can try focusing a lens on the ground glass to see if infinity on the ground glass agrees with infinity on the scale. You don't need to take a picture to do this, just check that the ground glass also agrees with the already-checked lens focusing scale. If so, then the camera and the focusing screen position are fine.

Then, it's just a question of whether the DOF scales are adequate for your purposes. It sounds like they aren't if your goal is to retain precision details at large distances. Hyperfocal focusing is about optics; it's not wrong, but it doesn't take into account pictorial goals and the relative sizes of objects in the frame. Pictorially, on one hand, out-of-focus objects in the foreground are usually distracting. On the other hand, details at large distances are small, so even a small blur can render them less legible. Only you can determine the balance of visual interest between foreground and background in your photos.

 

[snusmumriken]

Then, it's just a question of whether the DOF scales are adequate for your purposes. It sounds like they aren't if your goal is to retain precision details at large distances. Hyperfocal focusing is about optics; it's not wrong, but it doesn't take into account pictorial goals and the relative sizes of objects in the frame. Pictorially, on one hand, out-of-focus objects in the foreground are usually distracting. On the other hand, details at large distances are small, so even a small blur can render them less legible. Only you can determine the balance of visual interest between foreground and background in your photos.

That is the most eloquent explanation!

 

[BrianShaw]

I just ordered it. Thank you for reminding me to do that.

Ordered it? It’s downloadable.

 

[Alan Edward Klein]

Read just Chapters 4 and 11; about 5 pages...

This is basically Merklinger's advice summing up his DOF book on pg 73/74.

The traditional depth-of-field philosophy usually ends with the advice: to maximize depth-of-field, choose a moderately small lens opening, set the focus to the hyperfocal distance, and shoot. My parting advice would be a little different. For typical normal and wide-angle lenses, especially lenses having focal lengths less than about 50 mm no matter what the camera format, set the lens opening to somewhere in the 2 mm to 5 mm range, set the focus at infinity, and shoot. For lens openings larger than 5 mm, and for longer lenses that tends to mean all normal working f-stops, focus on what is critically important. The same is true of close-up photography no matter what the lens. But if you are taking scenic pictures with an 8x10 in. view camera on a tripod, and with a 300 mm lens, f/64 is not at all a bad choice (as a number of famous photographers have noted).

 

[Ulophot]

Next, you can try focusing a lens on the ground glass to see if infinity on the ground glass agrees with infinity on the scale. You don't need to take a picture to do this, just check that the ground glass also agrees with the already-checked lens focusing scale. If so, then the camera and the focusing screen position are fine.

Thank you. As noted in my OP, I did check three of my lenses, focused at Inf., at 1/1000 @ f/5.6, and the most distant details are sharp. I infer from what you said, as quoted here, that if this is fine, I don't need to perform the ruler test I outlined in #11, above, to confirm that when I focus on something closer, such as a portrait subject, the plane I view in focus will be in focus on the neg. Do I understand this correctly?

 

[koraks]

Regarding this test, if I choose closest possible focus at f/2.8 for the 55, to minimimze DOF, setting up a ruler test (angled rule scale to see where focus actually falls on neg in comparison to distanced in focus on the finder), is this sufficient, or this there more involved?
Thanks.

That's pretty much it, really. I usually place a piece of ground glass (can be improvised in several ways; transparent plastic with some scratches will do, too) on the film plane with the back open and then check focus on near and far/infinity settings. The viewfinder focus should agree with the ground glass/film plane focus. It doesn't require shooting any film. Just the back of the camera open and the shutter on bulb. It helps to set up the camera on a tripod indoors near a window where a distance object (e.g. the horizon) is in view as well as something inside a few feet away (the window frame for instance). No ruler necessary this way.

 

[Sirius Glass]

Ordered it? It’s downloadable.

Too late. It will arrive when I am out of town.

 

[grahamp]

This got me curious - a quick scan of my various cameras showed that only the venerable 35mm Vito B (50mm lens) had actual index marks at each distance. All the others (rangefinder or reflex) just had engraved numbers. So only the camera that required scale focusing even attempts to give a precise setting. At least infinity is usually a hard stop on a helical mount, presuming it is correctly set.