Mamiya 7 / 150mm focusing difficulties--camera or photographer?

[mikeseb]

Forgive me if this is an elementary question, but I'm having trouble sorting it

out. Though long experienced in photography, I'm new to rangefinders.

 

I've owned a Mamiya 7 (not 7II)--my first rangefinder--for about three months

now, shooting happily with the 80mm lens. It's tack sharp under all

circumstances, apertures, and distances.

 

I recently added the 150, used but in excellent condition, from a reputable

dealer. I probably have a few days left to return it if I need to, but I'm still

sorting out the problem. Not sure if it is me, the lens, or the camera.

 

As I said, the 80 is tack sharp, but the 150 is soft. There appear to be things

in focus in the images, but not always the things I thought I was focusing on!

It appears that the plane of sharp focus is maybe three to six inches--maybe

more--behind what I thought I'd focused on. The lack of focus seems more

pronounced the closer the intended subject, and the wider the aperture.

 

I've read of the Mamiya rangefinders that focusing is more difficult with the

longer lenses, and I have found this to be true. But is it possible that the

rangefinder can be off for one lens and seemingly spot-on for another?

 

Part of the trouble I'm having is that many of my images are of necessity shot

at f/8 or smaller since as you know the M7 shutter doesn't shoot faster than

1/500 sec, and I usually shoot ISO 400 film. So the images that do look sharp,

could be so due to depth of field. I finally shot a couple of rolls of 100 speed

film at f/4.5, and now the "problem" is quite apparent--but again, with closer

subjects and open apertures. Some shots taken at max aperture, but of distant

subjects, appear sharp.

 

Any advice on what might be amiss (including the chump on the fleshy side of the

viewfinder) and how to proceed nailing this down would be appreciated. Return

the lens? Send it in for calibration?

 

Thanks all.

[sergei_antonov]

Here is what you could do to check your setup:

 

- Set your camera on tripod.

- Find piece of ground glass that could fit inside of your camera, and that you could place inside of camera instead of film. I used the glass from my Mamiya rb67. You could open shutter permanently using locking remote release cable when you set shutter speed on B. Grounded surface of the glass should take exactly the same position as film.

- Focus your lens using 4x - 8x loupe and looking to the ground glass image.

- Check if it is in focus in the viewfinder.

- Focus in the rangefined, and look to the ground glass image. Measure distance to you focus with the tape, if it is close focus.

- Repeat the same with your 80mm lens.

 

This way you will get a good idea, what is going on when you focus looking into your viewfinder. After that you could decide, what and how should be adjusted. My 150mm lens is also sometimes soft on close distances, it is harder to focus -- image is pretty small.

 

Good luck, Sergei

[david_henderson]

If you camera performs well with the 80mm its less likely to be a rangefinder issue- more likely to be user or lens.

 

Find a sharply defined object with strong verticals a considerable distance away- at least several hundred feet. I have used pylons/poles/power cables for this purpose. Focus on it. Check the distance shown on the scale - it should be close to infinity but not at the end of its travel. If its at infinity or clearly focussing at or near the 20m mark then it is beginning to look like a lens focus issue. Take two photographs at say f11. One hand held, the second on a tripod. Now fit your 80mm lens, focus it on the same subject (it will be small) and take another shot

 

If the object you've focussed on is sharp in both 150mm pictures you have a user problem. If both are unsatisfactorily sharp you probably have a lens problem. If the tripod shot is sharp and the hand held one isn't, you've just learned that its not easy to keep a 150 medium format lens still whilst handholding.

 

A user problem can be one of the following.

 

Failure to focus properly using the rangefinder. This isn't always easy with the tiny focus patch on the 150 lens.

 

Failure to keep the camera steady

 

Failure to recognise that the dof on a 150 MF lens isn't great, and that the lens barrel markings are grossly over-optimistic.

 

The reason why I suggest taking a frame with your 80mm is in case there is a rangefinder issue that is being disguised by the better dof, small apertures you have been using. The 80mm shot should be pin sharp, and in the possibly unlikely event that the 80 and 150 tripod shots both look unsharp then its time to reappraise whether there's a rangefinder issue here.

[sfcole]

I had the same problem with my M6, and I'm awaiting return from Mamiya to see if it

will help. Mine focused consistently in front of the subject. I think the best thing is

have someone check it. Focus adjustment is only about $60. Try camerarepair.com--

they work on these. Frankly I don't think checking with ground glass can really telll you

definitively. The 150 also has its own adjustment.

[john_photo]

At f8 with this lens your DOF is extremely shallow. Remember that you always have more more DOF behind the object you are focusing on and less in the front. The 2/3 rule.

 

My experience has been that DOF markings on the Mamiya 7 are anywhere from 2 to 2.5 stops from reality so keep this in mind. The 50mm is the worse in my view. A solid 2.5 or maybe even 3 stops off.

 

I suspect this is your problem. Close focusing the 150mm lens is a chore because there is so little room for error in the rangefinder. Its a good lens stopped down with fast film handheld for landscape. For portraiture you would be better off with a MF SLR and a tripod if this is an option for you.

[mikeseb]

Thank you all for your assistance and ideas. I did some more impromptu testing today, what I could manage at work running out to the parking lot during slack times!

 

I shot ISO 100 film at max aperture of f/4.5 with the 150. Viewing the results, I am thinking it is more likely a photographer problem than a lens or rangefinder problem.

 

A variety of images of subjects both near and distant turned out quite sharp. Any focusing problem is evidently negligible based on what I'm seeing. There may be just a smidge of out-of-focus-ness but I couldn't reproduce it consistently, making me think the problem is my eye and hand.

 

I am amazed, however, at just how little DOF this lens has wide open, compared--let's say--to the 140mm for my Contax 645 at its max aperture of f/2.8. In one shot of a parking-lot sign maybe 9 inches wide, and angled slightly off parallel with the camera's film plane, so that one edge was maybe four inches farther from the film plane than the other; and standing perhaps 2-2.5m from the sign, only the edge I focused on was sharp--the other was out of focus! This strikes me as quite a bit less DOF than I have with the Contax's 140mm wide open at f/2.8! (Is that optically plausible?) I also realized that on some of the images i sho previously, I may have been at or within the 1.8m minimum focus distance this lens is capable of.

 

I am likely going to send the camera in for a CLA anyway, and I'll have them check the RF while they're at it. I'll also send in the 150 so they can check the two together.

 

@Scott: you recommend camerarepair.com; others have praised Mamiya and Precision Camera Works (Chicago). Anyone have any other thoughts on where to have this work done? I take it camerarepair.com did good work, and speedily? And what did you mean by "the 150...has its own adjustment...."? Do you mean the infinity stops?

 

@John Photo: damn that's some shallow DOF. I (almost) never look at DOF markings, since I've been in the habit with SLR's of checking the DOF preview pretty religiously to get the "gestalt" before I shoot. Another workflow difference I'm going to have to get used to with a rangefinder. I do a lot of portraiture, but I suspect with this system it's going to be full-body shots or "environmental" portraiture with a lotta "environment" in the frame, and everything eye-slicing sharp at f/11 or 16. Sigh.

 

Thanks again for everyone's thoughts.

 

Mike S.

[david_henderson]

"Is that optically plausible"

 

Sorry no. Although 140mm is less than 150mm if one assumes the same enlargement ratio and therefore the same COC, the fact of f2.8 vs f4.5 weighs heavier and the Contax lens wide open will offer less dof than the Mamiya 7/150mm. If you build in the need for greater enlargement ( smaller COC) from 645 this increases the advantage to the Mamiya. Depth of field is driven by format size, focal length, subject distance and aperture. It is not driven by camera brand or type.

 

The dof (bearing in mind that this is subjective) on a 67 150mm lens at f4.5 , focussed at 1.8 m is 7cm. So not a lot. The big problem with the Mamiya 7 is not that the dof is worse than other 67 systems (it isn't)- but that you get no indication of this whatsoever ttl and the lens barrel markings are next to useless. If you're going to use your rangefinder for dof critical applications at fairly close range , you're going to need to carry dof data or access one of the many online dof calculators as you go. For me, I'd take you Contax for that sort of application any time- not least because there would be no parallax issues that way and the finder is much more WYSIWYG than the Mamiya.

 

A couple of final points if I may. First I recall that when first posting here years ago I made the point that dof extended twice as far behind the point of focus than in front. Bob Atkins came on and made a comment along the lines of "ah, you've been reading Popular Photography again haven't you?" and explained gently that especially at close distances dof could often be very close to equal in front and behind the point of focus.

 

Which leads me neatly to your parking sign example. If you focus on the leading edge of the sign then at a range of 2/2.5m you waste half your dof , which at that range extends as far in front as behind. If you had focussed on the centre of the sign rather than the leading edge then you could achieve satisfactory focus across the whole sign- just at 2m, comfortably at 2.5m.

 

Useful, these dof calculators.

[oscar_ling2]

150mm lens wide open on mamiya7 only got slight problems when do the closest distance shots, may be one or two inches off, longer distant shouldn't have any problems. If got , most probaly is rangefinder off, all mamiya 7 lens should be focus at infinity at the end of the lens turns. That's my case. I calibrate the body myself because the was way off first bought it, but managed to get lower price due to off rangefinder.