Calibration and Manual Lenses

[TiCoyote]

I have a Hassie 500 c/m and a 150 f/4 CF lens. I'm finding that it's backfocusing. I brought it into the shop, and they told me that it could be mirror adjustment, a problem with the body itself, or lens adjustment.

Here's my question: it's a manual focus lens, so how could it be out of adjustment. I mean, if an object is 10 ft away, even if the distance scale on the barrel reads 12 ft, but the image in the viewfinder is in focus, shouldn't the image on the film plane be in focus too? If not, that seems like a body problem, not a lens problem. What am I missing?

 

[Derrel]

Is the viewfinder screen at the proper height? Is it the proper viewfinder screen? The screen is not installed upside down, is it?

It could be a body problem, very easily, if the lens mount is not at the proper distance, and a shim is either missing, or too many shims have been installed in a repair or cleaning. The lens mount to film plane distance is often made perfect by using very,very thin metal shims to correct for minor discrepancies. This camera might be 40 years old, perhaps the same with there lens; older mechanical cameras often needed mechanical adjustments; it is VERY possible, as in VERY possible, that in those decades, the camera or film back or backs have met a less-than-skilled repair tech.

 

[TiCoyote]

I bought the camera, back and lens from KEH. The production dates are 1987, 1975, and 1991 respectively. I agree that each of these parts may certainly have needed service over this time period.

My question is really just whether it's reasonable to blame the lens if an image is in focus on the VF but not on the film plane. It seems to me, that is more likely a problem with the body, back, or VF.

 

[Derrel]

The viewfinder screen needs to be in the exact, right location to determine focus. if the viewfinder screen needs a spacer underneath it (as in the form of, say a foam square, or a leather square, or a metal spacer) to equal the flange-to-film distance, then the viewfinder image will show **the wrong focus**.

If the flange-to-film distance is not exactly proper, to within a few thousands of an inch, then the focus will be way off at Infinity. This is what spacers are so,so commonly used inside the lens mount area, on hundreds and hundreds of film camera models: shimming the lens mount to the exact, correct distance is very commonly used as the way to regulate lens focus.


As to "blaming the lens"...it could be a lens issue, but it is more likely to be the viewfinder screen, or the lens mount and the flange-to-film distance--but who really knows? Does the issue persist with another lens? Does the problem persist with a different film back? You have not described in much detail the flaws, nor what cross-checks you've performed, so this is mostly speculative comments on what "might be" the problem(s) you're having.

I tend to agree with you that the lens is not to blame here...my money goes on a MIS-aligned viewfinder screen, or a MIS-aligned (out of specification) lens mounting flange that is not at the right distance. But again--not much information here, on a complex mechanical system.

But let's go back to the scenario you listed: " if an object is 10 ft away, even if the distance scale on the barrel reads 12 ft, but the image in the viewfinder is in focus, shouldn't the image on the film plane be in focus too? If not, that seems like a body problem, not a lens problem. What am I missing?"

Body problem: viewfinder screen is not at the right distance Lens mount is not at the right distance. 10 feet and 12 feet are NOT close enough to cover the depth of field. Lens mount, camera mount, viewfinder screen, film plane alignment: could be a problem anywhere in here.

Lens problem: who knows who has worked on the lens, or repaired the lens, our disassembled and reassembled the lens, over the past 24 years. it **is** possible that the lens could be improperly re-assembled. I am not a repairman, but...if the lens mount is not 100% at the right distance to the film....that could explain the problem of a 10 foot and a 12 foot discrepancy causing the problem. You have a pieced-together outfit made over decades...what about the old film back, made in 1975? That too could easily be out of specification. You have lens mount; flange-to-film, viewfinder, body of camera, and film back and film plane issues to worry about. Six areas. Six.

 

[LostLensCap]

I had an old 500C that had the same problem. I set an object exactly 10 ft away from the film plane, set the lens to 10 ft and then adjusted the screen screws until it was in focus. Problem solved.

 

[TiCoyote]

Hi Derrel,

Thanks for the detailed response. I agree with everything you've said. My real question was just how the lens could be at fault, if the backfocusing is consistent. Here are some test shots I did.

 

[LostLensCap]

In my non-expert opinion, the fault has to be with the focusing system of the camera body and not the lens.

 

[ashleykaryl]

Once upon a time I had a 500cm and later a 501. I can't say I ever experienced this but is it possible the film is not being held perfectly flat.

 

[Derrel]

I see from the test photos that there is about one inch worth of reasonable depth of field...this looks within normal tolerances to me. On both the newspaper shot, and the steel tape measure shot, the actual depth of field band is VERY narrow...within what I wouyld consider "normal" for a film camera shot at close range. These two test images show the type (degree of) of variation in focus and depth of field that "focus system micro-adjustment" systems were developed for.

I realize there could be other issues, or worse focus performance in some situations, but looking at the steel tape measure, I mean, at that didstancer, at the ;ens f/stop used, there is NOT much depth of field! And the focus placement is not off "by all that much".

There's a reason many professional photographers who shot medium format liked f/5.6 and f/8; some focus "cushion".

 

[ashleykaryl]

There's a reason many professional photographers who shot medium format liked f/5.6 and f/8; some focus "cushion".

I used to do a lot of beauty work on the 180mm at F4 and at typical head & shoulders distance the depth of field was tiny. It was very tricky to get eyes, lashes and lips all in sharp focus at the same time with the model facing straight towards the camera. A tripod was essential and as you say shooting at f5.6 or even f8 would offer some leeway.

NB I really miss my Hasselblad gear

 

[ashleykaryl]

Hi Derrel,

Thanks for the detailed response. I agree with everything you've said. My real question was just how the lens could be at fault, if the backfocusing is consistent. Here are some test shots I did. View attachment 130454 View attachment 130455

You've just reminded me of an experience I had with a Tamron zoom a few years back. It was initially fine, but after a few months it started back focussing. At first I thought it was the camera that was wrong, but it soon became clear that other lenses were fine and anything shot with a wide aperture was back focussing. A quick test shooting a wall at F4 and then at F11 made this clear. At F11 the additional depth of field would largely hide the defect.

I ended up sending the lens to Tamron who fixed it at not inconsiderable expense and it came back working properly. A few months later the same problem returned, only this time it was front focussing and I gather one of the elements was not staying perfectly seated. Tamron were unwilling to fix it without charging another repair bill, so I ended up selling it on eBay for spares and repairs. That was a lens that looked like new and had hardly been used, but I just couldn't trust it. I'll never buy another lens from Tamron.

It's not inconceivable after all these years that one element on your lens is now fractionally out of place. In the old days there were lots of small camera repair shops who could have looked at this for you very cheaply, but I don't know what the situation is like nowadays.

 

[TiCoyote]

So, the repair shop said that one of the elements is separating. They told me that I should probably return it if I can. I got the lens from KEH 7 months ago, and they have a 6 month warranty policy. I called them, and they said that there was nothing they could do. It's outside of warranty.

I'll ask the shop for a repair quote, but I might just end up replacing it.

What do you guys think about buying a lens from Japan on eBay?

 

[ashleykaryl]

That's a shame but I would investigate the cost of repair to see if it is viable. I once had a shutter leaf repaired on an 80mm lens that had literally come lose inside inside the lens. It wasn't expensive and never gave me another problem.

Personally I would be wary of buying from Japan. I don't know what import duties there might be but leaving that aside it's a real hassle if you have to return items abroad. I once had a bad experience with a vintage watch purchased from a jeweller in Switzerland that arrived broken and resolved never to buy or sell outside my home country on eBay.