Hasselblad 500 c/m focus issue

[Camera Cravings]

Hi I just joined the forum in hopes that someone really can help me with advice so that I can put my Hasselbad 500c/m back in service My Hassy was taking parfect, sharp photos and then one day something happened and it started taking very out-of-focus photos. I don't have the 'Hasselblad' tools and I don't have the money to service it. So I have to do it myself using regular tools that I have. If I fail the first time, I will just keep coming at it.

Some time ago I had to put away my Hasselblad 500c/m until I can afford to repair it because it developed focus problem. Last roll of film I shot was out of focus pretty bad. Today I tried to evaluate the scope of the problem. I mounted NPC Polaroid back and used ground glass pressed against picture plane of the NPC Polaroid back and a magnifier glass to compare focus through waist-level finder vs. through the lens. For this used 50mm f/4, 80mm f/2.8 and 150mm f/4 Zeiss lenses.


While all lenses showed good focus at infinity (except for 80mm which came up short) they all performed differently at the close distance of approximately 1.5-1.7 meters. 150mm showed the least discrepancy, and the 50mm showed the most discrepancy. Photos show my blue marker markings labeled 'W' for the viewfinder and 'L' for through-the-lens. Please note that my markings have no relation to the distance scale of the lenses.

I set the camera on a tripod and only changed the lenses. For each lens, I first established sharp focus through the viewfinder and then checked it through the lens. I found that the camera was back-focusing through the lens. I think this suggests that the flange to the ground glass distance (viewfinder) is shorter than the flange focal distance. I thought it is probably not the mirror / deteriorated mirror cushion issue, for, if the mirror sogged, the flange to ground glass distance would be longer, right?

At this point, I only know that the camera's focal distance is adjusted by moving the chassis against the outer body shell.

Next, I decided to check the camera's flange focal distance using depth gage with the wide base. I do realize that my method may be fundamentally flawed as I was not entirely sure what points I should measure to and from. So I would welcome any suggestions on this!

I mounted a lens and placed calibrated depth gauge with the wide base on the picture frame of the open Polaroid back, and measured the distance to the back side of the mounted lens. Here's what I measured:
top left corner 2.8" or 71.12mm
top right corner 2.797" or 71.04mm
bottom left corner 2.797" or 71.04mm
bottom right corner 2.796" or 71.03mm

I know that the flange focal distance for Hasselblad 500c/m is 71.4mm +- 0.03mm, so my camera is outside the tolerances by at least 0.3mm. Does this agree with my camera back-focusing through the lens? Can this error dramatically affect focus at close distance and be less noticeable at infinity? If not, then I should probably check camera back. ANY SUGGESTIONS TO IMPROVE MY MEASUREMENT? Once I am able to verify my measurements I will start figuring out how to adjust the camera.

Thanks everybody for your input! Really apreciate it!

Alex

 

[shutterfinger]

Being familiar with camera servicing but not Hasselblad I googled Hasselblad 500 C/M service manual and got
https://www.google.com/search?q=Has...anual&ie=utf-8&oe=utf-8&client=firefox-b-1-ab
and the first two pdf links should show how to set up the body.
With the information in the PDF's one should be able to adjust the body focal length without the special tool if one has a good digital caliper or similar. DIY adaptation should be to achieve accurate results but it may take longer than if the test bench special tools were used.
Many camera models use the same body shell.

 

[Camera Cravings]

When I removed focusing screen I noticed that the mirror in the up position has uneven spacing on the sides. While on the left side (top picture) space is even, on the right side (bottom picture) I notice that space is wider towards the back and narrower towards the front of the camera. And I guess mirror damper is shot too!

 

[BrianShaw]

You should search the forum for postings by HT Finlay (I might be spelling his surname wrong)... he worked this kind of issue to a successful conclusion, albeit after much time and consternation.

EDIT: Here's a start... he may be using a different user-name now...
https://www.photrio.com/forum/threads/hasselblad-infinity-desparity-question.98403/

 

[GLS]

When I removed focusing screen I noticed that the mirror in the up position has uneven spacing on the sides. While on the left side (top picture) space is even, on the right side (bottom picture) I notice that space is wider towards the back and narrower towards the front of the camera. And I guess mirror damper is shot too!
View attachment 201510
View attachment 201511

Yeah, from reading your OP my first thought would be a mirror alignment/calibration issue.

 

[Sirius Glass]

The body is out of alignment. A few minutes on the Hasselblad jig should get it properly aligned. My Hasselblad repairman did it while I waited and there was no charge. See if you can find a Hasselblad repair that you can walk into and talk to the repairman. Otherwise David Odess http://david-odess.com/ or Hasselblad repair in New Jersey.