Adjusting focus on hasselblad

dfoo · Mar 24, 2009

I did some test shots yesterday with my 150mm lens wide open. Examining the negatives with a loupe shows that either the lens is simply not very sharp at F4, or the focus was off. The focus point was about 6-7 feet away. I took some later shots at F32 and the object is very focused. I'm using a split-prism screen, using the focusing magnifier on the waist level finder. Is this just not accurate enough for such precise focusing, is the focus off? Is the lens not sharp? Is there a way to adjust the focus?

archphoto · Mar 24, 2009

The best way is to photograph a tape measure on the ground under an angle.

Focus on one point and write down.

If your focus is off then you will see how much.

Peter

dfoo · Mar 24, 2009

If the focus is off how do you adjust it?

keeds · Mar 24, 2009

I would have thought the problem is likely to be with the seating of your viewing screen?

bdial · Mar 24, 2009

What body do you have? On 500C's the positioning of the screen can be adjusted with shims, I believe.
For the newer ones, I am not sure.

dfoo · Mar 24, 2009

Its a 500C/M.

John Koehrer · Mar 24, 2009

The first thing you need to do is check infinity focus. If that's on everything else is. Pick a target around 500-1000 feet away, that's enough for practical purposes.
Check focus at BOTH the focusing screen and the film plane. Use a piece of ground glass for the film plane.
If they're the same, it's not the camera. If their different the plane of the screen needs to be adjusted. On the CM I'm not sure but on the C you had to remove the screen & fiddle with four adjustment screws beneath the screen.

dfoo · Mar 24, 2009

I just did a quick test. I focused at 3 meters through the lens & screen at F4. I then opened the shutter, took the focus screen and placed in at the back of the camera, and looked at the split prism. It was around 50cm off according to the focus scale on the lens. I'm not sure where the exact film plane is supposed to be, but I would guess it is pretty close to where i had the screen. What would be simplest would be to shim the screen slightly. The screen rests on 4 posts, but there doesn't appear to be an easy way to adjust the height of those posts. Any ideas?

Q.G. · Mar 24, 2009

It is unlikely that the focussing screen seat is to blame.

The mirror can be off, needing the pads it sits on replaced for new ones.

Could also be the body length. But unless you dropped the camera, or disassembled the thing and not put it back right again, not likely.

I would ask a repair shop to replace the mirror pads and realign the thing.

dfoo · Mar 24, 2009

Mm... where are the pads? The mirror in my camera sits on two metal brackets.

dfoo · Mar 24, 2009

Here is a repair manual I found online. Unfortunately, since I don't have the tools they mention its pretty hard to adjust the camera.

http://www.scribd.com/doc/3005241/Hasselblad-500555-manual-repair?page=14

Q.G. · Mar 24, 2009

That repair manual is for cameras with a slightly different construction.

The pads below the 500 C/M's mirror are shown in the image below (no. 4, sitting in the pan 3, below the mirror 5):

Foam pads deteriorate, and they would be the first thing i would look at.

If the pads are not to blame, there is a lot else to adjust.
All of this should be done using the proper jigs and know-how. So better ask a qualified repair person.

mike c · Mar 24, 2009

dfoo, last time I was in to my camera repair place at samys I told him I was buying a accu screen for my cm,he told me stop by after I bought it so he could check the focus. So I did he put it in some can of Jig,made some kind of measurements an it was fine.Took him 10 min and didn't charge a penny. Although I had recently had him do a CLR. It might be cheaper in the long run to have a good tech have a look at it. I would diffidently try the tape measure thing with flim in camera,also the infinity test.

Adjusting focus on hasselblad

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