Hasselblad focus/stability issues

[scinysnaps]

I recently acquired a 40mm DistagonCT* and a 150 Sonnar CT* to add to my 500 CM / 80mm Plannar CT*

I come from a very flash heavy background,so my experience with an ambient light / hand held / medium format type of situation is less vast.

I am seem to be experiencing occasional focus errors which I rarely have encountered in the past, be it Hasselblads, Mamiyas, Nikon etc etc

The image seems to be focused on an area behind the point at which I focused on through the viewfinder. I have eliminated bad eyesight ( just recently received a new prescription ) and mis-focus ( I had another photographer look through the viewfinder to double check my focus before exposing the film )
This is of course more apparent when I shoot close to or wide open.

Could it be the film magazine is not holding the film flat?

I also seem to experience some severe camera shake with the 40mm (all 1.3KGs of it..) and the 150mm with anything less than 1/250th ( Hand Held ) On occasion I can get away with 1/125th.

I have used the 40mm on a large Manfrotto tripod AND locked up the mirror, but with a shutter speed of 1/4 or 1/2 sec and maybe f5.6 or f4.0...I am getting a soft image. Is this normal, Should I be using a cable release?

I am planning to send the whole set in for inspection, but wanted to hear what you guys have experienced before...

Cheers

 

[mike c]

Seems like some thing is out of sync.125th sec on the 150mm hand held maybe some blur.If the focusing screen is improperly fitted maybe also.

 

[Ed Sukach]

If the focusing screen is removable, check to see that it is installed properly. The "ground" suface (frosted) should be down, facing the camera's mirror. If it is not, (shiny surface down) the focusing distance will not be the same as the distance to the film.

 

[André E.C.]

Are you using a prism finder?

 

[Sirius Glass]

If the focusing screen is removable, check to see that it is installed properly. The "ground" suface (frosted) should be down, facing the camera's mirror. If it is not, (shiny surface down) the focusing distance will not be the same as the distance to the film.

Also the focusing screen may be out of alignment. If so a Hasselblad technician will need to make the adjustment.

Steve

 

[scinysnaps]

Guys, thanks..
I am using a waist level with the magnifier.
I have inspected the focusing screen. Visually, it looks to be in order, but I assume a technician will be able to asses that better.
Would it be fair to say, the problem is more likely to be in the camera body or film magazine rather than a lens problem?

 

[André E.C.]

You may want to check mirror alignment also,you never know!

 

[Sirius Glass]

Guys, thanks..
I am using a waist level with the magnifier.
I have inspected the focusing screen. Visually, it looks to be in order, but I assume a technician will be able to asses that better.
Would it be fair to say, the problem is more likely to be in the camera body or film magazine rather than a lens problem?

Camera body. It needs to be put in the alignment jig and adjusted. It does not take long but even with the tools us mortals could not do it.

Where do you live? May be we can point you to a repair man in your area rather than ship it away.

Steve

 

[scinysnaps]

HAHAHA, unfortunately I live in Asia....
I do have the services of an experienced Hasselblad technician. However, I doubt he would have anything as fancy as an alignment jig.
Any other ideas? Film magazines would not be the issue? In the meantime, I will get him to check the mirror and the focusing screen.

 

[mesh]

Another possibility is that the mirror foam has disintegrated. It's the small pads between the mirror and it's holder. Obviously when the mirror has moved back slightly as a result, then you will always back-focus. It's certainly not a difficult fix for a tech. Apparently I've heard this foam should actually be replaced every 10 years or so. QG knows a lot about this if he's around - he kindly sent me a diagram on another APUG post a while back. Will try and find it...

 

[bdial]

On a tripod, assuming correct focus, there should be no softness issues, with the mirror up or down.

The film magazine isn't too likely to be an issue. But it's easy enough to inspect if you don't mind sacrificing some film. If you load the magazine and inspect it off the camera with the darkslide out, the film plane should be uniformly flat, with no (uneven) gaps along the sides.

I agree with the others that the screen, it's positioning, or the body alignment are the likely culprits here. Is the screen fully seated, with the catches on either side engaged? Is it a Hasselblad, or aftermarket screen? I'm not sure if the screen can go in upside down, but that might be a possibility too.

One way to check things would be to obtain/borrow a rear screen adaptor (not sure of the exact name). It allows a focus screen to be mounted at the film plane. It was mainly sold for composing through the lens on superwides but it can go on any body, it mounts in place of the film magazine.

 

[mesh]

(there was a url link here which no longer exists)

 

[scinysnaps]

Mesh, thanks...
bdial.. I will check the magazines as suggested. I doubt it is the screen as it is firmly seated in the proper orientation. As for your suggestion on the rear screen... would a piece of groundglass laid on the back be able to check the focus is correct and in sync with the image on the focusing screen?

As for the tripod shots, they were at 1/4 to 1/2 sec exposures at maybe f4.0 to f5.6. It was an overall softness.

After looking at my camera, the mirror seems to be slanted and not sitting level in the up position, and the foam on top of it has started to break up. However when it is in the down position, it's harder to tell if it's out of position. I would assume it may not affect the focus if it's not level ( when it's UP ) if it's only out of position when up.

 

[bdial]

would a piece of groundglass laid on the back be able to check the focus is correct and in sync with the image on the focusing screen

It would, if you can position it at the same place as the film plane. The film plane is a little bit behind the body, so you'd need to shim the GG a bit. Getting the exact location wouldn't be easy, and it needs to be exact, hence my suggestion about the focus screen adaptor.

The focus plane is marked on the right side of the magazine. If you measure from the mark to some fixed place on the camera body with the magazine in place, you can adjust the GG to that location with the back off. It might not be really precise, but from what you describe, it might be close enough to confirm things.

Another method is to place the camera in line with a ruler, at an angle. Focus at some point along the ruler, make an exposure and process the film, (or look through the GG you place on the back). Whatever is in focus on the film tells you the gap and whether the focus point is near or far from what you see in the viewfinder.

 

[scinysnaps]

Yeah, that sounds like I would never be precise enough. I think the ruler way is better. Regardless, I need to send it to the technician anyway to change the mirror foam and have a look at the pads while he's at it. Looks more likely that it's the mirror that's out of alignment amongst other things..

 

[John Koehrer]

Check focus with a ground glass at the film plane & then look through the finder & see if they agree.
If they don't the most likely culprit is the focusing screen being out of adjustment.

***note to self, read the entire post before commenting!****

 

[Q.G.]

Unless upside down, the focussing screen will not be the problem. It could be out of position, but it rarely is.

Most likely suspects have been named already: mirror position, body length and magazine. Out of these three, the first two are the ones to have looked at first.

Another possibility is the lens itself. Maybe it needs seeing to.

 

[scinysnaps]

Q.G. thanks. What exactly is "body length" ? and how does one check that?
I am not to sure it is the lens, because it seems to be happening with all three lenses.

 

[Shangheye]

You said you had an 80 before...is that working OK?....if yes then the alignement and camera seem OK, seems strange that all of a sudden your new 40 and 150 are not. K

 

[Q.G.]

Q.G. thanks. What exactly is "body length" ? and how does one check that?

Body length is the distance between lens mount and magazine mount, i.e. between lens and film.
It is checked by measuring the distance between lens bayonet flange and the rear plate. Easy if you have a jig made for that purpose. A bit tricky if you have to do that without.

The internal body of a Hasselblad is an assembly of plates, to which the several bits of the mechanism are attached.
That assembly of plates can, and may need to, be adjusted (which is done using a hammer, tapping it 'in shape') to adjust correct body length.

I am not to sure it is the lens, because it seems to be happening with all three lenses.

Then it would indeed not be very likely that it is an issue with that single lens, no.

 

[scinysnaps]

Quite sure it's not the lens as I experienced this with all three. I just tested all of them with a Lightphase H10 digital back, and the results are the same. All focused behind. I even got 2 other people to focus.... so I'm guessing it has to be the body.

 

[Q.G.]

Wait a mo'!

You're using a digital back?
If so, that thing will need to be matched to the camera, to put the sensor in the proper position.

P.S.
But i see (looked at your OP after replying) that you are using film backs as well.
Then the thing to do would indeed be to have the camera checked and put 'in spec'.

 

[Ed Sukach]

I still suspect a non-Hasselblad focusing screen.

The Hasselblad "Accu-matte" screen is actualy two pieces of glass held together by a metallic "wrap around" band. That band holds the bottom (ground" glass) a millimeter or so above where it would be without the band.
I have a replacement screen (supposedly superior) which is just one piece of glass ... rests too close to the optical action, and useless, for just the effect you describe.

Is there any way you can post an image of the screen?

 

[scinysnaps]

Wait a mo'!

You're using a digital back?
If so, that thing will need to be matched to the camera, to put the sensor in the proper position.

P.S.
But i see (looked at your OP after replying) that you are using film backs as well.
Then the thing to do would indeed be to have the camera checked and put 'in spec'.

I am primally shooting with A12s. Just thought I would test it with the Digital back to see if I am getting the same problem, as it is easier to see the results.. If the sensor position is going to be an issue, then I guess that renders the test useless.

 

[scinysnaps]

I still suspect a non-Hasselblad focusing screen.

The Hasselblad "Accu-matte" screen is actualy two pieces of glass held together by a metallic "wrap around" band. That band holds the bottom (ground" glass) a millimeter or so above where it would be without the band.
I have a replacement screen (supposedly superior) which is just one piece of glass ... rests too close to the optical action, and useless, for just the effect you describe.

Is there any way you can post an image of the screen?

Not too sure that the screen is a problem. I am assuming it is an original Hasselblad screen, and also I never used to have this problem.Will get a picture of the screen this weekend sometime..