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Incompatible focusing screens

A

antje

New Member
Hi all,

I'm a new user in distress. ;) I've posted that on APUG already and Eric told me someone here might know more about it - I have a 500C and sent it to Paepke in Germany for a CLA. I also bought a Acute Matte D and wanted them to install it, but they claim they cannot install any other focusing screen and want to replace it with a regular screen (oh, yes, forgot to add that they broke the screen that came with the camera). They told me the earliest model with screens that are changeable was the CM. Now I know that the CM is the first model that allows the user to change the screen, but shouldn't a repair shop be able to replace them...

I thought there were no incompatible screens. Please tell me that's just a lapse of reason on their part.
sad.gif


Thanks for listening!

Antje
 
Well.. the fun is that in order to install an AM into a 500C you need to remove the metal frame from the AM before you can fit into the 500C. The removal process has a reasonable chance of wrecking the AM screen so most repair people do not like doing it at all. Too expensive if the screen breaks. Standard screens are almost free these days so I can imagine they are willing to risk those.

After the screen exchange the repair folks need to adjust the screen distance & ensure it is plan-parallel.

At least this is what I was told. I own only 500C/M and 500EL/M so I do not have this problem. For me the C models were non-options when I considered buying a Blad for this particular reason.

Apart from all this screen stuff: will the repair folks also replace the foam behind the mirror? Knowing that a 500C is old, you are almost guaranteed to have degraded foam (old age turns it into sticky goo). The foam is crucial to ensure the mirror is in the right alignment, if it is not that means your focusing is a random process. Bad news..

Wilko
 
I don't think the "foam is crucial to ensure the mirror is in the right alignment".
So no worries there.
 
Maybe you should try talking to a veteran Hasselblad repair guy from Hasselblad Netherlands before you express your misguided and unfounded thoughts. You might even learn something.

The foam *is* critical for correct and reproducible focusing.

Wilko
 
Wilko,

I can only advice you to take your own advice.
The mirror position and focusing accuracy do not depend on a bit of foam...
 
Hi Wilco,

> The foam *is* critical for correct and reproducible focusing.

It seems strange to me that foam would be used for a mirror stop, since the mirror stop is critical positionally. The foam surely d&ens the stop, but may not be the actual final resting place of the mirror...there is probably some fixed metal tab that provides this function.

Regards,

Austin
 
I'm not going to argue with you anymore, as you obviously do not know what you are talking about.

Wilko
 
Sorry, guys - maybe I should just get a 500CM and we can all be friends?
uhoh.gif


Wilko, I asked them to do a full CLA, and I'm assuming it includes replacing bad foam and focus adjustment. I'm not so sure anymore... I'm anxious to get the camera back and see for myself. Hopefully this weekend. (crossing my fingers)

Antje
 
Hi Wilco,

> I'm not going to argue with you anymore, as you obviously do not know > what you are talking about.

I'm not sure which one of us you're directing this to, and I really think your comment is uncalled for, but I have to side with Q.G. on this one. But, I would certainly like to here from someone who actually knows for sure what the mechanisms involved here are.

Regards,

Austin
 
Hi Austin,

The foam is not a mirror stop. Note I never claimed it is..

In a 500C the foam lives under the actual mirror, and it forms a flexible joint with the mirror frame. When you cock a 500C you will see a slightly weird movement of the mirror relative to the frame. This movement is only possible without breaking the mirror because of the foam. Once the mirror frame snaps back into the cocked position it is, like you correctly observe, held there by metal locks.

But the trick is this: the foam needs to be in a good-enough shape, read: elastic enough, to push the mirror back to align with the mirror frame. If it is old and tired it will not consistently perform this task, or maybe not at all.

The result then is that the mirror is not correctly aligned. I guess it is obvious this is bad news for the whole focusing process.

I was shown exactly this problem by the Hasselblad repair guy last Sunday. If you gently push a 500C mirror with a soft cotton swab or similar you will notice the mirror 'floats' on the foam. If the pushing makes the mirror sit 'back' in the frame the foam is dead and needs to be replaced.

I hope this description makes sense to you? If not, please feel free to ask me to clarify.

Wilko

(NB: That QG is too stubborn and ignorant to believe this is not my problem.)
 
Hi John,

I absolutely agree with you: wars often start out of ignorance.

A well informed population is much less likely to start killing their fellow humans.

That leaves us all with the task to push back on ignorance and the spread of misinformation.

Wilko
 
Wilko,

I agree with you but your people skills leave much to be desired. This is supposed to be fun, not life and death. Dude, take a pill and chill.
 
Antje

I do not know in which state your 500C is , but if you want to keep it and work with it you could try the following : David Knapman , Pro Camera Service , Box115 , 43801 LANDVETTER in Sweden . TEL. 31919403 . Don't forget the swedish pre dial numbers . Best to contact information first . He is one of the remaining trained HASSELBLAD man . An honest and friendly guy . He might be able to help you . Best contact is by letter with a good description of your problem . Good luck .

Jürgen
 
Ease up folks. It's important to preserve the knowlege base of these cameras from folks like QG, Austin and Wilko. No one knows every single little detail ... so it is the collection of experiences that is of value ... and cross referencing that knowledge through out the Hasselblad user community.

Maybe consider a kinder way of challenging what you may disagree with ?
 
Hi Antje,

I just felt you should know about the mirror foam issue. The Hasselblad repair guy told me that during most CLAs this is 'conveniently' omitted as it is quite a bit of work to get access to the actual foam. That makes it obviously costly due to the time it takes.

There is other foam (at least on the 500CM, I guess also on the 500C) surrounding the focusing screen. This mainly serves to absorb the shock of the mirror moving up. Replacing that foam is easier to do as I understood it. But this is not the foam that influences the mirror position and therefore the focusing story.

Aligning the mirror as well as the focusing screen's position is typically done using special tools / test riggs that the Hasselblad factory designed for this purpose.

And sure: of course you want to go and make pictures :) That is what these mechanical wonders are made for. But I felt you better know about this and ask your repair folks about it.

Enjoy your 'blad and have 'Good light'!

cheers, Wilko
 
Hi Wilco,

I understand you didn't say it was a stop, but you did say it was responsible for critical positioning, and in a typical SLR the only thing that does that is the mirror stop.

You describe it as there is foam behind the mirror, between it and the mirror "frame". But, that the foam has a minimum thickness to push the mirror up against the top of the frame, so the mirror is at the reasonably correct "spot" when the mirror is returned. Hum. That sounds odd, but possible. The foam would not be what provides the critical positioning, it would be the mirror frame...but the foam pushes the mirror up against the frame, and without that, the mirror isn't positioned correctly. I do have a 500C somewhere, and can take a look if I get interested enough.

Regards,

Austin
 
Hi Peter,

If you feel my people skills are substandard that is of course your privilige.

My aim was to help with Antje's original question, and that is what I tried to do.

Seeing completely uninformed responses "you are wrong" is what ticks me off. Nothing more to it than that.

And of course, we should be enjoying the wonderful boxes they call Hasselblads. I know I do.

cheers, Wilko
 
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