Pentax 67 Ground Glass

<p>Hi Everyone,<br>

I have recently acquired a Pentax 6x7 (1976 MLU Version). I want to clean the ground glass and so I ideally want to remove it to do so.<br>

How can I do this? Any ideas? Links??<br>

Thanks everyone and thanks Photo.net. It's saved my neck a lot!<br>

Andy</p>

<p>I think if you remove the finder then remove the screws holding in the screen it will come out but you need to be careful of any washers or anything under there and that you replace them in their proper positions. If its not too dirty then I would just clean the screen in place. The ground side is the main problem and you want to avoid cleaning that if possible. To clean it I would get a clean microfiber cloth wet with alcohol and gently wipe it. That should get it clean enough.</p>

<p>I do not know if the focusing screen on the Pentax 67 is glass or plastic. If it is plastic, DO NOT use alcohol on it. That might cloud it and ruin it. Proceed with caution.</p>

<p>After you put it back together you should make sure the focus of the screen matches the focus at the film gate. Mine didn't and I had to adjust the screen.</p>

<p>From memory its a similar construction to the blad screen, which is glass on top of plastic. I would take the prism off and wipe the top with microfibre cloth. But I wouldnt take the screen out or clean the underneath. Its rare that the underneath of screens responds well to cleaning and are really delicate. Id leave it alone - even if its a bit hairy.</p>

<p>I think the screen is 2 parts also. Its plastic with a glass top all set in a frame. Alcohol doesn't damage the plastic. Acetone will probably eat it though.</p>

<p>I'd send it in. It's a legitimate business expense and I can't resew a loose button on a duvet without losing the freak'n button.</p>

<p>I've posted this so many times .. don't listen to the loose units with their "ooh,don't touch it..wipe with a cloth "stuff.<br>

If you are sure you can get it out,and replace it without losing any bits : do this : rinse the screen with running water. Swab gently ,both sides with a tissue saturated with Windex or a similar glass cleaner. Rinse again with water, and ,this is the clincher : blow dry with a bulb blower or ear syringe - don't even think about wiping it dry. If you don't have a blower,stand it upright to dry on some tissue,overnight.<br>

Repeat if required. I would not post this if I had not done it myself - it works.<br>

Some say : Vodka works just as well ,but I would avoid solvents like the plague.</p>

<p> </p>

<p>The P67II is easy, the screen just lifts out after the prism is removed... But, NOT with the previous models: These screens come out from the bottom, through the mirror box, using a special tool... as with the LX and MX screens. I've changed the latter, where the tool comes with the replacement screen, but it may be more difficult with the 6x7 since both of mine got their grid screens installed by a technician.<br>

As yours is getting elderly now, it might be time for a general CLA and checkup. I bought my first 6x7 in 1976, used, and it doesn't have the MLU introduced that year. Enjoy!</p>

<blockquote>

<p>... But, NOT with the previous models: These screens come out from the bottom, through the mirror box, using a special tool...</p>

</blockquote>

<p>Bummer. I often find myself wanting a brighter screen on my 6x7, and have even thought of grinding my own as a possible solution. But now I am thinking that the extra trouble and cost of sending it away for the install, tips that decision in favor of "upgrading" the body to a 67II (and selling the 6x7) rather than replacing the screen.</p>

<p>Hi Jeff - In regards screen brightness... My older 6x7 has a Pentax grid screen put in by Pentax Service; when I got the late 6x7 I bought a Beattie Intenscreen grid which was supposed to be brighter by a stop or so. I had it installed at CameraTechs in Seattle, figuring it would also need a meter recalibration. Well, it didn't, the meter was right on. And it doesn't look any brighter to me... But the 67II <strong>is</strong> brighter.</p>

<p>I'm sorry, but Doug Miles is incorrect, at least insofar as the original 6x7 (no MLU is concerned). It removes from the top (just did it myself) with all of the obvious screws. The only part that is NOT obvious is that the two posts (that engage the finder at the front) are also screws that hold in the front side of the screen holding apparatus. They have indentations on each side, at the base, so that they can be screwed out with a spanner set at small size. I didn't have a spanner and was able to spin them out with a regular small screwdriver head (turning them lefty-loosy).<br>

The focusing screen/groundglass appears to be a sandwich of three(?) layers held together with tape on each side. I have not taken my sandwich apart (yet) to confirm.</p>

<p>"...at least insofar as the original 6x7 (no MLU is concerned). It removes from the top (just did it myself) with all of the obvious screws."<br /> Interesting, Darren, thanks for the correction. I never saw the tech doing my 6x7 screen change. I have changed the 645NII screens and also the LX, both of which go in from the mirror box, so I made the unsafe assumption that this was also true for the 6x7. Of course the 67II screens drop in from the top.<br /> I'll look forward to your future post about that screen sandwich and putting it back possibly with a focus adjustment. :-)</p>

<p>Actually, I plan to leave the sandwich together and re-purpose it for another project. It came from a 6x7 body that was waaaay beyond redemption that came with a nice 165mm f2.8 lens.</p>