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  #1  
Old 21st January 2020, 01:30 PM
Chrisvclick Chrisvclick is offline
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Default Are all 4x5 dark slides the same ?

Have noticed with my MPP,(8) that some negatives are just not that sharp. Blamed my eyesight for a while but not so sure any more.

Putting a spare lens board in and measuring from the edge of the lens hole to the ground glass, then from the same position to one of my Toyo dds with an old negative in, i get 0.5 mm difference ?.
The ground glass is further from the lens than the negative would be !....
I know .5 of a mm dont sound a lot and appreciate when set at infinity the depth of field will possibly make up for it, but at closer ranges this might explain things ?
The mpp seems to be assembled correctly, the glass is as far forward as it can be, anyone got any idea's ?

Thanks in advance
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Old 21st January 2020, 02:19 PM
Lostlabours Lostlabours is offline
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Very early MPP cameras and DDS were a slightly different register.


Mk II / III, MkVI to S/No. 5999 Register 0.200 inch / 5.08mm

Mk VI from S/No. 6000 Register 4.85 - 4.90

Mk VII - VIII Register 4.85 - 4.90mm


It should be noted that the original register for US 5x4 cameras and that goes back over 100 years was 0.2"

The Modern ISO standard is .197 +/-.007", so 0.190" to 0.204" or 4.826mm - 5.181mm so a tolerance of around 0.3mm.

Film thickness can make a slight difference. but normally DOF will cover any slight variations.

I've had no issues with older MPP DDS compared to modern Fidelity, Toyo etc DDS.

It may be the screens not sat properly, my MkVII came with a Sinar screen that didn't sit correctly so the T distance (register) was out.

Another issue is all the MPP screens including on the MkVIII are quire dim so harder to focus. Ive changed all my screens and it makes a huge difference approx 2 stops. I usually ahve new MPP screens available.

Ian
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Old 21st January 2020, 02:37 PM
Chrisvclick Chrisvclick is offline
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Below should be a pic, if iv got it right (?)...
I am presuming the distance from the ground glass to the top of the "step" would be the register ?. As the top of the step seats where the dds sits when in the camera.
If so, distance im getting there is around 5.7 mm. Strangely, the pic appears in the draft but not below ?. Tis a mk viii by the way

https://drive.google.com/file/d/1LI7...w?usp=drivesdk
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Last edited by Bob; 21st January 2020 at 05:43 PM. Reason: Converted the image to a link so people can browse to it.
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Old 21st January 2020, 04:15 PM
Lostlabours Lostlabours is offline
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The MkVIII backs vary slightly mainly just variations to the Focus hood and the way it fits/hinges. I have a MkVII back in front of me and measuring the T distance ground side of the glass to the 4 slightly raised steps on the rear is 4.97mm so well within the 4.826mm - 5.18mm tolerance range. The 4 points vary slightly one is 5.02

So 5.7mm sounds odd, is it possible someone has tried adding shims between the glass and focus frame holder, it's only 4 screws to remove the spring clips that hold the GG.

The screens sit on 6 lugs 4 either side near the ends and two either end at the centre. My problem was a Sinar screen has quite large clipped corners so didn't sit on the side lugs and could rock either way on the end lugs.

Ian
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Old 21st January 2020, 04:47 PM
Chrisvclick Chrisvclick is offline
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Not taken it apart yet but cant see anything between the glass and the frame. Will take it apart later to check. Am presuming the glass is meant to sit ON the frame not shaped to drop into it ?. Can see 4 half moons cut into the frame giving a little bit of gain.
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Old 21st January 2020, 05:16 PM
Lostlabours Lostlabours is offline
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On the MkVIII the glass sits between 4 stainless steel pins that screw into the frameand onto machined lugs (from memory) that's probably the 4 half moons. I expect there's two more under the clips.

Ian
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Old 21st January 2020, 06:49 PM
Chrisvclick Chrisvclick is offline
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https://drive.google.com/file/d/1LWNFySmLa14wxpnTnabpQg5xriKY_V/view?usp=drivesdk

https://drive.google.com/file/d/1La_...w?usp=drivesdk

Tried again with pics. Under the glass, there are 4 black rubber pads, very thin though ?. Presume they are meant to be there or has someone added them to the "pillars" ? These measure approx .37mm thick each ?.
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Old 21st January 2020, 07:57 PM
Lostlabours Lostlabours is offline
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The two MkVIII cameras I've worked on had no rubber pads that I remember. That may be the extra 0.5mm but let me do some checks !!!

Surprisingly the MkVIII isn't as robust as the MkIII or Mk VI & VII. I spent some time rectifying quite major issues with a MkVIII early last year for a member of another Forum, the Ebay seller just hadn't been at all honest.

I just checked and while I have images of the issues not of the focus frame/ground glass for a MkVIII

I make quite a few GG screens for MPP's every year because the originals are so dim, the issue with MkVII's is the hinged focus hood won't close with a 2mm glass screen, So I use 1.5mm which is difficult to find (except at a premium price) but 1.5mm shatters easily which is why it can't be sold any longer directly to the public (EU laws).

With a 1.5mm screen it can shatter if a camera is knocked or just placed down a bit hard. OK it takes a bit of force but a metal bodied camera doesn't absorb shock like a wood & brass camera, That may be the reason for adding rubber pads

Are you missing the hinged focus hood ?

About 3 years ago I had someone visit with a MkVIII and Xenar I think 150mm, he was having sharpness issues like you. I tested the camera with his lens and one of mine and found no issues, We did end up changing the focus screen, in fact I re-ground the original but that 2 stops apparent brightness made a huge ditterence.

Ian
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Old 21st January 2020, 08:06 PM
Chrisvclick Chrisvclick is offline
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The screen has been changed on mine i believe, its not a good fit and the 6x9 markings are lettraset on one side and pencil on the other . The hinged focus hood is complete.
I have carefully removed the rubbery stickers and now the register is just inside the limits. So am presuming they were not origonal. Time will tell if they were needed ?. Glass appears held nicely, no rattles other than from the focus hood. Shall put a couple of slides through it tomorrow and check focus...
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Old 22nd January 2020, 12:02 PM
Lostlabours Lostlabours is offline
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I'm sure there were no rubber bits on the two MkVIII cameras when I changed the screens.

If you look here the Technical sheet has an illustration of the back with no rubber pads. See here as well.

Maybe it was shimmed for some type of wet plate holder, but I'm sure you've solved the problem.

Ian

Last edited by Lostlabours; 22nd January 2020 at 12:05 PM.
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