MPP Back focusing

[Ric Bower]

Hi
Advice appreciated, my MPP mkVIII is focusing 2ft further back than it should over a distance of 12 ft (symmar 150 apo wide open) my thinking has been the glass is further back than the film plane to cause this- (the back does look appallingly made- bumpy milling et al) so I have placed the focusing screen holder/ international back on sheet of wet and dry and ground off a fraction of a mil- rotating it as I go to keep things even- I am now having doubts as it is still considerably out.
The ground glass is facing the lens :) , no fresnels or anything and i am focusing with a loupe on the filament of a torch to ensure absolute precision.
thoughts gratefully appreciated
Ric

[Ole Tjugen]

Let me get this straight:

If you focus sharply on the ground glass, the image on the film is out of focus by 2ft with the film focus point being 2ft further back? Meaning that if the GG image is sharp at 12ft, the film image is sharp at 14ft?

That's a pretty serious difference! A quick-and-dirty calculation gives a difference in film/GG location of just about one millimeter, and that's way out of likely sample variations.

[Ric Bower]

Thats exactly it- I am also taking a careful look at all my darkslides, they are all either Toyo or fidelity so i ca'nt see any majour probs there

[Pete Watkins]

As I understand it some MPP's are set up for MPP darkslides which are different to Fidelitys etc. It might only be the earlier models but you might need to take it into consideration. MPP darkslides are readily available on The Bay.The MPP owners club have a good website.
Best wishes,
Pete.

[RichardRitter]

Is the focusing screen in backwards?

[Ric Bower]

As I understand it some MPP's are set up for MPP darkslides which are different to Fidelitys etc. It might only be the earlier models but you might need to take it into consideration. MPP darkslides are readily available on The Bay.The MPP owners club have a good website.
Best wishes,
Pete.
Thanks- that would make sense- my camera appears to have a strange back- with the springy arms on the body not on the back as per usual- not such a good system over all.

[Ric Bower]

Is the focusing screen in backwards?
That would explain the problem but is not the case- first thing i checked.

[Ole Tjugen]

http://www.mppusers.freeuk.com/registers.htm

... but yours seems to be out by a full millimeter, which is a lot more than the variation in register in this list.

Or maybe my calculation is off, but it "feels right" to me.

[Ric Bower]

http://www.mppusers.freeuk.com/registers.htm

... but yours seems to be out by a full millimeter, which is a lot more than the variation in register in this list.

Or maybe my calculation is off, but it "feels right" to me.

Yes this makes sense to me as well- I am inclined to return to my battered MPP press- small, light , simple and what you saw was what you got!

[IanG]

Something sounds very strange, are you sure that the camera has the correct back.

Maybe post some photos here.

Ian

[Ric Bower]

Something sounds very strange, are you sure that the camera has the correct back.

Maybe post some photos here.

Ian

Here we go- what do you reckon- I have transfered my decent ground glass to my working machine.
In the second photo of the back you can see the feet I have begun filing down

[IanG]

You might want to look on Ebay thers a MkVII back available, I think its the sameas a MkVIII

Ian