Thorton Pickard Junior Special focusing issue

[Nuffles]

I was lucky enough to be given this camera with a load of other photographic stuff a while back. After some quick research it looks like it's a very early one - it has a reversing back fitted. They were brought out in 1924, and changed to a rotating back in 1926. It's standard film size is 3.5x4.5 sheets and I originally gave it a miss fearing complexity. While clearing out the garage before I came to uni I found a 6x9 MF back for it and gears began turning. Now at uni I can dev colour/bw film for free and scan it in on either half decent Epson flat beds, or industry standard £20,000 beasts, or print it in the darkrooms. I decided to give the MF back a shot and see what results I got. I found that the shutter speeds are pretty accurate and that in general it works pretty well - especially for a 1920's era camera - around 90 years old now. The lens (a non-standard CZJ Triotar 150mm f/4.5 - if anyone could let me know what lens mount this is that would be great, I'm trying to find a slightly wider lens) is fantastically sharp even wide open - but herein lies my problem. The camera seems to consistently focus an inch or two behind my subject, getting worse the further away from the camera the subject is.

Now, logically, I believe I can simply raise or lower the focusing screen to compensate for this, yes? Raising it would be easy peasy - it's simply held in with two metal clips and lifts straight out. Lowering it would be much harder. I'm shattered after a night out last night and I can't work out which way it'd need to go though. Any help would be appreciated.

For those of you that are interested in the camera, here's a link:
http://www.earlyphotography.co.uk/site/entry_C40.html

Some shots from my first few rolls of film. Bear in mind that all of these were shot wide open. I understand that I could simply stop down to f/8 or smaller and enjoy insanely sharp images with no focusing issues, but one of the wonders of using a larger format on a camera like this is the DOF:

(Yes, I know the negs are filthy, I'm sorry)

On a side note, I also found some b/w film in the garage. Ilford HP5, around 8 rolls of it. The only downside is that it expired in 1986. I thought screw it and went with it anyway. I pushed the dev time from 5min to 8min and they didn't come out too badly - the shadows are pretty messy, and the backing paper has somehow burnt itself onto the film. I'm going to try shooting with it at iso200 next time to give the film time to thicken up a little:

 

[joxby]

Well, I can only muse about the focus problem.

What's the deal with the 6x9 back, was it made for the camera or was it a hack to make it fit because if it doesn't sit exactly where the original film plane did, there will be a focussing error.
What about the focussing screen, does it sit on some kind of light seal material, if so has the material deteriorated and changed the position of the focussing screen.
Mirror alignment, or maybe wear on the hinge mechanism will give focussing errors too.
These things are not easy to diagnose with any great certainty and harder to fix because everything is measured in fractions of a gnats knob, it does seem that altering the focus screen to suit is the easiest fix, but it'll be a trial and error affair...

 

[Nuffles]

The 6x9 back seems to be an 'optional accessory' - obviously not standard but built to a high quality to fit the camera well. From what I can see the it holds the film in the same plane that the standard 3.5x4.5 back does. The focusing screen simply sits in a recess in the wooden frame, held in by a metal clip on each side. The simplest way to raise it a few mm would be to flip it over so the ground side faces up, although I don't know whether this could correct the issue or make it worse.

 

[Marvin d martian]

You really need to do some proper test shots at a target to get an idea of what you need to adjust. Don't reverse the focus screen, just try packing it out a little. You might want to measure the distances of the film plane and match the screen to it.
Mart

 

[retrogamer1990]

Off topic, but...

at uni I can dev colour/bw film for free and scan it in on either half decent Epson flat beds, or industry standard £20,000 beasts, or print it in the darkrooms.

JEALOUS

 

[robhooley167]

JEALOUS

Me too, i can do BW for free and scan on a v700 and i thought that was good

 

[Nuffles]

I'm at Swansea Metropolitan, which was the old Swansea Art College. The campus I'm on is entirely arts and media based, although the whole of the Met uni has very little to do with the academic side of things. I haven't had a chance to play with the big boys yet as I haven't started the digital workshop and you have to have done it to be allowed to use them, but once I have done then I'll be seeing what kind of results I get. The images I posted were simply negs scanned in on the Epson V500 at 1200 dpi and tweaked in PS.

Thanks for the advice so far. I've loaded another film so I'll set up a scale of sorts when I have a minute and shoot a few exposures to see what's going on.

 

[Gandhi]

As has been mentioned above, so many things could be wrong.....

I suspect though, it will be the roll film adaptor causing the issue by moving the film out of the correct focal plane, it wouldn't need to be far out to cause an issue.

Could also be;

Film flatness issue
ground glass been replaced with wrong thickness