Testing ground glass register

[andrewch59]

I guess like most who are new to lf, it is not something you automatically think of. I have blamed my loupes or perhaps poor (clumsy) practices such as knocking the camera and the like. Now I am at least aware that this problem is more commonplace than I thought, my other cameras may now come under scrutiny. I have always been in awe of the image on my big Deardorff GG, I can see the lines in the irises of my sitters (victims) but that it is never reflected under scrutiny in the photos, it will be next on my hit list.

[consummate_fritterer]

I spoke with Bill Maxwell when I bought my Chamonix 45N-1. I knew the original Chamonix had GG alignment issues due to miscalculation of the factory Fresnel lens. I sent the camera and new focus screen to the technician Maxwell suggested, who installed it to very tight specs. I wouldn't do it any other way unless I could trust myself to do it right, which I can't.

[andrewch59]

I spoke with Bill Maxwell when I bought my Chamonix 45N-1. I knew the original Chamonix had GG alignment issues due to miscalculation of the factory Fresnel lens. I sent the camera and new focus screen to the technician Maxwell suggested, who installed it to very tight specs. I wouldn't do it any other way unless I could trust myself to do it right, which I can't.

My Shen Hao has been soft from purchase, I blamed it on the very dim GG image for a while, but eventually sent the gg and frame back to the seller, I wont mention names as I don't believe the seller of a camera is responsible for manufacturing faults. The seller in the US was excellent, no questions asked and the replacement was sent out promptly. There was no difference so I decided the dull screen must have been the problem and got the Maxwell, a very decent man to work with. Screen was much brighter but the problem remained, that's when I decided it could only be the registration of the GG. A long trial and error period but I am now confident in the camera.

[consummate_fritterer]

My Shen Hao has been soft from purchase, I blamed it on the very dim GG image for a while, but eventually sent the gg and frame back to the seller, I wont mention names as I don't believe the seller of a camera is responsible for manufacturing faults. The seller in the US was excellent, no questions asked and the replacement was sent out promptly. There was no difference so I decided the dull screen must have been the problem and got the Maxwell, a very decent man to work with. Screen was much brighter but the problem remained, that's when I decided it could only be the registration of the GG. A long trial and error period but I am now confident in the camera.

Did you send the back and new Maxwell screen to the technician Bill Maxwell recommends?

[Drew Wiley]

Greg - it has always astounded me that marketed sheet film adapters for trinocular microscopes weren't adapted for vacuum on a standard basis. It is easy to
do. Astronomers who used even roll film rather than glass plates figured that out long ago, but maybe they're fussier for measurement purposes as well as the very long exposures involved. I made a nice 8x10 vac holder, but it's inconvenient in the field, so for a long time have used adhesive holders instead,
mainly for color film since it's more likely to get enlarged beyond 20X24 than my black and white shots. But even without magnification, I can easily detect
the poor focus inherent to ordinary holders in a side-by-side light box comparison with the same 8x10 image shot using an adhesive holder too. With microscopy the photography tube is often pointed straight down, so the worst possible scenario in terms of sag. But a sad subject for me. I've been wishing for quite awhile to acquire a 70's vintage Zeiss research or medical microscope like I used in my school days. They're abundant on the used market; but I always have other equipment priorities on my limited budget. Mostly for just looking at lil' critters while I still can, and before they're feeding on me!

[andrewch59]

Did you send the back and new Maxwell screen to the technician Bill Maxwell recommends?

.
No, I retired the camera for a while in frustration and used my Horseman FA, but was restricted to smaller lenses. Then got it out of cobwebs and fixed it as stated above.

[Tim V]

All of this terrifies me... Focus with my Linhof cameras has always been 100% accurate, straight out of the box. I've my tested 4x5" and Techno cameras with my 60mpx Leaf Credo digital back, and both were spot on.

I'm now in the process of acquainting myself with my new (to me) Gibellini AC-D which I've had to do some work on due to a warped rear frame (I made a new one, to a higher quality than the original,) and that has worked out well. But to be honest, I'm suspicious of the accuracy of the GG back in the sense that one corner does not lie completely flat against the surface it should, I think due to a slightly misplaced pole that presses against the spring back. Hard to explain, but I'm guessing in one corner it's about 1mm, maybe less out. I have not done a register test on the GG frame itself, and fear that might be off–It might be accurate, too!–but know that one corner is definitely in need of some careful attention.

Anyway, good thread. Thanks for the info! It's something I like about these old fashioned cameras, that the basic build and servicing of them etc is easily learnable, even to someone like myself who lacks any real woodworking / metalwork technical skills. I like the struggle...

[Tin Can]

I am partial to metal cameras

Over time I owned

Calumet C1
Linhof Kardan Color 8X10, 5X7
Horseman LX 8X10, 4X5
Rittreck 5X7
Gowlandflex 4X5
Gowland 2X3 Pocket View

Some heavy as can be, but all stable

Weight, Mass is good

I don't hike

But I do have a pickup truck with a BedRug and cap

YMMV

[Tim V]

Obsessive compulsive alert...

After reading this thread I decided to test my camera for focus calibration, and I'm glad I did. It was way out, severely back focusing! After measuring the position of the GG relative to the edge of the frame with a digital depth metre, I found it was easily within tolerance (about 1/10th of a mm deeper than perfect) so got to checking how the frame itself was sitting in the camera. I found it was not seating properly on the area where the film back sits, identified the problem and fixed it. Have shot a test image and scanned at 2400dpi on an Epson V800–a very average scanner if one is looking to get the best out of 8x10", at least in my opinion. Anyway...

Attached is a resultant 100% crop of that scan. I can tell that it's about 6-8mm front focused, as the gridded lines resting on the horizontal surface of the table are spaced 10mm apart, maybe 1mm less when taking into account the thickness of the lines. The full resolution scan of the entire negative, printed at 300dpi, would measure 80" on the long edge, and this crop would translate to being a 6" wide area out of the near centre of that print. The lens used is a very average condition 12" Goerz Dagor AM Opt. Co., and the object pictured is the rear of a plastic CD case standing at 90 degrees to the tabletop. I've taped a laser printed grid of fine lines to the rear of the case to provide sharp lines to focus on. The focus distance was approximately 1.75m from the film plane.

I'm thinking that this result tells me that the limiting factor is my eyesight and, to a good degree the resolution of the ground glass, as it has very coarse grain. using an 8x loop over my 4x loop only made the focusing experience more frustrating as it offered no greater clarity of exact point of focus.

I wonder, considering the fine tolerances talked bout here–as little as 0.016"–Would others here find this result acceptable?

[Drew Wiley]

I suspect you have several variables to still iron out and not just one, though it seems you're making progress. But you're the ultimate arbiter of what is
"good enough". At then end, it all comes down to whether you're satisfied with your resultant prints or not, if that is in fact your end game. Incidentally,
Dagors aren't typically great at close range, as nice as they can be for other applications.