Registration

**Julio Fernandez** · 29-May-2002, 15:03

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With the Linhof jig you can set a groundglass on a Linhof without measuring anything, so what? Do you propose everyone should buy one? Will it cost less than a micrometer? Will the jig tell you which of your film holders are good and which are off and by how much? Now with your rulers, what kind of accuracy can you measure to? Can you measure to 0.005" and if you say you can how did you measure it? With another ruler? Do you also think that the Jig makers also used a ruler system to design their jig?

Pete Andrews posting makes excellent reading and his points are at the core of the issue and most convincing. If you are not yet convinced read the Sinar document dealing with the subject:

http://www.sinar.ch /down/sup/prka_kas_e.pd

One teaching photographer Joe Englander reportedly always begins his workshops with camera calibration and often finds that the groundglass settings of many of his student's cameras are incorrect. He also has written several articles on the subject that are worth reading. If I were you I would read those before offering advice.

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**Stuart Cankett** · 29-May-2002, 15:31

Another annoyed person missing the point! I am not offering advice. I started a thread. Measuring is fine. I expect we can all do it with the appropriate tools. Many people use cameras which no longer have jigs available for testing and setting. So you find your GG setting is within the specification. That isn't the most useful piece of information. What is important after that is that when you replace the GG with the film it is in the same plane as the GG was. So now you measure all your holders? Sinar's solutions are very good - at a price. Glenn's suggestion is good but in practical terms you will need to shoot and process a sheet of film for every holder. So I wonder is there a universal simple method for checking registration is correct not just on your GG but on your holders too. Perhaps I should say that my preferred solution is to use a Fuji or Kodak loader. Then you only need to compare the registration of the ground glass with the one holder. You can occasionally check using Glen's and Brian's method. However, does any person have any tips on using the gauges to measure the registration depth?

**Julio Fernandez** · 29-May-2002, 21:28

Stuart: no prblem, you are OK. Three things make up for registration: The GG alignment, the film's thickness and the depth of the film holder's septum. Unfortunately these things are all variables though in a perfect world they should be fixed constants in compliance with official standards. The film thickness esconced in the stadards is negative film with a thickness of 0.007", yet colour film has a thickness somewhere around 0.0091" to 0.0093". Additionally, the lowly holder where photographers usually display their control on expenses ends up as the weak link, unless your holders happen to be Linhof or Sinar. One brand tested within the ANSI spec, + or - 0.006" (a relatively lenient spec) but one of the 20 almost new holders was out of that range even then. Another, a better brand came at about half that range. The Holders' frames can warp or have warped septums or septums that tilt to one corner. Each holder is a unit which may share the same brand or mould as many others, yet may not be identical. Finally, the GG may not be set properly, even when those jigs you talked about were used. That happened to me once. Measuring is quite simple, the tools are quite simple, simpler in fact that what most LF photographers have to deal with in their craft. As for tools, the dial depth micrometers are OK for GG measurements but not as suitable for holders. Their -usually spring loaded mechanism, exerts too great pressure on the holders (6N or about 120 psi if my memory is right, remember the probe is a hemisphere and contact is on a very small area) and can flex the septums giving erroneous readings. The slide micrometers should not be used as the force applied to the sliding probe can be too great and damage the septums. The turning rod depth micrometers can be controlled with greater finesse and allow minimum pressure to be used. The best devices are laser micrometers. They are non contact and can be very accurate. Measuring with a micrometer is really basic stuff. You read a vernier instead of a straight ruler. You use a flat perforated plate as the reference plane, place the mic on the plate and dip the probe through a hole in the plate until it touches the glass or septum, then take a reading, that is all, well almost. Beyond that there are a few do's and don'ts that are easily learned. After checking and adjusting your equipment you will not have to do it for a long while so you can sell the micrometer and get your money back. You may have to toss out more than one film holder, that is about the real net cost (or benefit) plus of course a little time and patience. Good luck!

**Pete Andrews** · 30-May-2002, 05:31

Just a couple more points.In published test after test of registration accuracy; quickload/readyload type holders have performed very poorly compared with quickload film in a Polaroid holder, which in turn came out slightly worse than normal cut-film in a standard DDS. The best performer, unsurprisingly, was the $inar precision holder, which most of the tests used as a reference.

Another published survey showed that there was little agreement of film register across LF cameras either. The spread was about +/- 0.25 mm.Amazingly, there appears to be no international standard laid down for LF camera register.

A minor correction here: The standard thickness of film is not .007". The thickness printed on the box is the thickness of the base that the film's coated on. The emulsion thickness adds nearly another thou to it. Every sheet of B&W film that I've measured, using a good micrometer, reads 0.2 mm (.0079")Subtracting that thickness from the ISO standard 5 mm depth of a DDS gives a register of 4.8 mm, which ties in closely with the old glass plateholder register of 3/16" (4.7625 mm). So 4.8 mm is what your GG distance should be. Plus or minus as little as possible.Whether your filmholders tally with that is another matter.

After being panicked by those published tests into checking my own varied collection of holders, I concluded that Fidelities were OK when new, but tended to warp and wear quite badly. All of my Toyo holders were more than acceptably accurate, and showed little wear, and no warping.So, short of spending a fortune on Sinar or Linhof holders, the best of the plastic double-darkslides, in my opinion, are those made by Toyo.Kept clean, and checked for wear and tear ocassionally, I know I can rely on them, and without constant measuring.

**Stuart Cankett** · 30-May-2002, 18:51

My very best thanks to you all. In return for your time and trouble here are some links. For holders and more http://www.butzi.net/reviews/readyquick.htm For Sinar's view http://www.sinar.ch/down/sup/prka_kas_e.pdf For Verniers and callipers http://www.rit.edu/~vwlsps/VernierCaliper/caliper.html For info on polaroid 5x4 sheet film http://www.polaroid.com/service/userguides/photographic/protech_ug.htm l and the holder http://www.skgrimes.com/545/index.htm Rodenstock lenses http://www.rodenstockoptics.de/rodenstockoptics/index.htm and finally scroll to the bottom of this page to see how one company managed to have three Registers! http://www.mppusers.freeuk.com/microtec.htm

**Stuart Cankett** · 30-May-2002, 19:00

For what it's worth that should have been: www.polaroid.com/service/userguides/photographic/protech_ug.html Thanks

**Julio Fernandez** · 30-May-2002, 22:23

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My measurements of film thickness, -referring to the sheet of film rather than the backing indicate that Fuji color sheet film,(Velvia) is 0.00925". The 5 decimals are not a result of conversion, rather, measurements taken with a 5 decimal place micrometer. That would mean that all users of transparency film need a GG setting that is different from that required for negetive film.

My measurements of the thickness of color negative films were close enough to 0.007" that I did not anotate the other 4th and 5th digits. These were the figures measured on Fuji NPS and Vericolor III. I have not measured B&W negative film.

My measurements of a variety of holders also indicated that toyo holders are better and more consistent, although not quite as precise as the Linhof. I tested one Linhof and what was most astonishing was that the septum was almost perfectly flat , something I had yet to see even in Toyo holders. ( I realize a measurement of one has little statistical significance but that is all I had). I now have three more Linhof holders and am looking forward to testing those. The fidelity. and Righway holders fared a little worse than Toyo and the Liscos, even though new showed a peculiar curvature which resulted in one corner being always higher by a significant amount, that not being the only peculiarity. Looking at the rims of the holders, their convex curvature in relation to the septum was quite evident. Some of this curvature may flex back towards flatness from the pressure of the Graflock spring loaded mechanism, however that is speculation. The Linhof Technika is designed so that the tiny screws that set the GG depth are unlikely to shift position, since the screws are set in place by the paint used to cover them after GG settings. However, my GG was slightly off register after adjustment by the Linhof Rep. If you photograph in colour you will need a different setting than if you photographed in B&W so if for no other reason, it seems logical that checking and adjusting the GG should be a basic requirement for LF . As for holders, I agree the best thing is to buy good holders and forget the measurements. For many it is too late.

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