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Thread: Registration

  1. #1

    Registration

    Registration. Currently on ebay is a depth micrometer for sale. It is billed as a good tool fo r measuring film registration. I don't think you need it. Registration is the de pth, for focussing, the inner surface of the ground glass screen is away from th e back of the camera. Obviously if you focus on the inner surface of the ground glass then you hope the film (when a holder is inserted) will be in the same pos ition. The myth is you need to be concerned about this and measure it. In realit y what you might wish to do is CHECK your registration. Here is my method. Take two good rulers (perhaps steel ones). Lay the long edge of one across the raised inner surfaces (if any) of your ground glass holder(the width of the ruler shou ld be held perpendicular). Now take the second ruler and genly lower it so that its bottom short edge sits on the inner surface of the ground glass. It should b e held flat to the first ruler. Now check where the top edge of the first ruler comes against the marks on the second. The measurement is not important - what i s, is that you note carefully where the first and second rulers meet. Check it a gain. Now take your dark slide and lay the first ruler across the flats of the i nner surface. You will need to have a sheet of film inserted and the slide remov ed!. Now place the second ruler flat against the first and lower the end until i t rests on the film surface - compare where the two rulers meet. Is it the same as your first reading, against the ground glass? Now you can check other film ho lders - Fuji Quickload or Polaroid. I bet your eye will be able to detect very s ubtle changes in depth (registration) a few micrometres! I have not noticed sign ificant differences (perhaps luckily) with my holders. Be careful if you use a F uji quickload - it has a pressure plate which you shouldn't depress - obviously. This method is in effect a vernier - using a fixed point to check against a mov ing one. What you do if you have substantial differences in registration is anot her matter! I agree that for large format film in situations when the film plane is inclined then film sag may be a real problem - hence Sinar's sticky film hol ders etc.

  2. #2

    Registration

    Well that was very informative, but your point is??

  3. #3

    Registration

    Sorry! I didn't know I had to make one. Do you sell depth micrometers? No, seriously, do you know a better way of checking registration and is it important anyway?

  4. #4

    Registration

    You can have perfect registration on your GG if you have factory specks...and have a lousy film holder that is not within the industry standards. BTW...depth micrometers aren't worth a dam. You need a dial caliper from a good mfg. with or without a digital readout. I have a special gage a machine shop made me, to measure the precise depth of film holders. It WAS worth the money to have it made. Marflex (Linhof) has a factory jig with measuring equipment to shim the back into exact factory specs. Good luck.

  5. #5

    Registration

    "hence Sinar's sticky film holders etc." check the archives for the "you suck film holder". I work 810 macro vertical and insist on precise focus. The vac. holder insures that my film and focusing plane(GG)are precisely aligned. Thanks for the above illustration. JG

  6. #6

    Registration

    And you can read a ruler to better than 5 thousandths of an inch, can you?A 5 thou error will put your focusing out by nearly half a metre in 5 metres with a 90mm lens. At 10 metres subject distance, that error grows to nearly two metres!For a 5x4 camera; your register needs to be 4.8 mm, plus or minus a lot better than anyone can read a ruler to.

    Was this a troll?

  7. #7
    Format Omnivore Brian C. Miller's Avatar
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    Registration

    The human eye can see a differences of one one-thousandth of an inch. (everybody with dial calipers can try this at home) Whether you can precisly hold a ruler to measure this is another question altogether.

    I bought a dial caliper for other purposes, but it's great at getting the ground glass just right.

    I own a Graflex Super Graphic, and I just installed Brightscreen brand ground glass for it. The plane for the Graflex ground glass does not sit at the edge of the GG holder. It sits behind it. In addition, the Graflex setup is best suited for (you guessed it) Graflex film holders.

    (The following numbers are from memory) The depth of the Graflex holder is .195-in, and the Fidelity and Polaroid holders are .200-in. The Brightscreen comes in two parts, a plain glass .065-in, and a plastic fresnel-GG .055-in. The width of the holder is .139-in. My Ilford film is .007-in.

    The Brightscreen can be place for a focal plane position of .194-in (fresnel front) or .204-in (fresnel rear). Film plane (holder + film) is .202-in for Graflex and .207-in for Fidelity.

    There are a number of brick buildings and chimneys where I live, so I have ready test targets outside my window. With the fresnel to the rear and using Polaroid 55 for negatives, I can see that the real focal point is behind where I focus on the GG. (brick wall is soft, chimney behind it is sharp) That is a difference of THREE THOUSANDTHS OF AN INCH! And it still would have been slightly off with the Graflex holder (but less so).

    I flipped the fresnel around and shimmed it so that there is only a .001-in difference between GG and film. Not perfect, but it'll do with what I have. (certaintly far better than the .081-in thick GG the Graphic had in it!)
    "It's the way to educate your eyes. Stare. Pry, listen, eavesdrop. Die knowing something. You are not here long." - Walker Evans

  8. #8

    Registration

    I think the responses are really interesting so far. I suppose my point really is this - you can focus wherever you want (lens to subject) but will the image be as sharp on the film as it was on the ground glass. That's registration. Now does anyone know a reliable way of checking this from ground glass position to the film holders you have without using expensive gadgets. If not what is the best gadget to have and how do you conduct your checks. And, yes I do know the eye can resolve very small differences in position one point relative to another. You don't need to measure just compare!

  9. #9

    Registration

    By far, the best way to adjust registration is optically, using the film holders you will actually use.

    Robert A. Zeichner (info@razeichner.com) wrote a nice groundglass testing article that appeared in the November/December 1996 issue of ViewCamera magazine. It can also be accomplished with a target angled across the field of view of the lens.

  10. #10
    Format Omnivore Brian C. Miller's Avatar
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    Registration

    Well, my dial calipers only cost $20 new (made in China) and the quality is reasonably good. So it's not an expensive item, and any good hardware/tool store or automotive parts shop will have them.

    I don't think that I could effectively _adjust_ the ground glass without the calipers. There are too many things on a Graflex which need to be measured.

    I tried using a ruler, angled to the lens, to observe registration problems. But that's not good enough when the difference is a few thousandths of an inch. You need to have a series of objects at a distance to get an idea of the problem. If the problem is radical registration misalignment like I had at first, it's a great check. When I first suspected I had a problem, I verified it by making a step wedge out of cardboard and gluing newspaper print to each step. At 15 feet I found I had to focus a half inch in front of the subject for it to be in focus, and stopping down wasn't a good enough solution.
    "It's the way to educate your eyes. Stare. Pry, listen, eavesdrop. Die knowing something. You are not here long." - Walker Evans

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