Registration

[stuart_cankett]

Registration.

Currently on ebay is a depth micrometer for sale. It is billed as a good tool for measuring film registration. I don't think you need it. Registration is the depth, for focussing, the inner surface of the ground glass screen is away from the 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 position. The myth is you need to be concerned about this and measure it. In reality 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 should 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 be 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 is, is that you note carefully where the first and second rulers meet. Check it again. Now take your dark slide and lay the first ruler across the flats of the inner surface. You will need to have a sheet of film inserted and the slide removed!. Now place the second ruler flat against the first and lower the end until it 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 holders - Fuji Quickload or Polaroid. I bet your eye will be able to detect very subtle changes in depth (registration) a few micrometres! I have not noticed significant differences (perhaps luckily) with my holders. Be careful if you use a Fuji 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 moving one. What you do if you have substantial differences in registration is another 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 holders etc.

[nigel_turner]

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

[stuart_cankett]

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?

[richard_boulware]

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.

[john grunke]

"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

[pete_andrews]

And you can read a ruler to better than 5 thousandths of an inch, can

you?<br>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!<br>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.<p>Was this a troll?

[brian_c._miller]

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.

 

<p>

 

I bought a dial caliper for other purposes, but it's great at getting

the ground glass just right.

 

<p>

 

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.

 

<p>

 

(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.

 

<p>

 

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.

 

<p>

 

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).

 

<p>

 

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!)

[stuart_cankett]

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!

[glenn_kroeger]

By far, the best way to adjust registration is optically, using the

film holders you will actually use.

 

<p>

 

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.

[brian_c._miller]

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.

 

<p>

 

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.

 

<p>

 

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.

[upscan]

Stuart: </head>

 

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<p>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? </p>

<p>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:<br>

<br>

</p>

<p><a

href="http://www.sinar.ch/down/sup/prka_kas_e.pdf">http://www.sinar.ch

/down/sup/prka_kas_e.pd</a><br>

</p>

<p>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.</p>

<p></p>

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[stuart_cankett]

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?

[upscan]

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]

Just a couple more points.<br>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.<p>Another

published survey showed that there was little agreement of film

register across LF cameras either. The spread was about +/- 0.25

mm.<br>Amazingly, there appears to be no international standard laid

down for LF camera register.<p>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")<br>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.<br>Whether your filmholders tally with that is another

matter.<p>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.<br>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.<br>Kept clean, and checked for wear and tear

ocassionally, I know I can rely on them, and without constant

measuring.

[stuart_cankett]

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]

For what it's worth that should have been:

www.polaroid.com/service/userguides/photographic/protech_ug.html

Thanks

[upscan]

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<p>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.</p>

<p>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. </p>

<p>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.</p>

<p></p>

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