Saturday, June 21, 2003

Determining Lens Transmission (also from Knoppow)
The method of measuring the transmission through the lens may work
depending on a lot of variables. If done correctly, its a very
accurate method. I wouldn't trust it under the circumstances.
Since the lens magnifies the diaphragm you can't measure it
directly, the physical size does not correspond exactly to its optical
size. An acceptably accurate way of measuring is to place a piece of
paper over the front (or rear) of the lens, in contact with the apex
of the glass if possible. Then illuminate the lens with a distant
small light source. The further away the better but for a 150mm lens
probably 20 feet is enough. Adjust the diaphragm to find the point
where it no longer reduces the size of the circle of light on the
paper. This is the maximum stop. Measure it accurately. Since you
know the speed of the lens (f/4.5) you know that this opening is equal
to that f/stop. To find other stops, devide 4.5 by the stop and
multiply the size of the opening for f/4.5 by the result. Set the
iris to this size and mark it on the stop plate.
Say the size of the hole for f/4.5 is 30mm and you want to mark
f/16. Devide 4.5 by 16 = about 0.28. Multiply 30 by 0.28 = about
8.4mm. Set the iris so the the illuminated circle on the paper is
this size and mark the stop plate "16". This will at least give you a
cross check with the existing calibrations.

Restated in another post...
The effective stop depends partly on the magnification of the stop
so is not exactly the physical size of the stop devided into the focal
length. For many lenses its not a big difference.
To measure the _effective_ size of the stop put a piece of diffusing
material over the front of the lens, a scrap of paper will do, and
illuminate the lens from behind with a small source at a distance,
ideally at infinity but a distance of several times the FL will do.
Open the diaphragm to the point where it just stops obscuring the
circle of light. That will be the maximum stop. Mark it on the f/stop
plate. The ratio between this size and the physical size calculated
from the focal length of the lens can then be applied to all other
stops to determine the physical size which corresponds to the
effective stop size. You can then calculate the rest of the stops and
adjust the stop image to that size and mark the aperture plate to
correspond. You can probably use the Symmar plate turned around with
some paint or even tape over it to mark on.
While the direct interchange of cells is a good sign you should
re-mount the cells in their original barrel and measure the spacing
carefully. This can be simply the distance from the cell rims. The
distance should be _exactly_ the same when put into the shutter. The
distance is important since it affects the corrections of the lens.

Notes on how to set the F stop scale on a shutter for a particular lens. From Richard Knoppow.

While the ratio of the focal length vs the marked stops
will be close the _effective_ aperture size is affected by
the magnification of the lens in front of it. In many cases
this is negligible but since its easy to measure the
effective stop why not do it.
This is done by placing an illuminated pin hole exactly
at the infinity focus point of the lens. A translucent
screen is placed over the front of the lens. This can be a
piece of paper. Measure the diameter of the projected circle
of light on the paper. That is the effective size of the
stop. Since you know the focal length of the lens just
devide the circle into the focal length to get the f stop.
You will have to rig some sort of scale to mark the stops.
The easiest way is to put some masking tape over the
existing scale.
To find the exact infinty focus without a very distant
object place a mirror over the front of the lens. Put a
small light source, a pen light is satisfactory, on the
ground glass, near but quite at the center. The mirror will
reflect the light back to the ground glass. Focus the image
of the light. The lens is now _exactly_ at infinty focus.
This is called autocollimating. The pen light could be used
at the exact center of the ground glass to measure the stop
diameter but the edges of the projected image will probably
be fuzzy. Better to make a pin hole in a sheet of thin
cardboard and put the pen light, or some other small light
source behind it.
The variation in actual focal length from advertized focal
length will not be significant in determining the stops.

Notes from Richard Knoppow..
NO! NOT ACETONE! Acetone is a rather non-selective solvent which attacks all sorts of plastics and paint. It will take the anti- reflection paint off the inside surfaces of the shutter and may do other damage.

Lighter fluid is Naptha, which is safe for most stuff used in shutters. Trichlor was the best but is not available. Very pure Isopropyl alcohol can also be used but will leave a residue if not so pure.

Another solvent to absolutely avoid is MEK which will dissolve rubber. Clean an old large size Ilex shutter in MEK and you will have no shutter or diaphragm blades left.

Richard Knoppow
Los Angeles, Ca.


Date: Wed, 22 Nov 2000
From: Marv Soloff msoloff@worldnet.att.net
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Shutter Cleaning

LoveThePenguin wrote:

> Is there an on-line source for information about
> Cleaning a LF shutter (specifically Rapax)?
> Thanks
> Collin

Just for the halibut, and before this thread gets out of hand, both Thomas Tomosy and Joe Lippincott recommend removing both lenses (using a rubber stopper of adequate width - no wrenches of any kind) and injecting a quantity of common lighter fluid (I happen to use Zippo brand) into the shutter. Work the shutter at all speeds, re-inject the lighter fluid as needed. Air dry and reassemble the lenses. That should clean it out thoroughly. It is necessary to remove the lenses because lighter fluid MAY attack the coatings. I have used this method to clean many sticky or dirty Graflex shutters.

This is not for the novice and your results may vary. A competant camera repair shop generally charges $100 for a shutter CLA - you may want to go that route.




Date: Wed, 22 Nov 2000
From: dickburk@ix.netcom.com (Richard Knoppow)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Shutter Cleaning

LoveThePenguin dpcwilbur@my-deja.com wrote:

>Is there an on-line source for information about
>Cleaning a LF shutter (specifically Rapax)?

I am unaware of any on-line material on Rapax or other shutters. The Rapax is a very good shutter made by Wollensak. Generally shutters can be cleaned with minimal disassembly by using naptha (Ronsonol or similar) and canned air. I used to recommend 1,1,1, Trichloroethane but its no longer available. Ronsonol lighter fluid seems to be pure enough not to leave a residue and won't attack most plastics or paints.

It should be blown out of the shutter with canned or other compressed air.

Where some lubrication is necessary a very light oil can be used in tiny amounts. Watch oil is ideal but Nyoil or the very light LeBell oil available from model railroad shops works well. Often, if shutters are really clean they will run dry.

Sometimes, if a shutter is simply sticking at low speeds a touch of solvent on the retarder gear train will unstick it.

A proper CLA is better but often such makeshifts work very well.

The Rapax shutter, also sold as the Graphex shutter by Graflex, is rather complex inside, if you get into it be careful of stuff popping out.

I thought I had seen a reprinted factory repair manual for Rapax but couldn't find one in a web search and don't myself have one.

A Calumet shutter tester is a necessity IMHO for anyone using older shutters (most LF folks). They are about $80 US and a bargain. Very easy to use and will measure anything from 35mm focal plane shutters to #5 Ilex Universals. They will also measure effective strobe time over a rather wide range. They are about the size of an exposure meter and run on a 9V battery.

Since many older shutters have weak springs they run slow at the higher speeds. Provided the speed is consistent it doesn't matter too much as long as you know what it is, hense my recommendation.

Friday, June 20, 2003

Lubricants -- Oils and Grease

Local watchmaker supply shop stocks Moebius and others...

TMP Company
12549 Lake City Way NE • SEATTLE, WA 98101

PO BOX 25779 SEATTLE, WA 98125

SyntaViscoLube- Designed for slower moving units and larger watch movements. Ideal for lubricating the pivots of staffs, oscillating weights and other parts of automatic watches. Excellent to minus 68 F 2 ml OL420219 $18.05
KT-22 Lubricant Applicator Preloaded with KT-22 Microlubricant OL420325 $4.25

The clock man

Recommends using a heavier oil, such as Moebius 8141.
Notes on Cleaning Fishing Reels

Useful because he sets out a soaking method for really dirty units.

1. Disassemble reel completely and soak parts in mineral spirits for 30 min. to remove grease.
2. Soak or sonicate parts (as needed) in vinegar to remove verdigris, found mostly on the foot and spool.
3. Rinse with water, then sonicate parts for 30 min. in non-ammoniated watch-cleaning solution, followed by a brief sonication in the appropriate non-ammoniated rinse.
4. Rinse with water and dry parts.
5. Using a fine polish, such as Wenol, lightly polish the metal parts by hand.
6. Apply a few drops of silicone reel oil to the hard rubber parts, spread by hand, and allow to soak into the rubber for an hour or two. The oil tends to darken the rubber. Polishing the hard rubber may obliterate any light stampings or will make deeper stampings less "crisp." Wipe off the excess oil with a soft cloth.
7. Apply silicone grease or oil to the moving parts as needed and reassemble the reel.

Disassembly, Cleaning, Assembly, and Oiling
Notes on how to clean a pocket watch.

If you have a ultrasonic watch cleaner, that is the way to go. Since I don't have an ultrasonic cleaner (yet) we will discuss cleaning by hand.

To hand clean the watch parts you will need seven canning jars with a wide mouth. These can be obtained at the larger grocery stores and hardware stores. I use half pint jars. Note that a canning jar has a lid and separate thread ring. I take off all the threaded rings and leave the lids on so that my cleaning solutions don't evaporate. Following is the set up for the jars and their cleaning solutions.

First Jar: Commercial watch cleaning solution

Second Jar: Denatured Alcohol

Third Jar: Ammonia, distilled water and tincture of green soap.

A one gallon mixture is 28 ounces ammonia, 3 ounces tincture of green soap, and the remainder distilled water.

Fourth Jar: Tap water.

Fifth Jar: Distilled water.

Sixth Jar: Denatured alcohol.

Seventh Jar: Denatured alcohol.

Do not hold the watch parts in jars one or three longer than about 20 seconds to avoid having the shellac that hold the jewels in dissolve.

The larger parts such as the bridges and pillar plate can be strung on a wire and dunked into the solutions. The parts should be scrubbed gently with an acid brush after leaving jars one and three. The watch train may also be strung on a small wire and dunked. The smaller parts should be placed in a kitchen strainer and dunked into the solutions. Note that the ammonia mixture will brighten the parts. The alcohol is used to dry the parts and remove any remaining water.

The balance wheel, escapement wheel, and pallet should be dunked in a solution called "One Step" for just a few seconds. One Step can be purchased at supply houses.

After the parts are cleaned you will need to "peg" the hole jewels in their setting with peg wood. You should get 2mm peg wood and sharpen it to a point. Peg wood is also good for holding the click open and holding bridges down while you set the screws. Peg wood can be obtained from a supply house. You can also use a toothpick to clean the hole jewels. Which ever you use, simply twist the wood in the hole jewels to removing any remaining caked-on oil. The older oils used on antique watches would often turn hard and can be difficult to remove. You may also want to buff the jewels on a lint free towel.

Oiling Bearing Points
Now oil each hole jewel with Moebius 9010 oil. Make certain that the oil contacts the cap jewel. Not enough oil is better than too much. One or two small drops is good enough. The oil should be placed with an automatic oiler or a black spade tip oiler.

Grease for gears and worms
Now you can place some KT-22 grease on the square shaft of the stem, then assemble the clutch wheel and winding pinion on the stem. Put some KT-22 on the gears. Put a little KT-22 on the clutch lever wear it contacts the clutch.

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