Speed Graphic Focal Plane Shutter

[rdenney]

I just finished a fairly major overhaul of the Speed Graphic that I bought this week. This one had been rode hard and put up wet.

In my complete overhaul of the focal plane shutter, I followed the procedure in the factory service manual (a link to which I found on Graflex.org) and did it all--rewound the curtain, diassembled and cleaned the retarding regulator, and so on.

During reassembly, I wound the spring 8 turns as suggested by the manual. When I tested shutter speeds, though, the slower speeds were over half a stop slow and the high speeds weren't. The curtain closed reliably from O, so I think the tension was what it was supposed to be. But I still had to add about another 8 turns to get the slow shutter speeds in range. From 125 down, the shutter is within a small fraction of a stop.

But I can't get the 250 and up even on the right planet. Given that the slit is narrower, the fast speeds should be fast if the slow speeds are correct, and they really aren't. On the unretarded side, the speeds are nominally 1000, 250, and 50. 50 is dead on, 250 is about 190. 1000 is maybe 400. On the retarded side, the speeds should be 500, 125, and 30. 30 and 125 are perfect, 500 is about 250.

Given the design of the shutter, I'm at a loss as to why the fast speeds are dragging. My ears are certainly not complaining about the sound of the shutter--it is now quite crisp. I can live with it the way it is--I have the same useful speeds as any given Copal 3 (long as I don't need slow speeds)--but I'm curious. Anyone have any ideas?

Rick "who was unable to make the camera square and has to be content with locking the front standard down with a slight swing" Denney

[Bill_1856]

Accurate speeds of the Graflex focal plane shutters have always been a problem.
Do you know about "Packing?" For the highest speeds, the shutter is "packed" by winding it and releasing it at the highest tension setting four or five times before taking the shot where it counts.

[rdenney]

Accurate speeds of the Graflex focal plane shutters have always been a problem.
Do you know about "Packing?" For the highest speeds, the shutter is "packed" by winding it and releasing it at the highest tension setting four or five times before taking the shot where it counts.

That is standad practice with older shutters, of course. But in this case, I must have cleaned it well--I so no variation in speed over half a dozen complete windings.

Rick "wondering about the little phototransistor tester at those speeds, now" Denney

[BetterSense]

The phototransistor should be able to read the focal plane shutter pretty well at those speeds, if you put it fairly close to the shutter curtain. I measured my shutter and found that full speed was more like 1/500. I didn't measure the rest of them in detail because I was only using the FP shutter at the highest speed then. I went ahead and assumed the rest of the speeds were a stop slow as well but based on your information maybe I should not.

[BrianShaw]

I trust technology (even technology, like a shutter speed tester, that I don't own), but when I had this question about my camera I put a roll film back on the camera and shot a roll of B&W at a series of pics of a blank wall at equivalent exposure and examined the film for density differences (I'm such a techno-phobe that I don't even have a densitometer; I just looked with my eyes).

[jnantz]

hi rick

whenever i have re-speeded the shutter on
my speed i usually just have the shutter barely make it from the 1 1/2 to T ..
remembering the camera at 1/30th probably was held upside down to work against
gravity ... and then all the other speeds have more or less fallen into place.
i have done this with a series d too ... when i used a shutter tester ( at a camera shop )
it seemed to be within 1/3 of a stop ...

good luck !

john

[rdenney]

hi rick

whenever i have re-speeded the shutter on
my speed i usually just have the shutter barely make it from the 1 1/2 to T ..
remembering the camera at 1/30th probably was held upside down to work against
gravity ... and then all the other speeds have more or less fallen into place.
i have done this with a series d too ... when i used a shutter tester ( at a camera shop )
it seemed to be within 1/3 of a stop ...

good luck !

john

John, your description isn't helping my limited brain. What do you mean by "just barely make it", and "1 1/2"? Speed Graphics were held upside down at 1/30? That just doesn't compute in my brain.

(By the way, I just cleaned and relubricated the Graphex shutter on the lens, and it is within 10% on the slow speeds of 50 and longer. 100 is really 1/65, 200 is really 125, and 400 is about 210. That's with the transistor sensor in the middle of the shutter, but even when it was offset by a third of the diameter, it didn't change much. Easy shutters to service, too.)

Rick "who would appreciate a little more detailed description" Denney

[jnantz]

John, your description isn't helping my limited brain. What do you mean by "just barely make it", and "1 1/2"? Speed Graphics were held upside down at 1/30? That just doesn't compute in my brain.

(By the way, I just cleaned and relubricated the Graphex shutter on the lens, and it is within 10% on the slow speeds of 50 and longer. 100 is really 1/65, 200 is really 125, and 400 is about 210. That's with the transistor sensor in the middle of the shutter, but even when it was offset by a third of the diameter, it didn't change much. Easy shutters to service, too.)

Rick "who would appreciate a little more detailed description" Denney

hi rick

sorry about that .....

not sure where i read it ( maybe graflex.org? maybe here? maybe apug? )
the camera was usually held upside down to achieve 1/30th of a second
upside down meaning so the bed is above the lens like a sun shade ...
if the camera was held like this with the shutter traveling up ( against gravity )
it would be a slightly slower speed. whether it is true or not, not sure, but it
sounded good , the person who posted it seemed a way more knowledgeable about
graflex-stuff than me ... i've been using them and tinkering with them for
a few years, but i don't have anywhere the experience with them as a lot of other folks.

i misspoke when i said 1 1/2" ... on the series D slr the
shutter is labeled differently, the largest shutter opening / slot
in the shutter cloth is 1 1/2" and with the SLR when the shutter
barely travels from the 1 1/2 setting to the T setting (on the shutter)
everything is around in the right place with the rest of the shutter speeds ( kinda-sorta ).
i've used a shutter speed tester and most of the speeds were close enough
that i didn't worry about it ...

when i set the time on the shutter in the speed graphic i have i usually
wind it 10 revolutions and compare and exposed negative between 1/60thS with
the focal plane shutter and 1/60thS from a regular shuttered lens. or i use
a shutter speed tester. it is never "right on" for any of the speeds
but it is close enough that i don't worry about it.

when i say close enough, i mean maybe 1/30thS is 1/40th or 1/125thS is 1/160thS ...

hope that made sense ...
good luck !

- john

[Glenn Thoreson]

It's not easy to get an accurate reading using a photo transistor on these shutters. The slot in the curtain is too long and you get too much extraneous light, which screws up the reading. The way I do it is to take a junk film holder without slides, and drill a hole about in the middle of the thing. The hole wants to be a size that comes close to the diameter of your sensor. Remove the ground glass from the focus panel and put your drilled film holdler in, as you normally would. Put your sensor up to the hole and run your test. These things are not perfectly on the money, but they should be pretty close. . The initial winding tension should allow the curtain to close slowly but firmly from the O (open) position. Old timers used to crank the initial tension up a little for sports photogerring. The instructions in the manual should be very close to correct. One thing about a single slit curtain is it takes quite a lot of error in setting to make it unusable. It's funny that Graflex never menioned testing procedure on these that I've seen. There was a proceedure for testing them using a phonograph turntable, though. (don't ask)

[rdenney]

It's not easy to get an accurate reading using a photo transistor on these shutters. The slot in the curtain is too long and you get too much extraneous light, which screws up the reading.

Okay, here's what I did to try it again. I built a 3/4"-long "soda straw" made from flat black masking tape wrapped inside out, and then affixed it to make a tunnel visor for the photo transistor. Then, I held it up to the ground glass, and measured the projected image of a lamp through the 127mm Optar. I tested the measurement technique by measuring the Graphax shutter at 25, and measured exactly the same speed I measured with that shutter off the camera (and all the slow speeds on that shutter are well within 10%). I suspect my soda straw is preventing any weirdness from the slit, and I'm not seeing any effect of the ground glass in my control.

Here are the speeds I get:

1000: 1/300
500: 1/125
250: 1/136
125: 1/77
50: 1/45
30: 1/31

The ungoverned speeds (1000, 250, 50), where it seems to me spring tension might have more of an effect, are more wildly off at the high speeds than the governed speeds. That's just the opposite of expectations. The largest curtain opening, both free running and governed, is close to perfect, and I would think a curtain-speed problem would affect that opening as much as the narrower openings.

Tightening the spring beyond a certain point has no effect on speeds. The shutter sounds excellent, and the curtain is supple and looks in excellent condition.

I'm putting this in the "go figure" category unless someone has another suggestion.

By the way, I did test the 30 setting with the camera upside down, because I just couldn't help myself. It ran 10-20% slower than right-side up.

Rick "not unhappy with the available speeds, but who'll need a table to remember them" Denney