kb244
Well-known
Recently acquired a 1953 Argus C3 which needed a little bit of work but came with a cleaned up lens.
I cleaned up the other 'optics' such as behind the rangefinder view hole, back of the viewfinder glass, etc, and also adjusted the flash timing wheel so that the shutter was fully open at the moment the flash contact connects (for X-Sync once I adapt its two prong to a PC-sync of sort).
When I went to adjust the rangefinder since it seemed to be quite a bit off, so I measured out 5 feet from sheet to focus plane and adjusted, then again around 12 feet (not that much working distance inside). I used a focus screen out of an old Minolta SLR that has a split and micro-prism ring as a ground glass to check the actual focus of the lens, placed in diagonally so that it was level across the surface of where the actual film would be, fresnel facing forward where the emulsion would be. Tripoded of course.
The rangefinder and lens are pretty much paired up now by ground glass focusing, but the scale focus ring seems 'off'. It doesn't seem like the lens helicals are on incorrectly since the indexing slot wouldn't allow infinity if I had the lens any further on, and would be too far off the slot if I had it a single turn less. Where it's at now, the screw rides the slot exactly from 3ft to infinity (with the gears stopping right at each point, slightly closer than 3ft on the closer side).
The issue:
But when I focus on something that's 5 feet away measured out (focused in the rangefinder, and focused on the ground glass) it shows exactly 6 feet on the rangefinder ring. If I focus on something that's about 12 and a half feet away it shows exactly 15 on the rangefinder ring.
Was the scale focus rings not that spot on accurate?
To me it's not that huge a deal since it's not faster than f/3.5, but the scale being off that much would affect my ability to utilize some DoF guesstimates if I were going off the scale and not rangefinder.
I cleaned up the other 'optics' such as behind the rangefinder view hole, back of the viewfinder glass, etc, and also adjusted the flash timing wheel so that the shutter was fully open at the moment the flash contact connects (for X-Sync once I adapt its two prong to a PC-sync of sort).
When I went to adjust the rangefinder since it seemed to be quite a bit off, so I measured out 5 feet from sheet to focus plane and adjusted, then again around 12 feet (not that much working distance inside). I used a focus screen out of an old Minolta SLR that has a split and micro-prism ring as a ground glass to check the actual focus of the lens, placed in diagonally so that it was level across the surface of where the actual film would be, fresnel facing forward where the emulsion would be. Tripoded of course.
The rangefinder and lens are pretty much paired up now by ground glass focusing, but the scale focus ring seems 'off'. It doesn't seem like the lens helicals are on incorrectly since the indexing slot wouldn't allow infinity if I had the lens any further on, and would be too far off the slot if I had it a single turn less. Where it's at now, the screw rides the slot exactly from 3ft to infinity (with the gears stopping right at each point, slightly closer than 3ft on the closer side).
The issue:
But when I focus on something that's 5 feet away measured out (focused in the rangefinder, and focused on the ground glass) it shows exactly 6 feet on the rangefinder ring. If I focus on something that's about 12 and a half feet away it shows exactly 15 on the rangefinder ring.
Was the scale focus rings not that spot on accurate?
To me it's not that huge a deal since it's not faster than f/3.5, but the scale being off that much would affect my ability to utilize some DoF guesstimates if I were going off the scale and not rangefinder.
tunalegs
Pretended Artist
I've noticed the same thing on probably every C3 I have. The markings on the C3 are pretty much nominal, as I'm sure you'd find out if you had a shutter tester. In any event, try pointing the camera out a window and checking infinity focus, as long as the lens and RF are coupled correctly, the markings on the RF window don't really matter much.
kb244
Well-known
Hrm, when I check the ground glass outside now that there's some daylight, the lens itself can't quite get infinity. 50~75 away is *almost* focused but I can't get the lens there where it stops at infinity.
tunalegs
Pretended Artist
Remove the gear that couples the lens to the RF, and try.
kb244
Well-known
I can do it when I do that, one of the first things I checked. Except there's no way the indexing screw can line up to the slot for infinity (too close to the body), and all three entry points of screwing the lens on (seems there's 3 threadings which changes where the indexing hole lands) won't hit that slot without first stopping at the base.
I went with the threading that allowed me the closest-to-body position for infinity, which still doesn't get me infinity exactly, but now 50~75 ft is a little sharper at infinity.
And double-checking groundglass-vs-RF for 3ft, 6ft, 12ft, 25ft-ish seems like it's spot-on least to the pairing of the RF to the actual image captured. I just won't get crisp horizon past 50 feet at f/3.5
Timmyjoe
Mentor
I've worked on a number of C3's now and I found that there wasn't really a standard with the lens mounts. It seems that each lens was fitted and adjusted to each camera. Swapping lenses from camera to camera threw off infinity.
What I do is start with the body and lens (and it helps to have a collimator) and make sure the lens comes to a stop at infinity. Usually I find the opposite of what you're describing, usually I have to shim the lens so it doesn't "overstroke". Once I know the lens stops exactly at infinity, then I adjust the rangefinder and find the exact spot where it reaches infinity (the idler gear is not on the camera at this time). I make sure the rangefinder covers from infinity down to somewhere near 3ft, and once I've marked the exact spot on the rangefinder where it's at infinity, and I have the lens set at infinity, I put the idler gear back in. I completely ignore the number scale on the rangefinder wheel, and just focus the camera optically. Has worked great so far.
Good luck.
Best,
-Tim
What I do is start with the body and lens (and it helps to have a collimator) and make sure the lens comes to a stop at infinity. Usually I find the opposite of what you're describing, usually I have to shim the lens so it doesn't "overstroke". Once I know the lens stops exactly at infinity, then I adjust the rangefinder and find the exact spot where it reaches infinity (the idler gear is not on the camera at this time). I make sure the rangefinder covers from infinity down to somewhere near 3ft, and once I've marked the exact spot on the rangefinder where it's at infinity, and I have the lens set at infinity, I put the idler gear back in. I completely ignore the number scale on the rangefinder wheel, and just focus the camera optically. Has worked great so far.
Good luck.
Best,
-Tim
kb244
Well-known
I suspect that's what happened, that the lens is possibly not original to the body.
Because in every threading that I screwed the lens on, none of them seem to hit infinity spot on, though the closest of the three is "close enough".
The main thing I've managed to ensure is that the focus of the lens, and the focus of the rangefinder matches from 3ft on, with what seems to be a maximum focusing distance of roughly 30~50 feet (Something across the street from my porch won't quite 'connect' in the split focusing screen or RF).
The camera came from a guy who was selling a group of them with the lens cleaned and re-skined, but As-Is on every other portion of the camera. Except I got the wrong one I asked for, as a result he just simply refunded the purchase, so I'm just going ahead tweaking/tuning it up the most I can to get the most out of it, since I got little to lose on it. (wanted the older 1951 model because the skin looked cleaner on it, and had the 7-speed dial, ended up taking the dial off my 'parts' body).
I'm guessing it would a whole different can-o-worms if I tried to change the lens focus within the collar (meaning I unscrew the retaining screws, and rotate the collar until the indexing hole lines up to true infinity).
A look of it on the far right:
kb244
Well-known
Off Apug DaveT mentioned:
Sure enough when I went one more thread over I dropped from 1.15mm gap to 1mm gap, the next thread over being too close to line up, and going back thru the cycle sure enough there are 6 threads to go with.
So will re-check with the closer fitting.
It should be able to focus at infinity. I have never counted, but was of the impression the helical had even more than three possibilities (6?). Anyway, I recall the lens is not quite "bottomed" when at infinity, so you might want to try the next thread. Normally when the idler gear is engaged and all is lined up, the end of the idler gear teeth stops things at infinity, but there might be a bit more travel available in the lens.
There are manuals on the Argus Collector Group site that might shed additional light. I have a 1957 vintage C3 I bought new that I get out at least once a year for Argus Day, an ACG event. It will be "Argust 17th" this year. It sat in a closet for about 25 years and when resurrected in 2005 or so, I was more impressed with it than I expected to be. It's rather fiddly to use, and rather limited in shutter speeds, but outdoors in good light does OK. Gad, to think I began with it shooting Kodachrome Daylight at ASA 10!!!
Sure enough when I went one more thread over I dropped from 1.15mm gap to 1mm gap, the next thread over being too close to line up, and going back thru the cycle sure enough there are 6 threads to go with.
So will re-check with the closer fitting.
kb244
Well-known
Lost the damn indexing screw
Steve M.
Mentor
Unless you're shooting infinity wide open, which is rarely the case "almost infinity" should work fine. I once had a lens on a different SLR that would not get even close to infinity, and the photos were blurry wide open. Stopped down to f8 it was nice and sharp. Not what I expected, but that's what I got.
kb244
Well-known
I stole a focus locking screw from a Kodak Signet (that's inoperable), sanded down the front diameter of it (pointy) so that it would glide in the groove it goes into.
Which seemed to work smoothly, short of sticking out a little (I'll probably try to find a little washer cap if I can't find the original screw).
Before I lost the index screw, I locked the focus to infinity, and then removed the indexing screw putting it down in a lens cap. Turned the lens while watching on the focus screen until it hit infinity focus from some trees in a far distance (bout quarter mile or so). Once I was satisfied that infinity was achieved I loosened the 4x screws (marked in blue), and rotated the collar around so that it would line up to the slot. Tightened down the 4x screws, and then just as I was going to put the index screw in, I dropped it, and yet to be found.
Once I got that signet screw in, I re-adjusted the rangefinder calibration, first at a measured 5 ft, adjusted against a chart, then again at infinity, and then checked again at 5ft.
Now not only is the rangefinder and lens match, the distance scale actually seems accurate (measured 5 ft, focus at 5 feet, shows 5 feet on the scale).
Which seemed to work smoothly, short of sticking out a little (I'll probably try to find a little washer cap if I can't find the original screw).
Before I lost the index screw, I locked the focus to infinity, and then removed the indexing screw putting it down in a lens cap. Turned the lens while watching on the focus screen until it hit infinity focus from some trees in a far distance (bout quarter mile or so). Once I was satisfied that infinity was achieved I loosened the 4x screws (marked in blue), and rotated the collar around so that it would line up to the slot. Tightened down the 4x screws, and then just as I was going to put the index screw in, I dropped it, and yet to be found.
Once I got that signet screw in, I re-adjusted the rangefinder calibration, first at a measured 5 ft, adjusted against a chart, then again at infinity, and then checked again at 5ft.
Now not only is the rangefinder and lens match, the distance scale actually seems accurate (measured 5 ft, focus at 5 feet, shows 5 feet on the scale).
Attachments
farlymac
PF McFarland
When adjusting a rangefinder, Karl, you can save yourself a lot of time and trouble by setting infinity first. And don't mix up the 50mm Cintars between different bodies.
PF
PF
kb244
Well-known
I didn't, must have been the previous owner who cleaned the optics on his lot. But noted on the infinity bit.