My new collapsible Summicron

payasam said:
Roland, I did a tape measure test. At 3.5, 4 and 4.5 feet, the Summicron's distance scale showed a distance slightly less than the measured distance. At 4.5 feet, for example, the scale showed just over 4 feet. My Industar 61 L/D, by contrast, was bang on at 1.1 m and 1.5 m.

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If I were to do the tripod thing, Brian, I would have the lens axis at an oblique angle to the fence (or railings or whatever). I assume that is what you mean.

Here are two pictures taken with the lens at the same time, one at f/2 and the other at f/5.6. Both prints scanned in the same pass, nothing done other than cropping and -- to take care of the different colour casts the lab had managed -- desaturating.
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Hi Mukul,

half a foot or less is not so bad for a 50/2 wide open. Only a film test will show if there is a real problem.

For final collimation check, I usually do boring stuff like this:

121162442-L.jpg


Have to use a tripod though to avoid body back-lash.

But looking at your last f2 photo, I feel there might be another issue. Eyes are pretty much in focus, but the Summicron should produce a clearer picture. Can you check for haze with flashlight ?

AFAIK, Youxin does only CLA mechanics of a lens, not the optics.

Best,

Roland.
 
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You can also check the focus on the 50/2-M2 by putting the camera on a tripod, removing the back door (or just flipping it up). Put a piece of ground glass on the rails and focus through it. You can also use a piece of "drafting Mylar" a semitransparant film used for preciscion drafting. Use a measuring tape and set the lens at 1meter and look through it on the "ground glass" Set the camera on B and use a cable release with a locking screw on it or volunteer somebody to hold the release down while you are checking - it is an operation that requires at least three hands!. Is it sharp or is the focus off?
Remember that when you measure, You have to measure from the filmplane (about 5 mm from the back edge of the camera).
The 50 collapsible Summicron can be tricky. It is inherently a low contrast lens (compared to later ones) and that gives it a bit softer look and that can be viewed as "fuzzy" focus occasionally.
Once you got confirmation that your focus is "on". Get a roll of film and load up and shoot it of the same subject. Work through your apertures from f2 to f16 and once you have developed the film you can check sharpness and focus again. This will also tell you if there is any focus shift when you stop down.
 
Honestly, the two portraits look pretty good, especially for a $60 lens! The front has some marks, use a shade. Get a clip-on until you fix that rim-ding. Also, check the interior elements for haze with a flashlight.
 
Tom A said:
You can also check the focus on the 50/2-M2 by putting the camera on a tripod, removing the back door (or just flipping it up). Put a piece of ground glass on the rails and focus through it. You can also use a piece of "drafting Mylar" a semitransparant film used for preciscion drafting.
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I've found that there is a variation between different ground glass when doing this. I'm not very knowledgeable on the optics/physical reason behind this, but empirically, I've experienced some glass to be more reliable than others. I think if your glass is too thick, you may be mislead into adjusting the lens out of focus.

I don't know if what I just "said" made any sense, but what I'm trying to get to is that if you use some clear film (like developed, unexposed B&W film) and use that instead, it would be the best way to check collimation/focus on lenses with "fast" apertures (f/2 or larger).

Or am I just unwittingly perpetuating one of those Internet myths?
 
Gabriel, it is a bit of both. If your groundglass is to thick it can affect your focus-plane. Usually not enough to worry about with most lenses though (Noctilux@f1 at 1 meter yes, but a Summicron f2 no). This is why suggest the Mylar instead as it is closer to the thickness of a film. I simply tape it on the rails and use it like that. The problem is that however may times you do it - the damned lens is going to do what it wants! Sometimes a lens that works fine at 1m, will through focus at 2m or even 5 meter. You have to check, shoot, realign and pray that everything stays fine. The only time I really set myself to do this rather boring task is with fast lenses, Noctilux, Summilux 75, Nokton 35f1.2. Of course, you also have to dedicate a camera body to it for these lenses as even miniscule shifts in filmplane/lens will affect it.
Ow, to hell with it and stop down or get f2 -f2.8 lenses instead!
 
My first try at building a "great" Collapsible Summicron from two lenses resulted in a lens that was GREAT at 4ft. The actual focus and RF agreed at - 4ft. No where else. I found that front modules from Summicrons built several years apart could not be interchanged. A 115x lens and a 13x lens. I found the front elements could be swapped, and ended up with a great Summicron that worked at all distances.
 
Roland, I do pretty much the same sort of boring stuff. Nothing else is as precise. Youxin dealt with the M2 I bought from him, but not with this lens. Tom, in the past I have done what you advise, but at this time I don't know if I can find the right kind of tracing paper -- and I have no loupe. Therefore I am relying on photographs. Brian, I have a SOOFM. Damn thing cost $2 more than the lens, and I had to give its insides two coats of matt paint. Will do a flash-light check.

Thank you, all.
 
You need to verify the focus Helen. With old lenses, that have been cleaned, etc, getting the focus right is always problematic. If you find it is off, just give it to some smart tech guy for collimation - BTW you should not be expecting it to be very sharp wide open anyway, it becomes nice by f 2.8.
 
http://www.rangefinderforum.com/forums/showthread.php?t=53386

http://www.rangefinderforum.com/forums/showthread.php?t=53386

helenhill_HH said:
reviving an old thread, as in 'payasam's' Thread Title

I just picked up a 1955 collapsible, Beautiful glass....no cleaning marks, haze or fungus....now i just need to focus better.... :rolleyes:

Enjoy!
May your light be magic, your exposures true.

If lens is collimated correctly, it is sharp at f2 !
Mine has slight backfocus.
I have one, used since 1967.
It flares easily but is very sharp in center.
Often compared shots to a a few friends with newer Summicrons.
Difference is very small.
Use a filter at all times and a hood.
Try to never clean the glass, esp the rear element.:angel:

It has low contrast, but makes up in other areas.
I prefer it to all other 50mm lenses, because it collapses.
The newer Elmar is more contrasty and "appears" sharper.
Click to expand...
 
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