| Author |
Message |
    
newindustaR
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 09, 2006 - 01:55 pm: | 
|
I have some light internal fungus, not sure on what elements. This is the aluminum semi-automatic (requires lens cocking) version. The lens seems ok mechanically. Please advise on how to approach dealing with dissamble and fungus cleaning.
Thanks |
rick
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 09, 2006 - 09:14 pm: |
|
This would be the all-silver one, right? first unscrew the outer spanner ring in the rear: this allows the entire lens assembly to come out of the focusing mount in one piece. From here you can unscrew the front and rear cells. For the front one you will need to unscrew the ID ring first - I don't think there are any spanner slots in that one so you'll have to use a rubber tool like a crutch tip or a rubber-faced wooden dowel. The front cell has 2 air spaced elements in it, so there is a possibility of fungus being in between them, but try cleaning the outer surfaces first before taking out individual glass elements. The rear cell has only a single cemented pair, so there is nothing to clean but its outer surfaces at the front and rear of the cell. |
newindustar
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 10, 2006 - 08:37 pm: |
|
Thanks Rick for getting me off to a good start. I got it apart and back together. It had been apart before so nothing was too tight. I cleaned all the elements as best I could using a few different solutions. I believe the glass suffered some etching. It is much better but not perfect. it almost appears to have bubbles in the glass. Would Jena have let a lens go out with bubbles?
The only mechanical difficulty I has was upon reassembly. There is a brass channel from the apeture that is pushed by the lens cocker arm (or vice versa). This arm fit neatly into the middle of the brass channel and appears to be designed to do so. However if you assemble it this way you will lose 1/2 stop at the wide end and things bind up. The cocking arm must go ALONGSIDE the brass channel not IN it despite appearances. I lost some time over that.
I only shot one roll with this lens before this cleaning. It had a lot of flare and softness. Has anyone shot with this lens? It appears to be uncoated but I am not sure. What has your experience been. Are these well regarded? I read the 2.8 Tessars were much less sharp than the 3.5 wide open. If you have any comment about this lens I'd like to know.
Thanks |
newindustar
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 11, 2006 - 12:52 pm: |
|
Hmm not so quick. I found when I focus towards infinity it is binding the apeture (sticks open). Other wise it all works perfectly. Any ideas before I open it up again? |
Charles Fallis
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 14, 2006 - 05:10 pm: |
|
"it almost appears to have bubbles in the glass. Would Jena have let a lens go out with bubbles?"
Apparently they would. I have a Zeiss Skopar with two small bubbles that came with my Avus. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 14, 2006 - 07:51 pm: |
|
The Tessar did not like being opened up to f2.8 and the f3.5 version will out perform it at maximum aperture. This is why the 80mm/f2.8 Tessar that was fitted to the first few Praktisix produced, was soon replaced by the five element Biometar.
As for bubbles in Zeiss glass; there is a technical name for these (which I cannot recall at the moment)and they are a common occurrence in certain Zeiss optical glasses, they do not interfere with lens performance and there can be large numbers visible in some wide angle lenses.
The Jena factory issued a leaflet on the subject, explaining that they were normal and that the lenses were not faulty.
The little devils even occur in some of my M series Leitz lenses. |
newindustar
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 27, 2006 - 01:13 pm: |
|
I did solve the apeture sticking towards infinity, a little lube where the brass contacts the barrell did the trick. I also shot a roll of film with it. I was pretty flat and very prone to flare and not anywhere as sharp as I am used to with my Nikon lenses at any opening. As far an having an special "look" I was not moved much either. |
Michael Linn
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 27, 2006 - 06:55 pm: |
|
With only six air to glass surfaces, the Tessar design got it's original reputation for being a high contrast lens. When coated, after WWII, it was even better. Amazingly, when multi-coating became available, Carl Zeiss Jena quickly adopted it on it's Pancolars, Flektogons, Biometars, etc. But they never bothered with the Tessar because it really didn't benefit much.
As for bubbles in the glass, Glenn is correct of course. One of my favorite lenses is the 2/58 Biotar and the best performing example I have is the one which has a LOT of bubbles in the rear elements.
Modern Nikon lenses are splendid performers but a Tessar in as good condition should, at 5.6 or smaller, hold up well in comparison regarding both contrast and resolution. I think that your Tessar is still suffering from something other than a birth defect. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 28, 2006 - 07:37 am: |
|
As Michael says, your Tessar should give good results at f5.6 or smaller. You should check all dimensions, including the mount/film distance. Make sure all elements are seated and centred correctly and all the lens groups are screwed down properly. Slap-dash reassembly can turn a silk purse into a pig's ear. |
newindustar
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 30, 2006 - 06:14 pm: |
|
Thanks for the background on the Tessar. I was only shooting at f16 and f11 due to the limited choices in daylight as iso 100. Does the Tessar dislike min apetures? I believe I was pretty careful on the assemble. They were definitely seated and screwed down. I never consider centering however. Infinity come in correctly. By the way there were so pinpoints of light creating a few UFOs in the image. Would that ever come from this lens or is the Exacta Varex IIA likely the culprit.
I was interested in the 58mm, have you found this much bettert than the 50mm?
Can we post images here? |
Michael Linn
Rating: 
Votes: 1 (Vote!) | | Posted on Thursday, March 30, 2006 - 06:40 pm: |
|
Your UFO's were from pinholes in your shutter curtain.
As for the 58mm Biotar, it's only advantage over the Tessar was in speed. With the advent of SLR cameras, the difference in brightness on the ground glass focusing screen (yes, it was glass on the Contax S) between a 3.5 or 2.8 Tessar and an f2 Biotar was very noticeable. I have also had the opportunity to own and use west german 2.8/50 Tessars from the 60's (called 'recomputed") with reults that astounded me regarding resolution.
This lens appeared in apparently the same form in everything from the lowly Tenax (about $10 today on ebay) to the Contaflex and even the Contarex. |
