Cleaning an old brass Leitz Summar

[psychoanalyst]

I have the following lens that I am trying to take apart and clean:

http://farm4.static.flickr.com/3168/5848878901_e30eda0c64.jpg (http://www.flickr.com/photos/smiling_buddha/5848878901/)


Its fairly easy to take apart. I have removed the rear group of elements. But the front group is proving challenging since it sits in front of the diaphragm housing and I don't want to risk screwing that up.

The question is would it it be ok to soak both pieces (the rear group which I unscrewed out and the front group+iris assembly) in some kind of cleaning solution (windex, dish washing liquid(??) etc.) without causing too many issues?

I am pretty sure that it has haze/fog and it clearly shows up in my viewfinder. Its a lovely little lens that would be invaluable to me in photomicrography and I would love to get it up and running.

Can't justify the cost of a CLA........

Advice would be most appreciated.

Thanks.

Avi

[john wilton]

It looks as if the front group will unscrew from the barrel. Use latex gloves to get a good grip on the rim and the front of the barrel (put the iris in the middle of its travel so you don't apply torque to it.) Still didn't budge? Use a syringe to apply a bead of naptha (harware store) around the join between front cell and barrel. Very gently tap around it with a very small wood or plastic mallet (hardware store) and it will unscrew with astonishing ease.

Now you'll have to disassemble the cells. You'll need a lens spanner. If you don't have one, now is the time to get one, it's a must have. Don't mix up orientation of the lenses. As they are uncoated you can be quite aggresive in cleaning...acetone if necessary. Clean, fresh microfibre cloth. (Acetone on surface only as it might dissolve cement in a cemented lens). If any lenses are cemented pairs and there's trouble in the cement, thats beyond my pay grade, but others here can help you. You'd need V-blocks.

[alex from holland]

You also can put in a freezer for a few hours and after that give it another try.
It looks like the front and back is made os alu and the rest is made of brass.
You can also use a BIT silicon spray

[psychoanalyst]

Use a syringe to apply a bead of naptha (harware store) around the join between front cell and barrel. Very gently tap around it with a very small wood or plastic mallet (hardware store) and it will unscrew with astonishing ease.

John.....absolutely amazing advice! I went to Ace hardware and purchased a "super penetrant liquid wrench" and within 10 mins, the 2 parts came apart like there was never any problem to begin with!!!

Pictures will follow within the next few hours...I am cleaning the elements with soap and water and they already look good as new.....there are 4 cells in all, but can't really tell how many elements in all.

Quite thrilled about this, coupled with the fact that I just got done cleaning my Petzval as well.

Thanks!

Avi

[psychoanalyst]

Ok.....here are the pictures after removing all the elements/groups

http://farm7.static.flickr.com/6024/5991966945_387f2cf013.jpg (http://www.flickr.com/photos/smiling_buddha/5991966945/)

http://farm7.static.flickr.com/6140/5992524766_b5b5a96b96.jpg (http://www.flickr.com/photos/smiling_buddha/5992524766/)

THIS IS THE BRASS HOUSING WHICH ALSO HAS THE APERTURE BLADES:

http://farm7.static.flickr.com/6146/5991967629_2a325d6fd2.jpg (http://www.flickr.com/photos/smiling_buddha/5991967629/)

AND THIS IS WHAT ALLOWED ME TO REMOVE THE FRONT GROUP THAT WAS REFUSING TO BUDGE. THANKS FOR THE TIP JOHN!

http://farm7.static.flickr.com/6023/5991967191_1766e706f3.jpg (http://www.flickr.com/photos/smiling_buddha/5991967191/)

Maybe this information would be useful to the few people who have a copy of this lens.

Avi

[john wilton]

Well, I didn't suggest liquid wrench--I imagine it's petroleum based, you'll need to eliminate all traces of it as it has the potential to fog the lens over time.

[psychoanalyst]

John

I will make sure to remove all traces of it. But naphtha too is derived from crude...

Avi

[Dan Fromm]

Please tell us how well the lens works.

Do you have similar modern lenses, e.g., 100/6.3 Luminar, 100/6.3 Neupolar, 90/6.3 Mikrotar, 80/5.6 Photar, to compare with it?

[psychoanalyst]

Dan,

The only "equivalent" lens I have would be a Wollensak Micro Raptar 50mm. Other than that, I only have 35mm macros lenses.

I will conduct some basic in house tests with the Summar, Raptar and maybe my 90mm Macro Kilar and 105mm Kiron.

I don't have much experience running tests, so after I upload my results, maybe you can guide me?

Thanks a lot!

Avi

[Dan Fromm]

Avi, thanks for the reply. Which 50 Micro Raptar do you have? I have a 50/4.5 with diaphragm.

Read about how it performed for me and how I've tested macro lenses at http://www.galerie-photo.com/telechargement/dan-fromm-6x9-lenses-v2-2011-03-29.pdf

Cheers,

Dan

[psychoanalyst]

Dan,

I have the very same......thanks for very informative PDF document.

What test conditions would you recommend for the macro shots? I was thinking of a quarter or something similar under natural light. Don't have any other form of lighting apart from the on camera flash on my Nikon D300, which I hate using.

Avi

[Dan Fromm]

You want to test using a target that has a range of sizes of fine detail. The ideal would be a USAF 1951 target on glass, as sold by Edmund Optics. These cost, IIRC, around $125.

A less expensive but less informative target would be a microscope stage micrometer. This is a microscope slide with a bar with tick marks. The typical one has the tick marks .01 mm apart, can be used to determine whether the lens can resolve objects that close. Not perfect, was useful for my purposes, may not suit yours.

This eBay search will find some: http://shop.ebay.com/i.html?_from=R40&_trksid=p9999999.m570.l1313&_nkw=%22stage+micrometer%22&_sacat=See-All-Categories

More details on what I did in the .pdf

[psychoanalyst]

Dan,

I have conducted a basic test...please point out the flaws since I want to learn. I have not calculated reproduction ratios, but have provided bellows extension instead. The subject is a quarter, which has a diameter of 24.26 mm according to Wikipedia.


Test conditions: Leitz Summar 80mm lens wide open mounted on PB-4 bellows with Nikon D300. Lighting: combination of natural light and a desktop lamp with a GE white light source directly incident on the test subject. Setup mounted on a Benro Tripod and shot with a remote release.

I would like to apologize for posting pictures shot with a DX camera here, but the purpose was to run a quick test on the lens, which by itself is known to cover large format I believe.

THIS IS THE SUBJECT AT A MINIMUM MAGNIFICATION I USED: 77MM EXTENSION:

http://farm7.static.flickr.com/6139/5994200073_5f64f4ca39.jpg (http://www.flickr.com/photos/smiling_buddha/5994200073/)

SAME IMAGE 500 PX BY 500 PX CROP IN PHOTOSHOP:

http://farm7.static.flickr.com/6128/5994760526_f02946f0f6.jpg (http://www.flickr.com/photos/smiling_buddha/5994760526/)

SUMMARY OF TEST RESULTS: ALL 500 PX CROPS PUT TOGETHER:

Bellows extensions:

TL-70 mm
TR-99 mm
BL-127 mm
BR-max PB-4 extension=190 mm

http://farm7.static.flickr.com/6123/5994761136_d0f0faf214.jpg (http://www.flickr.com/photos/smiling_buddha/5994761136/)

To my untrained eye, the lens looks quite good at low magnifications. Can't say the same at higher magnifications. I guess here is where I would need to start stopping the lens down to refine the tests?

Comments/advice are of course very welcome.

But I am happy that I cannot detect signs of the earlier haze.

Avi

[Dan Fromm]

Its good that you tested at several magnifications. Most high performance macro lenses are best at a fairly narrow range of magnifications. Its dangerous to generalize, but I have the impression that lenses with focal lengths of 80 - 100 mm aren't the best, even when extension is available, for use above 8:1. They're typically best somewhere between 1:5 and 5:1, but the 100/6.3 Luminar is recommended for use between 1:8 and 8:1.

I don't know what sensor-to-diaphragm (the diaphragm's location is an ok approximation for the lens' rear node's location) distance is for any of your shots, so have no idea what magnification on the sensor is. Please tell us.

The weakness of tests like yours is that they don't give clear advice about what the lens can't resolve. That's usually what's of interest.

Targets with known fixed narrow spacing (those stage micrometers I suggested) check whether the lens can/can't resolve features the spacing apart. If the target's spacing is finer than the features that have to be resolved when you get to shooting real subjects, these targets were serve for go/no go testing.

Targets with known variable spacing such as the USAF 1951 on glass target I suggested yield actual resolution, give a clearer signal of what the lens can't do.

One of the big problems with working at any magnification at all is stability. I found that getting usable and reproducible results on film needed flash illumination to stop motion. Think about doing that when testing and when shooting for real.

Now go read the .pdf I directed you to and think about what I wrote there.

[psychoanalyst]

Dan

I just finished reading your write-up. That is a very through comparison across focal lengths.

I will try and employ the same testing method soon.

Thanks.

Avi