Effect of losing lens coating on image quality

ambaker · Oct 23, 2015

Any damage to a lens or coating reduces the performance. However, it would appear, after reading the linked article below, that w lens can sustain quite a bit of damage and still yield a useable image.

http://www.lensrentals.com/blog/2008/10/front-element-scratches

-They tie Mountain Climbers together so that the sane ones can't go home...

baachitraka · Oct 23, 2015

There is no loss on the coating. I have cleaned it again. Lens is looking good.

shutterfinger · Oct 23, 2015

There is no loss on the coating. I have cleaned it again. Lens is looking good.

Excellent.

I have 3 12 x 12 heavyweight microfiber cloths, 2 Pro Optics, 1 Microdear (the original); 1 15 x20 Microdear, and 1 15 x 15 Lee Optics. I purchased these at Dead Link Removed over the years. I have 2 Dust off 6x6 lightweight cloths that I use as lens wraps when I have a lens disassembled or for dusting the printer or scanner as they are not useful for anything more. I also have a few medium weight cloths that came with eyeglasses, they are only good for a wipe or two but not good for a thorough cleaning.
If you have questions about what you have available in your area send me a link to it and I will give you a fair opinion of the cloth.

itsdoable · Oct 23, 2015

baachitraka said:
No CCD. I tried to unscrews the two lens elements previously cemented by the bad grease from Agfa which was not possible with simple tools. Eventually I soaked it in a lighter fluid thinking it will dissolve the old grease and there by separting two elements. But that does not happen so, I ovened them at 150°C for 10mins.

Two elements came apart after considerable effort and I set to clean the gunk and surface of the elements.

I think I understand now - the front "cell" of the Agfa has 2 elements, where the front element rotates on a fine helicoid (threaded really) to focus (not a doublet). You were trying to unscrew the front element as the grease on the threads had resinified. btdt.

I prefer using a wet grease, but if it works, that the bottom line.

Luis-F-S · Oct 23, 2015

baachitraka said:
Is there any good lens cleaning agent available? I use contact lens lotion to clean the glass...

ROR; Residual Oil Remover by V-Max Products.

baachitraka · Oct 24, 2015

I am still looking for a nice lens cleaner.

Shutter took a short bath in lighter fluid and all speeds sounds correct now. Kind of happy but lens is not really clear when I look against light source.

I will live with it but in future looking something that really cleans the lens.

Nodda Duma · Oct 24, 2015

Well this

baachitraka said:
I am still looking for a nice lens cleaner.

....

Kind of happy but lens is not really clear when I look against light source.

I will live with it but in future looking something that really cleans the lens.

Would indicate that this

baachitraka said:
There is no loss on the coating. I have cleaned it again. Lens is looking good.

Is not quite true. If it's a haze that you can't remove, then the coatings are damaged.

In optical shops, the only thing that ever touches a lens surface for cleaning is acetone, isopropyl, lens tissue, cotton, or Kim Wipes. They also don't reuse tissue: a piece of cloth or tissue is *much* cheaper than a lens. One or two wipes and it's tossed, rather than risk surface damage.

Btw microfiber is *not* found in optical shops nor is it found on lens assembly benches. If I visited an optical shop making lenses for one of my designs I'd be like "wtf are you doing, keep that shit away from my optics." There must be a reason???

jerrybro · Oct 24, 2015

I spent almost 20 years in optical metrology. Cleaning optics before testing or assembly is SOP, and Nodda is correct, acetone, isopropyl and a cleaning solution that is mostly water is all you typically find. The process I use on all my optics are the ones I used there.
1. Remove all debris using air or a very soft brush
2. Using a lens tissue, folded up to finger width, dampened with a couple drops of lens cleaner, gently wipe the lens in a circular motion starting at the center and moving towards the edge. Toss the tissue.
3. If the lens is stil dirty repeat.
4. If clean but there is a dried residue from the lens cleaner repeat the process using alcohol.
5. If the alcohol leaves a residue repeat with acetone. Stay away from any plastic with acetone.

It is important to use the purest solutions you can find for the best results. Never put liquid on the lens. Never wipe with a dry tissue.

I know pros that never clean their lenses and suffer no ill effects, but I'm a touch neurotic and obsessive. All my optics are as clean as I can get them.

baachitraka · Oct 24, 2015

After cleaning and assembly.

I did some BS with dry grease which has caused damage to the front surface of the second element. Result fine circular lines.

Contact lens lotions has removed the cloud and it is clear now except the damage on the second element.

baachitraka · Oct 24, 2015

...and the damage.

shutterfinger · Oct 24, 2015

Are you sure that's damage to the coating/glass? Looks more like residue from the lubricant that may be very stubborn to remove.

baachitraka · Oct 25, 2015

I believe during soaking in lighter fluid, the dissolved grease might have settled down on the surface of the second element and subsequent heating in the oven might hardened it.

shutterfinger · Oct 25, 2015

Dried or baked on grease sometimes has to be scraped off. I do not recommend scraping a lens. Along the edge it will have little to no effect on image quality. It may have to be polished off by a lens polisher.

baachitraka · Oct 25, 2015

I think I can live with it. This lens can be good for portraits.

I presume the polishing can only be done by professional? For €30 camera, I don't know whether I can go for.

Its sad to see it but its okay.

shutterfinger · Oct 25, 2015

You may want to consider getting an Ultrasonic Cleaner such as http://www.ebay.de/itm/600ml-Digita...655218?hash=item567d511cb2:g:ESYAAOSw14xWKLUK
and some 90% Isopropyl Alcohol and give it a go. I purchased a very similar unit a while back. After sitting over night the Alcohol was warm so there is a low wattage heater in it. Running repeat cycles in succession for a total of 15 to 30 minutes works very well on disassembled shutters so it should work well on lens as well.

baachitraka · Oct 25, 2015

Thanks. I will give a try.

shutterfinger · Oct 25, 2015

I cannot guarantee it will work. I have had to scrape grease soap base off metal after ultrasonic cleaning but it may make it soft enough to scrap off easily with a finger nail.
My cleaner is the same as the sample I linked but with a 300 second max time per cycle with a digital display.

baachitraka · Oct 26, 2015

At f/8 and above I don't see those damage and that is perfectly okay for me.

weasel · Oct 26, 2015

I use a 50-50 mix of denatured alcohol ( paint supply store) and pure ammonia to clean lenses. Works very well.

Effect of losing lens coating on image quality

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