Effect of losing lens coating on image quality

baachitraka · Oct 22, 2015

I have cleaned the lens elements of Agfa Isolette and saw some streaks after cleaning them but they are not scratches and I presume they are loss of coating.

Will losing a bit of coating affect the image quality?

shutterfinger · Oct 22, 2015

Coatings improve local contrast and improve color. If you are seeing streaks I doubt it is coating(s) coming off. If the coatings are coming off the glass will be clear in those areas and tinted in other areas.
More thorough cleaning is needed to get rid of the streaks. A heavyweight microfiber lens cleaning cloth and you breath are the best cleaning agents.

baachitraka · Oct 22, 2015

I will check them again. I was careful when cleaning and used microfibre and no finger nails...

AgX · Oct 22, 2015

Coatings can have undergone corrosion. Cleaning the lens surface can then make the corroded parts look more distinct.
At, least that was my impression in some cases.

In any case, corrosion of the glass itself would have more affect than that of the coating.

Sometime this year there was a thread on severely damaged lenses and how they still produced acceptable or good images.

baachitraka · Oct 22, 2015

I do not see any damage or corrosion but I will give one more gentle clean on tomorrow.

baachitraka · Oct 22, 2015

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

ic-racer · Oct 22, 2015

baachitraka said:
I have cleaned the lens elements of Agfa Isolette and saw some streaks after cleaning them but they are not scratches and I presume they are loss of coating.

Will losing a bit of coating affect the image quality?

Low contrast scenes (overcast in shadows, etc) can be imaged quite well with foggy lenses. High contrast, beach, snow, specular reflections, sun, etc will wind up with flare that may spoil an image.

Nodda Duma · Oct 22, 2015

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

With saline? No wonder your coatings might be wearing away. MgF2 is slightly soluble in water. Salt water does even worse things. I dread salt spray requirements for optics, much less try to clean them with it.

Use alcohol or acetone to clean coated optics. Don't press down on the glass.

Gerald C Koch · Oct 22, 2015

Use a cleaner designed for camera lenses and follow the directions. Do not use a microfiber cloth. These pick up grit and can scratch. Use single use lens cleaning tissue instead. More lens have been damaged by over-zealous cleaning than any other events.

Dr Croubie · Oct 22, 2015

Lenspen.
Nothing else.

shutterfinger · Oct 22, 2015

[QUOTE ]Do not use a microfiber cloth. [/QUOTE]
If you cannot keep your lens cleaning cloth clean then I question whether you should be attempting to use a camera.
Microfiber cloths are easy to keep clean. Toss them in the washer with a load of cotton clothes with NO fabric softener, air dry.
Many other cleaning supplies pick up dust and grit also.

Your breath is one of if not the best lens cleaning agent.

Xmas · Oct 22, 2015

No simpler to screw or clip on a filter lenses get cleaning marks cause they are cleaned.

You then don't need to clean the filter...

If you are a dropper a hood will protect the filter and filter ring.

Only use a microfibre scratching cloth once, they are excellent for holding silica.

Washing machines ditto.

Beware sea gulls...

Compulsive lens scratching - CLS

Gerald C Koch · Oct 22, 2015

Your breath is one of if not the best lens cleaning agent.

+1

Kodak at one time sold a very effective lens cleaner. It contained both Triton X-100 and ammonium bicarbonate. Both were very effective in removing greasy marks like finger prints. Even though ammonium bicarbonate is an inorganic chemical it soon breaks down to ammonia, carbon dioxide and water when the cleaner dries. So the cleaner leaves no residue. I have always thought this to be rather neat.

Unless you wash the cloth after each use it is possible to encounter problems with subsequent lenses. This is why I prefer a single use product like lens tissue.

summicron1 · Oct 23, 2015

to answer your original question -- I've shot with coated and uncoated lenses. If you use a lens shade to reduce flare from side-light striking the glass you will not notice a lot of difference. Coating improves contrast a bit, and makes light transmission by the glass more efficient (it allows less light to bounce off, which is why coated glass surfaces are harder to see) but for an older tessar design like you have there, the difference should be minimal.

Clean carefully, take pictures, don't stress.

baachitraka · Oct 23, 2015

The tint is still there and I think those streaks are from cleaning. I will clean them today and see how it goes.

Xmas · Oct 23, 2015

baachitraka said:
The tint is still there and I think those streaks are from cleaning. I will clean them today and see how it goes.

The streaks won't be on the photo but scratches reduce contrast.

You got CCD bad.

Compulsive Cleaning Disorder...

Xmas · Oct 23, 2015

shutterfinger said:
[QUOTE ]Do not use a microfiber cloth.

If you cannot keep your lens cleaning cloth clean then I question whether you should be attempting to use a camera.
Microfiber cloths are easy to keep clean. Toss them in the washer with a load of cotton clothes with NO fabric softener, air dry.
Many other cleaning supplies pick up dust and grit also.

Your breath is one of if not the best lens cleaning agent.[/QUOTE]

If you must use them on lenses then Id buy new ones washers are full of silica grit.

baachitraka · Oct 23, 2015

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.

baachitraka · Oct 23, 2015

I have used two drops of dry tefol grease in-between two lens elements and it is a magic, I can say.

Do Pronto-S need any lubricants? I read some where it was designed to run dry. One crazy idea was to dip the shutter in dry tefol grease fluid but I am not sure what really will happen after that...

BobMarvin · Oct 23, 2015

I cut small pieces of cloth from worn out, well-washed knit cotton underwear; use them once and throw them away. These are softer than lens tissue.

itsdoable · Oct 23, 2015

baachitraka said:
I have used two drops of dry tefol grease in-between two lens elements and it is a magic, I can say.

Do Pronto-S need any lubricants? I read some where it was designed to run dry. One crazy idea was to dip the shutter in dry tefol grease fluid but I am not sure what really will happen after that...

Doublets are usually cemented with Canadian Balsam or UV cured optical polymer. Older doublets are usually Balsam, which can be prone to fungus infections (causing cloudiness). Balsam doublet can be separated with heat (I use water near boiling), cleaned with alcohol (or Xylene) and recemented. I don't know what "dry tefol grease fluid" is, but the "dry" and "fluid" are not compatible terms. If it is a grease, it will dry out in a relatively short period.

Most older leaf shutters are sparsely lubed with a very light oil. Excessive lube (even mildly) causes the extra lubricant to migrate into the shutter leaves and aperture, and attracts dust and grit.

Mainecoonmaniac · Oct 23, 2015

IMHO, I used to be over obsessive about cleanliness of my lenses. If there are minor streaks, there shouldn't be an issue. There might be a slight difference if your subject is back lit. It that case, there be a little bit more flare.

Gerald C Koch · Oct 23, 2015

baachitraka said:
I have used two drops of dry tefol grease in-between two lens elements and it is a magic, I can say.

What ever is used between the two elements must have a refractive index close to that of the two glass elements. I seriously doubt that that refractive index of the grease is proper for the use of "cementing" lens elements. Stick with Canada Balsam or one of the synthetic cements designed for the purpose. Doing anything else may effect the optical qualities of the lens.

baachitraka · Oct 23, 2015

I suppose they are two separate elements and used dry lube for free focusing. In Agfa Isolette the focusing is achieved my moving the front element.

shutterfinger · Oct 23, 2015

I have used heavyweight microfiber lens cleaning cloth(s) since Herb Keppler https://en.wikipedia.org/wiki/Herbert_Keppler introduced them in an article in Popular Photography.
I do not roll my lens in sand. I do not wipe down equipment rolled in dirt. I shake out the cloth before use, blow off loose dirt and dust, or use a camel hair brush when someone sends me poorly maintained lens for servicing.
Even in some if not all of the worst environments on this planet photo equipment can be kept free of dirt and sand/silica. A sudden sand storm in a dessert will be the only exception and then only if you leave/use the equipment during the sand/dust storm.
All I've read in this thread so far is condemning a product based on bad experiences due to poor habits of the user.

Effect of losing lens coating on image quality

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