How Front Element Scratches Affect Your Images (Lensrentals)

[JDMvW]

Science-based discussions from Lensrentals

https://www.lensrentals.com/blog/2022/11/how-front-element-scratches-affect-your-images/

It's pretty much what everybody has said except, of course, there can be too much....

Praktiflex with 58mm f/Biotar (scratched) on left. Clean Tessar on right. [https://www.photo.net/forums/topic/456572-biotar-58mm-f20-in-m40-mount-praktiflex/]

 

Edited November 9, 2022 by JDMvW

[PapaTango]

I first experienced this trouble in the 70s, with a Yashica J-5.  In low to medium light, no real issues.  Light things up, or frontal light and it was crap.  Had to save my $$$ for another lens...

[dan_fromm2]

Hmm.  The article says that scratches don't always have much effect and that they have less effects at large apertures.  My 80/2.8, whose front element has the highly coveted "cleaned with coarse sandpaper" look, doesn't agree at all.

[PapaTango]

One major thing that was not mentioned in the article was the coating.  My aforementioned Yashica has a yellow coating that seemed so soft that one could almost look at it and another set of micro scratches appeared.  Other coatings in Canon (FL)  lenses I came by for my FT/QL were a little bit deeper amber color, and resisted scratching.  My later FD lenses were a different coating and seemed more resistant to scratching.  In those days, pretty much the only time there was a filter on the camera lens was when doing BW photography.

Somewhere in this I started using UV/Skylight filters.  Saved a few lenses from catastrophe this way.  Then I found the B+W clear line and still use these for my largest and most expensive lenses.  Otherwise, the stable includes Hoya and Tiffen.  

I think that perhaps with softer and older multicoat systems the scratch effect may be more prominent in differing aperture and light environments.  The focal range of a lens seems to make a difference with wider angles more prone to light scattering from scratches and scrapes.  

[glen_h]

Yes, like everything else, it is much worse when the sun is directly on the lens.

But that is also when you get the other reflections of lens elements.

 

The one I am still wondering about is dust on the mirror of a Canon Pellix.

When I was young, my dad bought one.  After that, I usually got to use his

Canon VI, until I bought my own camera.

But then the Pellix got stolen, and replaced with an AT-1.

 

Remembering the one he had, I wanted one.  It was a good price, though

the mirror is a little dustier than I had hoped.

[rodeo_joe1]

IMO polishing grazes - like a gathering of tiny pixies have ice-skated across the lens - are much more damaging than one large knick that you can easily see. 

I've been caught out a couple of times buying used lenses that were obviously previously owned by someone suffering from OCD and with a dirty handkerchief as their cleaning weapon-of-choice.

I've read of filling in large lens scratches with matt black paint as a way to stop the scratch adding flare. However, the couple of times I tried it, it just added a dark patch to the image at smaller apertures. Even running a black dry-wipe marker over the scratch and cleaning off the excess seemed to spread the scratch, rather than subduing it.

Lessons to be learned: Look after your lenses; don't clean them excessively; use fresh lens tissues when you do need to clean 'em; carry a small LED flashlight when shopping for used lenses. 🙄

[rodeo_joe1]

6 hours ago, glen_h said:

Remembering the one he had, I wanted one.  It was a good price, though

the mirror is a little dustier than I had hoped.

1. Blow off loose dust with a 'rocket' blower. 

2. Lightly brush anything more stubborn with a large, clean sable or squirrel hair artist's watercolour brush. Followed up by another blast from the rocket. 

3. If there's still stubborn muck; fold a lens tissue to the width of the mirror. Hold the camera so that the mirror is horizontal. Drop one or two drops of pure ethanol onto the mirror. Drop the lens tissue over the wetted mirror and drip one or two more drops of alcohol onto the tissue. The alcohol should draw the tissue tight to the whole mirror surface. Now drag the tissue horizontally off the mirror against the capillary pull of the alcohol. After any remaining alcohol evaporates you should be left with a spotless mirror. 

The above technique was shown to me years ago when I had to regularly clean delicate semi-silvered etalons. 

Edited November 18, 2022 by rodeo_joe1

[glen_h]

8 hours ago, rodeo_joe1 said:

(snip)

The above technique was shown to me years ago when I had to regularly clean delicate semi-silvered etalons. 

Reminds me that I don't even know which side is silvered.

I might guess it is the lens side, but I don't actually know.