which is worse?

R Paul · Jun 22, 2012

Hi

I was wondering about something simple: Would a scratch on the front element of a lens cause more harm to an image than one on the back element?

Thanks

r paul

Chrismat · Jun 22, 2012

A scratch on the back element would be worse because it is closer to the film plane. The further away from the film the less noticeable a scratch would be (as long as it isn't too bad).

BobD · Jun 22, 2012

If the scratch is on the front, everyone will see it and think you are a bad photographer for using a scratched lens.
However, if the scratch is on the rear, no one will see it and your status will be unaffected.

Therefore it is far better to have scratches on the rear of the lens.

36cm2 · Jun 22, 2012

Chrismat is right, but Bob D is funny.

JLP · Jun 22, 2012

I don't have any lenses with a scratch on the front but i do have a Nikon 90 f4.5 LF lens with a pretty visible chunk of glass missing almost at the center of the rear element. The lens performs exceptionally well and i have never seen any problems in the photos taken with this lens. Can't explain how that is possible but just shows that small imperfections don't make much of a difference except on the sales price.

jordanstarr · Jun 23, 2012

...is this a trick question?

Neither matters if it doesn't effect the image.

But in seriousness, the front does not matter as much because of the amount of diffraction of light as it passes through each element hides any flaws better. Because in normal conditions, light will be "perfect" until the end element, (and assuming the rear is with the stratches) the problems that arise cannot be subdued by other lenses "correcting" it's flaw. That being said, I've shot plenty of lenses with marks on both front and rear with no "real" consequences noticed on film. For example, I just made an 11x14 print from a shot on my 50mm lens that has residual mould marks on the inside of the front element, cleaning marks and stratches on the front element and coating spotting on the front and rear elements. I held it up to an 11x14 print from a perfect 35mm lens and NO ONE IN THE WORLD would be able to tell the condition of the two lenses based on the photographs. As a result, I never shy away from saving a few hundred dollars on user-grade lenses with a mark here or there.

revdocjim · Jun 23, 2012

You might be surprised what you can get away with when it comes to scratches.
And interesting test!

Too old to care · Jun 23, 2012

revdocjim said:
You might be surprised what you can get away with when it comes to scratches.
And interesting test!

That is truly amazing. Thanks for posting this. I will stop worrying about every piece of dust on my front lens from now on.

Richard S. (rich815) · Jun 23, 2012

While it all makes sense in theory I think the scratch on the rear is better and have shot lenses with such scratches with seemingly no issues. The front scratches make the lens more prone to flare in my experience.

Prof_Pixel · Jun 23, 2012

rich815 said:
I think the scratch on the rear is better and have shot lenses with such scratches with seemingly no issues. The front scratches make the lens more prone to flare

That is my understanding as well.

semi-ambivalent · Jun 23, 2012

Chrismat said:
A scratch on the back element would be worse because it is closer to the film plane. The further away from the film the less noticeable a scratch would be (as long as it isn't too bad).

Additionally, with the rear element usually being smaller, the same scratch would affect a larger percentage of the figured surface. I would think that would amplify its effects.

Alan Klein · Jun 24, 2012

I scratched the back of a small micro 4/3 lens (14-42mm) It was some kind of goop about 1/4". You couldn't see anything on the picture if it was a complex subject. But on a blue sky, it showed as a darkened area about 1/4". I sent it back to Olympus and they replaced the back lens element free of charged including shipping. That was really nice of them.

lxdude · Jun 24, 2012

rich815 said:
While it all makes sense in theory I think the scratch on the rear is better and have shot lenses with such scratches with seemingly no issues. The front scratches make the lens more prone to flare in my experience.

The thing to do is to fill the scratches with black paint or marker. If they are too shallow to take paint they will probably not matter, unless there are many, which will cause problems. I know that at least some camera repairers will fill scratches very inexpensively.

250swb · Jun 24, 2012

I think one or two scratches (big or small) won't normally make any difference to the image. Its when you get the build up of years worth of cleaning marks that the flare goes up and the contrast goes down, and even then the image will still be sharp. Some amazing bargains can be had on Ebay if you don't mind the odd cosmetic mark on a front element.

Steve

R Paul · Jun 24, 2012

Thanks for all the input! I can now stop worrying about every little dust spot or smudge on the lens, and just go out and take some pictures instead.
That lens test in the link above was great

R paul

Stan160 · Jun 26, 2012

My Nikkor 105/2.5 AI has a big scratch/gouge on the rear element. I bought it a suitably discounted price on approval, but after a very careful image comparison with the 80-200/2.8 I had at the time (itself an excellent lens) I was unable to spot the slightest imperfection from the 105mm even when using a digital body and pixel peeping the images side by side at 100%.

Ian

one90guy · Jun 26, 2012

This is a very interesting post, shot down what I have always believed on lens glass. What about internal imperfections? I have a brand new looking Yashica 50mm M42 that has what looks liked a dried water spot, I was going to disassemble, probably destroy, just to try my hand at lens repair. Now I think I need to run some film with the lens.

E. von Hoegh · Jun 26, 2012

The effects of any scratch can be reduced or eliminated by filling it with black India ink. I found a 9 1/2" Dagor in a good Compound shutter at a camera show, the vendor wanted $50 for it - I traded a 35/2.8 pre Ai Nikkor for it. The Dagor, ecxept for a 3/8" gouge just off the center of the rear glass, was flawless. I filled the scratch with ink, the lens' performance cannot be distinguished from another 9 1/2" Dagor in barrel which I have.

No scratches at all is obviously the ideal situation, but don't let one mark scare you off of an otherwise desireable lens. The Dagor was just too good to pass up - my second $50 Dagor.

2bits · Jun 26, 2012

Very informative thread, thanks to the op and contributers! I learned a bunch!
2bits

E. von Hoegh · Jun 26, 2012

BobD said:
If the scratch is on the front, everyone will see it and think you are a bad photographer for using a scratched lens.
However, if the scratch is on the rear, no one will see it and your status will be unaffected.

Therefore it is far better to have scratches on the rear of the lens.

Also, if the scratch is on the rear I won't see it and be annoyed.

EdSawyer · Jun 27, 2012

rear is worse. Less glass in the way to correct it.

E. von Hoegh · Jun 27, 2012

Where on earth do you people get the idea that the lens can somehow "correct" for light scattered by a scratch or other flaw on the front?

LyleB · Jun 27, 2012

Here is another example of a terrible lens doing quite ok.

http://www.deansphotographica.com/deans_of_idaho/old_stuff_pages/dirtylenstest/dirtylenstest.html

lxdude · Jun 27, 2012

E. von Hoegh said:
Where on earth do you people get the idea that the lens can somehow "correct" for light scattered by a scratch or other flaw on the front?

My question too.

BobD · Jun 27, 2012

Who is "you people" ?

which is worse?

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