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I am looking to buy a CANON 28mm 1.8 EF lens. I found an offer, significantly discounted, of a lens with small scratches on the front element.

The offer is very tempting. Here is a photo posted by the seller:

Scratches on a lens

The scratches will probably affect my photos a bit. But how much exactly? Does anyone have experience with a similarly scratched lens?

I am an amateur and hobbyist, and I don't make money from my photography. I would use this lens as a 'normal' on my 60D, mostly for taking portrait photos of my family. I am getting this one because of the aperture (1.8), and I would be using it wide open most of the time.

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3 Answers 3

up vote 5 down vote accepted

Scratches in general have very little effect on image quality. You may have zones of slightly lower contrast due to the scratches and these areas may be slightly more prone to flare since its the lens coating which is most damaged.

The effect of scratches is inversely proportional to focus distance. The farther you focus, the more out of focus the ill-effects would be. Check out this extreme example. Using the aperture wide-open will blur-out the scratch more too but you may get more flaring.

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1  
more extreme example: lensrentals.com/blog/2008/10/front-element-scratches –  Matt Grum Sep 7 '12 at 18:42
    
OK I am convinced. Thanks! –  Jakub Kaleta Sep 7 '12 at 18:45
    
It should be noted that while small scratches are not a serious problem, they DO have an impact. I had a polarizer that had some scratches and later got a couple cracks in it. I kept using it, due to answers like this that I had read in the past. However once I got home and started processing the files, I realized there was a visible degradation of my photos, particularly once it was cracked. Fine detail that was sharp and clear before was muddy and fuzzy. Scratches may not be a huge problem... assuming you do not NEED to preserve fine detail! –  jrista Sep 7 '12 at 19:08
    
Links like the one Matt Grum posted simply show that a cracked or scratched lens does not make a lens unusable...however they also clearly show that a cracked or scratched lens has a visible impact on image quality, can greatly reduce contrast, and have a moderate to severe impact on resolution (sharpness, microcontrast.) –  jrista Sep 7 '12 at 19:10

You may improve the lens performance by taking a black sharpie and filling in the scratches. This will help reduce glare from the scratches, and it won't noticeably change the effective f-stop of the lens.

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Here are two lenses I got off Ebay - they look pretty nice on images. The Canon 85mm 1.8 does have marks visible to the naked eye on the front element but they are very small. The Helios looked perfect on front and back but on an internal glass there is some dust particles.

Canon 85mm 1.8:

Canon85mm

Helios 44-2 58mm F2:

Helios

[image examples from two lenses I got from ebay]

Here are two shots with them, with wide apertures:

Canon85mm

Canon85mm

Helios

Helios

Confirms that "dust inside" or "scratches in front" doesn't affect IQ.

But then I noticed spots when stopped down:

I used Helios when taking a macro of a brie and I needed to stop with to F16 to get just a little bit DOF - the black speckles are dust particles:

Dust shows up

But this turned out to be on the sensor, because the spots were the exact some place as the 85mm stopped down. I cleaned the sensor and it is fine now! Yeah :)

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