Checking lenses for scratches and defects.

[bluedot]

I am getting ready to buy my first couple of lenses to use with my yet-to-be-shipped D30, but I am quite concerned about some of the horror stories I heard here about defective units etc...

I was wondering if there is some advice you could give me about first how to check lenses for defects and scratches *at the store* before making a purchase and then what tests to do *after purchase* to make sure I don't have a lemon and to decide whether to keep or exchange the lens.

I am not talking about particular lenses, but in case it is relevant I am considering the EF 28-135mm F3.5 IS USM and the EF 50mm F2.8 USM.

Thanks in advance.

bluedot.

[nitwit3]

Fuhgettaboutdit bluedot, buy your stuff and enjoy it...and you will.

Nitwit3

[bluedot]

Thanks Nit!

All your replies to my posts have had the same tone: "stop worrying!"

Well, thanks to your and many other people's advice, I have taken the plunge and my D30 is already being shipped...

However, I am quite surprised that my post about defects in lenses has generated so little interest both here and at dpreview. I would have expected more feedback given how many people complain about "lemons" and defects...

I mean, is there no "standard" lithmus test to check lenses for defects and/or scratches before making a purchase or at least during the return period?

bluedot.

[Pekka]

bluedot wrote:
Thanks Nit!

All your replies to my posts have had the same tone: "stop worrying!"

Well, thanks to your and many other people's advice, I have taken the plunge and my D30 is already being shipped...

However, I am quite surprised that my post about defects in lenses has generated so little interest both here and at dpreview. I would have expected more feedback given how many people complain about "lemons" and defects...

I mean, is there no "standard" lithmus test to check lenses for defects and/or scratches before making a purchase or at least during the return period?

bluedot.



bluedot,

I'm sure this question about scratches is not replied a lot because it's not too common - people buy mostly new lenses.

I check lenses against strong light, look though them and tilt and move them so I can see all reflections I can see. If the lens is scratched, you'd most likely see it this way. Also, check the surface - it should be equally glossy (and not matte in any place).

Take test photos and see if you can see any dirt or imperfection artifacts.

Defects:

For checking defects in sharpness, I printed plain test patters with inkjet, aligned them on kitchen wall and shot with different apertures on a tripod. This way you see soft areas and barrel problems and get a good idea how lens works.

With Sigma 14 I was very determined to get a good sample (3rd one!), but with Sigma 20 I have a mixed feeling: this unit of mine has slightly uneven barrel distortion but in all other aspects it's excellent. So it's not probably worth the effort to try to find a better sample.

If the lens is second hand and without warranty I would make sure that the quality meets your requirements in all aspects!

Pekka

[DWerner]

I think we were worn down by the sheer number of similar posts during the holiday rush... ;)

When I get a new lens I look it, and its packaging over physically, to confirm that it is new. Pretty much what you’d expect, no dents, scratches fingerprints on the glass... With EOS lenses, look at the electrical contacts and mount, they may have light scratches due to testing at the factory but not multiple deep scratches.

Test the lens for general operation: focusing, aperture (use the camera’s Av mode for that). A well lit sheet of newspaper taped to the wall is good for that. Images of it should be sharp and without colorful circular distortions around the characters. You will also notice just how much better the lens gets as you move up in aperture from wide open to halfway closed (eg. f2.8-8 ) and how it softens a bit up at the high numbers (eg. f16-32). You will be able to determine the lens’ “sweet spot” (or sharpest aperture) this way (often f8 ).

There was a recent post on the DP review suite from a guy who had purchased a used 28 2.8 that he suspected was bad. He posted a photo of a sheet of newspaper shot that indeed did look bad. See if you can find it, (if not email me). I told him that I agreed that it looked bad and then posted a test shot with my known good 28 2.8 so that he would have a frame of reference. I don’t have many EOS lenses, but there are many people out there who will do the same thing.

Then take it outside on a sunny day and shoot some trees and shadows or other contrasty subject to see how the lens does with contrast and colors.

Now that I’ve said all that, I should point out that “Nitwit” (damn, I have his real name here somewhere...) is right, and that you really have very little to worry about with Canon midrange or better lenses, and only slight concern with Sigma’s or low end Canons.

So if you’re not sure post an image and someone will be out there with the same lens to re-assure you.

Good Luck!

[bluedot]

Wow.

For a long time nothing... and then an influx of some very detailed responses! Thanks Nit, Pekka and Dave for the great advice.

I will not be purchasing the lenses I mentioned second hand, but am still a little concerned after an incident where I tried to sell my Nikon N60 and "standard" zoom lens only to be told that there was a scratch on the *inner* side of the frontmost element and that it was a defect rather than "user induced".

Anyway, I will print out your responses and be sure to rigorously test any lenses I buy before deciding whether or not they are "keepers".

Thanks again. bluedot.