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09-04-2011, 07:36 AM   #1
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Micro scratches on offered Sigma 18-250mm

Hi there,
I am planning to buy a Sigma 18-250mm F3.5-6.3 DC OS HSM SLD for my K-r and also found a (maybe) good offer on ebay. But to know if it is a good offer or not I got two questions.
The seller (a photography trader with a 99,3% rating) is writing that the lens got "micro scratches" on the lens, but that they are not having any influence on the image quality. You can also not see the scratches on their pictures on ebay, but the pictures are pretty small anyway.
First questions: Is it true that the lens can have scratches without influencing the IQ? Or is it just visual if you are doing professional photography.
And am I able to test the lens on my own at home to see if the scratches are influencing the IQ? Or would I need some special equipment? I would be able to return the lens within 14 days after receiving it, so I could buy it, test it and return it if the scratches are actually messing the pictures up.
And since I am somewhat a photgraphy noob: please tell me if I am missing some important points when considering this lens for my camera.

PS: Since I am not able to start an introduction thread I will just do that here: My name is Ole, I am living in Sweden at the moment and I am a proud owner of a K-r and love it!

09-04-2011, 08:35 AM   #2
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QuoteOriginally posted by oleolsen Quote
Hi there,
I am planning to buy a Sigma 18-250mm F3.5-6.3 DC OS HSM SLD for my K-r and also found a (maybe) good offer on ebay. But to know if it is a good offer or not I got two questions.
The seller (a photography trader with a 99,3% rating) is writing that the lens got "micro scratches" on the lens, but that they are not having any influence on the image quality. You can also not see the scratches on their pictures on ebay, but the pictures are pretty small anyway.
First questions: Is it true that the lens can have scratches without influencing the IQ? Or is it just visual if you are doing professional photography.
And am I able to test the lens on my own at home to see if the scratches are influencing the IQ? Or would I need some special equipment? I would be able to return the lens within 14 days after receiving it, so I could buy it, test it and return it if the scratches are actually messing the pictures up.
And since I am somewhat a photgraphy noob: please tell me if I am missing some important points when considering this lens for my camera.

PS: Since I am not able to start an introduction thread I will just do that here: My name is Ole, I am living in Sweden at the moment and I am a proud owner of a K-r and love it!
Hello Ole, I have some older lenses that have small scratches on the glass and I don't see that they effect the pictures at all. What you could do is see how long you have to return the lense if the scratches bother your pictures. Then take it and photograph from the 250mm to the 18 mm and blow up the images to see if you can see any problems the scratches could be making.

Thats just my .02 cents worth.

And welcome to the Pentax club.

Jim
09-04-2011, 08:48 AM   #3
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Scratches can be small enough to not affect IQ. You can test this by putting a hair in front of a lens. Lenses don't focus closely for anything on the surface to show directly. With more damage, contrast starts to decline, then sharpness. A scratched lens will have more trouble with flare and stray light. Scratches on the rear element are worse. Scratches can be outside the area used for images - imagine a rectangle on the front element with the same proportions as the sensor.

I like to see the flaw in an auction photo, not wait until I've paid for shipping. In your case, I would skip this lens just because of that. Sellers don't use the term "scratches" if they can say something like "cleaning marks". The auction format means people will bid based on their own perceptions of the scratches, which no one has seen. An optimist will bid higher.

Since this lens is available new, you know what the undamaged value is. I think scratches could reduce its value by at least 50% of its new price. It would be difficult to sell in the future.
09-04-2011, 12:55 PM   #4
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Thanks for the fast replies and for the welcome
The time until I would have to return the lens would be 14 days. Should be good enough to do some testing with it.
The lense is used and it is around 130 cheaper then other offers, which is why I am considering it. And the right to return the item within those 14 days without any reason make it somewhat more attractive to just get it and test it. I can save 130 and lose max. the shipping costs of 20.

09-04-2011, 02:54 PM   #5
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Hi oleolsen,

I used to know some photojournalists back in the 70's who had some wickedly scratched lenses that they used all the time. They actually painted the scratches with black paint to cut down the flare effect they would cause if left alone. I also know two shooters who have/had A* 300/4 lenses with front elements that looked like they were last cleaned with a cinder block. Wide open, the scratches showed on the images, but stopped down a bit, and you couldn't tell the difference.

My most used lens, a well used FA* 300/4.5 was offered for auction by an exceptionally honest seller who noted that there were cleaning marks on the front element and a couple of clear spots in the coating on the rear element. This was well before the DA* 300/4 was introduced, and FA*'s were commanding $1200-1500 and were heavily bid on. I won the lens at under $700 after very light bidding and have gotten nothing but amazing results from it for the past 5 years.

Pristine glass is nice, but not necessary for the great majority of shooting. If there are a lot of these micro scratches, they might cause flare and noticeable loss of contrast. If there are only a few, I wouldn't worry too much about them.

Scott
09-04-2011, 03:02 PM   #6
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As mentioned, small scratches probably won't noticeably affect IQ, and big scratches can be finessed. What they DO affect is value, also as mentioned. If you're going to keep the lens, it's a bargain. If you may ever sell it, it might not be such a great deal.
09-04-2011, 11:07 PM   #7
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Thanks for all the feedback.
As of yesterday I yet had to convince my girlfriend of buying an used lens with a scratch, since she is at the moment the money maker. Now after reading the new replies I felt like I could be able to convice her by reading the replies, buuuut the lens is sold. So gotta keep the eyes open again.
Anyway, thanks again for all the help, I didn't get the lens but I learned something about scratches

PS: It is really nice to get to read some of your peronal experiences with scratches.

Last edited by oleolsen; 09-04-2011 at 11:14 PM.
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