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Smoli4
Joined: 01 Jul 2011
Posts: 606
Location: Haifa, Israel
Expire: 2013-06-07
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 Posted: Wed Jul 06, 2011 7:03 pm Post subject: Scratches on the Coatings? how does it affect image quality? |
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Smoli4 wrote:
Does someone has an example of scratched lenses vs non scratched, or an explanation of how in theory it would affect image quality of those lenses? |
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martyn_bannister
Joined: 23 May 2010
Posts: 1151
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| Posted: Wed Jul 06, 2011 7:26 pm Post subject: |
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martyn_bannister wrote:
In a similar vein |
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Attila
Joined: 24 Feb 2007
Posts: 57865
Location: Hungary
Expire: 2025-11-18
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| Posted: Wed Jul 06, 2011 10:12 pm Post subject: |
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Attila wrote:
http://www.mflenses.com/fs.php?sw=scratch
http://forum.mflenses.com/what-is-impact-picture-quality-if-a-lens-damaged-what-is-not-t8850,highlight,%2Bdamaged.html
less than 20 scratches not effect anything invisible on pictures, if there is lot of small cleaning marks , result is visible image has low contrast.
Even on wide angle lenses (ultra wide) some scratch not effect anything.
On rare side if you have big scratch it will be coming visible above F8.
I have several badly damaged lens I enjoy them , due silly buyers didn't take it and I go them for next to nothing. 35mm f1.4 Distagon Contax one of the most extreme example it has a few small scratches on front I bought for 200 EUR , another similar example is Nikon 20mm f2.8 AIS for 100 USD etc ,etc. Usually I sell MINT copies and keep scratched ones, need to care less and they are works really well.
But ... even if any people say thousand times scratches are not a big problem really , there will be thousand people (who never had scratched lenses) who are know very well scratches are ruin pictures ...
so I suggest to take an 5 USD lens take picture with that , scratch it take another one , sand it  and take another one and you will be a beleiver as I am scratched lenses are good as MINT ones.
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peterqd
Joined: 28 Feb 2007
Posts: 7448
Location: near High Wycombe, UK
Expire: 2014-01-04
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| Posted: Thu Jul 07, 2011 9:14 am Post subject: |
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peterqd wrote:
If scratches don't show on the image, I'd love to know what caused this:
This is on film, so I thought at first the negative was scratched, but I've looked with a loupe and there is nothing. It looks to me as though the scratches are highlighted by the sunlight, so that can't be a damaged neg.
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martyn_bannister
Joined: 23 May 2010
Posts: 1151
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| Posted: Thu Jul 07, 2011 9:33 am Post subject: |
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martyn_bannister wrote:
It might, of course, be the enlarger lens ? My other thought, and I'm not joking, is a spider's web! |
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Nordentro
Joined: 24 Jun 2010
Posts: 4713
Location: Lillehammer, Norway
Expire: 2015-01-29
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| Posted: Thu Jul 07, 2011 9:48 am Post subject: |
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Nordentro wrote:
| martyn_bannister wrote: |
| It might, of course, be the enlarger lens ? My other thought, and I'm not joking, is a spider's web! |
Yes, and I see 2 spiders too 
Scratched lens coating is not a big problem for IQ IMO, but a scratched back element could be really bad for IQ.
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Pancolart
Joined: 04 Feb 2008
Posts: 3705
Location: Slovenia, EU
Expire: 2013-11-18
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| Posted: Thu Jul 07, 2011 10:37 am Post subject: |
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Pancolart wrote:
Ask a friend to borrow you his glasses. They must be few years old though. I think you'll get the idea. Mine are around ten years old. MC is very scratched but i am so used to them  .
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Spotmatic
Joined: 18 Aug 2008
Posts: 4045
Location: Netherlands
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| Posted: Thu Jul 07, 2011 11:49 am Post subject: |
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Spotmatic wrote:
| peterqd wrote: |
If scratches don't show on the image, I'd love to know what caused this:
This is on film, so I thought at first the negative was scratched, but I've looked with a loupe and there is nothing. It looks to me as though the scratches are highlighted by the sunlight, so that can't be a damaged neg. |
I'd guess it was the enlarger's glass that was scratched (if used, of course).
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fuzzywuzzy
Joined: 18 Dec 2010
Posts: 1258
Location: Down East, Canada, eh?
Expire: 2013-11-30
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| Posted: Thu Jul 07, 2011 12:36 pm Post subject: |
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fuzzywuzzy wrote:
I'll vote for a spiderweb catching the sun.
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peterqd
Joined: 28 Feb 2007
Posts: 7448
Location: near High Wycombe, UK
Expire: 2014-01-04
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| Posted: Thu Jul 07, 2011 1:08 pm Post subject: |
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peterqd wrote:
Not an enlarger, it's a slide not a neg, sorry. It could be the scanner, although I would have expected it to reflect blue scanner light, not golden sun. I'll try scanning it again.
I doubt it's a spider's web. Looking closely at the lines I've never seen a web like that, And there was nothing nearby to which a web could have been attached.
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martyn_bannister
Joined: 23 May 2010
Posts: 1151
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| Posted: Thu Jul 07, 2011 4:05 pm Post subject: |
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martyn_bannister wrote:
When I said spiders web, I meant as in gossamer. But you are probably right, it's on the lens. |
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Orio
Joined: 24 Feb 2007
Posts: 29545
Location: West Emilia
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| Posted: Thu Jul 07, 2011 4:08 pm Post subject: |
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Orio wrote:
is it possible to see the whole image at a large size?
(you can paint faces black if privacy's a concern)
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peterqd
Joined: 28 Feb 2007
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Location: near High Wycombe, UK
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| Posted: Thu Jul 07, 2011 4:35 pm Post subject: |
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peterqd wrote:
| Orio wrote: |
is it possible to see the whole image at a large size?
(you can paint faces black if privacy's a concern) |
Hello Orio, I cropped the pic to enlarge the scratches, privacy wasn't a concern. I'm also posting the next pic on the roll - if there were any scratches they would be on the left side. I don't see any but the light angle is different. Pentax P30n with M 1.7/50 on Provia 100F
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martyn_bannister
Joined: 23 May 2010
Posts: 1151
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| Posted: Thu Jul 07, 2011 5:04 pm Post subject: |
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martyn_bannister wrote:
Seeing the whole image makes me lean towards something in the processing/scanning. I don't know exactly what, but notice the debris I have higlighted
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peterqd
Joined: 28 Feb 2007
Posts: 7448
Location: near High Wycombe, UK
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| Posted: Thu Jul 07, 2011 5:43 pm Post subject: |
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peterqd wrote:
| martyn_bannister wrote: |
| Seeing the whole image makes me lean towards something in the processing/scanning. I don't know exactly what, but notice the debris I have higlighted |
Yes, you're perfectly correct there Martyn. Even though I clean the scanner glass every time and I dust the sllides with a very soft brush, I still get this amount of debris showing up, or even more sometimes! Both pictures I posted are the raw scans, I've been over them with the clone stamp for the album copies.
The transparency unit lamp in the Epson V700 scanner has a strong blue colour, and I don't think the golden colour of the scratches could have come from that source. However, I've remembered there's another warmer lamp under the platen that's more likely to be the culprit. I'm going to dig the slide out later and scan it again.
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Orio
Joined: 24 Feb 2007
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Location: West Emilia
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| Posted: Thu Jul 07, 2011 9:11 pm Post subject: |
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Orio wrote:
Considering the apparent focal lenght and aperture, I would say that the chances that those scratches are coming from the lens surface are nearly zero.
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