Impact of lens dirt & scratches on image quality

BillN

Hall of Famer
Aug 25, 2010
123
S W France
Bill
as I understand it - buy lens with scratches on front element really cheap as they have no or very little effect on IQ, (for us humans!)

Paul, Arne today, (in the rain), if I can persuade my wife!!!!
 
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Brian

Top Veteran
Jul 7, 2010
103
Internal haze is "IMO" the worst offender to image quality. It can cause color shift and loss of sharpness.

I had a Summarit with internal haze, sent it out to be cleaned. Big difference in quality.

Cleaning marks on the front element cause the least impact.

I have a 90/2 Summicron with a fracture in the second element a few millimeters long. No real problem on the image unless in direct sunlight. Pixel-Peeping, you can find a minute effect.
 
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pdh

Legend
Jan 2, 2011
123
i was counting myself as one of the obsessives Brian :) ... though the seller in question was not the one I had returned a lens to because of severe haze ...

Bill - take your 10x bins if you're going to the hide although today the rain will make visibility a bit of a 'mare down there
 

defektive

Veteran
May 4, 2011
43
Tasmania, Australia
Sam
Great article and test, I will certainly consider "bargain" lenses with a bit more confidence. I am with Brian though, haze does have a big influence on the optical performance of a lens.
 

lenshoarder

Veteran
Mar 7, 2012
43
This has been around for ever. It is true though. I personally am not one of those people that need to go into a clean room to clean off their lenses. I use my shirt. The qualifier to this I'll add is isolated bits of dust and dirt don't degrade IQ that much. Lots of fine scratches, like on the coating really do though. It's all just foggy.
 

Isoterica

Hall of Famer
Dec 6, 2011
123
The lens of my Ansco Memar Pronto lens is so hazed up the photos look like something shot with a pinhole, has a very dreamy effect. This favorable result is probably not the norm but I had several people want to buy the camera because of it. Nope I haven't sold it :D
 

HeatherTheVet

Top Veteran
Apr 23, 2011
103
Scotland
Heather
I have a problem with little black specs on my photos, but I suspect it is bits of stuff between the lens and the sensor. I find it quite hard to keep everything clean and clear.
 

lenshoarder

Veteran
Mar 7, 2012
43
If you can make them out as little black specs, then it's on the IR filter over your sensor. Use a handblower and blow them off.
 

BillN

Hall of Famer
Aug 25, 2010
123
S W France
Bill
I have a problem with little black specs on my photos, but I suspect it is bits of stuff between the lens and the sensor. I find it quite hard to keep everything clean and clear.
take a photo of a white wall at your highest f value - f32 and post it - probably dust on the sensor which is easily removed


(Edit - as lenshoarder suggests above)
 

HeatherTheVet

Top Veteran
Apr 23, 2011
103
Scotland
Heather
Thanks, I do try to blow them all away but I seem to collect more every time I change lenses. It's nice to know exactly where the problem is though, I'll stop obsessively cleaning the front glass now! The big prob is I can't see them at the time, only later when I get the pics uploaded. I guess I just need to be a bit more careful.

I spotted a whole load of dandelion heads today at just the right stage for playing macro photography. I might nip out later and pick a couple up - I've never tried that classic shot yet.
 

Isoterica

Hall of Famer
Dec 6, 2011
123
Make sure to get a shot of the sun behind them.. makes an excellent halo and really accentuates the details.
 

HeatherTheVet

Top Veteran
Apr 23, 2011
103
Scotland
Heather
Example of little black specks. There's one above the cloud on the right. What really annoys me is when I take a pile of pictures in a row, and these blobs are on them all in exactly the same place. Fixable but annoying! Cleanliness is the answer I suppose, difficult for one who spends so much time covered in a variety of unpleasant stuff.

[/url] Torridon by heather_t_vet, on Flickr[/IMG]
 

pdh

Legend
Jan 2, 2011
123
yep that's sensor dirt as others have said. this was at f/13 - bet you can't see it at f/8 or below though?

if you can't blow it off with a rocket puffer then it's time to invest in either a sensor cleaning kit or take it into a photographic shop who'll clean it for you
 

HeatherTheVet

Top Veteran
Apr 23, 2011
103
Scotland
Heather
I *think* I've got it clear now. If not I might take a wee trip into town and speak to some camera peeps. Interesting point about being able to see it at wider f/, never thought about it but all the blobby holiday pic were in France in bright sunlight so stopped down.

To celebrate the discovery of what they are and what I need to do I have bought a new lens on ebay - Canon FD 135mm. Just because. £15 inc postage :)
 

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