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04-19-2012, 12:41 PM   #1
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Future Lens Problems?

I recently purchased a Pentax-F 70-210mm f/ 4-5.6 lens of eBay. It was a risky move but I was able to get it fairly cheap so it was worth the risk. My problem is there is a slight discoloration inside the front element/glass. See the photos below.





I have taken a good amount of photos with this lens and it doesn't seem to have any affect on the IQ. See the attached photo I captured with this lens on my K-r. [F/5.6 210mm ISO200 1/1000 sec]

Will this cause problems in the future? Should I send it for repair? What am I looking into for repair cost? Any advice would be helpful. Thanks



Last edited by jaywes; 03-08-2015 at 06:03 PM.
04-19-2012, 12:46 PM   #2
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Can you tell if the discoloration is on the outside or inside of the glass?
04-19-2012, 12:50 PM   #3
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it looks like a mar in the coating, in most cases it will have no effect, it may cause flare with some oblique light hitting it. A good hood will prevent most of that since it is at the edge. Not worth a repair (or maybe not even possible)

OTOH it could be from liquid getting inside and drying like that leaving residue. it is then possible that it may have activated fungal growth just keep it dry and it should be ok though
04-19-2012, 12:52 PM   #4
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QuoteOriginally posted by luftfluss Quote
Can you tell if the discoloration is on the outside or inside of the glass?
Seems to be on the inside of the front glass.

04-19-2012, 12:54 PM   #5
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QuoteOriginally posted by eddie1960 Quote
it looks like a mar in the coating, in most cases it will have no effect, it may cause flare with some oblique light hitting it. A good hood will prevent most of that since it is at the edge. Not worth a repair (or maybe not even possible)

OTOH it could be from liquid getting inside and drying like that leaving residue. it is then possible that it may have activated fungal growth just keep it dry and it should be ok though
OK. I use a rubber hood and have not had any IQ issues. Hopefully it stays that way. I will keep an eye on it. [I keep all my photo gear protected and dry. ]
04-19-2012, 12:59 PM   #6
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QuoteOriginally posted by jaywes Quote
OK. I use a rubber hood and have not had any IQ issues. Hopefully it stays that way. I will keep an eye on it. [I keep all my photo gear protected and dry. ]
then you should be good

If you got a good price and it doesn't seem to affect the iq then really there is nothing to fret over, just watch for signs of fungus (which can be cleaned)

I saw a blog once that shot buy a lens with a shattered front element. the pictures were surprisingly good

found it

How Dust and Damage on Lenses Affect Image Quality
04-19-2012, 01:50 PM   #7
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There's a game we can play with (cheap) lenses: HOW MUCH PUNISHMENT CAN THIS F*CKER TAKE? Game play usually involves using a geologist's hammer on a lens objective. Give it a few whacks, take a few shots, whack it a few more times, etc. You'd be amazed how horribly the glass must be damaged before IQ starts to decline. Slight discolorations of the front are trivial. Now, gunk or trauma to the REAR element can be more serious. But don't worry about the front. No twisted knickers needed. Have fun!

EDIT: I just noticed that this is my post #9900. Top of the world, Ma!
04-19-2012, 02:38 PM   #8
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QuoteOriginally posted by RioRico Quote
There's a game we can play with (cheap) lenses: HOW MUCH PUNISHMENT CAN THIS F*CKER TAKE? Game play usually involves using a geologist's hammer on a lens objective. Give it a few whacks, take a few shots, whack it a few more times, etc. You'd be amazed how horribly the glass must be damaged before IQ starts to decline. Slight discolorations of the front are trivial. Now, gunk or trauma to the REAR element can be more serious. But don't worry about the front. No twisted knickers needed. Have fun!

EDIT: I just noticed that this is my post #9900. Top of the world, Ma!
Thanks for that information, because I have two that I got in a package deal that are F series zooms that have pristine rear elements but the fronts are a mess. My, few, shots so far area all fine. I'm wondering if they're worth keeping and I think I'll put more effort into evaluating them because of what you said.

04-19-2012, 02:57 PM   #9
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QuoteOriginally posted by Docrwm Quote
Thanks for that information, because I have two that I got in a package deal that are F series zooms that have pristine rear elements but the fronts are a mess. My, few, shots so far area all fine. I'm wondering if they're worth keeping and I think I'll put more effort into evaluating them because of what you said.
Scratches and gouges on the front can be bothersome but are easily dealt with. Small ones can be touched-up with black magic marker or india ink, which keep light from bouncing off crack edges. Bigger ones can take some of that instant-windshield-repair gunk that dries with a refractive index close to glass. But splotches and scraped coatings just usually don't matter. I have a couple mistreated lenses that prove this.

Hmmm, I should do a reversed-lens trauma test. Flip a lens for close use, then whack (or at least discolor) the REAR element, which when reversed is now the objective. But I really don't like whacking lenses. That's almost as bad as squashing kittens.
04-19-2012, 03:02 PM   #10
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Could be oil from the lubricating grease, if it is left in a hot place the grease breaks down and
the oil in it spreads around.
Once bought a 35-70 F lens and it looked like it was full of water droplets inside but
turned out to be the Silicone oil, cleaned it up and the lens was fine.
The oil will give that rainbow like color if lit from the side.
If it was cheap it could be a good time to practice ...
04-19-2012, 03:02 PM   #11
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QuoteOriginally posted by RioRico Quote
Scratches and gouges on the front can be bothersome but are easily dealt with. Small ones can be touched-up with black magic marker or india ink, which keep light from bouncing off crack edges. Bigger ones can take some of that instant-windshield-repair gunk that dries with a refractive index close to glass. But splotches and scraped coatings just usually don't matter. I have a couple mistreated lenses that prove this.

Hmmm, I should do a reversed-lens trauma test. Flip a lens for close use, then whack (or at least discolor) the REAR element, which when reversed is now the objective. But I really don't like whacking lenses. That's almost as bad as squashing kittens.
One is worse than the other, but the AF works and its intact otherwise, and effectively has 0 resale value so experimenting with it might be educational. Thanks.
04-20-2012, 12:04 AM   #12
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QuoteOriginally posted by RioRico Quote
There's a game we can play with (cheap) lenses: HOW MUCH PUNISHMENT CAN THIS F*CKER TAKE? Game play usually involves using a geologist's hammer on a lens objective. Give it a few whacks, take a few shots, whack it a few more times, etc. You'd be amazed how horribly the glass must be damaged before IQ starts to decline. Slight discolorations of the front are trivial. Now, gunk or trauma to the REAR element can be more serious. But don't worry about the front. No twisted knickers needed. Have fun!

EDIT: I just noticed that this is my post #9900. Top of the world, Ma!
Somebody already had fun: LensRentals.com - Front Element Scratches
04-20-2012, 05:13 AM   #13
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QuoteOriginally posted by sterretje Quote
That's only a vicarious thrill. Too remote; not tactile enough. Down-home do-it-yourself funfunfun is more rewarding. More adrenaline. More sweat. Ooh ooh. Where's that hammer? [/me goes bestial]
04-20-2012, 06:21 AM   #14
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More fun with damaged lenses can be found here. It's really remarkable just how abused the front element can be without having a noticeable effect in most shots.
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