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12-21-2014, 05:36 PM   #1
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Removing yellow tint from pentax lenses

Removing yellow tint from 50mm 1.4 takumar

12-21-2014, 05:43 PM   #2
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Brian Ayling's photographic repair tips

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12-21-2014, 05:47 PM   #3
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Direct sunlight can clear up yellowing lenses. There are a variety of threads here with differing opinions on how long, natural vs. artifical, etc. but the bottom line is UV is your friend.
12-21-2014, 06:29 PM - 4 Likes   #4
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I've found that the $10 Ikea LED desk lamp works as someone had discovered -- I just jam it practically right into the lens (with some tinfoil on the other side of the lens to reflect back) and it clears up within only a day.


Last edited by vonBaloney; 12-21-2014 at 10:05 PM.
12-21-2014, 09:48 PM   #5
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With great effect I have used a reptile UV lamp (pet stores have them). The one I used was for desert reptiles (greatest UV output). My method takes a few weeks though ;(
12-21-2014, 10:15 PM   #6
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QuoteOriginally posted by Wild Mark Quote
With great effect I have used a reptile UV lamp (pet stores have them). The one I used was for desert reptiles (greatest UV output). My method takes a few weeks though ;(
Yeah, that's what I did at first -- bought a fancy $20 UV reptile bulb (the one with the most UV), put it in this small decorative lamp where I lined the whole thing with foil on the inside (and again, foil underneath), and then put it upside down over the lens. The LED lamp was faster, although I could do several lenses at once with the reptile bulb.

The question of course -- is why? LEDs are not supposed to be emitting UV, some will tell you it is impossible. Others say otherwise: Nouvir Lighting - News.
12-22-2014, 01:59 AM   #7
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I just left it near enough a window for the past 12months when I wasn't shooting with it, was enough to clear mine up a bit. Aka I just left the lens cap off. / wasn't overly interested in clearing it up but cleared it up accidentally. :P

Last edited by tromboads; 12-22-2014 at 02:25 AM.
12-22-2014, 02:11 AM   #8
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QuoteOriginally posted by vonBaloney Quote
Yeah, that's what I did at first -- bought a fancy $20 UV reptile bulb (the one with the most UV), put it in this small decorative lamp where I lined the whole thing with foil on the inside (and again, foil underneath), and then put it upside down over the lens. The LED lamp was faster, although I could do several lenses at once with the reptile bulb.

The question of course -- is why? LEDs are not supposed to be emitting UV, some will tell you it is impossible. Others say otherwise: Nouvir Lighting - News.
There's different kinds of UV light. I won't go into detail. But at the same pet stores they have the UV light bulbs with which you kill bacteria and algae in aquaria and ponds. They are very damaging to you eyes! With the help of such a lamp, and ductape, it took only a few days to remove all yellow tint. Kill fungus too. Only the loose bits remain.

12-22-2014, 08:10 AM   #9
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QuoteOriginally posted by Clavius Quote
There's different kinds of UV light. I won't go into detail. But at the same pet stores they have the UV light bulbs with which you kill bacteria and algae in aquaria and ponds. They are very damaging to you eyes! With the help of such a lamp, and ductape, it took only a few days to remove all yellow tint. Kill fungus too. Only the loose bits remain.
You misunderstood -- obviously the reptile UV bulb has UV -- that is it's purpose. The question is why does a cheap LED lamp (presumably just a flashlight would work as well) also remove the yellowing (and much faster than the reptile bulb) when they aren't supposed to have UV?
12-22-2014, 08:33 AM   #10
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Equator facing window works. Have you tried shooting with it? Try shooting with awb or just experiment with different wb settings.
12-22-2014, 08:39 AM   #11
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QuoteOriginally posted by vonBaloney Quote
You misunderstood -- obviously the reptile UV bulb has UV -- that is it's purpose. The question is why does a cheap LED lamp (presumably just a flashlight would work as well) also remove the yellowing (and much faster than the reptile bulb) when they aren't supposed to have UV?
I wasn't trying to answer your question. I was merely responding to the thread by adding another option.

The atomic structure of the lens glass is altered by radiation from trace amounts of radioactive thorium in one rare-earth glass element, creating the yellowish-brown color; and this change is reversed by exposure to ultraviolet light.

All light sources, including your flashlight, emit some amounts of UV light. There are even special LEDS that intentionally produce UV light in various ranges. I'm personally using LED fixtures above my aquarium that emit Ultraviolet light to activate the zo÷xanthella and make them "glow". I have no idea why you think LEDS aren't supposed to emit any UV light. I can imagine though that a mere flashlight isn't restricted by rules for harmfull UV light exposure as much as other fixtures. Because the exposure from the light of flashlights is only very short.

For the purpose of removing yellowing and/or killing fungus, more UV means quicker results. That is why I mentioned the UV-canon for ponds.
12-22-2014, 09:00 AM   #12
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QuoteOriginally posted by Clavius Quote
I wasn't trying to answer your question. I was merely responding to the thread by adding another option.
Well yes, but since I described how I already had bought a reptile bulb and yet you were telling me about their existence at the pet store, it seemed you had not actually read/understood my post.

QuoteQuote:
I have no idea why you think LEDS aren't supposed to emit any UV light.
That's what everyone insists, including the manufacturers of LEDs. And if you search for "Do LEDs emit UV light", you'll see a bunch of pontificating about how they emit zero UV. The counter-argument is given in my link above from the people trying to sell "museum quality" true no UV, no IR lamps, who say (and measure) that LED lamps emit plenty of UV.

All I know is a $10 lamp from IKEA clears a yellowed lens overnight and the UV reptile bulb takes much longer (but also works). How much this is a function of being able to concentrate the LED more where it is needed, I don't know. But with my set-up with the reptile bulb I had it only a couple inches from the lens glass (bulb hung upside down directly over lens with foil on the underside of the lens and foil all around the inside of the lamp creating a UV chamber). With the LED lamp (which has a head no bigger than a handheld LED flashlight) I jam it right onto the lens, even touching it.

The question is bigger than just yellowed lenses of course. Is my desk lamp (used a desk lamp) damaging my skin with its UV rays? Of course it is not supposed to, but since it is more powerful than a reptile bulb that actually has a warning on the box for UV exposure, you have to wonder...
12-22-2014, 09:35 AM   #13
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i had excellent results placing mine in the window(facing south) for a couple of weeks.
12-22-2014, 10:38 AM   #14
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QuoteOriginally posted by vonBaloney Quote
Well yes, but since I described how I already had bought a reptile bulb and yet you were telling me about their existence at the pet store, it seemed you had not actually read/understood my post.
...But I wasn't talking about reptile lamps...
12-22-2014, 10:57 AM   #15
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QuoteOriginally posted by Clavius Quote
...But I wasn't talking about reptile lamps...
Ahh...it was I who misread you. My apologies.
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