Ikea Lamp and Takumar Lens

stevebrot · 11-16-2020, 10:23 AM - **1 Like**

Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.

Originally posted by pepperberry farm

I use a different lamp to get the yellow out of my thoriated lenses:

amazon.com: UV LED Black Light, HouLight High Power 10W LED Blacklight Flood Light IP65-Waterproof (85V-265V AC) for Blacklight Party Supplies, Neon Glow, Glow in The Dark, Birthdays, Blacklights, Curing: Home Improvement?tag=pentaxforums-20&

While I like my JANSJÖ, I have been tempted to get a compact UV lamp, if they make such that is AC or USB powered.

Steve

**psoo** · 11-16-2020, 02:40 PM

Originally posted by stevebrot

The short answer is yes. Yellow is not a very good description for the discoloring. It is closer to tobacco stain in tint. There is also the matter that it is due to a disruption of the physical structure of the glass at the molecular level with attendant change in refractive character. (At least that is the theory.) My experience as well as that of others is an improvement in optical performance when cleared. Of course, YMMV.

Steve

Thanks for the reply Steve. However, I have an old Pentax lens that has an overall yellow tinge. Don't remember which lens but it's squirreled away somewhere. I don't think it's because it has degraded over time. Isn't it likely that it's the original coating?

stevebrot · 11-16-2020, 03:08 PM - **1 Like**

Originally posted by psoo

I have an old Pentax lens that has an overall yellow tinge. Don't remember which lens but it's squirreled away somewhere. I don't think it's because it has degraded over time. Isn't it likely that it's the original coating?

The Super Takumars have coatings that reflect yellowish, but when white paper is viewed through the lens, the paper appears white. That is completely normal and is not the same a lens having one or more elements where the glass itself has been altered due to radiation. Reports on the Web of thorium coatings that have gone yellow are inaccurate.

Steve

titrisol · 02-13-2021, 12:56 PM

I didn't bother clearing the lens for a long time, since my line of thought was same as yours and I used BW film anyway.
However images look better after clearing the lens, I don;t know how to described the difference but they seem snappier
Also the lens regained 1 stop exposure and can be used for color.

Originally posted by psoo

I'm sure that for psychological reasons it's nice to remove the yellow tint from a lens. However, does yellowing significantly change the color of the image? If it does, some photos may benefit from a warmer glow. If not, why bother?

moggi1964 · 02-14-2021, 11:49 AM - **1 Like**

I bought a UV torch that outputs at 365nm at 3w maximum (it reduces to about 2.3w after 3 minutes continuous use).

I have sat it about 6" from my Takumar (50mm F/1.4 and it doesn't heat the glass. After about 8 hours use the glass is clear.

Very simple to use.

One word of warning: don't start going all CSI with it if you live in a rented house/flat; you do NOT want to know what may be on the carpet

**Bob 256** · 02-14-2021, 12:08 PM

Can't beat that price. You can get a UV LED and make a small source that will do the job if you can't get this lamp. The LED will have to have a means of limiting its current but is small and can be made into a compact source (avoid eye and skin exposure). One source is Mouser Electronics but there are a lot of others out there. It will most likely come in at a higher price point than the IKEA alternative.

Asahiflex · 12-01-2023, 02:18 AM - **1 Like**

I tried the cheap IKEA Jansjö LED light (the weak USB version) to cure my yellowed 50mm f/1.4 Super-Multi-Coated Takumar. After 7 days of continuous exposure of the lens, which sits on a mirror, this is the result. It's still a bit yellow (slightly more than the photo shows, my 8 element 50mm f/1.4 Takumar does not show a cast). Maybe I should give it another week... :-)

I noticed that the yellowing was cloudy / uneven in the middle. The discoloration is now pretty evenly.

Before:

After 7 days:

The cure in progress:

Last edited by Asahiflex; 12-01-2023 at 04:09 AM.

titrisol · 12-02-2023, 09:09 AM

The 8 element doesnt have a thorium element and should need any treatment.
Looks cleand, but if I were you I'd compare the meter readings between the lenses and see if there is still a difference or not.

Dartmoor Dave · 12-02-2023, 10:06 AM

De-yellowing my 50mm/1.4 was one of the worst photographic mistakes I've ever made. I took a yellowed lens that took beautiful, characterful, unique photos and turned it into a clear lens that utterly bored me. I ended up selling it.

I'd urge anyone to think very carefully before de-yellowing. You might get rid of exactly what made you love the lens.

Asahiflex · 12-03-2023, 03:52 AM

Originally posted by Dartmoor Dave

De-yellowing my 50mm/1.4 was one of the worst photographic mistakes I've ever made. I took a yellowed lens that took beautiful, characterful, unique photos and turned it into a clear lens that utterly bored me. I ended up selling it.

I'd urge anyone to think very carefully before de-yellowing. You might get rid of exactly what made you love the lens.

Interesting take.

But it doesn't matter to me as I have lots of other lenses with character. So to me this is not a "loss" at all.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Can a UV lamp kill fungus and make the lens safe for use?	Boris_Akunin	Pentax SLR Lens Discussion	25	01-04-2015 06:51 PM
Auto-Takumar and Takumar lens hoods	Baard-Einar	Pentax SLR Lens Discussion	7	08-03-2012 11:15 PM
Frontfocus problem and focus assist lamp	GabrielFFontes	Pentax K-r	5	07-06-2012 07:17 PM
Misc Lamp and a Chair	Sailor	Post Your Photos!	5	12-13-2011 06:59 AM
AF Assist Lamp and Tungsten Focus Inaccuracy	GrinMode	Pentax DSLR Discussion	11	01-28-2011 09:45 PM

11-16-2020, 10:23 AM - 1 Like	#16
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here. Originally posted by pepperberry farm I use a different lamp to get the yellow out of my thoriated lenses: amazon.com: UV LED Black Light, HouLight High Power 10W LED Blacklight Flood Light IP65-Waterproof (85V-265V AC) for Blacklight Party Supplies, Neon Glow, Glow in The Dark, Birthdays, Blacklights, Curing: Home Improvement?tag=pentaxforums-20& While I like my JANSJÖ, I have been tempted to get a compact UV lamp, if they make such that is AC or USB powered. Steve

11-16-2020, 02:40 PM	#17
psoo Site Supporter Join Date: Jan 2012 Location: Long Island, NY Posts: 485	Originally posted by stevebrot The short answer is yes. Yellow is not a very good description for the discoloring. It is closer to tobacco stain in tint. There is also the matter that it is due to a disruption of the physical structure of the glass at the molecular level with attendant change in refractive character. (At least that is the theory.) My experience as well as that of others is an improvement in optical performance when cleared. Of course, YMMV. Steve Thanks for the reply Steve. However, I have an old Pentax lens that has an overall yellow tinge. Don't remember which lens but it's squirreled away somewhere. I don't think it's because it has degraded over time. Isn't it likely that it's the original coating?

11-16-2020, 03:08 PM - 1 Like	#18
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by psoo I have an old Pentax lens that has an overall yellow tinge. Don't remember which lens but it's squirreled away somewhere. I don't think it's because it has degraded over time. Isn't it likely that it's the original coating? The Super Takumars have coatings that reflect yellowish, but when white paper is viewed through the lens, the paper appears white. That is completely normal and is not the same a lens having one or more elements where the glass itself has been altered due to radiation. Reports on the Web of thorium coatings that have gone yellow are inaccurate. Steve

02-13-2021, 12:56 PM	#19
titrisol Pentaxian Join Date: Dec 2007 Location: In the most populated state... state of denial Photos: Gallery \| Albums Posts: 1,852	I didn't bother clearing the lens for a long time, since my line of thought was same as yours and I used BW film anyway. However images look better after clearing the lens, I don;t know how to described the difference but they seem snappier Also the lens regained 1 stop exposure and can be used for color. Originally posted by psoo I'm sure that for psychological reasons it's nice to remove the yellow tint from a lens. However, does yellowing significantly change the color of the image? If it does, some photos may benefit from a warmer glow. If not, why bother?

02-14-2021, 11:49 AM - 1 Like	#20
moggi1964 Senior Member Join Date: Feb 2021 Location: Manchester Posts: 178	I bought a UV torch that outputs at 365nm at 3w maximum (it reduces to about 2.3w after 3 minutes continuous use). I have sat it about 6" from my Takumar (50mm F/1.4 and it doesn't heat the glass. After about 8 hours use the glass is clear. Very simple to use. One word of warning: don't start going all CSI with it if you live in a rented house/flat; you do NOT want to know what may be on the carpet

02-14-2021, 12:08 PM	#21
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,375	Can't beat that price. You can get a UV LED and make a small source that will do the job if you can't get this lamp. The LED will have to have a means of limiting its current but is small and can be made into a compact source (avoid eye and skin exposure). One source is Mouser Electronics but there are a lot of others out there. It will most likely come in at a higher price point than the IKEA alternative.

12-01-2023, 02:18 AM - 1 Like	#22
Asahiflex Pentaxian Join Date: Jan 2008 Location: Netherlands Photos: Gallery Posts: 2,795	I tried the cheap IKEA Jansjö LED light (the weak USB version) to cure my yellowed 50mm f/1.4 Super-Multi-Coated Takumar. After 7 days of continuous exposure of the lens, which sits on a mirror, this is the result. It's still a bit yellow (slightly more than the photo shows, my 8 element 50mm f/1.4 Takumar does not show a cast). Maybe I should give it another week... :-) I noticed that the yellowing was cloudy / uneven in the middle. The discoloration is now pretty evenly. Before: After 7 days: The cure in progress: Last edited by Asahiflex; 12-01-2023 at 04:09 AM.

12-02-2023, 09:09 AM	#23
titrisol Pentaxian Join Date: Dec 2007 Location: In the most populated state... state of denial Photos: Gallery \| Albums Posts: 1,852	The 8 element doesnt have a thorium element and should need any treatment. Looks cleand, but if I were you I'd compare the meter readings between the lenses and see if there is still a difference or not.

12-02-2023, 10:06 AM	#24
Dartmoor Dave Pentaxian Join Date: Aug 2012 Location: Dartmoor, UK Photos: Gallery Posts: 3,882	De-yellowing my 50mm/1.4 was one of the worst photographic mistakes I've ever made. I took a yellowed lens that took beautiful, characterful, unique photos and turned it into a clear lens that utterly bored me. I ended up selling it. I'd urge anyone to think very carefully before de-yellowing. You might get rid of exactly what made you love the lens.

12-03-2023, 03:52 AM	#25
Asahiflex Pentaxian Join Date: Jan 2008 Location: Netherlands Photos: Gallery Posts: 2,795	Originally posted by Dartmoor Dave De-yellowing my 50mm/1.4 was one of the worst photographic mistakes I've ever made. I took a yellowed lens that took beautiful, characterful, unique photos and turned it into a clear lens that utterly bored me. I ended up selling it. I'd urge anyone to think very carefully before de-yellowing. You might get rid of exactly what made you love the lens. Interesting take. But it doesn't matter to me as I have lots of other lenses with character. So to me this is not a "loss" at all.