[Effi]

...does the the yellowing have any effect on digital cameras where you can change the white balance?

[Gooshin]

...does the the yellowing have any effect on digital cameras where you can change the white balance?

no

but it does cut out some light, so its still beneficial to remove it, less work down the road.

[Zewrak]

It steals light. Some reports state that their lense lost a whole stop.

[Nesster]

Apart from cutting the light, I can report that even with auto wb (I think that was the setting, as it usually is) a yellowed lens does render much warmer than a non-yellowed one.

I did a lens test, of a SMC Tak 105/2.8, a Soligor TX 105/2.8, and for fun, a SMC 50/1.4 + 2x converter. Apart from the expected effects of the converter, the SMC 50 shots were very much warm - stone that was cool grey on the other two was sunlit warm with the 50. And this was after I've already mostly de-yellowed it last summer...

[StephenMerola]

You can expose it to sun light and it should eventually go away. However, I do not know how long you have to do this for. I believe it is because of certain radioactive elements that were used that the glass turns yellow.

[monochrome]

Many on this board have cured yellowed Tak 50's by using this method:

1. Remove both caps
2. Wrap the lens from the front element backward in aluminum foil (reduces heat and reflects some light back into the lens).
3. Place the lens on a south-facing windowsill angled to receive the most direct sunlight at your latitude.
4. Mine took three weeks of winter sun. Some have taken less time.
5. Glass should be gin-clear when the "cure" has worked.

[k100d]

Many on this board have cured yellowed Tak 50's by using this method:

1. Remove both caps
2. Wrap the lens from the front element backward in aluminum foil (reduces heat and reflects some light back into the lens).
3. Place the lens on a south-facing windowsill angled to receive the most direct sunlight at your latitude.
4. Mine took three weeks of winter sun. Some have taken less time.
5. Glass should be gin-clear when the "cure" has worked.

wrong! Brian Ayling's photographic repair tips

[Gooshin]

11/10

good post Simon.

[cpopham]

[*]Place the lens on a south-facing windowsill angled to receive the most direct sunlight at your latitude.

Something tells me your directions might not work so well for me.....

[HarryN]

Hi - I do a lot of work with LED lighting (as a hobby). There are some LED setups that might work to fix this problem without the heat exposure of sunlight - just the wavelength that would reverse the effect. The light would be going only through the glass, not shining all over the place on the lens.

I am toying with rigging up a simple test bench to do this test, but of course would need a lens to test it out on.

If anyone would like to loan a rather yellowed lens to me for testing (when I am ready), that would be great. A junker would be ideal. Of course I would return it when finished. You could document for us if the result is adequte or not.

As this is just a hobby testing sort of thing, success is not assured.

Thanks

HarryN

[ovim]

I cleared the yellowing from my S-M-C Takumar 1.4/50mm recently with a energy saving UV bulb in only 24hrs.

The trick was to dismantle the lens so that there was no glass (to block the uv-rays) between the yellowed element and the uv-bulb. The usual advice is to expose the rear of the lens to the sunlight but there is two elements blocking the rays in the rear before the yellowed piece of glass. Actually majority of the yellowing was cleared after 10hrs but I didn't have time to put the lens back together so I let it stay under the lamp.

Dismantling the lens is not that hard (there's instructions on the net) but you need a clean workspace, some tools, patience and it's good to make notes (and/or take pictures) to remind you how everything was. Usually there will be couple of small dust particles left inside the lens no matter how careful you are (I can live with that).

Here's a few pics (taken with a cellphone):
#1 = Before (the rear part of the lens with only the yellow element and diaphragm)
#2 = After 24hrs (same part shot against my laptop screen)
#3 = Comparison shot of my yellowed Super-Tak 2/35mm against the laptop screen (the yellowing on the 50mm was worse)

[HarryN]

Hi Ovum - That is great.

I was going to use a slightly longer wavelength, narrow band LED to see if that would work first, then move to a shorter wavelength if really needed.

The reason is that I really don't want to have to take the lens apart, and time is not that big of a problem, esp. since you can expose these 24 hrs/ day at full intensity.

[SOldBear]

You can expose it to sun light and it should eventually go away. However, I do not know how long you have to do this for.

It took my Takumar 50mm 2 days outside in the sun. It was No. CA in August.

Window glass blocks most of the UV, which is needed for the treatment, so if you leave the lens behind a window, it will take a long long time.

It's best if you have a friend in tanning salon business. Then the lens will stay in an air-conditioned environment, you don't have to worry about it getting heated up.

I wonder if an old EPROM eraser would work.

The reason is that I really don't want to have to take the lens apart, and time is not that big of a problem, esp. since you can expose these 24 hrs/ day at full intensity.

No need to take the lens apart. I sure didn't. This week is sunny in Pleasanton. It should not take more than 2 days for your lens.

[ovim]

It took my Takumar 50mm 2 days outside in the sun. It was No. CA in August.

Window glass blocks most of the UV, which is needed for the treatment, so if you leave the lens behind a window, it will take a long long time.

It's best if you have a friend in tanning salon business. Then the lens will stay in an air-conditioned environment, you don't have to worry about it getting heated up.

I wonder if an old EPROM eraser would work.



No need to take the lens apart. I sure didn't. This week is sunny in Pleasanton. It should not take more than 2 days for your lens.

I did this in the middle of winter when we have about 6 hours of daylight /day here where I live in Finland (in northern parts of the country the sun doesn't rise at all). It's usually cloudy and even when you can see the sun it doesn't get that high and the uv-levels stay low...

[regor]

I'd think that the UV light box barber shops use to sterilize clippers would work pretty good in such situation as well.
R