[Matt_Dodwell_UK]

Hi All,

I picked up a Spotmatic SP 500 in excellent condition from a charity shop the other day. Paid £10 for it and seems to be in perfect order, very little sign of use with clean VF. Light seals need replacing but that's it.

I also picked up 4 lenses with it all very dirt cheap under £30 each, and all seem it very clean condition. Focusing rings are still smooth, no mould, haze or scratches. I am not sure if any of these (see below) are decent lenses, I'm not knowledge about Pentax equipment, but the SP500 called to me and I want to run some HP5 or Tri-X through it for each of the lenses regardless.

The query I have is, how do I know if any of my lenses are yellowing? The 55mm 1.8 has a slight yellow tint to is when I tilt it in the light but if I open up the aperture to look straight through the barrel it looks clear.

Should it have a slight natural yellow tint to it? Or should it be completed clear of any yellow colour?

Takumar 55mm 1.8
Takumar 35mm 3.5
Pentacon 30mm 3.5
Takumar 135mm 2.5

Thanking you of any advice you can offer

Regards
Matt

[BigMackCam]

Hi All,

I picked up a Spotmatic SP 500 in excellent condition from a charity shop the other day. Paid £10 for it and seems to be in perfect order, very little sign of use with clean VF. Light seals need replacing but that's it.

I also picked up 4 lenses with it all very dirt cheap under £30 each, and all seem it very clean condition. Focusing rings are still smooth, no mould, haze or scratches. I am not sure if any of these (see below) are decent lenses, I'm not knowledge about Pentax equipment, but the SP500 called to me and I want to run some HP5 or Tri-X through it for each of the lenses regardless.

The query I have is, how do I know if any of my lenses are yellowing? The 55mm 1.8 has a slight yellow tint to is when I tilt it in the light but if I open up the aperture to look straight through the barrel it looks clear.

Should it have a slight natural yellow tint to it? Or should it be completed clear of any yellow colour?

Takumar 55mm 1.8
Takumar 35mm 3.5
Pentacon 30mm 3.5
Takumar 135mm 2.5

Thanking you of any advice you can offer

Regards
Matt

Hi Matt - welcome to the forums from another UK member

Congratulations on your camera, and those lenses - they're all very decent! I wouldn't worry about the slight yellowing at all - just shoot and enjoy them as they are

[Topsy]

I believe the Takumar 55/1.8 has thorium in it and thus would yellow with age.
UV/sunlight should clear it. Don't eat it or sleep on it an you'll be fine.

The other lenses are very nice as far as I know, wonderful deal.
I'd also like to find a 135/2.5 for that price!

Enjoy the camera and the lenses!

[kiwi_jono]

Welcome and - excellent buy!
Don't know about the Pentacon but those Takumars are all well regarded and should still perform well.
More information on the lenses can be found here:
Pentax M42 Screwmount Lenses - Pentax Lens Reviews & Lens Database

As far as yellowing goes, my Takumars do have a slightly yellowy sheen to the coatings and this is normal. Mainly the Takumar 50 f1.4s are effected by radioactive yellowing. If your lenses look clear looking through them then they are probably fine.

I have both the Takumar 55 f1.8 (love it) and 35mm 3.5 (useful wide angle). I don't have the 135 f2.5 but this is a highly regarded lens (I do have the 135 f3.5 and like it)!

---

Last edited by kiwi_jono; 01-06-2018 at 05:52 PM.

[boriscleto]

That Pentacon looks interesting...

Pentacon 30mm f3.5 M42 lens review

Must control LBA...lots of CLAs to pay for...

Some sources say the 55/1.8 is thoriated. Others say it is only the 7-element 50/1.4 & 49mm filter 35/2.

[aslyfox]

Welcome to the forums

is this one of the lenses?

Takumar 135mm F2.5 Bayonet Reviews - Non-SMC Pentax Prime Lenses - Pentax Lens Reviews & Lens Database

[boriscleto]

is this one of the lenses?

Takumar 135mm F2.5 Bayonet Reviews - Non-SMC Pentax Prime Lenses - Pentax Lens Reviews & Lens Database

That's the Takumar bayonet. The OP has one of the screw mount versions...

[aslyfox]

That's the Takumar bayonet. The OP has one of the screw mount versions...

oops

sorry about that

[twilhelm]

Nice set of lenses. Those Takamurs are a great find. The 55 is likely to have a slight yellow tint, mine does, but it won’t affect the image quality. Enjoy your find!

[UncleVanya]

With digital you can adjust white balance and avoid the effects of the yellowing to a large degree. With film the problem would be more annoying but if slight I wouldn't worry about it.

---------- Post added 01-07-18 at 12:13 AM ----------

With COLOR film I should have said. B&W will actually be slightly enhanced by it if you like increased contrast. Yellow filters are typically used with B&W film to enhance contrast.

[stevebrot]

With a few exceptions, most variants of the Super-Takumar 55/1.8 are mildly radioactive and will yellow with age.* The yellow coloration is due to radiation-induced structural changes in the glass and affects both tint and performance. The changes are reversible with the most popular methods being exposure to sunlight, UV light, or high intensity light from the IKEA JANSJÖ desk lamp (JANSJÖ). I have used the JANSJÖ lamp with several of my lenses with good success and can recommend it as a solution.


Steve

* Not the same as yellowish lens coating color. Radiation-induced color tints the glass of one of the rearward elements and is visible when looking through the lens at a sheet of white paper. The dingy yellow-brown tint is readily visible.

[stevebrot]

I don't have the 135 f2.5 but this is a highly regarded lens

My comment as well, particularly the version with eight aperture blades...

Super-Multi-Coated TAKUMAR/Super-Takumar 135mm F2.5 Reviews - M42 Screwmount Telephoto Primes - Pentax Lens Reviews & Lens Database


Steve

[Matt_Dodwell_UK]

Welcome to the forums

is this one of the lenses?

Takumar 135mm F2.5 Bayonet Reviews - Non-SMC Pentax Prime Lenses - Pentax Lens Reviews & Lens Database

Hiya,

I didn't realise there are multiple versions of the 135mm :-)

I'm not sure which version it is, I'll check it as soon as I get home, currently staying with the in-laws this weekend.

I take it one is better than the other.

[Matt_Dodwell_UK]

Hi Matt - welcome to the forums from another UK member

Congratulations on your camera, and those lenses - they're all very decent! I wouldn't worry about the slight yellowing at all - just shoot and enjoy them as they are

Thanks you for replying. Great to hear from you.

I was surprised by how much I liked it when I picked it up. I did a quick Google search before paying for it all to see what it was and what it was worth.

The body felt really nice to hold and had a great action and sound to it which is why I bought it, plus I think it looks cool, so at £10 if it was broken or rubbish I would have used it as an ornament :-). Maybe not now with the radioactive lens lol.

But, the biggest thing it did was immediately turn me on to mechanical cameras. I shoot a Canon AE-1 Programme and A1, both of which are lovely, but need a battery for the shutter.

This SP500 and the mechanical shutter just felt so nice and satisfying, I don't know why, I can't tell you, but it felt very different. I'm definitely going to look for other fully mechanical bodies, Pentax and other.

I use a light meter, never the in camera meter, so a broken meter or no battery doesn't matter to me.

The only thing that wasn't quite as nice was the VF is darker than the Canon's probably owning to the micro prism focusing screen rather than the Canon's split screen. The SP500's focusing screen is something I will need to get used too.

I'm really pleased with the lenses set, it's going to be fun to play with once I've found some light seals to put in. The currently seals are very brittle or gunky.

[Matt_Dodwell_UK]

With a few exceptions, most variants of the Super-Takumar 55/1.8 are mildly radioactive and will yellow with age.* The yellow coloration is due to radiation-induced structural changes in the glass and affects both tint and performance. The changes are reversible with the most popular methods being exposure to sunlight, UV light, or high intensity light from the IKEA JANSJÖ desk lamp (JANSJÖ). I have used the JANSJÖ lamp with several of my lenses with good success and can recommend it as a solution.


Steve

* Not the same as yellowish lens coating color. Radiation-induced color tints the glass of one of the rearward elements and is visible when looking through the lens at a sheet of white paper. The dingy yellow-brown tint is readily visible.

This is what I am wondering. I've looked at that lamp on IKEA and I can get it in the UK. It looks really small and not a UV, but for £10 it's worth a go. How close to the lenses will I need to place the bulb? Would it need to be facing into the rear or front elements do you recommend? Or would I need to do both?