[GUB]

I have a Pentax M 100mm f4 macro with a light to moderate case of the "swirl".
I thought I would put it up against my s-m-c Takumar bellows 100mm f4 which is supposed to have the same optics and is crystal clear.
There is a difference and it is enough to justify why I haven't been using the M.
Note the difference in image magnification. I did a few sums and feel it can be 100% attributed to the fact the bellows was mounted on the tripod via the bellows while the M was mounted via the K-1 body. That meant the M lens was closer to the subject by 5 -10%.

[Michael Piziak]

I have a Pentax M 100mm f4 macro with a light to moderate case of the "swirl".
I thought I would put it up against my s-m-c Takumar bellows 100mm f4 which is supposed to have the same optics and is crystal clear.
There is a difference and it is enough to justify why I haven't been using the M.
Note the difference in image magnification. I did a few sums and feel it can be 100% attributed to the fact the bellows was mounted on the tripod via the bellows while the M was mounted via the K-1 body. That meant the M lens was closer to the subject by 5 -10%.

The Takumar definitely has a superior image.

I suspect the classic swirl is a definitive sign of lens separation (and not haze) - ?

[GUB]

I suspect the classic swirl is a definitive sign of lens separation (and not haze) - ?

I think so.
Interesting that it is considered an issue only with the M series. The design is considered unchanged back to the Tak. I guess it is the cement choice.

[ZombieArmy]

I also had this when I bought a pentax m 100m f4 and subsequently returned it.

[Michael Piziak]

I think so.
Interesting that it is considered an issue only with the M series. The design is considered unchanged back to the Tak. I guess it is the cement choice.

It's just considered a high percentage flaw of the one M lens, the one discussed in this thread. I don't know why. My personal theory is that the balsam/glue used in that lens wasn't up to standard....

[whojammyflip]

I agree, I bought two copies of this, both had it and were sent back to the folks selling it.

I like my Tamron SP 90mm 2.5, which is readily available, produces nice bokeh, and mechanically, its a nicer lens.

For digital I have the DA 35 Limited.

[tonyzoc]

I have the 100/4 M and I've experienced the same issue as the OP. I see kind of a bluish cloud in the coating. The lens is fairly clear otherwise and still makes excellent images. I don't know if it's balsam separation or coating degradation or something else. I don't use the lens much anymore as I have the 100/2.8 WR and a 50/4M also. I tried selling it a while back, with pictures of the effect, and resultant images, but no one bit for $60 so I figured I might as well keep it.

[Michael Piziak]

I have the 100/4 M and I've experienced the same issue as the OP. I see kind of a bluish cloud in the coating. The lens is fairly clear otherwise and still makes excellent images. I don't know if it's balsam separation or coating degradation or something else. I don't use the lens much anymore as I have the 100/2.8 WR and a 50/4M also. I tried selling it a while back, with pictures of the effect, and resultant images, but no one bit for $60 so I figured I might as well keep it.

Yea.

I sometimes wish I would have just kept the 1st copy I had obtained for just $20.00 USD.

Near mint copies of this lens can be obtained; however, I only trust the Japanese sellers - they have been spot on with their detailed and accurate rating(s) of every lens I've purchased from Japan.


However, expect to pay a high premium ($) amount of money if your OCD kicks in and you want a near perfect copy of the lens.

Addendum: I just checked the auction site, and there seems to be a lot of these up for auction right now and an unusually high % of copies that don't have the haze (at the current time). This may well be a good time to pick up a near mint copy.


Regards,

Michael

[Wasp]

I recently took a chance on one these lenses that was described as having a haze problem. It was fairly cheap and I thought that the haze could be fixed. The problem appears minor but images taken with the lens lack that SMC Pentax magic. I should have read this thread before I shelled out my hard earned. If my copy does have balsamic separation it means that I now have yet another ornamental lens. Sigh...

I have now shone a light through it. There is some milkiness. Looking from the back I can see a circle that varies with angle and distance from the light. Could this be the dreaded seperation? None of my other Pentax telephoto primes does this. I have quite a few and checked all of them: M 100/2.8, K 135/2.5, K 135/3.5, M 200/4, K 200/2.5.

Maybe it will clean up. Maybe not. I will take it to my repair guy next week.

[jcdoss]

...Your thoughts/comments please on the mystery of this hazy SMC...

Michael, any chance of fixing the links in the OP of images showing the defect? Thanks!

[GUB]

I have a M50mm 1.4 which a blotchy type of separation and have seen another showing it in an auction site. So not just the 100mm f4.

[martin42mm]

Mine has some dusty looking stuff inside which I had attributed to dust or slight fungus, but not the swirl. It seems to give some milkiness to my pictures. I have tried to dismantle it but I cannot shift one of the five crosshead screws in the mounting ring. I cannot see how to get into it from the front.

I'm confused when you say :

Is that a typo for the 50mm macro? I thought you were talking about the 100mm F4 from the start.

That one you linked for sale on Ebay is in much poorer condition than mine. Mine is mint apart from the optical haziness. $180 is seriously over-priced.

Old thread I know, but when you have a stuck lens-mount screw, try applying the tip of a soldering iron to it for about 15 seconds. This will melt the locking paste that many manufactuers use on these screws, meaning the screw should remove more easily without damage to the screw-head.

[Wasp]

An update on my post above. It is almost definitely balsamic separation. I have given up on the lens. Luckily for me, a copy of the A version turned up in my valley and I snapped it up. It is in perfect shape and delivers the SMC magic.

[martin42mm]

An update on my post above. It is almost definitely balsamic separation. I have given up on the lens. Luckily for me, a copy of the A version turned up in my valley and I snapped it up. It is in perfect shape and delivers the SMC magic.

Never give up on balsam separation if you have a practical streak.
I use modern synthetic balsam,and after cleaning and recentrering the separated elements, put a drop of the cement between them, then put the element block under a UV light-I use one that is designed to harden modern nail varnish! The only issue with cemented elements, assuming they are still connected, is to separate them. I use dichloromethane, or a derivative of it, which will separate the elements if they are soaked in it over about 24 hours. One thing to be aware of is that the liquid is VERY evaporative, so make sure the container is air-tight, both the one the elements are soaking in, and the original container.

[UncleVanya]

Just be very careful with that solvent:

Dichloromethane - American Chemical Society

It isn’t as bad as some, but it’s not without concerns.