[macTak]

I have an old Rokkor 50/4 enlarger lens. I am wondering what kind of adaptor I need to fit it to a K-mount bellows. (I also have a m42-K adaptor.) The Rokkor lens has a thread that is about 38.8mm OD, but I cannot deterine the thread pitch. I used to use it on a Lucky II-C enlarger.

Almost certainly an M39 (very common for enlarger lenses). You need an M39-M42 adaptor.

[macTak]

Also, I highly recommend the K50/4 or the M50/4 macro lenses (which others have mentioned). They are even cheeper than the A50/2.8, and their optical quality is, in my opinion, peerless. I'll take the Pentax 50/4 optic over any other macro lens I own (including the Bokina). As an added advantage, the lens is quite compact and the front element is well recessed, so no need for a hood. If you do want the convenience of 1:1 and A-functionality, someone's recommendation of the Sigma 50/2.8 was a good one (the earlier, non-AF versions can be picked up very cheaply on ebay, about the same price as the M50/4). I have the Sigma too, and it's an excellent lens--I don't think anyone would be dissapointed with it--although I do find the Pentax 50/4 to be the better optic.

[RioRico]

I have an old Rokkor 50/4 enlarger lens. I am wondering what kind of adaptor I need to fit it to a K-mount bellows. (I also have a m42-K adaptor.) The Rokkor lens has a thread that is about 38.8mm OD, but I cannot deterine the thread pitch. I used to use it on a Lucky II-C enlarger.

L39-M39-LTM was a common thread for enlarger lenses (ELs). I use cheap M39-PK or cheapest M39-M42 adapters. Many USA-made enlarger and utility lenses had non-metric or non-standard threads (or none!) but those are easily accommodated: Get some el-cheapo black plastic M42 or PK body caps. Cut holes in them. Insert lenses. Voila!

A 50mm EL on a bellows is macro-only -- I mean, it's in 1:1 to 3:1 territory, beyond just closeups. Depending on how close you want to go, I find that tubes are handy for closeups (to 1:2) for lenses shorter than 80mm, and for macro with 35mm-50mm ELs. A 35mm EL mounted on the body with adapter only, no other extension, is at around 1.3:1. Working that close, focusing is better done with camera placement than with lens diddling.

[tim60]

MacTak, RioRico,
Thanks for the advice. Now I know what to buy so I can try it. Turns out to be quite cheap, so it is not frightening to experiment.
My main reason is that I have read that enlarger lenses can be useful on bellows and I thought it would be nice to use it for something. In digital imaging enlargers are not very useful! Nice to use the legacy things - pursuing the Pentax design philosophy.

[RioRico]

My main reason is that I have read that enlarger lenses can be useful on bellows and I thought it would be nice to use it for something. In digital imaging enlargers are not very useful!

I have a pile of ELs, and fewer projector-copy-utility-etc lenses, and a few bellows. None are leftovers from my film days; all the old stuff is gone but not forgotten. I've reloaded over the last 3.5 years. sometimes almost for pennies acquiring great glass by Leitz, Nikon, Schneider, Rodenstock, Komura, Kodak, Steinheil, etc.

Lenses longer than 80mm (and a few weird shorter ones) can reach infinity focus on most bellows, so I can be seen wandering around in the world with an M42 bellows mounting some 90-105-127-140-162-190mm lens (hood is mandatory) shooting stuff near and far. I'll put 75mm ELs on tubes, adjusted for portrait distance or infinity or whatever. ELs in the 30-55mm range really are best for getting REAL close.

Yes, rescue those lenses that no longer serve their intended purpose! And almost any optical material can be put to use (for good or evil!) in tubes and/or bellows. Fun fun fun.

[tim60]

MacTak, RioRico,
The M39-M42 adaptor arrived this week. I have fitted it and found that the 50mm EL witht he bellows fully extended got real close, with magnification close to double. But it is a challenge to get the picture to work, so I still need to work on technique. Promises to be interesting. I like to get small flowers, or parts of flowers. Yesterday I tried the longan tree. One flower gets a good frame coverage. But no chance today, must do other things.
Thanks for the advice about what to get.

[RioRico]

But it is a challenge to get the picture to work, so I still need to work on technique.

Yes, a 50mm EL on a bellows extended to ~150mm gives magnification of about 2:1. Yes, working real close pretty much demands a tripod or other immobilization, and maybe focusing rails, and practice practice practice. This is not a pastime for the impatient. But macro shooters are supposedly the happiest photographers. Have fun! Get happy!

[rvannatta]

Yes, a 50mm EL on a bellows extended to ~150mm gives magnification of about 2:1. Yes, working real close pretty much demands a tripod or other immobilization, and maybe focusing rails, and practice practice practice. This is not a pastime for the impatient. But macro shooters are supposedly the happiest photographers. Have fun! Get happy!

I've owned and used both 50 and 100 mm manual and auto focus Pentax macro lenses over a good number of years. I have bellows, extension tubes, and lens reversing rings, and alas, a pentax ring flash.

I have disposed of all of my Pentax-A and older lenses. And it has nothing to do with optical quality, which I regarded as just as good.
the Pentax-F and later macros are F2.8 in speed and have a longer throw. I find both invaluable. While the depth of field is so little
that you would rarelyl want to take a photo at F/2.8, it gives you a really sharp focus point which is what you need. While I suppose exactly what you do depends on how you want to manage the brokeh, but I usually like to black out the background which sort of comes natural
if you use a ring flash with around an f16 or smaller aperature.

I find the Exif quite valuable, particularly if you also record the GPS data on macro work if you are doing it in the field, because other wise
you can never find your way back to what you did. This drives me to want a Pentax F and later lens and irritates me that I can't use both the
O-GPS1 and the ring flash at the same time.

I"ve been both ways on the 50 vs 100 mm length. when I had the old ring flash-- the afc080 I used the 50mm because it was short on power
to work at the distances required for the 100mm. Now I have the AFC160, and it has a minimum distance in which it will work which is more consistent with the 100mm lens.