[Steinback]

I know there was a thread in Russian on one of the Russian Pentax forums on doing FD to K conversions. They covered the 85mm f/1.2 and possibly some other long lenses with lots of photos of the process but I'm not sure if they also did shorter focal lengths. This would have been around 2 years ago but there were a couple of links from threads on this forum and it might be worth looking into.

I would be tempted to sell the 55mm f/1.2 and purchase one of the K or KA mount f/1.2 lenses available in Pentax mount or another mid level lens to fill a hole in my lineup. That or pick up a different and less valuable FD lens in the 50mm range to practice on.

[ripit]

Do you already have an f 1.2 lens? If yes, I would just sell the canon (unless you think its better than the one you have and want to try it). If you don't have one, I would either sell it or do a non destructive conversion that is reversible. Keep all the canon parts and do not modify any of them to work with your conversion (I don't think I would destroy a lens worth that much). You could probably get something with more complete function for the money.

I don't know a thing about fl mount but read they will fit an fd camera. If the mount is similar, it should be an easy conversion (not sure why people say its hard, still trying to figure that one out). The only issue I have ran into is that with minolta and canon lenses, I have always had to shorten the screws a lot, and that is not reversible. I'm not sure if you could find screws the same size to use. I have either gotten m42 type operation or wide open only on minolta and canon lenses (without modification). My initial impression is that with most canon lenses you may get wide open only (of course wide open is what is desirable about an f1.2 lens I would think). Keep in mind, I have only messed with a canon fd 50mm 1.8 sc (tore the mount off but haven't gotten around to converting it), and a soligor 35-70mm 2.5-3.5 FD mount (just got done converting it). You will have to loose about .140" or about 3.5mm thickness on the mount (for fd anyway). The canon 50mm 1.8 mount is .370" and the soligor 35-70mm was .395". I'm thinking its the design of the mount that they have to be that thick. Figure about .080 thickness for a k mount macro adapter or about the same for a thin k mount from an M donor lens (A can be a lot thicker), plus .140 that you have to subtract for the focal difference, leaves you with maybe needing a .150" spacer to push the lens back out some. If yours is like that you have ample room to work with.

Basically remove the old mount, drill a pk macro adapter and countersink the holes for the screw heads. I have always used the old mount as a guide for drilling but I wouldn't even tear the old mount apart if I were you. Make a spacer the right thickness or a little more (you can always thin it to fine tune it), and a second spacer to hold the aperture ring down (doesn't have to be precision as long as its thin enough to move freely). blem, that would be about it I would think unless you want to make parts (if necessary) to try and get some aperture control. Fyi I know you have some experience doing this, I was just stating what I had to do with canon.

On a side note, I will never, ever use an m42-pk adapter again unless it must be that thin. Things are so much simpler with the added thickness of a k mount macro ring. I used a 58mm-k macro ring and it was the perfect size for canon but I don't know if that would apply to all canon mounts. Had the main spacer been much thinner, the threaded part would have sat nicely to hold the aperture ring down (not sure if that will interfere with a second spacer). I havent done the second spacer yet as the soligor lens had other parts that retained the aperture ring down on one side.

Hope some of that helps with your decision and or conversion.

[aliasant]

Here are some shots of my recently converted Topcor RE 35mm f2.8 to PK mount with aperture control.

This was not an easy project for me but a lot of trial and error finally got me a working version.
Its not very pretty but it does work.
Unfortunatly my K5 is being repaired so I cant really test it yet

When testing using an old Pentax A3 it works well. I can focus wide open and the camera will close the aperture when I take the shot.
its an amazingly nice lens and being able to use it on my K5 is thrilling!.
It focuses down to 23cm from filmplane and that is almost macroish. About 1:4 and change

I have used a "left over" PK/A mount and modded it to fit the Topcor.
The mount has its own spring system.
I have also modded the mounts thickness a bit but not much was needed. Just parts of the edges.
Many other little things modded and most likely way to much. Now that I finally know what is needed to make it work i think I could make a much better version next time I find one of these lenses.
They are not cheap though.
In the process I also managed to break one of the blades. One of the two little nibbles fell off. I glewed another one on that I cut from a scrap lens. It works great but the new nibble didnt end up exactly right so now the aperture is almost rectangular instead of round. Will make an intersting bokeh I hope

Anywas.

its possible and thats great!

[aliasant]

Got my K5 back today so I threw the Topcor 35 on and this is wide open.
Scaled down to 1024 for forum.
Second is a 100% 1024x1024 crop of that and last is closest focus, wide open and also scaled down.

I havnt touched the pictures. Straight from camera and camera with default settings straight from repair shop

It works perfectly just as any M lens. Green button stopdown metering and it seems to meter well too.
I love this lens.

Attached Images

     

[unixrevolution]

So, I have an interesting dilemma. I was at the flea market today, and stumbled across a camera bag with a very nice looking lens sticking out the top. I took a closer look and there in front of my eyes was a Canon FL 55mm f1.2 lens attached to a Canon FT camera. Without looking too interested, I looked over everything and was pleasantly surprised to find the lens, camera, bag, filter assortmant, camera instruction manual, flash and other doodads all in very good and well cared for condition. I looked around some more and talked to the guy about some other items and then asked how much for the camera. The guy told me $100 bucks, I told him $50 +throw in the lizard toy my son was begging me for and he had a deal. We shook hands, the camera became mine and 50 of my hard earned dollars became his. So the dilemma is, do I keep this nice piece of glass and risk destroying/devaluing it in an extensive, difficult, and irreversible lens conversion, or do I sell it on flea-bay for the roughly $300 these are currently going for and use that money to buy a lens I don't have to convert. I already have some very very nice 50ish glass. I don't really 'need' another, but 'need' isn't the point of LBA is it? Anyway, opinions from informed canon lens owners/hackers would be apprciated. I have been wanting to try a canon conversion, just wasn't planning on cutting my teeth on a relatively expensive piece of glass.

Throw the FT 55/1.2 to the Canon FD shooters and find a K-mount 1.2 you don't have to bumrape in order to fit to your DSLR.

[Green&White]

From my understanding of how the contacts on an A lens work, wherever the pins touch the bare lens mount they essentially short out and the camera can sense this. Where they hit an insulator and don't short, the camera can sense this. The combination of pins that are shorted vs. not is what tells the camera what the max aperture is of that lens. Spacific to the bellows mount conversion I spoke of earlier, if I take the front of the teleconverter mount and place it on the front of the bellows, and put the back teleconverter mount on the back of the bellows, I'll have A mounts on both ends, but no way for the camera to know if any of the pins are shorting out or not. So I would have to somehow connect the pins on the back of the bellows to the pins on the front of the bellows to transmit the electrical current from one side to the other. With exception of the A pin that tells the camera that the lens aperture is set to A, I think everything else should work. The A pin will have to be spring loaded or something to tell the camera the lens is set to A. I'll figure it out when I get further in I guess.

Regarding the Linear, non-Linear thing. From what I understand, and I could be wrong, the camera actually opens the iris to the correct aperture via the stop down lever based on information it collects about what max aperture the lens is. I may be wrong about that point though. I know that A lenses the aperture stop down is linear, and M lenses it's progressive. Or something like that at least. Anyway, the camera calculates exposure based on the wide open value. So if the lens mount says it's a 2.8 lens, and in reality it's a 3.5 lens, then it will think it's much darker then it is and over expose the image upon stop down. The thing is, the camera does not meter when it stops down. It calculates the proper value based on the wide open meter reading. So if the camera thinks that the lens is faster or slower then it really is, when you stop down it will have done the wrong math and exposure will be wrong. When the camera stops down to take the picture, it actually only moves the stop down lever the correct distance to allow the iris to open to the selected aperture. So if it's an M lens with progressive aperture mechanism, then the stop down lever will not move the correct distance to properly expose the picture. So it's possible you could run into issues with exposure, but again, I could be wrong. It's been a while since I read about all this stuff. You should probably do some research and see what the facts are, as I'm pretty sure I may have just messed some things up there. The gist of it should be right though.

As far as I know, thats right what you wrote. I converted successful a Soligor CD 2.8 28 from PK/R to PKA. I have two lenses with both, the PKA pin and contacts and the Ricoh pin and they are working well in Pentax A mode. And I thought the aperture works mechanical on both Pentax and Ricoh cameras. So I drilled only three holes on the right positions, filled two with epoxy resin and used the original Ricoh pin as an A pin. The lens works well in A mode, the aperture ring has a fixed "P" position witch I can use as a "A" position, the aperture is then fixed on f22.

Sorry about my english, I hope you understand what I wrote. If needed, I can post some pictures but I don't have them on my computer at the moment.

[Damian]

I know there was a thread in Russian on one of the Russian Pentax forums on doing FD to K conversions.

Thanks for the info. I saw that thread not long ago. Thankfully Google Chrome translates Russian. I will eventually try a FD or FL conversion, but not on this lens. It's worth too much and I'm sure someone else will appreciate it far more then I.

Do you already have an f 1.2 lens?

Actually no I don't. I have 3 50ish f1.4 lenses though and rarely use them wide open. So it's hard to justify the need for an f1.2 lens considering I usually shoot 1.4 lenses at f2.

Throw the FT 55/1.2 to the Canon FD shooters and find a K-mount 1.2 you don't have to bumrape in order to fit to your DSLR.

I've pretty much decided to do just that. Well except the throwing part. I'd much rather sell it and I think it would be worth far more undamaged. I'm not decided on what to purchase with the profits. I probably won't get a Pentax 50mm f1.2, I'll probably get a Limited lens of some sort. I've been eyeing the 31mm limited and the 77mm limited for some time now. The 70mm limited looks damn good too. Though I won't make enough from the sale of this lens to purchase what I want, I have several other items i'm getting rid of. Hopefully I can raise enough money to have my choice.

Here are some shots of my recently converted Topcor RE 35mm f2.8 to PK mount with aperture control.

Great work on the Topcor 35mm f2.8. It looks like it takes a pretty sharp picture too. I'm jealous, but not of the rectangular aperture of course. I'm still looking for one myself. Hopefully I will eventually find one at a decent price. Like under $50. I have trouble justifying spending more then that on something I have to convert. Unless it is truly special.

[ripit]

I have trouble justifying spending more then that on something I have to convert. Unless it is truly special.

For me the purpose of converting is saving money. If I can get a lens dirt cheap in a different mount (or there is a particular lens I want not available in k mount) then I might convert it. If I can get a k mount for the same price or close, I would rather save the hassle not to mention the possibility of limited function.

So with the A pin, is it just a ground that gets turned on and off to tell it it is in A mode, and the lens knows the aperture based on the other pins being grounded or not grounded?

[excanonfd]

Thanks for the info. I saw that thread not long ago. Thankfully Google Chrome translates Russian. I will eventually try a FD or FL conversion, but not on this lens. It's worth too much and I'm sure someone else will appreciate it far more then I...

I think your decision not to mess around with this lens is the right one. This focal length lenses are fairly common, you don't gain anything other than acquiring an f1.2 lens. On the other hand if you find a Canon 200mm macro, I'd be urging you to get it converted to a K mount no matter the risk or value. If I ever find a 200mm macro of any brand (at a price that I can afford), I'd send it out to be converted to K mount - until then I'll make do with P645 120/4.0 macro with P645 to PK adapter.

Thanks,

[Damian]

So with the A pin, is it just a ground that gets turned on and off to tell it it is in A mode, and the lens knows the aperture based on the other pins being grounded or not grounded?

That sounds right. I know the A pin tells the camera the lens is set to "A". I'm not sure if it does that via grounding out or if it acts like a button.

[Douglas_of_Sweden]

I think your decision not to mess around with this lens is the right one. This focal length lenses are fairly common, you don't gain anything other than acquiring an f1.2 lens. On the other hand if you find a Canon 200mm macro, I'd be urging you to get it converted to a K mount no matter the risk or value. If I ever find a 200mm macro of any brand (at a price that I can afford), I'd send it out to be converted to K mount - until then I'll make do with P645 120/4.0 macro with P645 to PK adapter.

Thanks,

If you mean the Canon FD 200mm f4 macro 1:1 and your intention is to use it for macro, I would suggest you don't convert it, but just buy the scoptic adapter FD to K, unscrew the optics in the adapter and use it in that way. You can focus up to almost 3m and get a max macro ratio of about 1.1:1 (since the adapter and the difference in registration distance acts like a thin extension tube). See https://www.pentaxforums.com/forums/pentax-camera-field-accessories/96884-ada...diction-4.html.

[Squier]

Well, this big old astro scope ( 600mm ) was never meant for my camera, but by stripping a K mount lens of the mount, using some West Systems 2 pak expoxy, i glued the mount onto some 2" tubing ( the diameter of the focus tube of the scope )
and that was that. Posted some in the 300mm lens club and other places but it still quailfies here too, so here they are.

Excuse the poor 1mp Camera phone shot of the lens with K-7 attached

[aurele]

wow ! quite big, but it gives nice results

I really like the 1st one, but the next are like ... bleached ? with some sort of fog on it.

Is it just me ?

[Squier]

Thanks !

It was just the distance involved on the 2nd. Heat haze i think

[aurele]

Hello, dear impossible member

I have some Fungus problem on my very first lens (sentimental attachment ... ahhhh !) a A50/1.7.
Right now, fungus are doing a circle on the extreme border of the back element, so, there is no consequences for the moment.

My question is what do some of you used to clean fungus, without destroying the coating (Damian ?) ?

Thanks to all of you !

Another and last question : where do you get some K mount you put on "impossible lenses" ?