Converting k-mount camera to m42 -- permanently?

[Bill Burk]

I got an ES attached to a lens, but it's rather heavier than I prefer, so still haven't tried it out.

1/1000 is often more than enough, but if one wants to shoot at f1.4 on a bright sunny day, even with ASA 50 film one may need to go faster.

Oh my yes it is a pleasure walking about daytime with an f/1.5 lens and film that needs EI 4. Finally a chance to shoot wide open.

Funny. For me it’s the same film, just 70 years apart… I have a bulk roll of old Super-XX that needs EI 4

Yes Pentax M42 are heavy. No way around that except to just bring one lens.

 

[Lucius]

Oh my yes it is a pleasure walking about daytime with an f/1.5 lens and film that needs EI 4. Finally a chance to shoot wide open.

The Cyclop?

Yes Pentax M42 are heavy. No way around that except to just bring one lens.

For me it's not the overall weight (I often take a couple of bodies and a few lenses and carry them in my backpack), and not even the pressure on my neck, but rather how it sits in the hands when I'm actually shooting. Perhaps it has more to do with the shape than with the weight of the camera -- I find it I'm more comfortable shooting a small light body with a bid lens than a bid heavy body with a small lens.

 

[dynachrome]

If you want to save weight, get a camera like the Vivitar V4000S. You will have your top shutter speed of 1/2000. Together with an ND filter or two, you will be able to shoot wide open all day without having to use film that needs an EI of 4.

 

[Lucius]

If you want to save weight, get a camera like the Vivitar V4000S. You will have your top shutter speed of 1/2000. Together with an ND filter or two, you will be able to shoot wide open all day without having to use film that needs an EI of 4.

My Chinon (CE4s) is pretty light-weight, goes up to 1/2000 and has auto-exposure; in what respect is the Vivitar better?

 

[Snoop]

would avoid superglue, its not that reliable, epoxy is incredibly strong and always works
However often happens that as soon as you make a permanent modification something comes op that makes u wish it wasnt permanent...
There is the chance that 3 set screws (I think its grubs for u guys) can solve your problem and still keep the modification easily reversable
That said the Pentax named adapters also snug up with the lens, the issue if I remember were some lenses too narrow to "clamp" but AFAIK that way of working is an actual feature of the adapter to register different lenses

 

[Lucius]

There is the chance that 3 set screws (I think its grubs for u guys) can solve your problem and still keep the modification easily reversable

That's an interesting suggestion. How exactly would I do that?

That said the Pentax named adapters also snug up with the lens, the issue if I remember were some lenses too narrow to "clamp" but AFAIK that way of working is an actual feature of the adapter to register different lenses

Lenses being too narrow (or their 'shoulders' being ever so slightly recessed) is one issue; another is that the mount itself can vary slightly between different makes (I get way more wobble on my Chinon than on my Pentax).

 

[dynachrome]

The Chinon weighs 485 grams. The Vivitar weighs 370 grams. Whether auto exposure is important depends on what your subjects are. By wanting to shoot wide open, it looks like you are photographing subjects that are not too far away. With distant subjects, photos shot wide open and closed down do not look very different. For more distant subjects try using a lens with a maximum aperture of f/2, for example. That will also cut down on weight.

 

[Snoop]

That's an interesting suggestion. How exactly would I do that?

you will have to thread 3 holes in the throat of the adapter, where there is meat for the tip if the grub to grab onto the original camera mount, 3 or 2 grubs should do it, Its awhile I havent had stuff with that mount in hand, if u look at it you can easily spot where its more convenient (IF there is a convenient spot)
If im picturing the mount right you should end working right at the end of the tabs that slide into the adapter. Its not difficult to thread a couple holes for the grubs
Once the adapter is set into the camera tightening the set screws would fix it in place

you dont need to make any hole in the camera mount itself, set screws are made to just grab onto what they touch and you arent using them to hold the whole thing up, they merely wouldnt allow any slack. Undoing the grubs u can remove the adapter if you ever needed the original mount for some lens

The adapter should already have one threaded hole where there is the screw that holds the locking spring, chance is that just one grub that fits that thread will fix the adapter in place, just one in the long term will get loose but should give you an idea if its something that works or not

Lenses being too narrow (or their 'shoulders' being ever so slightly recessed) is one issue; another is that the mount itself can vary slightly between different makes (I get way more wobble on my Chinon than on my Pentax).

lenses are supposed to register by sitting against the front of the camera mount, adapters and method of mounting is just the way to get (and keep) the lens fully to the camera, my understanding has always been that the function of the slack on the adapter was to allow any of the lenses to sit where they were supposed to independently from small mount differences and always be at the right distance. U noticed the difference in slack from one mount to the other but you should also see that the wider lenses dont care and fit well nicely held against the camera in either of them, that is because of that slack. Its not a badly made adapter, its an actual feature of it, the badly made ones are the ones that fit tight.
The narrow lenses snug up to the adapter before touching the camera so the whole system doesnt work.
With the wobbly lens u get to infinity fine? I.e. does it register properly despite not touching the camera face?
It could be worth to look into modding the lens rather than the camera, since it is the actual contact of the back of the lens with the camera that helps supporting its weight rather than allowing leverage right onto the working parts of the mount (not sure if I explained myself). in some lenses there little to no space to work so it all depends on what you have in hand
There are also adapters with a flange, u lose infinity though.
That I know many that had your problem just solved it with rubber o-rings or other rubber seals for shafts which would take up the slack, not sure it works for all or if it allows proper registering of the lens, but if it works for them it might be just the easier way to solve your problem
The ones that have the shoulders slightly recessed might require sanding down the face of the adapter, if there is enough meat
Either way the lens shoulder should be flush with the surface of the camera mount to be registered properly

 

[Lucius]

you will have to thread 3 holes in the throat of the adapter, where there is meat for the tip if the grub to grab onto the original camera mount, 3 or 2 grubs should do it, Its awhile I havent had stuff with that mount in hand, if u look at it you can easily spot where its more convenient (IF there is a convenient spot)
If im picturing the mount right you should end working right at the end of the tabs that slide into the adapter. Its not difficult to thread a couple holes for the grubs
Once the adapter is set into the camera tightening the set screws would fix it in place

The adapter should already have one threaded hole where there is the screw that holds the locking spring, chance is that just one grub that fits that thread will fix the adapter in place, just one in the long term will get loose but should give you an idea if its something that works or not

I like the idea! I'd need to be able to thread holes, and get some 'headless' screws of the right length that wouldn't interfere with the m42 threads, but it sounds doable.

lenses are supposed to register by sitting against the front of the camera mount, adapters and method of mounting is just the way to get (and keep) the lens fully to the camera, my understanding has always been that the function of the slack on the adapter was to allow any of the lenses to sit where they were supposed to independently from small mount differences and always be at the right distance. U noticed the difference in slack from one mount to the other but you should also see that the wider lenses dont care and fit well nicely held against the camera in either of them, that is because of that slack.

That's not the case, unfortunately: even wider lenses sitting snuggly on the Pentax are quite wobbly on the Chinon; on the latter the lens hits the adapter before it hits the mount, which makes me think that the mount is thinner.

Its not a badly made adapter, its an actual feature of it, the badly made ones are the ones that fit tight.
The narrow lenses snug up to the adapter before touching the camera so the whole system doesnt work.
With the wobbly lens u get to infinity fine? I.e. does it register properly despite not touching the camera face?

I think so. And my general impression was that with k-mount m42 lenses focus slightly past infinity anyway.

It could be worth to look into modding the lens rather than the camera, since it is the actual contact of the back of the lens with the camera that helps supporting its weight rather than allowing leverage right onto the working parts of the mount (not sure if I explained myself). in some lenses there little to no space to work so it all depends on what you have in hand

Don't wan't to modify the lenses, as I'll want to be able to use them on the m42 cameras.

There are also adapters with a flange, u lose infinity though.
That I know many that had your problem just solved it with rubber o-rings or other rubber seals for shafts which would take up the slack, not sure it works for all or if it allows proper registering of the lens, but if it works for them it might be just the easier way to solve your problem

That sounds fiddly, esp. when changing lenses.

The ones that have the shoulders slightly recessed might require sanding down the face of the adapter, if there is enough meat
Either way the lens shoulder should be flush with the surface of the camera mount to be registered properly

Sanding down the adapter might actually work. It will mean that the lens's focus registry mark screws on past 12 o'clock (I wonder how far past), but that's not a bid deal.

But no solution that doesn't fix the adapter firmly in the mount, by either gluing it or tightening it with screws, will fix the light-meter lever in place (one could always glue the lever itself, but that's an even less reversible mod than gluing the adapter to the mount).

 

[Lucius]

The Chinon weighs 485 grams. The Vivitar weighs 370 grams. Whether auto exposure is important depends on what your subjects are.

With non-native m42 cameras where I don't have auto-stopdown, I prefer to shoot in auto-exposure mode (it's less fiddly), but of course I will often use exposure lock in unevenly lit situations. And as long as the camera sits comfortably in my hands (and the CE4s does, unlike e.g. the huge CE), weight isn't too much of a consideration.

By wanting to shoot wide open, it looks like you are photographing subjects that are not too far away. With distant subjects, photos shot wide open and closed down do not look very different. For more distant subjects try using a lens with a maximum aperture of f/2, for example. That will also cut down on weight.

Yes, distance shots I would normally shoot at around f5.6, and at this aperture I don't need 1/2000 shutter speed, so there are a few native m42 options (including the Chinon CS4) I'm reasonably happy with.

 

[Snoop]

I like the idea! I'd need to be able to thread holes, and get some 'headless' screws of the right length that wouldn't interfere with the m42 threads, but it sounds doable.

the grubs can be made easily by cutting the head off a micro screw and cutting a slot and for threads a set of micro taps is about 15$
If there is enough meat you could instead drill the face of the adapter to catch the mount tabs and countersink the head of a flathead screw (the ones made like a cone), in that case there are microscrews that are selftapping, you wouldnt even have to mess around the M42 thread

Whatever works, if you have the small tools needed u can use mechanical fasteners otherwise do not rely much on solvents to reverse the mod if u use glues, just shim it to be tight (if all focus past infinity you have room) and epoxy glue it with a few dots of glue where u can put heat to with the tip of a soldering iron if you wanted to soften the glue in the future...

PS: the ones that tried to bend the tabs of the adapter to tighten the fit, ended with the thing tight when putting it on the camera, wobbly when on and very difficult to take off the camera... careful about that in case you thought about it

 

[mshchem]

Nevermind

 

[Lucius]

sanding down the face of the adapter, if there is enough meat

I've got now a cheap adapter, but it protrudes above the camera mount, preventing the lens from focusing to infinity (as well as from screwing in fully to the 12 o'clock position). Some tenths of a millimeter need to be sanded off. What grade of sanding paper (or something else?) should I use?

(And speaking of infinity focus, is it really that important that the lens can properly reach infinity? At such distance, one will normally shoot at a smaller aperture, making the depth of field deep enough to cover infinity anyway, am I wrong?)

 

[Paul Howell]

That is really odd, M and K have the same flange to film distance, just crappy design. Can you return it?

 

[Snoop]

I've got now a cheap adapter, but it protrudes above the camera mount, preventing the lens from focusing to infinity (as well as from screwing in fully to the 12 o'clock position). Some tenths of a millimeter need to be sanded off. What grade of sanding paper (or something else?) should I use?

(And speaking of infinity focus, is it really that important that the lens can properly reach infinity? At such distance, one will normally shoot at a smaller aperture, making the depth of field deep enough to cover infinity anyway, am I wrong?)

it depends on the lens you are using and how you use I think
In some cases you have the one lens that you use only for portraits, and maybe you dont even care about landscapes or getting to infinity, if you then dont even ever need to shoot using only the marking on the lens then I would guess it matters little. Some I know couldnt care less if they lose infinity, they never look at the lens scale, they never shoot in conditions where they cant look in the viewfinder, it works for them and they are happy
What if you were taking pics of the moon?
In your case also its not even just one lens that is off, its every lens that goes on that adapter.
(plus the nag thing of having something that is supposed to work properly but it doesnt, and that you can make to work properly without too much fuss...)

You can start with a 150 or 220 and work finer and finer, dont skip from 150 directly to a 400 though, it takes a lot of time for very fine grades to cut down the scratches of a much coarser grade and you use more paper because u will wear it down before it finishes the job. If its really just a hair to take off you can start with a 320 too, or if you are worried the 150 is too coarse to begin with.
Know that is best to have a light touch and take your time than going ape on it and leave gauges, each gauge is a lot more work to eliminate later on
take a measurement of the thickness at different spots around with a caliper before sanding, if you can check how much you need to take off, slack included
Put the sheet of sandpaper on a flat surface, the flatter the better, marble countertop or glass sheet would be ideal, try to use the best you have at hand. Put the adapter face down on the sandpaper and sand it in a small circular motion or drawing 8s. Do not keep the fingers on the same spot as the pressure is not the same and you will end sanding more on one side, just switch the hold all around the adapter, measure the thickness, repeat until good then finish it smooth, a 1000 or so will leave a nice surface, if you have the tools you can polish it fully
I know many would stop much earlier than 1000 or polishing but polishing the surface is to not ruin the lenses overtime
If you ever think to try it on the camera half way along the work to see if its good or to check if you are actually done before putting work in polishing then wash the adapter well with soap first and an old toothbrush, the suds will carry away every small part of dust, you dont want any of it near the camera body and just brushing it leaves always some, dry well with an hair dryer.

PS: do yourself a favor, remove the spring and replace the screw in the adapter, you wont have to deal with dust going under it or in the screw hole

 

[Lucius]

it depends on the lens you are using and how you use I think
In some cases you have the one lens that you use only for portraits, and maybe you dont even care about landscapes or getting to infinity, if you then dont even ever need to shoot using only the marking on the lens then I would guess it matters little. Some I know couldnt care less if they lose infinity, they never look at the lens scale, they never shoot in conditions where they cant look in the viewfinder, it works for them and they are happy
What if you were taking pics of the moon?
In your case also its not even just one lens that is off, its every lens that goes on that adapter.
(plus the nag thing of having something that is supposed to work properly but it doesnt, and that you can make to work properly without too much fuss...)

I understand that, I was just wondering if there was something 'special' about infinity focus -- which the increased depth of field at narrow apertures couldn't substitute for. I guess tele lenses may never cover infinity even at f16, where a normal or a wide lens would do fine.

You can start with a 150 or 220 and work finer and finer, dont skip from 150 directly to a 400 though, it takes a lot of time for very fine grades to cut down the scratches of a much coarser grade and you use more paper because u will wear it down before it finishes the job. If its really just a hair to take off you can start with a 320 too, or if you are worried the 150 is too coarse to begin with.
Know that is best to have a light touch and take your time than going ape on it and leave gauges, each gauge is a lot more work to eliminate later on
take a measurement of the thickness at different spots around with a caliper before sanding, if you can check how much you need to take off, slack included
Put the sheet of sandpaper on a flat surface, the flatter the better, marble countertop or glass sheet would be ideal, try to use the best you have at hand. Put the adapter face down on the sandpaper and sand it in a small circular motion or drawing 8s. Do not keep the fingers on the same spot as the pressure is not the same and you will end sanding more on one side, just switch the hold all around the adapter, measure the thickness, repeat until good then finish it smooth, a 1000 or so will leave a nice surface, if you have the tools you can polish it fully
I know many would stop much earlier than 1000 or polishing but polishing the surface is to not ruin the lenses overtime
If you ever think to try it on the camera half way along the work to see if its good or to check if you are actually done before putting work in polishing then wash the adapter well with soap first and an old toothbrush, the suds will carry away every small part of dust, you dont want any of it near the camera body and just brushing it leaves always some, dry well with an hair dryer.

PS: do yourself a favor, remove the spring and replace the screw in the adapter, you wont have to deal with dust going under it or in the screw hole

Thanks, that's incredibly detailed -- and extremely helpful! I've ordered different grades of sandpaper, and will give it try. There doesn't seem to be a lot of metal, so should be feasible.

 

[Snoop]

I understand that, I was just wondering if there was something 'special' about infinity focus -- which the increased depth of field at narrow apertures couldn't substitute for. I guess tele lenses may never cover infinity even at f16, where a normal or a wide lens would do fine.

As practical thing the lose infinity focus becomes "no matter what objects far away are not in focus" a wide angle is gonna be more forgiving, they have greater DOF at wider apertures, but on a tele you cant really substitute the aperture for a lack of focusing, specially on the ones that need more light (at least in my experience), so sometimes yes you can use DOF to solve, sometimes you cant.
when the problem is at the lens well then you can compensate, ignore it, recalibrate the lens, when its on the body it messes up with everything u put on it

Thanks, that's incredibly detailed -- and extremely helpful! I've ordered different grades of sandpaper, and will give it try. There doesn't seem to be a lot of metal, so should be feasible.

No problem, hopefully you will enjoy making it work as it should, lots can be done even with minimal tools, important thing is to be a bit anal in measuring and modifying, just dont rush it.

 

[Paul Howell]

All of my M42 to Pentax, Minolta A mount and Sigma SA mount adaptors fit flush , all will focus to infinity.