I know this was recently covered to some extent recently, but can't find that thread, so I want to focus this thread on an issue only suggested in that thread.
To adapt a Pentax K mount lens to Canon full frame, you need an adapter and to trim off the aperture control lever from the K lens mount. However, if you ever wanted to use the lens (particularly, an older one) on a future Pentax or Samsung DSLR (supposedly several in the works according to a Japanese investment analyst report) you are out of luck.
Instead (and hopefully I've got this right), how difficult is it to just open the lens mount and remove the aperture lever, and save it for later, just in case you might need it? I'm this is going to be different for different K-mount lens across different manufacturers, but should this be easily do-able?
Is there anyone who has done it? Any tips and/or advice for anyone tempting this? Thanks.
Lotusm50 wrote:
To adapt a Pentax K mount lens to Canon full frame, you need an adapter and to trim off the aperture control lever from the K lens mount.
You don't have to remove the aperture control lever for a 1.6x CF body. You do have to remove it for a FF body. I'm not sure if you need to do it for a 1.3x CF body (but I can check at home tonight).
Lotusm50 wrote:
However, if you ever wanted to use the lens (particularly, an older one) on a future Pentax or Samsung DSLR (supposedly several in the works according to a Japanese investment analyst report) you are out of luck.
In this recent thread: https://www.fredmiranda.com/forum/topic/694185/0#6245645, mawz pointed out that -A and more recent lenses (with electronic contacts), were a problem with Pentax DSLR bodies, but earlier Pentax K-mount lenses (i.e. -M and "plain K" lenses) are still completely useful on Pentax DSLR.
Lotusm50 wrote:
Instead (and hopefully I've got this right), how difficult is it to just open the lens mount and remove the aperture lever, and save it for later, just in case you might need it? I'm this is going to be different for different K-mount lens across different manufacturers, but should this be easily do-able?
It depends on the lens. On my SMC Pentax 18mm f/3.5, the aperture control lever is one continuous part (albeit, very bendy) all the way from the offending lever to the diaphragm itself. On this lens, removing the aperture lever would disable the diaphragm, so I cut it off.
Generally, it's not difficult to take off the mount ring and base cover (if the lens has one). Then you can have a closer look at the aperture control lever to see if it is a simple job to remove it (as it is on some lenses), or if it extends further into the lens body. In the latter case, you're on your own. I've opened and successfully closed many Pentax and third party K-mount lenses, right down to the aperture blades (and beyond), but there's a few in a drawer that weren't so easy to put back together. I'm confident that they could be reassembled by a repair pro, but that would cost more than getting another copy of the lenses in question.
jcolwell wrote:
You don't have to remove the aperture control lever for a 1.6x CF body. You do have to remove it for a FF body. I'm not sure if you need to do it for a 1.3x CF body (but I can check at home tonight).
This would definitely be for a full frame Canon -- but would like to be able to keep my options open for the future. I'm still rooting for the underdog Pentax to come through with something spectacular. ;-)
If you cut the lever and the guard you will still be able to use the lens on a Pentax body
but it will be fully manual. If you are interested in mounting a lens without cutting and
devaluation, Nikon AIS lenses can be mounted successfully on a 5D as they are.
There are a couple of informative posts on the net. Search Pentax lens to 5D.
gtmerideth wrote:
If you cut the lever and the guard you will still be able to use the lens on a Pentax body
but it will be fully manual.
I am aware of this, but am looking to see if i can b used and be reversible so it would function fully on a Pentax.
gtmerideth wrote:
If you are interested in mounting a lens without cutting and
devaluation, Nikon AIS lenses can be mounted successfully on a 5D as they are.
I currently have 5 manual focus Nikon AIS mount lenses that are used on a 5D so I am well aware of this. I was asking specifically about Pentax K mount lenses and how adapting them for use on a Canon full frame camera can be reversible.
jcolwell wrote:
You don't have to remove the aperture control lever for a 1.6x CF body. You do have to remove it for a FF body. I'm not sure if you need to do it for a 1.3x CF body (but I can check at home tonight).
To convert a K mount lens to be used on a Canon 1.3x or FF body you need to remove the stop-down lever and (on most) cut off the guard that protects the lever.
Disassembling most Pentax primes to do this in a reversible fashion is not terribly difficult. If you can do a Rokkor conversion you're more than set to do the Pentax conversion. The guard removal is irreversible but does not affect function. Removing the stop-down lever only affects function on A and later Pentax lenses for Pentax DSLR's, it in fact can improve function of pre-A lenses on the Pentax DSLR's as it would turn the lens into a preset lens and thus enable Aperture priority metering with pre-A lenses (which is not possible with non-preset lenses normally).
Of course this would cause all sorts of issues with the film bodies (all of which have the aperture simulator that would cause metering issues with preset-converted lenses. The few which don't have an aperture simulator don't support pre-A lenses anyways).
Frankly, if I ever do get a 5D, I'd be seriously tempted to do this for a set of FA Limited primes.
hotwire wrote:
I don't even own any Pentax kit and the thought of that makes me cringe.
Why? Unlike the Rokkor conversions, a properly done leverectomy is completely reversible from a function standpoint (The only permanent change is removing the lever shield).
In fact I'm kinda tempted to get a SMC-M 50/2 and try a Nikon-mount conversion just for the hell of it. If it's doable, maybe some nice Pentax glass too.
On some Pentax lenses (like my SMC Pentax 18/3.5), the aperture control lever is a single, solid (and very twisty) piece of steel that goes from the outside end, all the way in to the diaphragm itself. If you remove this lever, then the aperture is completely disabled, and will not respond to the aperture ring. It might be possible to get a replacement aperture lever from the Pentax spare parts department, and make a "short" one, but that wasn't practical for me, so I cut it off. I use it frequently, and so it's no sweat off my nose. Also, based on my experience with selling other Pentax lenses that have had the "irreversible" procedure performed on them (including the sought-after SMC Pentax 200/2.5), it has no effect on resale value.
