M42 Screw-mount lenses on Pentax DSLR cameras Overview

Today I’ll be showing you some M42
screw mount lenses, and how they work with Pentax cameras. Have three lenses
with me today. Have a 128mm F/2.8 Mamiya Sekor M42 mount. Screw type mount. Aperture pin. There’s an auto/manual knob you can
change. The pin become spring-loaded and it cycles the aperture. Not cycles…
but it changes the aperture. Pretty simple layout. Got your manual aperture
control. Auto aperture setting. We don’t use that on current cameras, so just
leave that in manual. You’ve got your focus ring. This lens is pretty tight, so it makes
it difficult to use. I also have a Chinon 55mm F/1.7 this is my favorite M42 lens that I have. Nice smooth… it’s clean. Aperture works nicely.
It’s pretty rounded for an older cheap lens. Also have a Mamiya Sekor 55mm F/1.4. Really rough, glass is dirty. Aperture does work, but it’s kind of…
Not sure what I would call it. It’s not really close at all to being round.
Probably changes as I cycle it. Focus ring gets looser as I rotate it.
Anyways, so we’ve got three M42 lenses here. I have a Pentax *ist D camera body
to use as an example. Of course, it’s got the K-mount. Have an adapter here this is
the M42 to K-mount adapter. This is the official Pentax one. It’s got a metal
piece here. That locks the adapter into place once you rotate it. The pin will
slide and then won’t be able to rotate until you push down on this metal. And
then I’ll show you an example. It’s got an orange dot. So orange dot to orange dot. So it’s in place. You have to rotate it. That’s locked in. See it won’t move. To
unlock it.. you’ve got that metal piece in there you push down on it rotate it backwards.
Pull it out. So once I get this back in. Lock it into
place… It’s locked down. Use the Chinon. All you
do is rotate it until you can tell that it’s no longer going to move. Put your
aperture into manual. You don’t really need to deal with that. Got your aperture
ring. That’s how you control that. Focus ring… Ahh, Pentax cameras… this is an older body, but all of them you’ll get focus confirmation. You know, the red dots in
the viewfinder with manual lenses. This is an older body. It doesn’t have Shake
Reduction, but all of the more recent Pentax bodies have in.. in-body shake
reduction. So with M42 lenses you’ll get — shake reduction. Which is a great
feature to have with, you know, older thirty-year-old lens or something. You
can also get catch-in-focus setting. So what you do.. You’ll put that catch-in-focus setting on. And you’ll rotate your focus ring and the camera will take a
photo once it sees that the picture is in-focus. Based on, I guess, I haven’t used it much, but… on whatever focus point. So besides that, metering
will work just fine with the M42 lenses. So all you really need to care
about is your aperture, and of course your focus.

11 Replies to “M42 Screw-mount lenses on Pentax DSLR cameras Overview”

  1. Great info man. Can you tell me about the m mount lenses? will those work with the pentax dslrs without an adapter? I have a pentax KR and I want to buy the m-50 1.2 prime lens

  2. @Amithrius The Leica M mount? I don't think that would work on 35mm SLR cameras. Maybe you mean the Pentax-m lenses? Those will work fine on all Pentax DSLRs, but they are of course completely manual with aperture and focus.

  3. They do take longer to take off. Generally the adapter will stay in the camera unless you remove a thin metal piece from the adapter. If you do remove that piece of metal you can basically use the M42 lens like a k-mount one because the adapter will have more friction with the lens and stay on there.

  4. Hi, for shake reduction on an old zoom lens,what focal length I have to set. let's say 75-300mm?75mm or300mm? thanks

Leave a Reply

Your email address will not be published. Required fields are marked *