K-mount adapters for Pentax new-mount cameras

Started 11 months ago | Discussions thread
TacticDesigns Veteran Member • Posts: 6,092
Re: Another adapter variant . . . no motors + focus aid switch

Skip py wrote:

TacticDesigns wrote:

. . . with mirrorless, would it be possible to just let the lens stop down as you turn the aperture dial on the lens.

(For lenses that don't have an aperture dial, a dial on the adapter would let you open up and close down the aperture.)

The camera then takes a light reading on the stopped down lens for exposure calculation. And then just brightens up the EVF or rear screen to make composing possible? Basically a WYSIWYG way of displaying the scene.

To help with manual focusing . . . there could be a lever on the right side of this adapter that you press with your middle finger on your right hand. Sort of like the opposite of a DOF preview button. So when you press this focus aid switch, it opens up the lens so that you can focus with the lens at the shallowest depth of field.

This switch could be locked into position so that you can just concentrate on focusing. And then be release for the actual picture.

But this switch could also be pushed and held to focus, and then just released to take the picture. Locking is an option, not a requirement.

I like the idea. I'll have to think more about it : seems interesting ...


Yeah. It's a bit of a weird idea.

I guess I see two downsides.

#1 Without an aperture actuator, the camera loses the ability to control the aperture on the lens, which means . . . no shutter priority mode, full program exposure mode, or for that matter, no fancy scene modes either. So the camera, with this adapter, would only be able to do metered manual and aperture priority.

I would be ok with that. It would be like going back to a Pentax K1000 or Pentax ME Super. I used both. My sister had a Pentax K1000 and I had a Pentax ME Super.

#2 With Pentax-M and m42 lenses . . . the aperture value is not automatically recorded to the EXIF data.

But it's not like we had this with Pentax-M and m42 lenses with any Pentax dSLR anyway, so its not like we are losing anything. A work around could be that you could use the front dial on the camera to dial in an aperture value that then gets recorded down to EXIF. So if you have the lens set to f/2 . . . you could just dial f/2 into the camera with the front dial and that would get recorded in the EXIF info.

I guess the way I look at it is . . . these are old lenses.

If I could get a nice metered manual and aperture priority mode on a modern full frame mirrorless camera, I'd be laughing!

If I want the full program mode, shutter priority or scene modes, I could either get the more expensive adapter (with built-in aperture actuator) or get native mirrorless lenses.

But . . . with the focus assist switch (reverse DOF preview button), it could add aperture priority to Pentax-M and m42 lenses, without the need to press the AE-L button to do a stopped down meter reading.

Hey . . . maybe even bring in one for m42 auto lenses? So when you press the focus aid switch it would activate the auto aperture pin of the auto m42 lenses.

... even more if I can use my old K/M/m42 lenses !



I sold off my Pentax 50mm f/1.4 m42 mount lens. I'm kicking myself for doing so. LOL.

A built-in switch to stop down / open up the lens would make it easier to use a m42 lens. And if there is an adapter, there would probably be space to put in a switch to push / release that m42 pin on the lens mount.

For me . . . a big bonus potential of mirrorless is to bring back the match needle metering in the viewfinder.

The last film camera I used was my sister's Pentax K1000. And I still remember how fun and simple it was to use that match needle metering system.

I can understand why this system isn't used in dSLR cameras. LOL.

But for mirrorless cameras with an electronic viewfinder . . . it would just be a program running to display the current meter reading as a needle in the viewfinder.

That . . . would be cool!

Take care & Happy Shooting!

Regards, Fred

-- hide signature --
 TacticDesigns's gear list:TacticDesigns's gear list
Fujifilm XP80 Nikon D5100 Pentax Q Nikon D750 Nikon D7000 +7 more
Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow