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Forum: Pentax Mirrorless Cameras 03-02-2018, 12:35 PM  
Behind-the-Mount 20-40 for K-01
Posted By Fogel70
Replies: 16
Views: 5,343
That is the problem. As with an optical design like EF-M 22 mm the front lens would have to be behind the mount on K-mount camera. The rear lens barrel on EF-M 22 is quite large and looks to be more than 24mm in diameter which is the height of the mirror box. Where to fit motor and electronics on a lens like this?

It may be possible if making a non backward compatible version of K-mount where power zoom contacts and mechanical aperture lever is removed from the camera, and new AF contact is added on the mount.
Forum: Pentax Mirrorless Cameras 02-28-2018, 02:43 AM  
Behind-the-Mount 20-40 for K-01
Posted By Fogel70
Replies: 16
Views: 5,343
Then why do you not explain how to design fast pancake lenses with help of an protruding rear of the lens.


Are you saying that lenses like DA21 is not possible?


---------- Post added 02-28-18 at 01:28 AM ----------

So what is the relation between exit pupil position and vignetting/color shifts?
Forum: Pentax Mirrorless Cameras 01-23-2018, 11:37 PM  
Behind-the-Mount 20-40 for K-01
Posted By Fogel70
Replies: 16
Views: 5,343
I would say it performes quite bad. A f/5.6 FF lens that performs that bad on APS-C is not what I would call OK. If you want a compact 12mm lens for APS-C mirrorless, Zeiss Touit seems to be a better choice. The Zeiss is a little larger, but it is f/2.8 and has AF.

I don't see any rear lens element protruding a couple of centimeter into the mount on DA15. As you know the problem increase the closer the rear lens element sits to the sensor.
Forum: Pentax Mirrorless Cameras 01-22-2018, 09:45 PM  
Behind-the-Mount 20-40 for K-01
Posted By Fogel70
Replies: 16
Views: 5,343
Lens design like that would not work well for digital as it would lead to lost IQ in the corners and severe vignetting.
On digital the rear lens element must be big to avoid problems like that, which means the lens mount must be close to the sensor if to design ultra compact wide angle lenses.

With a short register mount APS-C 12/5.6 lens would be quite compact.

Does the above lens even have any focusing mechanism? I can imagine it would be difficult to fit inside a tiny lens barrel like that.
Forum: Pentax Mirrorless Cameras 01-14-2018, 10:57 PM  
Behind-the-Mount 20-40 for K-01
Posted By Fogel70
Replies: 16
Views: 5,343
JuThat is not a way to design lenses for mirrorless if mirrorless is a system designed for the future users.
K-mount will just be a severe limitation on lenses designed for mirrorless, and much of the point of using K-mount is lost if lenses are designed not being compatible with K-mount.

And designing lenses that protrude into the lens mount will also put severe limitation on optical and mechanical design. So it can only be used on very slow lenses, but once the lenses get very slow they can be designed very compact without protruding into the mount.

It's not by chance all manufacturers of mirrorless have choosen a new mount for mirrorless. It is the only way that make sense on a future proof system. It's only on a new mount that lenses can be fully optimised for mirrorless.
Forum: Pentax Mirrorless Cameras 01-14-2018, 12:34 AM  
Behind-the-Mount 20-40 for K-01
Posted By Fogel70
Replies: 16
Views: 5,343
The retractable 18-50mm zoom is very compact.
K-01 had made more sense if that lens had been available as kit zoom for K-01.
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