[mars76]

Hi All,

I recently bought a Sigma Sigma 135-400mm 1:4.5-5.6 APO lens and it has "for SA/KPR" written on the back cap.

Is this a Sigma Mount ? what ever i have read so far tells me that it has to be either Pentax PK Mount or Sigma Mount.

From the pictures it doesn't look like it is Pentax PK Mount.

What options do i have to mount on K-50 if that is feasible.

Note: when i tried to mount on one of my K-r it didn't fit securely.

Thanks

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[surfar]

Its a K mount,small amount of play in the mount...about the same as the 10-20 Sigma.

[boriscleto]

Sigma mount.

[surfar]

Sigma mount.

Yes...For K mount.

---------- Post added 11-28-18 at 07:43 AM ----------

What options do i have to mount on K-50 if that is feasible.

All the Sigma lenses i own have a small amount of play,its nothing to worry about they wont fall off!

[boriscleto]

Yes...For K mount.

---------- Post added 11-28-18 at 07:43 AM ----------



All the Sigma lenses i own have a small amount of play,its nothing to worry about they wont fall off!

Look at the photos. That is not a K-mount lens. It is Sigma SA. Seven electrical contacts similar but not identical to Canon EF and an electromagnetic aperture...no aperture lever...

Sigma used the same rear lens cap for both SA and K-mount. The are very similar mechanically, but electrically they are different, and the SA has a shorter register, 44mm like Canon EF.

[mars76]

Thanks for the info.

Is there a way i can use the SA mount on my Pentax K-50 ?

[boriscleto]

Thanks for the info.

Is there a way i can use the SA mount on my Pentax K-50 ?

No. The focal flange distance (register) of SA is 44mm, K-mount is 45.46mm. There isn't a direct way to use K-mount lenses on Sigma cameras either (you have to remove the aperture lever). Also the aperture is controlled electromagnetically...

[surfar]

Look at the photos.

Yes, just did...you are correct,I only looked at the lens cap.Also looked at my 135-400...its different from the photo.

Is there an adapter to K-mount?

[mars76]

I found a video of a guy converting Sigma SA mount to Canon Mount.

You Tube

You Tube

( Not sure whether the focal flange distance of Sigma SA and Canon EF are same).

It looks like the Register distance is same for Sigma SA and Conon (44mm)

https://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html

Not sure whether it will be same for pentax as well.

[FozzFoster]

All the Sigma lenses i own have a small amount of play

No Sigma glass I've ever owned had play when mounted on my K-S2..

[pres589]

If Sigma offered this lens in k-mount, the have a service to change the lens over. If the lens wasn't offered in k-mount, then it's off the table. You can contact Sigma to find out if this is viable for your lens.

I don't know how good or bad this lens is. If it's really good it might be worth it. Or you just sell it and get something else. I have a hunch that the latest Pentax 55-300 would outperform it. You can crop long shots down to make it like a 400 to make up for the shorter max reach.

The SA mount always seemed like Sigma ripped off Pentax and Canon for ideas for their mount. Kind of a Sigma thing to do. The old Sigma SA-1 film camera actually was a 100% true k-mount (they didn't make it themselves). Sigma lens caps work on true k-mount lenses but aren't as nice as real Pentax caps as they only go on in one position and not three like Pentax's. They're larger though and cover contacts on the back of the lens better which may be of some benefit.

[boriscleto]

If Sigma offered this lens in k-mount, the have a service to change the lens over. If the lens wasn't offered in k-mount, then it's off the table. You can contact Sigma to find out if this is viable for your lens.

That only applies to "Global Vision" lenses(Art, Sport, Contemporary). This lens is much older...

[pres589]

Ah. Bummer.

[mars76]

Yes i contacted Sigma and said they don't offer conversion for this lens as it is much older.

Thanks for all the info.

[swestin]

I found a video of a guy converting Sigma SA mount to Canon Mount.

Sigma SA to Canon EF - YouTube ( Not sure whether the focal flange distance of Sigma SA and Canon EF are same).

It looks like the Register distance is same for Sigma SA and Conon (44mm)

Camera Mounts Sorted by Register

Not sure whether it will be same for pentax as well.

This page has been superseded by https://stephen-westin.com/misc/mounts-alphabetical.html; I haven't worked at Cornell for over 15 years, and I don't have any way to replace that page to redirect it.

And my comparison between Sigma and Pentax K mounts is at Comparison: Sigma SA mount vs. Pentax K. One visible difference is that the KA and newer mounts have electrical contacts in the surface of the mount itself, but the Sigma SA mount puts them inside the throat of the mount.

– Stephen H. Westin