[aslyfox]

there is a thread about photos taken by 28mm lenses

https://www.pentaxforums.com/forums/122-lens-clubs/168895-dslr-fun-28mm-club-any-28mm-lens.html

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I have one that I like a lot

Kino Precision Japan Kiron 28mm F2 MC P/KA prime 55 F

Kiron 28mm F2 MC Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database


For contemporary magazine reviews of this lens see here.

Page 50

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Fast 28mm wide angle, also sold under the Vivitar marque, can be found in M42, PK and, more rarely, PKA, mounts.

Construction; 8 elements in 8 groups
Filter Diameter: 55mm
Aperture: f2 - f16, half clicks, with DOF scale on barrel
Iris: 6 blades
CFD: 0.3m / 12"
Focus throw: ~ 120 deg rotation
Length: 5cms.
Weight: 284g / 10oz
FOV: 66 Degrees (Horizontal) on full frame.


Read more at: https://www.pentaxforums.com/userreviews/kiron-28mm-f2-mc.html#ixzz5KOga2ZOW

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Last edited by aslyfox; 07-05-2018 at 09:18 AM.

[Ronald Oakes]

Warning! Ricoh Pin may jam with the AF drive pawl.

While not all "P" series Rikenons have the "pin" variant that is sure to foul your Pentax AF camera, all potentially are sources of significant grief. Do a Web search on the term "Ricoh Pin" for many sad stories as well as guides for detection and assessment of risk.


Steve

Never jammed on any of the 7 Pentax bodies Ive used.....ever. The pin on these is rounded on the end.
Also....if the worry over this still persists , its super easy to remove the pin !
This is somewhat specific to the exact lens used. 28mm is fine.....50mm 1.4 ISNT.

[aslyfox]

Warning! Ricoh Pin may jam with the AF drive pawl.

While not all "P" series Rikenons have the "pin" variant that is sure to foul your Pentax AF camera, all potentially are sources of significant grief. Do a Web search on the term "Ricoh Pin" for many sad stories as well as guides for detection and assessment of risk.


Steve

Third Party Variants of the K-mount
Pentax made the original "K" mount available for other camera manufacturers to adopt. The goal was to create a universal standard bayonet mount much like the M42 screw mount had been. Ricoh, Chinon, and others produced cameras and lenses with the "K" mount. Unfortunately, with the introduction of the "KA" mount, Pentax reversed the decision with the result that the other manufacturers either abandoned the "K" mount or developed their own, somewhat incompatible, enhancements. Several third party lens manufacturers produce or has produced lenses with a K-mount. There are no issues with current third party lenses in K-mount, but for older lenses there are two traps to watch out for:


The infamous "Ricoh pin". Where Pentax created the "KA" mount in order to support Program and Tv exposure automation, Ricoh had to create their own variant, which has a protruding pin placed in a somewhat unfortunate location, namely in the exact spot where Pentax years later placed the autofocus drive shaft. Such a Ricoh lens will get stuck when mounted on a Pentax autofocus body - the Ricoh pin will get lodged in the drive shaft and prevent the lens from being removed without deployment of finesse, patience and tools.

The other trap is the shield that protects the aperture stop down lever. The image to the left shows what the shield should look like and does look like on a genuine Pentax lens. Some older third party lenses have a much larger shield which prevents mounting the lens on a Pentax DSLR. Current third party lenses (Sigma, Tamron, Rokinon, etc.) have correctly shaped shields (or no shields) and pose no problem.


Read more at: The Evolution of the Pentax K-mount - Articles and Tips | PentaxForums.com

[stevebrot]

Never jammed on any of the 7 Pentax bodies Ive used.....ever. The pin on these is rounded on the end.

That is fine for your specific lens. My warning stands.

Also....if the worry over this still persists , its super easy to remove the pin !

...before or after having to carve the lens off the camera with a hacksaw? (Worst-case scenario)

Sorry to sound reactive, but the risk is real. I have dodged the bullet a couple times when I noticed the "P" on the aperture ring of a 3rd-party lens having a dangerous variant of the pin. FWIW, I own a Rikenon-P 50/2 that is safe on my K-3...so far. I have other non-P Rikenon 50/2 and the "P" resides on an XR7.


Steve

[stevebrot]

The infamous "Ricoh pin". Where Pentax created the "KA" mount in order to support Program and Tv exposure automation, Ricoh had to create their own variant, which has a protruding pin placed in a somewhat unfortunate location, namely in the exact spot where Pentax years later placed the autofocus drive shaft. Such a Ricoh lens will get stuck when mounted on a Pentax autofocus body - the Ricoh pin will get lodged in the drive shaft and prevent the lens from being removed without deployment of finesse, patience and tools.

Thanks for copying the text with explanation. The difficult aspect of the Ricoh Pin is that there are at least three variants in the Rikenon-P line, only one of which is deemed "safe".* 3rd-party offerings are even less predictable. Awareness and vigilance with legacy K-mount glass is the price we pay. What is even more confusing is the existence of combined KA/RP mounts on 3rd-party lenses where both Pentax and Ricoh contacts are present. People should not black-list all Rikenon lenses, but when equivalent offerings (say the XR Rikenon 28/2.8) are available.


Steve

* The safer variant is a low profile ball-type contact similar to those on Pentax-A lenses. This version is less likely to foul, but care should still be taken to retract the AF pawl before mounting.

[Ronald Oakes]

That is fine for your specific lens. My warning stands.



...before or after having to carve the lens off the camera with a hacksaw? (Worst-case scenario)

Sorry to sound reactive, but the risk is real. I have dodged the bullet a couple times when I noticed the "P" on the aperture ring of a 3rd-party lens having a dangerous variant of the pin. FWIW, I own a Rikenon-P 50/2 that is safe on my K-3...so far. I have other non-P Rikenon 50/2 and the "P" resides on an XR7.


Steve

Ok...Ok....You win !
I learned long ago this "generalization" doesn't affect all Ricoh "P" lenses.
Due diligence is in order mounting ANY third party lens.

[kiwi_jono]

Depends on budget. I have a K 28 f3.5 which is good, but also have a FA28 f2.8 which I prefer for its colours, good performance (similar to K 28 f3.5 actually) and convenience.
Of course I use the DFA28-105 even more as its pretty good at 28mm (surprisingly it has better average sharpness but at the expense of higher distortion and vignetting).

[pinholecam]

Pentax K28/3.5 is probably the best one from Pentax for landscape.
Its pretty bland for anything else though imo.

M28/3.5 is very sharp for closer subjects, but has lots of field curvature and there will be problems on FF for edge sharpness because of this.

Kiron 28/2, is only not a bad lens on apsc and if its cheap. I find that its far weaker on FF.

I have read good things about the FA28/2.8, though I have not tried one nor looked at its photo samples on the edges stopped down.

In general, the 3rd party 24, 28mm generally are so cheap as to be harmless to try.
Usually, poorer contrast and flare tolerance, and not Pentax colors, though they can be sharper and/or focus closer.

[jawats]

Hmm...well, I just unexpectedly won a Super-Tak 28/3.5 on an auction, so I am going to give it a whirl. Now I'll have Taks in 28/3.5, 35/3.5, 50/1.4, 55/1.8, 135/3.5.

[Ronald Oakes]

Hmm...well, I just unexpectedly won a Super-Tak 28/3.5 on an auction, so I am going to give it a whirl. Now I'll have Taks in 28/3.5, 35/3.5, 50/1.4, 55/1.8, 135/3.5.

That's a nice Takumar kit you have there. All your bases are covered.

[jawats]

That's a nice Takumar kit you have there. All your bases are covered.

Thank you, Ronald. I just ordered a couple extra "ring" adapters, as well.