[Sandy Hancock]

I don't know if you'll find anyone that owns both

You can add me to the list

[pevik]

The only difference to my knowledge is that the A version has the A position available on the aperture ring. This allows the A version to be used in auto-exposure modes, opens up advanced metering modes, allows aperture to be controlled from the body, and records aperture in the EXIF. I have the K version, and I think it's an excellent lens even though I need to use the green button for stop down metering.

Good to know, thanks!

the optics are the same, but I would imagine that there were changes to the coatings over the years also....

the difference in the K/M/A series isn't quality or price, but age - the K series were the first K mount lenses, which progressed through the M series, to the A series of lenses ..

So it means K is an ancestor of an A

In addition to the above, the "A" version has 9 aperture blades compared to the "K" 's 8. Although I guess most owners don't use them much

How does number of aparture blades affect the final result? Providing you shot the same object, same light, same aperture (f5.6 for instance) - how would final pictures differ? Does it affect bokeh? :?

In addition to the above, the "A" version has 9 aperture blades compared to the "K" 's 8. Although I guess most owners don't use them much

Yeah I just decided to buy one from an eBay for $330. Not very cheap but all the "A" lenses were more expensive by $100-250...

Other than the aforementioned modern benefits there really isn't a world of difference between the two lenses, I'm personally much happier with the older "K" version.




Pentax K-1 SMCP-K 50mm f/1.2 @ f/1.2 ISO 100 1/640th

That's amazing!

I don't know if you'll find anyone that owns both, they're pricey lenses and not that easy to find for reasonable prices.

TBH it sounds like you'd be better off starting with an M or A 50mm f/1.7 to see if you like manual focus, especially with fast lenses wide open (which is where the f/1.2 lens's advantage lies). Even go for a 1.4 which is a bit pricier but much easier to find and would give an experience closer to a 1.2 Focusing such lenses on a DSLR is not easy.

A 50/1.7 would cost around a tenth of an f/1.2 and be much easier to find.

I own Jupiter 135mm on M42 and did some shooting already. Manual focusing is kinda painfull, but I'm not 100% satisfied with my AF, either... not sure if it's camera or lense's fault, but it keeps missing with some lenses. It is terrible with smc 50mm F1.8 DA lens, and misses a lot with smc 31mm F1.8 Limited (not as much as 50m DA, but still...). I think it's about time to get F1.2 lens And from the very first day after I got my K-50 (which I later erplaced by K-70) I always shoot at M mode. Feels like I'm in control, not the camera

If you do not need (or desire?) the small DOF and dreamy expression of the 50/1.2, I would suggest to buy a F 50mm / 1.7 instead. That will be the more convenient lens on both cameras, it has autofocus, supports all modes of the cameras and it is cheap an available.

If you really want the 1.2 you have to decide between built quality (K) and convenience (A). I would go for convenience, I have more difficulties to get manual focus spot on on the K-1, then on the K-70. If using a manual A lens (50/1.7 in my case) you can concentrate on focusing and do not have to fiddle with the green button in addition.
But that is my complete personal opinion and as you can see in the postings above other forum member follow the contrary approach.
My suggestion as a decision help: Get a 50mm/1.7 wich is the cheapest possibilty of a manual Pentax prime and try it on your K-70.

Thanks, I already own 50mm F1.8 and I'd like to expriment with small DOF as you mentioned. From what you said chancec are that K version has greater build quality. Combining this with cheaper price (looking at eBay) I'll go with K version

[Lowell Goudge]

For a new to manual focus, and manual exposure, you may find a non A lens frustrating. On many Pentax bodies, (I can’t speak of the K70 directly) the green button metering is not consistent across all apertures. There have been many posts over the years on this topic.

Years ago I posted this curve that shows the difference between f stop and exposure on different bodies.



To explain the graph,

Different lenses and cameras were used (some of which I won, some of which other forum members contributed to in the process). What was found to be consistent was that exposure was almost perfect in the F4-F5.6 range, which makes sense because virtually all consumer kit lenses etc are in that aperture range.

As manual lenses meter in stopped down mode, you can see the true performance of a lens at each aperture. In automatic aperture mode as shown by the A 50/1.2 the exposure is perfect, this is because the camera knows not only the native aperture, but also the curve of aperture vs metering performance (assumption on my part but the evidence speaks for itself) and compensates accordingly.

If you are going to use a non A lens, you need to measure this performance for your lens and camera, or, just take a shot if a uniformly lit monochrome subject, (sidewalks, roads, block walls and tree trunks are all good) and adjust your exposure to be centered on the histogram

[5r82]

50mm f1.2 is shot most of the time at f1.2 and at such shallow depth of field it is in controlled environment (perfect for portraits) hence there is no issue if lens is fully manual. Actually I prefer this arrangement and always shoot in M mode irrespective of the lens (manual or autofocus). I only shoot in TAv when there is action going on and then it is autofocus lens. So I would recommend older K lens because it is excellent. But be aware of certain issues highlighted online with this lens and that is balsam separation. This one seems prone to it especially at this old age, however old but gold I'd say or like old wine.

[pevik]

50mm f1.2 is shot most of the time at f1.2 and at such shallow depth of field it is in controlled environment (perfect for portraits) hence there is no issue if lens is fully manual. Actually I prefer this arrangement and always shoot in M mode irrespective of the lens (manual or autofocus). I only shoot in TAv when there is action going on and then it is autofocus lens. So I would recommend older K lens because it is excellent. But be aware of certain issues highlighted online with this lens and that is balsam separation. This one seems prone to it especially at this old age, however old but gold I'd say or like old wine.

Thanks for the comment confirming that the auto lens or newer lens is not necessarily better. I guess everything depends on photographer, and I do like to work with manual settings from time to time. But I've never heard of balsam separation How do I detect this once I get the lens?

[pevik]

If you are going to use a non A lens, you need to measure this performance for your lens and camera, or, just take a shot if a uniformly lit monochrome subject, (sidewalks, roads, block walls and tree trunks are all good) and adjust your exposure to be centered on the histogram

I think I will be fine testing exposure manually than, but the analysis you made is very interesting! Thank you

[halfspeed]

id like to have either of these 1.2s!

[5r82]

Thanks for the comment confirming that the auto lens or newer lens is not necessarily better. I guess everything depends on photographer, and I do like to work with manual settings from time to time. But I've never heard of balsam separation How do I detect this once I get the lens?

Can you please study this old thread: "Optics Separation" is common with Pentax 50mm f/1.2 lens - PentaxForums.com

Photos of balsam separation can be seen in this thread, although this relates to 50mm f1.4

Asahi Pentax-M 50mm f1.4 Lens Haze with Balsam Separation Suspected, Repairing... - PentaxForums.com

Just pay attention when purchasing. Good luck.

[pevik]

id like to have either of these 1.2s!

There are number of them on eBay right now, but the price is not low.

---------- Post added 04-20-23 at 04:44 AM ----------

Can you please study this old thread: "Optics Separation" is common with Pentax 50mm f/1.2 lens - PentaxForums.com

Photos of balsam separation can be seen in this thread, although this relates to 50mm f1.4

Asahi Pentax-M 50mm f1.4 Lens Haze with Balsam Separation Suspected, Repairing... - PentaxForums.com

Just pay attention when purchasing. Good luck.

Thanks a lot! Some say it is not neccessarily common to Pentax 50mm f/1.2, but a problem that can happen in general. I'll be carefull, I will try to search on how to prevent this (if anyhow possible). Thanks again

[robbiec]

A good 'K' will be better than an average 'A' but a good 'A' is a joy. Not as good as a DFA* but a great lens nonetheless. I suggest you invest in a O-ME53 as it'll help nailing focus.

[pevik]

A good 'K' will be better than an average 'A' but a good 'A' is a joy. Not as good as a DFA* but a great lens nonetheless. I suggest you invest in a O-ME53 as it'll help nailing focus.

Thanks for the recommendation, I had no idea such a thing as "O-ME53" exists!

[gofour3]

I've got two K50/1.2 and one A50/1.2 and the only other difference than previously mentioned, is that the K Series weighs 40 grams more than the A Series.

Phil.

[angerdan]

I've been searching web and the forums but couldn't find anything... I'm just curious if anyone owns both: "Pentax 50mm F1.2" AND "Pentax-A 50mm F1.2" lenses?
1: SMC Pentax 50mm F1.2 Reviews - K Prime Lenses - Pentax Lens Reviews & Lens Database
2: SMC Pentax-A 50mm F1.2 Reviews - A Prime Lenses - Pentax Lens Reviews & Lens Database

But is there any other difference resulting in image quality?

Is the former just a grandfather of the latter? Or are they siblings?

The A replaced the K in 1984:
<= F1.2 Lenses | PentaxForums.com

[pleo]

As been mentioned before:
the K ist heavier thus resulting in a better feeling when focussing.

Others have mentioned to start with a 1.7 or 1.4 instead:
I had the K 1.2 and compareed it with all of the 50s I could get.
Beside sharpness/contrast at different apertures (the 1.2 was the best, the other Pentax 50s needed to be stopped down 1.5 -2 f-stops to get similiar (not equal) results):
They have different "character"!
The K 1.2-results have more "crisp", more 3D-effect than the (M or A) 1.4 or 1.7.
The Pentax 1.2 is a superb lens - but the Zeiss Planar ZK (!) 1.4/50 comes close - but will be even harder to get.
I'm still sad that I sold both years ago (just to get me an AF-lens that I could buy nearly everywhere right now)

[Benz3ne]

As been mentioned before:
the K ist heavier thus resulting in a better feeling when focussing.

Others have mentioned to start with a 1.7 or 1.4 instead:
I had the K 1.2 and compareed it with all of the 50s I could get.
Beside sharpness/contrast at different apertures (the 1.2 was the best, the other Pentax 50s needed to be stopped down 1.5 -2 f-stops to get similiar (not equal) results):
They have different "character"!
The K 1.2-results have more "crisp", more 3D-effect than the (M or A) 1.4 or 1.7.
The Pentax 1.2 is a superb lens - but the Zeiss Planar ZK (!) 1.4/50 comes close - but will be even harder to get.
I'm still sad that I sold both years ago (just to get me an AF-lens that I could buy nearly everywhere right now)

What I'd add to the above is that the M50/1.7 is probably a better bet than the A50/1.7 for someone starting out with manual-focus lenses.
The A50/1.7 can suffer from a lack of adhesion on one of the glues for part of the aperture ring assembly so makes it difficult to turn.