[cyberjunkie]

The two Pentax 28mm AF are both costly and not so easy to find.
I already have a few nice MF 28mm's, but I realized that having the choice of a modern AF objective would be nice.
The obvious choice seemed the Sigma EX DG 1.8/28mm, but the price is not exactly affordable.
I found that, like most other Sigma lenses, there is a previous Aspherical version released in film time.
It's smaller and the reviews are not bad.
Any first hand experience with the K-1?
Does the AF work correctly?
How does it compare to the more recent EX version?

[angerdan]

I recommend the much smaller, more lightweight FA 31mm 1.8 Limited. Which offer filter size 58mm instead of 77mm.
And the lens hood is already integrated
SMC Pentax-FA 31mm F1.8 AL Limited Reviews - FA Prime Lenses - Pentax Lens Reviews & Lens Database
Sigma 28mm F1.8 EX DG Aspherical DG DF Macro Lens Reviews - Sigma Lenses - Pentax Lens Review Database

[pres589]

For those of us at home who are excited about 28mm lens options, Mr. Junkie is refering to this lens;

Sigma 28mm F1.8 Aspherical II Lens Reviews - Sigma Lenses - Pentax Lens Review Database

Is this lens actually easy to find on the ground for less cost to purchase than either the F or F 28's?

It seems kind of hard to recommend this lens unless it's fairly inexpensive. Meaning, I think the F 28 is worth more, and probably the FA as well, based on complaints of CA and flare. I have the EX DG Sigma and the IQ is quite nice, it has a nice pop / 3D effect to the images taken with it, although it's large and quite heavy.

I think I'd rather find the cash for either of the Pentax options or the EX lens. I could see paying $150 for this lens in good condition, which is what I valued my just-CLA'd Kiron 28 f2, so take all that with a grain of salt.

[Just1MoreDave]

Sigma made both AF and MF versions of that lens. I have the manual focus version - labeled to the right of the focus indicator "Sigma Manual Focus". It has a KA mount. It is optically excellent IMO. It's the sharpest 28mm I have used, although that class includes a lot of cheap stuff. My Pentax-F 28mm f2.8 is not that far behind but the Sigma has already gotten quite sharp at f2.8. The other lens close in sharpness is my Kiron 28/2. I think the sharpness makes it very easy to focus because the in focus zone is very clear in the viewfinder. My guess is that AF should work just as well. The aperture has 7 blades. Coatings are better than my Sigma Superwide II 24/2.8 which is slightly older, better than the Kiron, not as good as the Pentax-F.

The speculation in post #3 pretty much nails its value as I see it. I like the size of the F28/2.8 so much, similar to the DA Limiteds, so I don't use the Sigma a lot. I bought mine because I knew I definitely would not use the 77mm filter EX. It's not outrageously huge.

[pepperberry farm]

hmmm... I have the Sigma 28mm f1.8 EX DG, but not with the K-1...

it's a stupendous lens - I bought mine refurbished through Adorama a while back and ceased all LBA for that focal length for me....

[zapp]

My M 2/28 performs better on K1 than any Sigma 1.8/28.
I had the first version of the Sigma for film and was quite happy with it. Later I played with the 20 and 24 mm 1.8 versions on digital - Canon FF at that time. The 20/24/28 were stretching the limits too far, I did not like any of the designs. Colurful dark edges. Stopped down the edges did not become crisp. I did not try the later 28 myself, but the whole line of lenses felt wrong. Only with the ART line large aperture Sigma lenses performed well.

[cyberjunkie]

hmmm... I have the Sigma 28mm f1.8 EX DG, but not with the K-1...

it's a stupendous lens - I bought mine refurbished through Adorama a while back and ceased all LBA for that focal length for me....

Yes, my friend. I guess you are right. Unfortunately it's beyond my budget.
This kind of lenses (read: discontinued Sigma EX DG objectives in PKAF mount) are usually quite expensive on eBay/Amazon/whatelse, and come up as eBay auctions very rarely. When it happens, most of the times shipment is restricted to the same country (90% of the times it's the USA).
So finding them at a very good price is not very likely.
There is one factor that I have to keep in mind. Actually I already have some very good manual 28mm's, like the two SMC Pentax (f/3.5 and the valuable f/2 "Hollywood").
I also have a nice Sigma Mini Wide II in PKA mount and a Kino-made 2/28mm (well, two... branded Vivitar and Kiron, unfortunately both are PK, not PKA).
If I have the M42 adapter on my K-1, and I go out with screw mount lenses only - as I do quite often - I also have a choice of 3 or 4 nice M42 optics, like the Soligor C/D P 2/28mm or the Komura 2.5/28mm.

You see that I have a good number of 28mm lenses that perform well enough, if I don't need AF and I can use them at their sweet spot.
If I didn't need an AF prime, preferably of low weight/size, I would probably forget about a 28mm. I have plenty of them and the focal is also covered by a couple of very good f/2.8 zooms.
To be sincere, I really can't say I "need" it, let's say I "want" an AF prime, better if fast and not too big.
I'm still trying to find a Pentax-F/FA, it's quite good and it's easy to carry around. A pity it's usually priced above what I'm ready to pay (and above what it's worth, IMHO). Same thing applies to the 2.8/135mm AF, btw.
There is not much else to choose from. The only alternative that's cheap enough and maybe good enough is the old Sigma Aspherical AF.
It's fast but still manageable.
I haven't found anything else with my searches.
Any other suggestion is appreciated.

I'm interested in first hand impressions of the Sigma Aspherical on FF (K-1, Sony mirrorless, or even Nikon, cause for example the D810 shares the same sensor of the K-1).
If it performs well enough only at medium apertures it's definitely worth waiting for a nice deal involving the EX DG or a Pentax AF. If it performs in a satisfying way wide open I'd be happy to go for the old version and be fine with it.

EDIT:
As I've already said, I often like to go out taking pictures using only a set of M42 lenses.
While I found that many very old 35mm lenses are still very usable, especially taking care of avoiding stray light, the older 28mms are more problematic.
I like to experiment with very old lenses. Some 50/55mm are still impressive, either because of great center sharpness or because of a very particular optical signature. Recently I enjoyed a lot the Meyer Primoplan, the 8-elements Super Tak, and two old chrome nose Tomiokas. The 28mm's of the same age have been disappointing most of the times. So I have decided to stick to more modern designs for 28mm and lower.
There were a few exception. I've mentioned two in the text above.
I'm curious to know if any of you found a sixties/early seventies 28mm that performed above expectations.

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Last edited by cyberjunkie; 11-06-2018 at 02:34 PM.