[madbrain]

Is there such a thing in K-mount ?

[Adam]

I think the FA J 18-35mm is what comes closest. There's also the FA 20-35mm and 20mm.

Full Frame Lenses between 4mm and 50mm with Autofocus | PentaxForums.com

[clackers]

Is there such a thing in K-mount ?

The rounded front elements protrude on a high-performance wide angle so it's unusual in any mount.

The Pentax DA 12-24 does take threaded filters and works on full frame starting at 17mm. That's still wider than 12mm on APS-C.

[madbrain]

The rounded front elements protrude on a high-performance wide angle so it's unusual in any mount.

Yes, it appears to be so. But isn't it more likely in wide apertures lenses ? I don't need a wide aperture.
Ultrawides on APS-C have managed to take threaded lenses somehow. Why not FF ?

The Pentax DA 12-24 does take threaded filters and works on full frame starting at 17mm. That's still wider than 12mm on APS-C.

Thanks. I have recently learned at my expense, after buying a Tamron 10-24, that the definition of "works on full-frame" for APS-C lenses is really quite subjective.
Some said the lens is usable at 15mm+, but to me, it's really not. In FF mode, there is uncorrectable vignetting at all focal lengths, and the edges and corners are just not sharp at any aperture. So, that lens is going back to KEH.

I would want to see some test target shots before I would buy the 12-24 APS-C lens to see how usable it really is in FF mode.

I am in the process of testing all my lenses, both APS-C and FF, with test targets, to see how good or bad the sharpness is on each. It's been an enlightening process. I am happy to share all the test shots with fellow Pentaxians, but there are a lot of them and it will take a lot of space, many gigabytes for RAW files. So far, I have 331 test images, and I'm not done testing, so somebody would need space to host them all.

---------- Post added 05-25-21 at 05:37 PM ----------

I think the FA J 18-35mm is what comes closest. There's also the FA 20-35mm and 20mm.

Full Frame Lenses between 4mm and 50mm with Autofocus | PentaxForums.com

Thanks. FA J 18-35mm might do the job. I don't see any for sale anywhere at the moment, though. I'll keep an eye.

[jatrax]

Irix 15mm? Not AF but with ultrawide maybe its not as necessary?

[clackers]

Ultrawides on APS-C have managed to take threaded lenses somehow. Why not FF ?

The correlation is with whether the lens has a bulbous front element or not. That's a high performance feature, lots of corrective glass to converge light from the extreme parts of the frame back into the same place instead of spreading it (aberrations).

A crop sensor camera has less frame to do correcting for, so the DFA 15-30 has a bulbous front element, the DA*11-18 doesn't.

BTW, I have both the FA-J 18-35 and the FA20-35, they're too small to be high quality. Stopped down, the latter does an okay job for what it is (see pics by Northcoastgreg for good examples).

The 18-35 is probably the weakest lens I own. Probably the DA18-55 kit lens would be better on the K-1 at 24mm.

My ultrawide of choice that takes threaded filters on the K-1 is the Irix 15mm f2.4.

[madbrain]

The correlation is with whether the lens has a bulbous front element or not. That's a high performance feature, lots of corrective glass to converge light from the extreme parts of the frame back into the same place.

A crop sensor camera has less frame to do correcting for, so the DFA 15-30 has a bulbous front element, the DA*11-18 doesn't.

BTW, I have both the FA-J 18-35 and the FA20-35, they're too small to be high quality. Stopped down, the latter does an okay job for what it is (see pics by Northcoastgreg for good examples), while the 18-35 is probably the weakest lens I own.

Thanks. Do you have any opinion about the Sigma 17-35mm EX DG ? A forum member in Singapore has one listed and PM'ed me.
Also appears to be a small lens, even though it's f2.8. But takes 82mm filters. Inexpensive, though.

[clackers]

Thanks. Do you have any opinion about the Sigma 17-35mm EX DG ? A forum member in Singapore has one listed and PM'ed me.
Also appears to be a small lens, even though it's f2.8. But takes 82mm filters. Inexpensive, though.

I've no idea!

On my Sony A7 I do use an older Tokina 17-35mm f4, it's quite good, and has an 82mm filter like that Sigma.

It's not small, though. I don't think that Sigma is either, with an 82mm filter.

[termy]

Thanks. Do you have any opinion about the Sigma 17-35mm EX DG ? A forum member in Singapore has one listed and PM'ed me.
Also appears to be a small lens, even though it's f2.8. But takes 82mm filters. Inexpensive, though.

ahhh, no no.
It isnt the EX DG version.
Is the EX Asph version
(There's two versions of this AF Sigma 17-35 in K mount).

[madbrain]

ahhh, no no.
It isnt the EX DG version.
Is the EX Asph version
(There's two versions of this AF Sigma 17-35 in K mount).

Is the Aspherical designed for full-frame or APS-C ?

[termy]

Is the Aspherical designed for full-frame or APS-C ?

Fullframe lens.

[UncleVanya]

I have recently learned at my expense, after buying a Tamron 10-24, that the definition of "works on full-frame" for APS-C lenses is really quite subjective.
Some said the lens is usable at 15mm+, but to me, it's really not. In FF mode, there is uncorrectable vignetting at all focal lengths, and the edges and corners are just not sharp at any aperture. So, that lens is going back to KEH.

I would want to see some test target shots before I would buy the 12-24 APS-C lens to see how usable it really is in FF mode.

My personal thinking after trying the 12-24 on my Sony A7RII is that it is nearly a Fisheye at 24mm on full frame. I’m not sure how sharp it is since that wasn’t the aim of my testing.

Pentax DA 12-24 @ 24mm by -vanya_42nd-

Here’s the 10-17 @ 17 on the Sony A7rII:

DA 10-17mm at 17mm by -vanya_42nd-

[clackers]

My personal thinking after trying the 12-24 on my Sony A7RII is that it is nearly a Fisheye at 24mm on full frame.

I think it's more your scene, UV, everything so close it's converging around you.

Have a look at: DA12-24 on Full Frame - PentaxForums.com and the rest of that thread.

[madbrain]

My personal thinking after trying the 12-24 on my Sony A7RII is that it is nearly a Fisheye at 24mm on full frame. I’m not sure how sharp it is since that wasn’t the aim of my testing.

Pentax DA 12-24 @ 24mm by -vanya_42nd-

Here’s the 10-17 @ 17 on the Sony A7rII:

DA 10-17mm at 17mm by -vanya_42nd-

Thanks. Nice images ! I'm more concerned with the wider end. The overwhelming majority of pics I took with my Sigma 10-20 on APS-C were at 10mm - about 2/3. The remaining third at 20mm. Very few in between. I would prefer rectilinear to fisheye, though.

---------- Post added 05-25-21 at 10:38 PM ----------

I think it's more your scene, UV, everything so close it's converging around you.

Have a look at: DA12-24 on Full Frame - PentaxForums.com and the rest of that thread.

Many crop images in that thread :-) A lot of the FF pics have pretty bad vignette, but it works as an artistic choice. Vignette is mentioned as high as 19mm. I'm aware that all lenses can vignette at some apertures, even lenses designed for 35mm full-frame, but the instances I have seen of using the Tamron 10-24 on FF was at all apertures and all focal lengths. My main use for the lens would be landscapes and nightscapes. I love panoramas. I wouldn't be shooting wide open, or with a tripod. High ISO on the K-1 II, is perfectly fine for me for night time. Would use the lens indoors too, of course.

[Joetitch]

Tokina 19-35 is FF and takes screw in filters and the hood doesn't rotate with focus. I have used it on the K1 and didn't notice any vignette but I might not be as critical.
There is also a Cosina version but I have no experience with it