[Henrico]

Over the years I gathered lots of old glas for little money when they appeared on Marketplace. It seems many people got rid of their Pentax gear switching to digital Canons and Nikons. Now Pentax also offer decent full frame cameras the offerings on Marketplace dried up so I am happy to have my cabinett filled. These four lenses are my widest full frame lenses, I know how they behave on film and APS-C, I was just curious how they stand up on a full frame 36 Mp sensor. My back yard was an ideal test scene this morning with the rising sun from the left.

My quick observations:

Rokinon 14 mm F2.8 => Fits nice on the K1, balances well and is a real eye catcher. It suffers some mustache distortion, no real issue to my opinion. Amazing: This thing is equal clean and sharp at all apartures, even in the far corners it is sharp and shows only very little aberrations. Very usable already full open, it only vignettes up till F8. It is difficult to focus with this lens due to lower contrast full open. I also had to calibrate the focus scale using the 16x magnification function of the camera. Now infinity is infinity. Very nice lens for nature and indoor. For indoor use it is important to keep it straight horizontal/vertical to avoid disturbing perspectives.

Tokina RMC 17 mm F 3.5 => My oldest of these four lenses. Full open it shows low contrast and it is rather misty, avoid this setting. At 5.6 it offers decent center sharpness, only corner sharpness suffers unsharpness, fringing and coma. At F8 - F11 this gets more acceptable but it stays an issue. This lens also renders some flatter than the others do.

Pentax M 20 F 4.0 => Like all miniaturized M-lenses compared to their K-siblings this M20 performs very well on APS-C but less good on Full Frame. It offers very good (F4) to excellent (F8) center sharpness, it also has nice contrast, it renders briliant even with the sun in the frame and is very compact. Borders suffer a bit even stopped down and become acceptable at F8 - F11, far corners never live up totally. Anyway, this is a very usable lens, even on full frame. It looks like a dwarf on the K1 but in fact is a 40 years old masterpiece. My one looks like new without any dust in it.

Pentax A 24 2.8 => Apperture calibration is not OK, Av-setting results in overexposured pictures so I use it in the M/green button setting, then it works fine. This is a fine lens, already usable full open, it produces warm and contrasty pictures with only some purple fringing in the far corners.

In practice all four lenses deliver nice pictures used well. The Rokinon is a very good lens on full frame, only focussing is a bit difficult (low contrast) unreliable distance scale. The Tokina is very soft wide open and shows coma and purple fringing in the far corners. The 20 mm has a briliant contrasty center performance, the borders and far corners get acceptable at F8 - F11 but there still is some purple fringing even then. The 24 mm is a nice lens without any serious flaws, it already is usable full open.

Some full pictures now taken at F5.6, details (Full Open) are 200% and 400% expanded (F5.6 and F11)

14mm@5.6:


17mm@5.6:


20mm@5.6:


24mm@5.6:


Far corners wide open:


Center@5.6


Center@11


Far corner@5.6


Far corner@11

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Last edited by Henrico; 01-03-2020 at 08:00 AM.

[texandrews]

It's ok for non-critical work, and its small size makes it handy. Distortion is more of a problem (no lens profile in Lightroom...), and basically the 15-30 spanks it in terms of overall IQ. So does the Irix 15, although stretching distortion is obviously worse, but the aspect slider in Lightroom helps there.

[MarkJerling]

Over the years I gathered lots of old glas for little money when they appeared on Marketplace. It seems many people got rid of their Pentax gear switching to digital Canons and Nikons. Now Pentax also offer decent full frame cameras the offerings on Marketplace dried up so I am happy to have my cabinett filled. These four lenses are my widest full frame lenses, I know how they behave on film and APS-C, I was just curious how they stand up on a full frame 36 Mp sensor. My back yard was an ideal test scene this morning with the rising sun from the left.


My quick observations:


Rokinon 14 mm F2.8 => Fits nice on the K1, balances well and is a real eye catcher. It suffers some mustache distortion, no real issue to my opinion. Amazing: This thing is equal clean and sharp at all apartures, even in the far corners it is sharp and shows only very little aberrations. Very usable already full open, it only vignettes up till F8. It is difficult to focus with this lens due to lower contrast full open. I also had to calibrate the focus scale using the 16x magnification function of the camera. Now infinity is infinity. Very nice lens for nature and indoor. For indoor use it is important to keep it straight horizontal/vertical to avoid disturbing perspectives.


Tokina RMC 17 mm F 3.5 => My oldest of these four lenses. Full open it shows low contrast and it is rather misty, avoid this setting. At 5.6 it offers decent center sharpness, only corner sharpness suffers unsharpness, fringing and coma. At F8 - F11 this gets more acceptable but it stays an issue. This lens also renders some flatter than the others do.


Pentax M 20 F 4.0 => Like all miniaturized M-lenses compared to their K-siblings this M20 performs very well on APS-C but less good on Full Frame. It offers very good (F4) to excellent (F8) center sharpness, it also has nice contrast, it renders briliant even with the sun in the frame and is very compact. Borders suffer a bit even stopped down and become acceptable at F8 - F11, far corners never live up totally. Anyway, this is a very usable lens, even on full frame. It looks like a dwarf on the K1 but in fact is a 40 years old masterpiece. My one looks like new without any dust in it.


Pentax A 24 2.8 => Apperture calibration is not OK, Av-setting results in overexposured pictures so I use it in the M/green button setting, then it works fine. This is a fine lens, already usable full open, it produces warm and contrasty pictures with only some purple fringing in the far corners.


In practice all four lenses deliver nice pictures used well. The Rokinon is a very good lens on full frame, only focussing is a bit difficult (low contrast) unreliable distance scale. The Tokina is very soft wide open and shows coma and purple fringing in the far corners. The 20 mm has a briliant contrasty center performance, the borders and far corners get acceptable at F8 - F11 but there still is some purple fringing even then. The 24 mm is a nice lens without any serious flaws, it already is usable full open.


Some pictures now, details are 200% (Full Open) and 400% expanded (F5.6 and F11)

Nice comparison! Thanks for posting.

[pinholecam]

Have to agree that most of the lenses in your list are really far better than what many have written them up to be.


My Soligor 17/4 (probably a variant of the Tokina) is the weakest of the UWA that I have.

[pentax360]

Thanks for putting in the time to test all these and give your findings.