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12-31-2018, 10:38 PM   #31
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Pentax FA 20mm f2.8

Full scene followed by crops of the centre and corner at f2.8, f4 and f8

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12-31-2018, 10:43 PM   #32
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SMC Takumar 20mm f4.5

Full scene followed by crops of the centre and corner at f4.5 and f8
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12-31-2018, 10:52 PM   #33
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For the extreme pixel peekers

Extreme corner crops for the FA 20mm, FA 20-35mm and M 20mm
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01-01-2019, 01:34 AM - 1 Like   #34
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Thanks Mark. The Tokina is quite sharp all over wide open. The FA 20-35 has softness and CA/PF in the extreme corners wide open, and the others seem to be in between. I appreciate those test images.

01-01-2019, 05:05 AM   #35
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Yes, the Tokina performed very well. And the copy I have has haze on one inner element.

The FA 20-35 had a surprising amount of CA. I have not attempted any post processing to see how difficult the removal is. This is one of the strengths of the FA20 - but the weakness is distortion. I am looking at various ways of solving this through a lens profile.
01-01-2019, 01:49 PM   #36
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The Tokina ATX-Pro 20-35mm F2.8 is a good performer if you can find one. Not light or small, but not stupidly big and heavy for a F2.8 zoom.
01-01-2019, 04:00 PM   #37
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QuoteOriginally posted by niblue Quote
The Tokina ATX-Pro 20-35mm F2.8 is a good performer if you can find one. Not light or small, but not stupidly big and heavy for a F2.8 zoom.
It would be interesting to see how this lens performs against the f3.5-4.5 version as shown here.
01-01-2019, 04:04 PM   #38
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QuoteOriginally posted by Wild Mark Quote
It would be interesting to see how this lens performs against the f3.5-4.5 version as shown here.
Unfortunately I don't have the slower Tokina however I have loads of other lenses in the 20-35mm range so might get round to doing a comparison test one day!

01-01-2019, 09:03 PM   #39
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QuoteOriginally posted by Wild Mark Quote
Yes, the Tokina performed very well. And the copy I have has haze on one inner element.

The FA 20-35 had a surprising amount of CA. I have not attempted any post processing to see how difficult the removal is. This is one of the strengths of the FA20 - but the weakness is distortion. I am looking at various ways of solving this through a lens profile.
Thanks for posting these. From what I can tell, the difference between the FA20 and the M20 is not as significant as I would have expected from the various comments in the forum. If there are quality differences that are not reflected as much in this test but might be important, have you noticed any?
01-01-2019, 09:18 PM - 2 Likes   #40
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QuoteOriginally posted by DSLRnovice Quote
Thanks for posting these. From what I can tell, the difference between the FA20 and the M20 is not as significant as I would have expected from the various comments in the forum. If there are quality differences that are not reflected as much in this test but might be important, have you noticed any?
The FA20 optical design seeks to limit CA/ purple fringing. The extreme corner crop shows this well (compared to the M 20mm and FA 20-35mm). I have found correcting the CA/ PF in the M 20 and FA 20-35 to be a little difficult.

For the above reason it seems that the FA 20 delivers better colour rendition across the whole frame.

However, this comes at a cost. The FA20 appears to suffer from some distortion greater than the M 20mm and FA 20-35mm. Barrel and pincushion distortion is evident.

Overall, the FA 20 is substantially sharper in the middle with almost no CA/PF. Colour rendition is better too.

Why choose f2.8 over f4? While shooting at f2.8 has a clear downside in the corners (nasty) it does give you capacity for DOF creativity if you intend to crop out the upper and lower portion of the frame (i.e. crop to 16:9 ratio). It also gives you the same flexibility in low light if the landscape scene you are capturing is best represented in that ratio.

If you want the M20mm then you are probably paying about US$350-400. For an extra US$100 you get greater performance at f8 and more flexibility wide open knowing the limitations in the corners. Also, the aperture setting can be changed within the camera. Flare control has not been tested, but, I suspect the coatings on the FA20 to be better in this department.

For an investment of that amount I would upgrade to the FA20 without hesitation.
01-02-2019, 02:36 AM - 2 Likes   #41
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I find my "Good Lady” (Pentax-A 20mm F2.8) to give quite acceptable results, here's a few randomly picked examples.
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01-02-2019, 02:43 AM   #42
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I admire your good lady: stopped down she performs very well.
01-02-2019, 02:48 AM   #43
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---------- Post added 01-02-19 at 02:58 AM ----------

Only have my rokinon 20mm 2 weeks but no complaints so far





wide open












01-02-2019, 04:17 AM   #44
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Rokinon 20mm is much better than vintage 20mm lenses including Pentax glass. Vintage wide angle glass falls apart on 36Mpx sensors unfortunately, definitely not good for any kind of pixel peeping or to be used at 100%. Vintage normal and telephoto lenses perform considerably better than vintage wide angle lenses on modern sensors. The above photos from Pentax A 20mm f2.8 (old lady) are among the best I have seen so far but even they have been post processed heavily, albeit to great artistic and creative achievements which I admire.
01-02-2019, 08:32 AM - 4 Likes   #45
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QuoteOriginally posted by 5r82 Quote
Rokinon 20mm is much better than vintage 20mm lenses including Pentax glass. Vintage wide angle glass falls apart on 36Mpx sensors unfortunately, definitely not good for any kind of pixel peeping or to be used at 100%. Vintage normal and telephoto lenses perform considerably better than vintage wide angle lenses on modern sensors.
None of this really accords to my experience with vintage wide angle glass. The main advantage of modern wide angle glass is sharpness wide open and sharpness in the corners even when stopped down. There can also be some advantages in terms of light transmission (superior coatings), as we often note with the DFA 15-30, but I'd be careful about being too dogmatic about that. As long as you're willing to stop the older lenses down (which you're going to do if you're shooting landscapes in any case), you can get images that come surprisingly close, in terms of sharpness, contrast, and saturation, to what you can get out of a great lens like the DFA 15-30. The only thing you're really giving up with vintage wide angles is wide-open performance and sharpness in the very far corners.

The Rokinon 20 looks like a very nice lens. It would be great for astrophotography. But one reason I would not buy that lens is that, outside of astrophotography, I prefer what I see from my FA 20-35 and M 20/4 . To my way of seeing things, those older lenses produce better color and rendering than what the Rokinon/Samyang's generally provide.

As far as vintage normals and teles being better than vintage ultra-wides: while that may be true for the normals (but they're not better by all that much), that hasn't been my experience with vintage teles. I own the M 135/3.5, the K 200/4 and the A 70-210. Excluding the very far corners, my M 20/4 is sharper than any of those lenses.

A couple of sample images, first from the FA 20-35:



And the M 20/4:

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