[wstruth]

That is true for you, me and a whole pack of Pentaxians, as the photos in this thread demonstrate

My 21 hasn't seen that much use since I got the 20-40. Both are good for sure, but the 20-40 is also just a bit more versatile since it's a zoom. It's my go to on my KP.

[northcoastgreg]

Given the talk of equivalence on the forum, this may open up a can of worms, but what's available in the DA 21 or 20-40 doesn't compare in max aperture.
Perhaps the Sigma 20mm F1.8 EX Aspherical DG DF RF Lens Reviews - Sigma Lenses - Pentax Lens Review Database or the Samyang 20mm F1.8 ED AS UMC Lens Reviews - Samyang Lenses - Pentax Lens Review Database would give similar perspectives but certainly not similar results at the wider aperture. A good example of the difference in rendition would be this: Wide Open: Pentax 31 Limited & Leica 35 Summilux ASPH – Steve Huff Photo

This illustrates some of the shortcomings of the obsession with aperture equivalence. Unless the only type of images you take involve defocused background, this factor is of little if any importance. On the other hand, every image you take is affected by the contrast, the color and the rendering of the lenses in question. The sigma and rokinon lenses have different color and sharpness rendering than the FA 31. Every image from these lenses, therefore, is going to look different, regardless of aperture equivalence or lack thereof.

The lens that's come closest, in terms of contrast, color, and sharpness rendering is the SMC DA 21 --- a lens using the same coating technology (ghostless + SMC) and following similiar lens design philosophy in regards to rendering. In comparison, considerations about aperture equivalence quickly veer toward the trivial.

[sutherland]

I would rather have the DA 21mm f/3.2 and DA 40mm f/2.8 over the 20-40mm f/2.8-4.
- I think both primes can be had for less than the zoom
- I think both primes take up less space than the zoom

28mm is my favorite focal length (thanks to the Ricoh GR II). The DA21mm is sharp in the center at f/3.2, and just about perfect at f/5.6.

[normhead]

I would rather have the DA 21mm f/3.2 and DA 40mm f/2.8 over the 20-40mm f/2.8-4.
- I think both primes can be had for less than the zoom
- I think both primes take up less space than the zoom

28mm is my favorite focal length (thanks to the Ricoh GR II). The DA21mm is sharp in the center at f/3.2, and just about perfect at f/5.6.

I tend to confine that type of comparison to lenses I actually own. Sometimes real usage alters preconceived preferences.

- I think both primes can be had for less than the zoom

But you still have to buy a 24, 28 and 35 to even close to the same capability, at which point the 20-40 is the cheaper option.

- I think both primes take up less space than the zoom

As above, you achieve space saving by buying the minimum. If you buy all 5, the primes are definitely bigger. Not to mention the time you save in lens changes. So, if you only want 20mm or 40 mm available you still save lens changes with the zoom.

And I left the 31 and 43 off the list, so it didn't get too ridiculous.

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Last edited by normhead; 01-30-2019 at 09:38 AM.

[pres589]

I wonder about either the Sigma or Samyang 20 1.8's, used on crop, acting about like the FA 31.

[normhead]

I wonder about either the Sigma or Samyang 20 1.8's, used on crop, acting about like the FA 31.

Both are going to have less narrow DoF capability and messier bokeh... two of the big reasons for buying a 31.

[pres589]

Agreed, which is more of a crop vs. full-frame argument than against these lenses specifically. Depth of field going less narrow will also impact the 31 the same way once mounted on a crop body.

Of the two, I would make a rash assumption that the Samyang is going to deliver generally more pleasing image quality (including bokeh), and the OP mentioned that this wasn't just about wide-open IQ. I don't think the Sigma 20 EX DG is especially bad at anything, I just don't think it's especially good either, based entirely on conjecture and internet postings so grains of salt should be taken with extreme prejudice at this point.

[normhead]

Agreed, which is more of a crop vs. full-frame argument than against these lenses specifically. Depth of field going less narrow will also impact the 31 the same way once mounted on a crop body.

But it will be a longer focal length and less DoF at minimum focusing distance for that reason.

[UncleVanya]

Both are going to have less narrow DoF capability and messier bokeh... two of the big reasons for buying a 31.

absolutely true - but the specific use I am mainly interested in is not narrow DOF it is stopped down landscape shots with deep DOF. I understand the limitations of the f/stop and crop sensor use.

At this point I own the SMC DA 40 f/2.8 Limited and the HD DA 20-40 f/2.8-4 - and many other zooms that cover 21mm (16-50, 18-135, 18-50) but I have never owned the DA 21. The aspects I have interest in is how the shots look compared to the DA 20-40 on the wide end. I don't really want to buy the DA 21 just to test this - I'd like to see some comparison shots just to see if there is any real difference seen. My suspicion is that at f/5.6-f/8 this will be of limited difference. It is hard to justify another lens already owning the 20-40 and the 40.

[Ash]

This illustrates some of the shortcomings of the obsession with aperture equivalence. Unless the only type of images you take involve defocused background, this factor is of little if any importance. On the other hand, every image you take is affected by the contrast, the color and the rendering of the lenses in question. The sigma and rokinon lenses have different color and sharpness rendering than the FA 31. Every image from these lenses, therefore, is going to look different, regardless of aperture equivalence or lack thereof.

The lens that's come closest, in terms of contrast, color, and sharpness rendering is the SMC DA 21 --- a lens using the same coating technology (ghostless + SMC) and following similiar lens design philosophy in regards to rendering. In comparison, considerations about aperture equivalence quickly veer toward the trivial.

That is indeed the point I have made in that thread, since there cannot be equivalence in image rendition between different lens designs. Pragmatically though, the 31 can be used at f/2, even wide open. That's where there is little in the way of competition with this lens as an APS-C equivalent. But I certainly agree, for f/4 and above, the DA 21 is excellent.

[Sandy Hancock]

I somehow managed to miss the fact that you already own the 20-40. From the brief time I had with mine I found the colours, bokeh and general rendering to be very much in keeping with the other DA limiteds. In other words - lovely.

If your copy is good at the wide end (where mine wasn't) I'd say the rest of the conversation is moot.

[UncleVanya]

I somehow managed to miss the fact that you already own the 20-40. From the brief time I had with mine I found the colours, bokeh and general rendering to be very much in keeping with the other DA limiteds. In other words - lovely.

If your copy is good at the wide end (where mine wasn't) I'd say the rest of the conversation is moot.

Thanks for that clarification. I'll have to shoot some with more with it (oh darn excuse to trek to beautiful landscapes!) and do some shots of the type I want and see. I have often used the DA 15 for my landscapes but sometimes that's too wide.

Funny thing Sandy - My dad and I both shot Pentax for a time and he had a GAS. He was always buying some deal here or there and trying to avoid duplication of my lenses so I ended up with a hell of a collection when he went m43 and traded me his Pentax gear. For example the 60-250, 12-24, 20-40 and 70 were all things he "couldn't live without" that I was happy using my DA 50-135 with 1.4x or my DA 55-300, my DA 15, my FA 77 for. In the end I have too much gear in some ways. I am thinking of culling the herd a bit but then I always worry he will pick back up APSC and I'll need to split my collection again.

[Des]

But you still have to buy a 24, 28 and 35 to even close to the same capability, at which point the 20-40 is the cheaper option.

Yes, and unlike the Limited primes, the 20-40 is WR. Since we are talking landscape here, the slower aperture of the 20-40 at the long end compared to 24, 28, 35 and 40 primes isn't going to matter.

@BigMackCam has noted that he found the 20-40 to have a lot of field curvature at the long end, even stopped down: Why would somebody buy the DFA28-105? - Page 2 - PentaxForums.com (He posted some samples somewhere but I can't find them at the moment.) It might not be obvious in a lot of situations, but something to bear in mind.

Here's one at 40mm wide open (f4). You get the lovely Limited colours.


I use it disproportionately at the wide end, where it's really good (or my copy is anyway). Even wide open at 20mm f2.8 I find mine quite sharp, and I find the bokeh quite pleasant.


It does really well for landscapes at 20mm f8.






Comparable to my DA 12-24, I think, with perhaps slightly stronger colours and the added benefit of HD coatings (no starbursts but better resistance to flare and pf).

Maybe someone who has both can compare, but the look for landscapes seems to me a bit similar to images I've seen from the DA 16-85. Which is to say, very "digital", if you know what I mean. More predictable and reliable than the FA 43, for example, but without its occasional brilliance.

To take up Sandy's point, there does seem to be some variation in the test results and user experience with the 20-40. Perhaps it's like the girl with the curl in the middle of the forehead - when she was good she was very very good, but when she was bad she was horrid. ;-)

[Sandy Hancock]

I am thinking of culling the herd a bit

That's just crazy talk.
Seller's remorse is a harsh mistress.

[ZombieArmy]

That's just crazy talk.
Seller's remorse is a harsh mistress.

You can avoid seller's remorse by just mailing them to me for free