[ChristianRock]

So many choices.

I find it's easier on the mind when you have a weather resistant lens (or two). In my case I ended up going for an SMC DA*16-50mm f/2.8 as I found one (converted to screw-drive AF) for about half of what it would cost me to get a 20-40mm Limited. But it is a bit big and not always practical, such as for hikes and bike rides, or when you want to wear wear on your neck all day. So I bought an HD DA 18-50mm f/4-5.6 and I'm very pleased with it. Sure it's slower, but it's WR and silent focusing if I need that, and I find it to be sharp throughout the range. HD coatings make for beautiful rich colors and contrast.

With time I ended up buying the 21, 35 and 70 Limiteds anyway, whenever a deal was presented that I couldn't refuse... and now I don't find myself wanting any other lenses, even some that I have really wanted in the past, like the 20-40. The quality of the images I get from the 16-50 (I have a good copy, superb everywhere for my uses from f/3.2)), 18-50, and the Limiteds (plus my other lenses) is really good, I think the only step up in APS-C might be the new DA*PLM 16-50mm, but even that wouldn't be a mind-blowing difference I think. Oh and my old DA 16-45mm f/4 is still capable of absolutely beautiful results as well - as long as I hold the front of the barrel up at 16mm, as the famous 16-45 "lens wobble" has gotten pretty bad and affects optics if I don't keep the lens straight... so if I ever needs a total "beater" lens, I can take that one.

To summarize: I'd get whatever the best deal is, because you'll end up getting both the zoom and primes anyway.

[Jonathan Mac]

I would take the 20-40mm over the 21 and 40. I'd be frustrated at the f/4 limitation at 40mm but the 20-40 is better at the wide angle than the 21 is. Add in the compact body, WR, in-lens focus motor (even if it's a bit slow) and that it does feel like a Limited despite being a zoom, I think it's the better choice. Ideally I'd have the 40mm too because it's much smaller and the difference between 2.8 and 4 is appreciable for things such as portraits.

[ChristianRock]

I would take the 20-40mm over the 21 and 40. I'd be frustrated at the f/4 limitation at 40mm but the 20-40 is better at the wide angle than the 21 is.

I've seen this being said here before, and I'm not disputing it, as I don't have the 20-40mm to compare... but my copy of the HD DA 21mm f/3.2 Limited is one of the sharpest lenses I own. It required fine focus adjustment in basically all my bodies but once I did that, what a world of difference... as sharp as my DA 35 Limited on the 24MP K-3 and 20MP K-S2 in medium to long focus distances (I'm not even kidding...) and the colors and color transitions are just superb.
The problem with the DA 21 is that because it's a wide angle lens, when the focus is a big off and needs adjustments, it doesn't really look out of focus, it just looks like it's not quite as sharp as other lenses. When you look at pictures on a smaller screen like a notebook computer, you don't even see that the focus is off, everything seems sharp until you pixel peep, at which point things get uglier.
I'd love to own the 20-40mm one day if it's even better than my DA 21.

Add in the compact body, WR, in-lens focus motor (even if it's a bit slow) and that it does feel like a Limited despite being a zoom, I think it's the better choice. Ideally I'd have the 40mm too because it's much smaller and the difference between 2.8 and 4 is appreciable for things such as portraits.

Even better would be pairing the 20-40mm lens (if that ends up being the lens for the OP) with a 50mm or 70mm lens for portraits (or even the FA 77mm Limited if one can afford it...), which would give even better subject isolation and smaller apertures.

[MaineNative]

I have the DA 21, 40 XS and 18-135. For me, the 18-135 is my choice for a travel lens or walk-around lens. The 21 mm lens takes some beautiful pictures, but it is often too wide for a lot of shots. It is very compact and I use it for shooting panoramas.

I also have the DA 16-85. While it has a little better IQ in my opinion, it is heavier and lager than the 18-135, so I only take it when I want the best image quality like shooting flowers, portraits or artwork.

I have the 40 XS because of its small size, but I don’t use it much.

[AstroDave]

With all the feedback, it seems like the 18-135 is something I should really consider to replace the kit lens and act as a short telephoto lens especially for future travels.

Definitely! That's what's on my K-3/K-3 III when I travel.

What about selling your 40 to raise some extra cash for the 20-40?

[ramseybuckeye]

Hi all,

Thanks to you I picked up Pentax K5 with the kit lens and SMC DA 40mm F2.8, which I love and exceeded my expectations considering the costs. Was tempted to upgrade the body but thought glass would be a better investment.

Iwanted to know from your experience, is it better to have a 21mm f3.2 and 40mm f2.8 combo or the 20 - 40mm f2.8-4 lens?
The 20 - 40mm is currently on sale on BH for about USD 500, I can pick up the DA SMC 21mm second hand here in Singapore for about USD 100 - 150.

Was wondering if that convenience of the zoom is really worth the premium, or going with a two lens combo since I have the 40mm and saving money would be better.

Fyi, general just shoot when I travel on holiday in cities and some hiking photos.

Many thanks!

I bought my 20-40 a couple years ago before traveling to London, I wanted weather sealed zoom, that was decently fast and small, I had been using a Sigma 17-50, which of course was not sealed. Well the 20-40 just blew the doors off of the Sigma, which was a good lens, but just not of the same class. I had wanted the 21 before, but the 20-40 told me I no longer needed it (I still would like it, but don't have the big desire any more). I can't compare the 3 lens because I have never had the 40 or 21, but I do love the 20-40, and the WR part of it is really a big deal since I shoot mostly nature and landscapes. The only other limited I have is the 15, which I love, but it is not as good as the 20-40.

[Jonathan Mac]

I bought my 20-40 a couple years ago before traveling to London, I wanted weather sealed zoom, that was decently fast and small, I had been using a Sigma 17-50, which of course was not sealed. Well the 20-40 just blew the doors off of the Sigma, which was a good lens, but just not of the same class. I had wanted the 21 before, but the 20-40 told me I no longer needed it (I still would like it, but don't have the big desire any more). I can't compare the 3 lens because I have never had the 40 or 21, but I do love the 20-40, and the WR part of it is really a big deal since I shoot mostly nature and landscapes. The only other limited I have is the 15, which I love, but it is not as good as the 20-40

I have the Sigma 17-50mm too and in fact I'd say it has better image quality than the 20-40mm. Not in terms of sharpness, I didn't notice any differences there, but in terms of rendering, especially subtle colours.

I've seen this being said here before, and I'm not disputing it, as I don't have the 20-40mm to compare... but my copy of the HD DA 21mm f/3.2 Limited is one of the sharpest lenses I own. It required fine focus adjustment in basically all my bodies but once I did that, what a world of difference... as sharp as my DA 35 Limited on the 24MP K-3 and 20MP K-S2 in medium to long focus distances (I'm not even kidding...) and the colors and color transitions are just superb.
The problem with the DA 21 is that because it's a wide angle lens, when the focus is a big off and needs adjustments, it doesn't really look out of focus, it just looks like it's not quite as sharp as other lenses. When you look at pictures on a smaller screen like a notebook computer, you don't even see that the focus is off, everything seems sharp until you pixel peep, at which point things get uglier.
I'd love to own the 20-40mm one day if it's even better than my DA 21.

I loved my 21mm for a long time, despite being occasionally frustrated with the green blob flare, but someone on these forums mentioned that often their copy had trouble focusing accurately at longer distances or infinity, leading to slightly out of focus images, but that at medium and short distances it was fine. Sure enough, when I checked back and pixel-peeped some landscapes taken with the 21mm I noticed they weren't too sharp. I don't remember if that was just before or just after I bought the 20-40mm but it was the mail in the coffin for the 21mm for me. Now I have neither, I kept the 15mm, the 16-85mm and the above-mentioned Sigma for wide angle.

[mikesbike]

The advantages of both the DA 20-40mm Ltd and the DA 18-135mm WR lens are both offer WR over your kit lens, and also a much quieter, more accurate AF. The bigger zoom lens offers much more versatility, while still being compact for what it is. It is a great performer. The 20-40mm Ltd is yet more compact, but this at the expense of zoom range. However, even though so compact, it offers a larger aperture of f/2.8 at 20mm. I have both of these lenses.

Regarding the K-5, its AF is sometimes not reliably fast or accurate with some lenses. The AF performance was upgraded with the K-5 II and K-5 IIs. I use my DA 20-40mm Ltd only on my KP or occasionally my K-S2. I have never had it on my K-5 or K-5 IIs for that matter. But I have often used my now quite old (over 10 years) DA 18-135mm WR on both of these cameras, and I can report that AF with this lens on the K-5 makes the K-5 perform as if it too had the greatly improved AF ! The DA 18-135mm WR makes for a great match with the K-5, even in its physical size and balance with this camera. At such a reasonable price, I'd suggest going for a new one. Some used ones have developed zoom creep when carrying the camera lens-downward. I always carry a camera in a shoulder-strap + belt-loop holster case, never on a strap hanging around my neck. I just draw the camera out of the case when needing to shoot, sliding it back into the case when done. I bought mine new, and after all this time it has never developed zoom creep.

[Hayashi]

20-40 is one of the most interesting APSC lenses in Pentax lineup.

I owned it back in 2015, sold it in 2017 because moving to K-1 FF body, then bought another one back in 2021 while I switched back to K-3III APSC.

The image quality and bokeh is just exceptional.

Here are some shots of HDDA20-40mm with K-3 and K-3III:

1)



2)



3)



4)

[mikesbike]

Those look very nice. If wanting to see sample images from the DA 18-135mm, just look in this section for the thread entitled "DA 18-135mm WR Show us what it can do". Start with the last page (most recent) and work backwards.