| Author: | | Site Supporter Registered: September, 2011 Location: Hampshire, UK Posts: 2,129
1 user found this helpful
| | Review Date: July 17, 2015 | Recommended | Price: $750.00
| Rating: 10 |
| Pros: | IQ, general solidity and 'feel', construction quality, zoom smoothness, manual focus over-ride smoothness | | Cons: | None | | Sharpness: 10
Aberrations: 9
Bokeh: 9
Autofocus: 9
Handling: 10
Value: 10
New or Used: New
Camera Used: Pentax K-5
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I bought this lens during a special offer period, and it has hardly been off my K-5 since. My previous standard zoom was the 16-45 which was itself a step up from the kit zoom, but the images from the 20-40 have something about them. Flare resistance is incredible. The supplied hood is a little small but with the HD coating, this is not an issue. Any necessary additional shading can be provided with the hand. Sharpness is very good indeed across the range, and at the sweet spot of around f8 it really is a cut above my other lenses.
The K-5/20-40 package is very compact, and the lens is just such a pleasure to use. The zoom is silky as is the manual focus fine adjustment, and the all-metal construction just feels so right. I also like the simplicity of the design: no knobs, switches, levers - just the zoom ring and the fine focus ring. Yes, the focus ring turns when the autofocus operates, but that's not an issue. The DC autofocus itself is almost silent and locks quickly, even on my veteran K-5. Strongly recommended.
| | | | | | | Veteran Member Registered: July, 2011 Location: Eastern Oregon Posts: 856
9 users found this helpful
| | Review Date: April 21, 2015 | Recommended | Price: $695.00
| Rating: 10 |
| Pros: | Sharp, great contrast, thick lush color saturation | | Cons: | none | | Sharpness: 10
Aberrations: 10
Bokeh: 10
Autofocus: 9
Handling: 10
Value: 10
New or Used: New
Camera Used: K3, K5IIs
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I LOVE this lens. The review(s) are wrong. They must have got a bad sample. This lens is as good as the primes it covers, namely the 21/31/35/40/43 LTD's. And most importantly it has that LTD magic photo dust sprinkled all over it, the shots are rich, lush and have that "artistic" something that we all crave. This lens (and the LTD's in general) make me want to photograph things just to see what they look like through it. This lens covers my 17-50 Tamron with WR and better IQ. I still use the 17-50 for weddings as a backup etc, but this 20-40 is my goto everything lens. With the 15 and 70, it is my travel/landscape foundation lens. I don't find the zoom range limiting at all. It's a very convenient fine tunable normal. If I need wide or tele, then I switch lenses. But for everything else it's perfect. Just buy one. At $695 USD it's a great deal.
| | | | | New Member Registered: April, 2014 Posts: 4
4 users found this helpful
| | Review Date: March 2, 2015 | Recommended | Price: $800.00
| Rating: 10 |
| Pros: | Small size, build, styling, bokeh, image rendering, weather sealing | | Cons: | none | | Sharpness: 10
Aberrations: 9
Bokeh: 10
Autofocus: 10
Handling: 10
Value: 9
New or Used: New
Camera Used: K3
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This lens is well worth having. Like another reviewer said, don't let some of the negative reviews scare you off. I found that none of the negative points are relevant. The f/4-2.5 aperture range is not a problem on a camera like the K3 with or K5 with their high ISO capability. The limited zoom range is not relevant either. The 20-40mm focal range covers the most-used normal-wide focal lengths on a crop sensor camera. All of the other lens makers, Canon, Nikon, Sigma, make zooms with similar restricted focal lengths and they sell just fine.
I tested the rendering capability against the FA-43 and SMC K 30mm (sire of the FA-31). The 20-40's rendering capability is equal to those two legendary lenses. The bokeh is very smooth resulting from the rounded aperture blades. The lens weight is deceivingly light. The size is small so it's not obtrusive nor obnoxious to carry. So many of the other zoom lenses in this range are as big as water bottles. I really like the tasteful styling with the Takumar-style zoom ring. All in all, it's a very excellent lens, capable of excellent results, on par with all of the Pentax Limited primes, and looks good to boot. Highly recommended!
| | | | | Site Supporter Registered: May, 2014 Location: Minnesota Posts: 2,046
7 users found this helpful
| | Review Date: December 25, 2014 | Recommended | Price: $574.00
| Rating: 9 |
| Pros: | Small, Light, Weather sealed, Quiet | | Cons: | Limited range | | Sharpness: 10
Aberrations: 9
Bokeh: 8
Autofocus: 9
Handling: 10
Value: 8
New or Used: Used
Camera Used: Pentax K-5 IIs
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First of all I can't give an extensive review for this lens since I only had it a couple of weeks. Maybe after a few months I'll update this review to give you a better perspective on how I feel about this lens. I have lusted for this lens for quite a while now, but the thing that held me back was the price. Due to the limited range and due to some negative reviews I was hesitant to fork over that much money for it. A few weeks ago I was looking at the BH website and saw that this lens was selling for only $574 Used in 9+ condition !
This was about the lowest price I had yet to see for this lens new or used, so I got it. I figured I could always send it back within 31 days if I did not like it.
So, lately I have been testing this lens under as many real-life conditions as possible, hoping I would not have to send it back. Like I said, it's only been a few weeks if that many, but so far I'm pleasantly surprised. This lens is a marvel of engineering and so fits well with my K-5 IIs which is a marvel of it's own.
First I will describe the Aperture which some people have complained about being too slow. At 20mm you can open up to f2.8, at 25-30mm f3.5, at 35-40mm f4.0. Not bad considering that even some limited primes within those focal ranges are not much faster.
I compared the Sharpness of this lens against my 16-45mm f4 and 35mm Macro f2.8. The good thing about this lens is that it does not extend much from the body like my 16-45mm does. At 20mm it extends about 2/3 of an inch. at the other focal lengths it does not extend past 1/2 of an inch from the body. The distance scale on this lens is quite limited in that after 5 feet it goes straight to infinity with nothing in between, but that might have to do with lens design for zooms which I now little about
From what I can tell, this lens is a tad sharper than my 16-45mm across all focal lengths except maybe the 30mm focal length, why I don't know ? What this lens got going for it, is the way it renders the colors and the contrast. Not artsy, not over-saturated, but amazingly life-like. At 35mm, my 35mm f2.8 Macro is sharper across the length of the frame, but to tell you the truth, there is not much difference between all 3 lenses unless you really pixel-peep. If you really want sharp though, set the camera to ISO 80. Then you start moving into 3D territory...
Handling : Although this lens is supposed to be all metal, it is very light to the point where I think it's some kind of aluminum instead of real metal ? Nevertheless it is very well built, but I wish it had the heft of my other limited lenses just my opinion... The focusing is very well damped as well as the Zoom dial. So there is no problem there. One thing is the very fancy lens cap. I am so afraid that I might drop it and lose it (@$40) that I keep it in my left hand when shooting. This lens is light and well balanced enough for me to do that thankfully.
Autofocus is nearly silent and pretty quick. You really have to put your ears pretty close to the camera to hear it. This is perfect for places like museums, operas, churches, funerals, where the loud buzzing whirl of other lenses might become annoying. One thing I noticed is that the AF is faster and much more accurate if you limit the auto focusing points. I set my AF to Sel Mode and only use one focusing point, so far this has worked best for me.
Bokeh is reasonable mild/smooth a little better than on my 16-45mm, but not better than on my 35mm, or 77mm. I have not had the time to test this much so I can't say much about it.
Aberrations: What I like about this lens is this new Pentax Anti Flare coating. This really helps when shooting into the light, not just sun light, I'm talking about street lights and car lights and things like that. This lens does not fall apart like my Limited and other lenses do in those conditions. Another thing I noticed though is that this lens produces a little bit more CA under certain circumstances than my 16-45mm. It could be my copy, but I'm still investigating.
If you take all the features into consideration, not just pixel-peeping sharpness, this is a wonderful lens and a marvel of engineering. Time and experience will tell whether I will send it back, but so far so good. | | | | | | | New Member Registered: May, 2013 Posts: 13
9 users found this helpful
| | Review Date: July 29, 2014 | Recommended | Price: $825.00
| Rating: 9 |
| Pros: | Sharp, Color, Weather Sealed, Light, Compact, Flare Resistance | | Cons: | Slow Autofocus, Price, Lens Cap | | Sharpness: 9
Aberrations: 9
Bokeh: 10
Autofocus: 6
Handling: 10
Value: 8
New or Used: New
Camera Used: Pentax K-5IIs
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I bought this looking for an upgrade over the DA SMC 18-135 which I had used for a year or so and actually liked but I purchase a few of the limited series lens and was astounded at much better they rendered color and, in general, how much sharper they were over the 18-135. The HD 20-40 obviously doesn't have the zoom range and it isn't as useful in that regard but it renders colors so much better and is much sharper. I apparently got a good copy since I have found mine to be decently sharp wide open and very sharp when stopped down just a little more. The new HD coating works amazing well in tough, high contrast conditions. The autofocus motor is quiet. Not as quiet as SDM but much quieter than screw drive. It is a bit slow sometimes to lock onto a subject. Can be a tad frustrating at times.
Construction is top level and then lens feels good on the camera. Not too heavy but substantial enough. The weather sealing works very well. I was recently involved in a kayaking mishap where mine and my wife's tandem kayak sprung a leak in the middle of a bay in the Florida Keys. Eventually the kayak became too unstable to paddle and flipped. My wife saved the camera but it did get partially dunked in the bay. We were stranded out there for a couple hours till a boat came by and rescued us. The lens held up totally fine and the camera has of course okay as well. I was impressed! We of course were exhausted, dehydrated, and glad to be out of the water.
The price is steep for what it is but I wasn't willing to pay the equivalent to get the DA* 16-50 with potential SDM issues and the extra weight. I did find a good deal on this lens lurking Amazon but I do think the lens is a little too expensive for what it is. Maybe $799 for it brand new.
The lens cap is 62mm in size, the filter size is 55mm, and expensive! Don't lose it because it costs $40 to replace! It fits over the "lens hood" if you can call it a lens hood. My opinion is that flare is such a minimal problem with this lens that it could go without the lens hood the majority of the time.
I really enjoy using this lens. It stays on my camera 90% of the time.
 | | | | | Inactive Account Registered: January, 2014 Posts: 76
1 user found this helpful
| | Review Date: July 4, 2014 | Not Recommended | Price: $1,060.00
| Rating: 6 |
| Pros: | Built, Bokeh, design, WR | | Cons: | IQ, AF, hood | | Sharpness: 7
Aberrations: 9
Bokeh: 10
Autofocus: 7
Handling: 10
Value: 6
New or Used: New
Camera Used: K-5ii
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This is my first pentax lens that I dislike.
First impression was very good. Lens is really nice piece of metal. Handling is very pleasant. But photos were lacking of something... And I didn't know what is not right. So I have done some testing (tripod, MUP...) between this DA20-40, DA L 18-55 Tamron 17-50 and DA18-135 and DA 35 AL. And that show, that this lens is really lack of sharpness! It isn't absolutely horrible, in fact it's quite mediocre - but for $1000 lens it is not acceptable. Kit lens has same IQ on 20mm as this lens, and my 18-135 is better! On 35mm is standing: Tamron, prime DA35 2.4, 18-135, DA-20-40, and kit lens. It has worse IQ thru all FL than my Tamron 17-50 and somewhere on par, somewhere worse than 18-135.
Autofocus is quite strange. Its quiet but not quick. My screwdrive lens are faster. And behavior of AF motor is like screwdrive, lik zzzzzzzzzzzzzzzzzzzz...tz. My other DC lens lock focus instantly, no need to microadjust, same on my SDM lens... And with multiple presses of AF button - multiple microadjustment - even on contrast scene.
What is good: This lens has very low CA, good flare resistance, nice built. And very, really very nice bokeh (maybe best for wide zoom that I ever seen). And it can handle images at higher ISO then others - I don't know how, but photos from this lens seems have less noise than photos from other lenses on same ISO.
Bottomline: I'm glad, that I had bought this lens from shop, where wasn't problem to return it and change it for another lens. But he had only one piece of 20-40, so I picked another lens. Maybe I'm just "lucky" for dud - but, apparently, I'm not alone.
| | | | | New Member Registered: February, 2013 Posts: 14
3 users found this helpful
| | Review Date: May 7, 2014 | Recommended | Price: $1,300.00
| Rating: 10 |
| Pros: | IQ, bokeh, build quality, WR | | Cons: | Not constant 2.8, not internal focusing | | Sharpness: 10
Aberrations: 9
Bokeh: 10
Autofocus: 9
Handling: 10
Value: 9
New or Used: New
Camera Used: K-5
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Before this lens, my main lenses was DA*16-50 and DA*50-135, but usually I left the 16-50 at home. It was too big and I felt the pictures it produced varied too much in quality.
I bought this as soon as it came out and fell totally in love with it. It's been constantly on my camera ever since and I have no desire to remove it.
The "weired" zoom range, wich I was a bit afraid would turn me off, really doesnt bother me anymore.
I tend to threat it as a 30mm prime with "adjustment possibilities".
I've used it alot with extensiontubes, and it produces great macro results with the tubes. The transition between the sharp and the blurred, I find to be just lovely.
The only trouble I have is that I cannot access the menu on my K-5 with the extensiontubes and it refuses to go beyond f. 3.5. Wich is weired because all my other lenses communicate perfect with my camera through the extensiontubes. It might be the DC, it might be a software issues with the firmware. I don't know.
All in all I find this to be a great lens. It has reignited my interest in photography and cured my LBA. So now it's all about the pictures, instead of the gear, for me.
It might not be everyones cup of tea, but for me this is the gem I've been looking for (with a few minor flaws).
(Sorry for the bad grammar. English is not my mother tongue.)
| | | | | Site Supporter Registered: May, 2011 Location: Arlington, VA USA Posts: 1,060 | | Review Date: April 22, 2014 | Recommended | Price: $900.00
| Rating: 10 |
| Pros: | Excellent build, quiet fast focus and very good image quality | | Cons: | The lens hood | |
This is a lens you have to hold and feel, the quality is amazing, a welcome new addition to the Limited line up in my opinion. I admit with all the unfavorable discussion on this lens, I was a bit hesitant. Thankfully my local camera store had their semi annual sale and I was able to try for I buy. I was sold when I was using it. I have put the lens through its paces and I am very pleased. The sharpness is very good through out the range, very little distortion, and very quite focus. Focus is accurate and decisive. Blazing fast, no, but still fast. It also gets in pretty close for decent close ups!. Anyway, I can see this being my main lens for my URBEX photography as it lightens my gear a bit. I know the price is on the high side, but it is a well crafted lens that deserves a second look.
| | | | | New Member Registered: May, 2012 Posts: 3
5 users found this helpful
| | Review Date: March 31, 2014 | Recommended | Price: $1,000.00
| Rating: 10 |
| Pros: | sharp, build quality, silent | | Cons: | size, hood | | Sharpness: 10
Aberrations: 10
Bokeh: 10
Autofocus: 10
Handling: 9
Value: 9
New or Used: New
Camera Used: K5
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I have had this lens for a week and the following are just some of my observations and opinions. I am a bit of a "pixel peeper" thus was looking something that would be smaller than 16-50, give some flexibility and be SHARP!
My take on commonly debated points:
1. SIze: Yes, it is bigger. Get over it! It's an awesome lens, much smaller than any zoom with such IQ. And as it is so light, it doesn't weight down the front end so I forgot the size of it and treated it the same way as rest of my Limited's. People seem to forget that Limited's are incredibly small primes, this should be compared to zooms of equivalent IQ and it fares incredibly well in terms of size.
2. Aperture: At this size and IQ I am fine with the non-fixed aperture. If you want fixed aperture, set it to f4 and be happy If you want extreme aperture get FA 43 or A 50 f1.2 
3. AF: Slouch? No, but it is slower than the rest of DA lenses. This is not an action lens, it is a lens where you take your time to compose the shot and AF is more of a helping hand so the slower speed doesn't bother me. I did not feel the need for it to be any faster at any point.
4. Zoom: People compare it's size to primes and zoom range to 16-50? Really? I see this lens as a "flexible prime". It gives the handling and IQ of a prime while allowing some flexibility, not much but some when changing lenses is too slow or a very bad idea.
Pros:
1. Bokeh! This thing is wonderful, the rounded blades definitely do help. In comparison to FA 43 the bokeh of the background tree branches was a bit too nervous, but that is me splitting hairs already.
2. Sharpness. Mine is sharpest at 40mm, almost the same at 30 and a softer at 20mm. At f8 it has more resolution at any focal length than K5 "can handle", when wide open it softens up but only marginally. This thing gives the FA 43 run for its money and I personally think DA SMC 21 is on par with this thing in terms of IQ.
3. Build quality: The metal construction is sweet, it came to me as a surprise that the zoom ring is not metal, its rubber or plastic not sure, but very good quality one. I was not sure about the non-metal ring at first, but then realised that zooming all the time will rub the paint off the zoom ring and this thing will look...not so great. So now I think the non-metal ring is an awesome idea.
4. AF: Ouh, the sweet silence
6. WR: As it is new I am babying this thing, but friend of mine dropped a full cup of coffee over the lens and camera. Result? Wash under the tap and continue the walk  Works like nothing happened and all good
Cons:
1. Quickshift: Even though this lens has quickshift, the focus ring rotates when focusing and sometimes catches my fingers when doing that. Full time clutch like the one on other DA lenses would of been useful.
2. Hood: This thing is there for show and protect the front element. I think I will replace mine with 55-58 step-up ring and de-glassed filter to make a DIY hood and simple clip on cap. Just as useful and no drama when lost. Also makes the lens more wear proof as lens cap is usually first one to wear.
3. Price: This thing is expensive! I got a deal on it £200 off so was worth it, but at £850 it is just simply not worth the money!
In total this is a good addition to the Limited series and worth the money at around £650, not sure at £850 though. Incredible optics in a nice and small body
It's impossible to make a lens that satisfies everyone and every situation and I think comparing the zoom range to 16-50 and size to other Limited's is just non-sense. Zooms are always bigger and this one is small considering it's IQ.
| | | | | Junior Member Registered: January, 2013 Location: Texas Posts: 32 | | Review Date: March 10, 2014 | Recommended | Price: $950.00
| Rating: 9 |
| Pros: | Build Quality, Light Weight, Image Quality | | Cons: | Price, limited range | | Sharpness: 9
Aberrations: 9
Bokeh: 9
Autofocus: 9
Handling: 10
Value: 8
New or Used: New
Camera Used: Pentax K30
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Except for the limited zoom range, this lens is very practical: small, light, all-metal, low minimum focusing distance, 49mm filters, very good autofocus and manual focus.
I took only 5 'test' photos with it, the brick house of my neighbor. The results are really excellent, and I don't understand some other reviews:
- I cannot see vignetting!
- Sharpness:
- at 20mm / 2.8: Center 90, Edges 80
- at 20mm / 4.0: Center 100,Edges 90
- at 20mm,5.6: Center 100,Edges 90
- at 40mm/4.0: Center 90,Edges 80
- at 40mm/5.6: Center 100,Edges 90
'100' being near-perfect.
I love it!
| | | | | Senior Member Registered: November, 2009 Location: San Jose, CA Posts: 103
8 users found this helpful
| | Review Date: February 24, 2014 | Recommended | Price: $996.00
| Rating: 10 |
| Pros: | light, sharp, great build, WR, zoom range | | Cons: | lens hood, price | | New or Used: New
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For me, this is a great lens. And I may be the only one who actually likes the strange zoom range, but I do. First a little background. I have all the DA limiteds and use them whenever I have the time to play around with composition and enjoy shooting - which mostly means whenever I am by myself. When I go out with group of non-photography friends though, or whenever the weather isn't exactly right, I would end up going out with my 18-135. Which is WR and very small for the zoom range, but slow, not very great optically and no fun to use. It's much more fun to use limited primes (limited in more then one sense), because creativity often comes from that limitation. With 18-135, I just get complacent, zoom from where I stand and shoot.
But 20-40 changes all of that. It's a zoom, but still very limited. It gives me that possibility to go from 20-40 without changing the lens, and it gives me beautiful photos, very much comparable to limited primes.
It also creates beautiful travel kit with other DAs. My goto ultra light travel kit could easily be 15 for wide angle, 20-40 as basic walkaround and WR lens if it starts raining, 70 for short small telephoto. Replace 70 with macro for little extra reach and macro at the price of added weight. Or with 55-300 for real telephoto. Can't ask for much more. See I do like to travel light.
Scared by reviews here, I did some of my testing when I got the lens. It's sharp as sword in the center! And, I do not think there's a significant issue with corner sharpness, at least on my copy. The lens does have, though, a significant field curvature. If you focus the center at the open aperture, corners, especially at the close focus will be very much out of focus. You can focus the corners - then of course center will be out of focus. I believe for this type of lens it's normal behavior and refuse to be bothered by that. It pretty much disappears once you close the aperture enough, it gets much better at distance. Would I take this lens to take pictures of the artwork in the dimly lit gallery? Hell no, but that's not its purpose either. That's what macro lenses are for. Other then that, the lens is perfectly sharp on my K-3.
Some comparisons.
Compared to DA 21
21 pros:- tiny (this may actually play big role sometimes)
20-40 pros:- better sharpness over the field
- WR
- zoom
Compared to DA 40
40 pros:20-40 pros:
Compared to DA 35 Macro
35 pros:- macro
- uniform sharpness across the field
- I believe picture quality is a tiny bit better overall
20-40 pros:- WR
- faster focus, especially when macro start hunting
Compared to 18-135
18-135 pros:- zoom range
- price
- internal focus
20-40 pros:- much better optically (it better be for twice the price though)
- faster
- lighter
- parfocal! - this lens is completely parfocal, which allows you to do nice things, like focus on the (40mm) end, then zoom out and the focus stays the same.
 | | | | | New Member Registered: December, 2013 Posts: 2
1 user found this helpful
| | Review Date: February 7, 2014 | Recommended | Price: $996.00
| Rating: 9 |
| Pros: | Sharp,great built, compact, good contrast | | Cons: | Poor quality control - first sample required RMA exchange, marginally useful lens hood | | Sharpness: 9
Aberrations: 9
Bokeh: 10
Autofocus: 8
Handling: 10
Value: 7
New or Used: Used
Camera Used: K-3
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My first copy was badly decentered, with the left side very soft and a weird lack of sharpness at 30mm, f/5.6. BH Photo was very good about making a prompt and hassle-free RMA exchange.
The second copy was noticeably better, with excellent sharpness across entire field at all focal lengths when used between f/5.6 and f/7.1 except for lower right corner at 20mm. Closed down, this lens is very good, but it's not really suitable for dim indoor light due to the need to stop down for best results. A bit of localized sharpening and increased clarity in Lightroom generally solved this problem.
Excellent build, weather-sealing, and compact size/light weight were the deciding factors when compared with the much larger and heavier Sigma 18-35mm, which I might have bought otherwise. It is somewhat sharper than my non-VC Tamron 17-50mm toward the edges, but not by a great margin.
It took some time to determine the best way to use this lens for maximum image quality, but I now find it very suitable for general use. Overall, it's sharper than I expected from the Pentax Forum and DXO reviews.
| | | | | Senior Member Registered: July, 2008 Location: montreal Posts: 136
1 user found this helpful
| | Review Date: January 16, 2014 | Recommended | Price: $1,000.00
| Rating: 10 |
| Pros: | small, WR, build quality, IQ | | Cons: | Some vignetting at 40mm but easily corrected. | | Sharpness: 9
Aberrations: 10
Bokeh: 10
Autofocus: 9
Handling: 10
Value: 9
New or Used: New
Camera Used: K-01 and K20D
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I rated it a 10 for me because it does exactely what i wanted from it, that's why i bought it. Sharpness is very good at any focal length and apertures, except at 20mm at f/2.8 in the corners but i don't care. At 40mm there is still some vignetting even at f/13 but it's easily corrected in LR.
I really like it's small size, Limited build quality but with the addition of WR, just perfect !
| | | | | Veteran Member Registered: December, 2009 Location: Georgia, VT Posts: 1,657
19 users found this helpful
| | Review Date: January 3, 2014 | Recommended | Price: $896.95
| Rating: 9 |
| Pros: | Light, Small, Build Quality, Picture Quality | | Cons: | Small-ish Aperture, Slow Auto Focus | | Sharpness: 9
Aberrations: 10
Bokeh: 8
Autofocus: 8
Handling: 9
Value: 8
New or Used: New
Camera Used: K-3, K-5, K-x
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I have every SMC Pentax Limited lens with the exception of the 35mm Macro, and that's pretty much my carry-around kit (in addition to a Sigma EX DG 100-300mm F4 on occasion). Out of those lenses, the DA 21mm, FA 31mm and FA 43mm are my most-used, with the FA 31mm taking up the majority of time on my cameras. So when this 20-40mm Limited was announced, I was pretty excited. A Pentax Limited zoom that covers my most-used range? AND weather resistant? YES PLEASE!
I agonized over this lens vs the Sigma 18-35mm F1.8. I'm a real slave to wide apertures, and that Sigma has some mouth-watering specs at a lower price. It's a hard sacrifice going from F1.8 to a variable F2.8-4. But in the end the 20-40mm won me over with its weather resistance, much lighter weight and reasonable size. Also, it's a Pentax Limited.
Of course, the first thing I did when I received the DA 20-40mm is physically compare it to the FA 31mm since that's the one most often on my camera. Turns out the 2 are pretty close. The 20-40mm with the hood removed is almost exactly the same length as the 31mm. The hood is only 1/4" long and no wider than the lens, so it adds no real bulk. The 20-40mm has a slightly larger diameter than the 31mm, presumably to accommodate the focus motor. And surprisingly, the 20-40mm is 2 ounces lighter than the 31mm (10.5oz vs 12.5oz). As far as fitment on my cameras goes, the 20-40mm makes the setup lighter while keeping the overall size about the same.
Build quality is jaw-droppingly good. The zoom and focus rings are flawlessly damped, and there's no give anywhere. Everything is made of aluminum and finished to perfection. I got a silver one to go with my silver K-3 and K-5, and I'm in awe of how well made this lens is. It even surpasses my other Limited lenses. The zoom ring has a great machined look that's reminiscent of my old Super Takumar 50mm F1.4 (although it was a focus ring on that one).
Auto focus is impressive, though less than I'd hoped. The auto focus accuracy is spot-on with my K-3, even in ridiculously low light. It gets perfect focus without any need for the AF assist light, even when I can't see the object I'm focusing on with my own eyes. I guess that's as much because of the K-3 as anything else, but I expected the smaller aperture to have more negative impact.
But as far as auto focus speed, I expected the built-in motor to perform a little better. It's no faster than most screw-drive auto focus lenses I own, and noticeably slower than many, including the DA 15mm, DA 21mm and FA 31mm. Sure, it's silent, but I've never been bothered by the sound of screw-driven auto focus. I would've preferred a screw-drive mechanism in this case if it meant faster performance.
The aperture is something everyone's been talking about ever since this lens was announced. While no DA Limited has ever had a large aperture, for some reason many Pentaxians were surprised when this one followed the exact same trend. There's nothing terribly surprising about a small-ish aperture on a DA Limited lens. I *was* a bit surprised by the variable aperture, but then this is the first Limited zoom ever, so it's not like there was any precedent to make me think it should be otherwise. At first I wasn't sure if this aperture range would suit my needs. Lately most of what I shoot is my baby daughter indoors, for which the FA 31mm was perfect. I was spoiled by being able to shoot at F2.2 and low ISO and having perfect results every time. So the small aperture of the 20-40mm threw me for a loop, and initially I really didn't like it. It was annoying enough that I contemplated sending the lens back and waiting for the Sigma 18-35mm F1.8 after all.
But then I did something weird... I cranked up the ISO. All the way up to 3200! (I almost never went beyond 800 before). Lo and behold, the pictures turned out beautiful! Sure, there was grain, but there was also tons of fine detail. A quick trip through denoising software and a little sharpening made those pictures come out as clean as anything shot at ISO 800. It was a revelation. I'm sure the camera's denoising engine would do an admirable job as well, but I've been a RAW shooter for years and that won't be changing anytime soon. The point is, the small-ish aperture of this lens doesn't have to be a limitation as far as low-light shooting goes.
As for bokeh, the 9 rounded blades do an absolutely stunning job here. Sure, there's less out-of-focus area in the scene due to the smaller aperture, but even F4 gives some very nice bokeh at 40mm when the subject is close enough. It's creamy smooth in front and behind the plane of focus, and it transitions beautifully. On the downside, starbursts from points of light are somewhat disappointing. I needed at least F22 to get any respectable star shape, and having 18 points makes it look a bit odd.
If you read this whole review, I kept the best for last: picture quality! This is what ultimately convinced me that I made the right choice with this lens, despite the smaller aperture. The old cliché "like a prime lens at every focal length" might just apply here. The only softness happens wide open at 20mm, and then only away from the center. Anything else is amazingly sharp, especially on a K-3 with the AA filter disabled. I can't believe the amount of detail and micro-contrast this lens delivers, it's like magic. As far as zooms go, it's quite possibly the best I've ever seen.
edit: to clarify, the edges and corners ARE soft wide open at 20mm, but the center remains very sharp. This is the only range I came across where sharpness takes a noticeable dip. By F4, the sharpness has caught up to the rest of frame again. And I personally don't find the softness objectionable, it's what I'd expect from the wide end of a lens in this focal length range.
Flare? Glare? Nope, not with this lens. I shot right into the sun on a bright Winter morning and only got the faintest amount of glare in the frame, barely discernible at all. I got no flare whatsoever, though. Shot wide open, I can make out the merest hint of purple fringing in the far corners of the frame, but that's it. And that's pixel-peeping at 2x magnification. This is unbelievable, and puts the CA-monster FA 77mm Limited to shame.
I read some comments from other people who ended up with decentered samples of this lens. I know that feeling too well, I experienced the same thing with my DA 15mm Limited. But with this 20-40mm, I struck gold; no quality control issues that I can see whatsoever. Call me lucky... this time.
I've found my new favourite lens, and it is the 20-40mm Limited. I'll be sure and try the Sigma 18-35mm F1.8 as soon as I have a chance, but it would have to be absolutely perfect to get me to change my mind. For now, the 20-40mm is taking the honored place of the FA 31mm as the featured lens on my camera.
UPDATE - January 6th, 2014
I just read the PentaxForums.com "In-Depth Review" for this lens, and I find it interesting that their findings on image sharpness are completely reversed from my own. They found this lens softer wide open at 40mm, but sharper wide open at 20mm. I guess it's either due to sample variation or different testing methods.
In any case, to give an idea of how sharp this lens is, here's a photo I took at 40mm, F8 and ISO 3200 using a K-3:
You can click on the image to see a full size version. Pay close attention to the eye closest to the camera at 1:1 magnification. That's where the camera was focused.
Second example (sorry, all I have are baby photos recently). This one was taken at 40mm, F4 (wide open), ISO 3200 using a K-3:
Again, on the full size version, pay attention to the eye closest to the camera. The eyelashes are about as sharp as can be. Also, if you look at the right edge of the picture, you can clearly see some in-focus texture in the cushion fabric. Same on the left edge with the blanket, the fabric texture can clearly be made out. Again, this is wide open.
UPDATE - February 1st, 2014
I continue to love using this lens daily for all kinds of different subjects. As far as I'm concerned, this is a constant aperture F4 lens, with F2.8 available to me as a bonus when I really need it. Some of the best zoom lenses ever made have an F4 constant aperture (Sigma 100-300mm F4, Pentax 60-250mm F4, 20-35mm F4, 24-50mm F4, 12-24mm F4, Nikon 16-35mm F4, etc, etc) so when I look at it that way, this lens becomes even more awesome.
UPDATE - July 13th, 2014
I'm starting to think there are some serious issues with quality control regarding this lens' manufacturing. Apparently I got a perfect copy, unfortunately other pentaxians haven't been so lucky. It's impossible to dismiss the complaints from people who have received a decentered copy, or are getting poor results. My copy of this lens continues to excel in every way, not least of which is autofocus accuracy. The focus for ALL my shots taken with this lens is always spot on, it's almost magical. I've needed no focus adjustment on either my K-5 or K-3 with this lens, even at F2.8. Based on this, I've had to increase my autofocus rating from 5 to 8, despite the occasional slowness of the focus motor.
Today I had a chance to try the other lens I was considering before deciding on this 20-40mm: The Sigma 18-35mm F1.8. Sure enough, the image quality with that lens was amazingly good, just as good as the 20-40mm in most cases and somewhat better in extreme cases (like at full zoom). However about 1/3 of my shots with the 18-35mm ended up being misfocused, usually not enough to be obvious on the camera's LCD at a glance, but enough to make some pictures disappointing. It's like the 18-35mm induces a bit of front or back focus, but only randomly, so it can't really be corrected for in the camera. Very frustrating. It even happened on 2 nearly identical shots, back-to-back. One shot was in perfect focus, the other was slightly back focused. This is never an issue with the 20-40mm.
Also, the 18-35mm is HUGE and HEAVY for the type of shooting I've been doing lately. All in all, I'm glad I decided on the 20-40mm rather than wait for the 18-35mm. It turned out to be the perfect choice for my needs. But then I'm lucky I got a good copy... apparently not everyone is so lucky  | | | | | Inactive Account Registered: June, 2011 Location: Gulf Coast Posts: 45
3 users found this helpful
| | Review Date: January 2, 2014 | Recommended | Price: $896.00
| Rating: 9 |
| Pros: | Size, classic 35mm focal lengths | | Cons: | None. | | Sharpness: 10
Aberrations: 10
Bokeh: 10
Autofocus: 6
Handling: 9
Value: 9
New or Used: New
Camera Used: K5 ll
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My FA31mm has not been used since it's arrival ! Using in a disciplined manner, not just zooming, I now have classic focal length reportage lenses on my camera. I have found this to be very sharp (maybe to sharp) in the center at all focal lengths even wide open ( f5.6 at 40mm) which is not really my style anyway, f5.6 f8 is what I use for the most part.
Now I have had this for a while I now can give a more realistic review update. I find the auto focus is not very good at all. When it focuses on a subject, very slow by the way, gets a fix on it and will not focus on a new area just a few feet away. It needs to be encouraged to refocus by manually putting it out of focus first. This procedure makes for a very slow lens handling and therefore consider the auto focus very poor. Hope they can fix this with some sort of update. | | |
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