HD Pentax-DA 20-40mm f/2.8-4 Limited Lens Review

Gary Wolstenholme reviews the new HD Pentax-DA 20-40mm f/2.8-4 Limited DC WR lens - the first Limited edition zoom lens from Pentax.

30/01/2014 - 09:38

Handling and Features

HD PENTAX DA 20 40mm F2 8 4 ED Limited DC WR Lens Black (4)

This 2x zoom lens provides an angle of view equivalent to a 30.5-61.5mm lens on a 35mm format camera, when mounted on a Pentax Digital SLR, which is neither very wide, nor very telephoto. It sports a relatively fast variable maximum aperture of f/2.8-4 and costs around £850, which isn't cheap for a lens covering this range. The price may be explained in part by this being the first weather-resistant zoom lens in their 'Limited' range. In this review we'll take a look at how it performs.

HD Pentax-DA 20-40mm F2.8-4 ED Limited DC WR Handling and Features

HD PENTAX DA 20 40mm F2 8 4 ED Limited DC WR Lens Black (7)

The build quality of this lens is very solid indeed with a metal lens mount and a mixture of high quality plastics and metal used for the construction of the lens barrel. It appears to have a touch of retro styling going on, with a zoom ring reminiscent of how the focus rings were on the old screw-mount Takumar lenses from the era of the Spotmatic SLR. The lens is lightweight, weighing only 291g with the lens hood attached and it balances well with the Pentax K-5 IIs body used for testing.

Focusing isn't performed internally, so the lens barrel extends during focusing and during zooming. Even so, the filter ring does not rotate, which makes it perfect for use with polarising and graduated filters. A shallow metal hood is supplied with the lens that screws into the 55mm filter thread.
HD PENTAX DA 20 40mm F2 8 4 ED Limited DC WR Lens Black (2)

The manual focusing ring rotates during auto-focus, so care may need to be taken to it catching your fingers as it moves back and forth. Manual focusing action is smooth although there is very little damping on the focus ring, which can make applying fine adjustments tricky. The Pentax 'Quick Shift' focusing system has been implemented on this lens, which means manual adjustments can be applied once the lens has focused automatically. Auto focus is powered by a motor in the lens, but it isn't as quiet as you might expect from an ultrasonic lens. The minimum focus distance of 28cm is typical for a lens of this type and it is close enough to pose no issues when shooting in claustrophobic environments.

HD PENTAX DA 20 40mm F2 8 4 ED Limited DC WR Lens Black (6)

HD Pentax-DA 20-40mm F2.8-4 ED Limited DC WR Performance

At 20mm and maximum aperture, sharpness is outstanding in the centre of the frame, but the lens doesn't perform as well towards the edges of the frame, only producing fairly good sharpness. Stopping down to between f/5.6 and f/8 produces excellent sharpness across the frame at this focal length.

Zooming to 30mm results in a slight increase in sharpness across the frame at maximum aperture. Here clarity is outstanding in the centre, but falls just short of good sharpness towards the edges of the frame. Stopping down to between f/5.6 and f/11 results in excellent sharpness across the frame at this focal length.

Finally, at 40mm, sharpness is very good in the centre of the frame at f/4, but still only fairly good towards the edges of the frame. Again, stopping down improves performance greatly, with peak sharpness across the frame being realised at f/5.6.


How to read our charts

The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column.

The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple.

For this review, the lens was tested on a Pentax K-5 IIs using Imatest.

Chromatic aberrations are extremely well controlled, barely exceeding a quarter of a pixel width towards the edges of the frame throughout the zoom range. This level of fringing will be difficult to spot, even in harsh crops from the edges of the frame along high contrast edges.


How to read our charts

Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software.

Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimize the problem, hence they usually cost more.

For this review, the lens was tested on a Pentax K-5 IIs using Imatest.

Falloff of illumination is fairly typical for a standard zoom. At 20mm the corners of the frame are 1.25 stops darker than the image centre and at 40mm the corners are 1.21 stops darker. Visually uniform illumination is achieved with the lens stopped down by two stops from maximum aperture or beyond throughout the zoom range.

Distortion is also fairly typical for a lens of this type. Imatest detected 2.92% barrel distortion at 20mm and 0.627% barrel distortion at 40mm. Fortunately the distortion pattern is uniform across the frame, which should make it relatively easy to apply corrections in image editing software afterwards.

During testing, this lens proved itself very resistant to flare and contrast levels are good, even when shooting into the light. The shallow metal hood doesn't provide much shade for the front element, but is useful for preventing bashing the front of the lens, at least.

Pentax HD Pentax-DA 20-40mm f/2.8-4 ED Limited DC WR Sample Photos

Wide-angle | 1/50 sec | f/6.3 | 20.0 mm | ISO 80<br /><a target="_blank" href="https://www.magezinepublishing.com/equipment/images/equipment/HD-PentaxDA-2040mm-f284-ED-Limited-DC-WR-5417/highres/Pentax2040mm_272_1390476950.jpg">High-Res</a>

Wide-angle | 1/50 sec | f/6.3 | 20.0 mm | ISO 80

Telephoto | 1/100 sec | f/6.3 | 40.0 mm | ISO 100<br /><a target="_blank" href="https://www.magezinepublishing.com/equipment/images/equipment/HD-PentaxDA-2040mm-f284-ED-Limited-DC-WR-5417/highres/Pentax2040mm_273_1390477008.jpg">High-Res</a>

Telephoto | 1/100 sec | f/6.3 | 40.0 mm | ISO 100

Sharpness is very high in the centre of the frame throughout the zoom range at maximum aperture | 1/80 sec | f/4.0 | 40.0 mm | ISO 400<br /><a target="_blank" href="https://www.magezinepublishing.com/equipment/images/equipment/HD-PentaxDA-2040mm-f284-ED-Limited-DC-WR-5417/highres/Pentax2040mm_275_1390477084.jpg">High-Res</a>

Sharpness is very high in the centre of the frame throughout the zoom range at maximum aperture | 1/80 sec | f/4.0 | 40.0 mm | ISO 400

Contrast is retained well when shooting into the light  | 1/80 sec | f/4.0 | 40.0 mm | ISO 100<br /><a target="_blank" href="https://www.magezinepublishing.com/equipment/images/equipment/HD-PentaxDA-2040mm-f284-ED-Limited-DC-WR-5417/highres/Pentax2040mm_274_1390477050.jpg">High-Res</a>

Contrast is retained well when shooting into the light | 1/80 sec | f/4.0 | 40.0 mm | ISO 100

1/100 sec | f/6.3 | 20.0 mm | ISO 80<br /><a target="_blank" href="https://www.magezinepublishing.com/equipment/images/equipment/HD-PentaxDA-2040mm-f284-ED-Limited-DC-WR-5417/highres/Pentax2040mm_266_1390476725.jpg">High-Res</a>

1/100 sec | f/6.3 | 20.0 mm | ISO 80

1/60 sec | f/11.0 | 23.0 mm | ISO 400<br /><a target="_blank" href="https://www.magezinepublishing.com/equipment/images/equipment/HD-PentaxDA-2040mm-f284-ED-Limited-DC-WR-5417/highres/Pentax2040mm_271_1390476871.jpg">High-Res</a>

1/60 sec | f/11.0 | 23.0 mm | ISO 400

1/60 sec | f/6.3 | 20.0 mm | ISO 80<br /><a target="_blank" href="https://www.magezinepublishing.com/equipment/images/equipment/HD-PentaxDA-2040mm-f284-ED-Limited-DC-WR-5417/highres/Pentax2040mm_268_1390476756.jpg">High-Res</a>

1/60 sec | f/6.3 | 20.0 mm | ISO 80

1/50 sec | f/11.0 | 20.0 mm | ISO 200<br /><a target="_blank" href="https://www.magezinepublishing.com/equipment/images/equipment/HD-PentaxDA-2040mm-f284-ED-Limited-DC-WR-5417/highres/Pentax2040mm_270_1390476796.jpg">High-Res</a>

1/50 sec | f/11.0 | 20.0 mm | ISO 200

Value For Money

Being priced at around £850, this lens is quite expensive for a standard zoom with a variable aperture, especially when you consider that for around the same price, you can pick up a Pentax 16-50mm f/2.8 DA* ED zoom lens. Not only does the 16-50mm lens have a more useful zoom range, but it has a constant f/2.8 maximum aperture and internal focusing.

Another alternative, covering a similar zoom range is Sigma's 18-35mm f/1.8 DC HSM, which sports a fast f/1.8 aperture throughout the zoom range and costs around £650. With alternatives like this available, it makes it increasingly difficult to justify the expense of this Pentax 20-40mm lens.

HD Pentax-DA 20-40mm F2.8-4 ED Limited DC WR Verdict

As far as variable aperture standard zoom lenses go, this is one of the better ones as far as optical performance is concerned. Unfortunately, due to the price, it is easy to expect more from a lens like this. The zoom range is reminiscent of making do with what was available when APS-C DSLRs first came out and the maximum aperture range is nothing special.

In summary, this lens may represent poor value for money for many. Others who like the excellent build quality and retro design may appreciate the small niche this lens fills.


HD Pentax-DA 20-40mm F2.8-4 ED Limited DC WR Pros

Very good sharpness in the centre at maximum aperture
Excellent sharpness when stopped down
Very good build
Weather resistant construction
Low CA
Retro styling

HD Pentax-DA 20-40mm F2.8-4 ED Limited DC WR Cons

Expensive for a variable aperture standard zoom
Odd zoom range is not really very wide, nor very telephoto
Neither focus or zoom are performed internally


Pentax HD Pentax-DA 20-40mm f/2.8-4 ED Limited DC WR Specifications

Lens Mounts
  • Pentax K SMC-DA
Focal Length 20mm - 40mm
Angle of View 39 - 70
Max Aperture f/2.8 - f/4
Min Aperture f/22 - f/32
Filter Size 55mm
Stabilised No
35mm equivalent 30.5mm - 61.5mm
Internal focusing No
Maximum magnification No Data
Min Focus 28cm
Blades 9
Elements 9
Groups 8
Box Contents
Box Contents Lens hood MH-RA55, Lens cap O-LW65A, Lens case P70-150
Weight 291g
Height 68.5mm


Related Photos


Link Posted 30/01/2014 - 15:00
Looks way overpriced for the performance, it should be priced at 400-500 not 850.


Link Posted 30/01/2014 - 19:17
The test shots look great on the LHS... but soft
on the RHS... Is that the lens or the camera?
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff



Link Posted 01/02/2014 - 14:39
Overpriced for its specification maybe, but its range is more than satisfactory for a relatively discreet walk round lens, when looking for a natural perspective. Teamed with the K3 or the rumoured K60 etc. you could easily have a 50% crop, which would give it a nominal maximum of 120mm (35mm equivalent) and still get very extremely good resolution. Even with the K5/ii/iis / K50 / K500 50% cropping would be feasible (all other things being equal). It has the makings of a partner for the 55mm-300mm as has, incidentally, does the rumoured 18mm-70mm. Now if SRS could do a deal including a Hoya Pro 55mm UV or Clear Filter (for protection) for, say 395.


Link Posted 01/02/2014 - 17:53
Do not expect a rush to buy this lens given its limited optical qualities and versatility. Nevertheless it looks the part and with the badge, 'Limited' it may well sell do those who love that feel good factor from 'Limited'. To its advantage is that it weighs 291gm. However, I do think the bigger and heavier Sigma 18-35 f/1.8 would deliver a better performance and it is around 650 - a rather high price too.


Link Posted 05/02/2014 - 10:08
Cripes, 850 for a lens that could possibly be a little frustrating as its neither wide enough or long enough. Seems an odd lens for Ricoh to spend lots of R&D money on considering they already have the excellent DA* 16-50 with better range coupled with a constant f2.8 and internal focusing.
And it looks even more unappealing when you take into account the Sigma 18-35 1.8, which has the useful 18mm at the low end coupled with a constant f1.8 and 200 less.
Guess you'll need to be a die hard Pentax Limited fan who wants every lens in their collection.
Last Edited by Russ on 05/02/2014 - 10:09


Link Posted 02/05/2014 - 13:47
850!! Thanks, but no thanks

Link Posted 17/08/2014 - 00:17
I love this lens. I have been using it far more than the 12-24 or my 50mm prime. very good image clarity and I have never had to work on any CA's in post. Love it.
Forgotten Heritage Photography
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Link Posted 02/10/2014 - 16:25
Having purchased this quality zoom lens despite the cost (for less than suggested retail price) rate this unique zoom lens as a sharp-shooter; in the tradition of classic lens design in terms of appearance and handling. No expert; but I like to be in possession and control of a lens that reaffirms my passion for photography. To me this solid zoom lens departs from all other Pentax lenses in its traditional styling. If marked ZEISS or SUMMICRON it would look the part. Granted the 20~40 zoom range is limited but at X2 the imaging results make it a perfect compromise. Pentax should be rewarded for defying the doubters by producing this optical masterpiece. 5 STARS!


Link Posted 15/09/2016 - 11:46
This is an extraordinarily good lens of perfect build quality. Optically it's among the best on the market (I've tested mine against some renowned lenses - and it more than holds its own):
IQ is gorgeous being razor sharp at practical working apertures (I do not venture farther than f/11 on any lens, if I can help it). More over CA's, fringing (if any at all) and distortion are negligible. Flare and reflexes are next to non-existent (Sigma Art's are a pain in this department), and it does an unbelievable job of retaining information and details in highlights and shadows (something that distinguishes excellent lenses from the rest - ask Leica-aficionados).
The zoom range is perfect for street photography and the likes, and the size and weight of the lens - though larger than the rest of the DA-Limited lenses - are non obstructive. The Sigma Art's are way to large and heavy in comparison (I do, in fact, own a couple of them).
IMHO this piece of Pentax-glass is worth every last penny (SRS Microsystems price is 659 UK Pounds these days) - and if you still don't believe it, please read this review: http://www.pentaxforums.com/reviews/sigma-18-35mm-f18-dc-hsm-art/introduction.ht...
Clearly a FIVE STAR Lens. And Pentax does make a lot of them ...
Last Edited by STES on 15/09/2016 - 12:07


Link Posted 07/08/2018 - 11:35
The quality of this DSLR is really good and I think this is the cheapest DSLR at that level. The ghanaembelgrade.com is the place which you can use to buy.


Link Posted 07/09/2021 - 10:24
A bit overpriced but i love it!
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