There’s no denying the Pentax DA 40mm and 70mm Limited lenses are pretty special. Their incredibly compact design is pretty much unique to Pentax and unlike anything offered by other DSLR manufacturers.

The DA 40mm f2.8 Limited is particularly impressive in this regard, measuring just 15mm thick. Indeed when viewed from the side you really have to give it a double-take and verify the photographer isn’t trying to take a shot using a hefty body cap.

The choice between them of course depends on your coverage requirements, and almost inevitably the DA 40mm feels less exciting due to its effective field of view being close to a standard lens.

But that said the DA 70mm did prove to be the sharper of the two in our tests, and despite coloured fringing being visible even in the middle of the frame on some occasions, it was the model we ultimately preferred. Its longer focal length and brighter aperture allow for a very small depth-of-field and it unsurprisingly excels for portraiture.

Beyond a little fringing on the DA 70mm and some softness on the DA 40mm samples we tested, there’s not many bad points to mention. Their tiny dimensions unsurprisingly mean there’s not a great deal to hold onto, and if you inadvertently grip the focusing ring you’ll get a nudge as they turn during auto-focus, The focusing with the K10D was also quite audible, but that’s more a criticism of lenses without internal focusing motors.

Finally, some of the style decisions made by Pentax slightly reduce the usability of both models: the DA 40mm’s screw-on lens cap is classy, but can’t be removed as quickly as a clip-on cap, while the DA 70mm’s cap only fits on the supplied hood – but to be fair you’ll probably have this permanently attached anyway.

So as in the old world of film SLRs, Pentax continues to be the leader in tiny lenses, and if compact size matters (or appeals) to you, then the Limited range of pancake style lenses are pretty much no-brainers. Both are technically impressive models and good choices for Pentax DSLR owners looking for quality fixed focal length options.

Pentax DA 40mm f2.8 Limited Good points Extremely thin lens – only 15mm thick Quality construction Aluminium lens hood and cap supplied Unique standard lens option Bad points Hardly anything to hold onto Slow to unscrew lens cap Some softness on our sample Audible auto-focusing with K10D Scores (relative to kit zoom)   Build quality: Optical quality: Specification: Value: Overall: 23 / 25 19 / 25 19 / 25 20 / 25 81%   Pentax DA 70mm f2.4 Limited Good points Very thin lens – only 26mm thick Fast f2.4 aperture Quality construction Aluminium lens hood and cap supplied Bad points Coloured fringing seen across frame Not much to grip onto Audible auto-focusing with K10D Lens cap only fits over lens hood Scores (relative to kit zoom)   Build quality: Optical quality: Specification: Value: Overall: 23 / 25 21 / 25 20 / 25 20 / 25 84%