17-70mm lens (Pentax or Tamron advice please)

Started 3 months ago | Discussions thread
Hythloday Senior Member • Posts: 2,220
Re: Proof is in your pudding
1

Massao wrote:

DA 17-70mm hidden behind terrible image quality. In any case, you can always edit the colour profile but can't make a lens sharper in PP. Increasing (micro) contrast in PP is not the same as actual sharpness captured by lens.

A zoomlens is a compromise and will give its best result when you stop it down two stops. Your tests are too limited because you tested the lenses nearly wide open. That may be valuable to you, but is worthless for me. Nearly wide open a zoomlens will hardly produce excellent results. The DOF is very shallow and when you have made focussing errors, the IQ will suffer.

For landscape photography I always use aperture 8, in which case the DOF is better. As The DA17-70mm is parfocal, you can focus at 70mm, lock focus, zoom out and take your picture. Focussing speed is not important for my kind of photography.

If you want to use aperture 4, you had better use a prime. The Pentax plastic fantastics are an excellent choice in that case. My 50mm backfocussed on my KS2, but is focussing OK on my KP.

I used to have a Sigma 17-70mm on my Canon 300D and on my K100D Super. The yellowish colour cast was a bit of a let down for me. The Sigma 17-70mm was at its best at the tele end. At the WA end the sharpness was not perfect. The DA 17-70mm is best at the WA end and a bit weaker at the tele end. The test of the Sigma 17-70mm at DXOMARK reaches the same conclusion, see:

Pentax smc PENTAX DA 16-45mm F4 ED AL on Pentax K-3 vs Sigma 17-70mm F2.8-4 DC MACRO HSM C Pentax on Pentax K-3 (dxomark.com)

I used the DA16-45mm because a test of the DA17-70mm is not available.

Does this mean that Sigma lenses are a bad choice? No, but it depends on your photographic needs. In everyday photography there is not much difference in sharpness. I sold my Sigma 17-70mm because of the yelllowish colour cast it gave. The SMC coating gives a typical Pentax colour cast, whereas the HD coating gives a more neutral colour cast. I have had the DA16-85mm for over 5 years now, but it has never become my favourite lens.

If you need wide apertures, Pentax may not be the right choice for you. You can find far better lenses for your needs, such as a Sigma 85mm/f1.4 or a Carl Zeiss Distagon lens.

 Hythloday's gear list:Hythloday's gear list
Pentax K-3 Pentax K-3 II Pentax KP Pentax smc DA 16-45mm F4 ED AL Pentax smc DA* 50-135mm F2.8 ED (IF) SDM +7 more
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