Originally posted by Wulifou Hi all,
I have a question for you all who own SDM lenses. I want to acquire a wide zoom and am hesitating between the DA* 16-50 and the Tamron 17-50 F2.8. My local reseller says I should take the Tamron, since for approx. 300$ less, I would have similar if not better IQ. For my uses the weathersealing alone would not justify spending more money on the Pentax lense, but since I do a lot of low light, noisy and endless AF hunting would be a real issue.
So here is my question : in your experience, is there really such a big difference in speed and noise when using SDM lenses ? (I cannot compare, because prior to my K20D, I only owned a all-metall-all-manual Praktika SLR and a bridge camera ...)
thx for your input
Bonjour, Wulifou!
I saw in your profile that you have the same camera as I do so my experience applies and hopefully will help you to choose. The Tamron is a nice lens from what I saw but my choice was largely based on the weather sealing factor and secondly on the SDM. I was also a bit worried reading all the stories about bad copies of the DA* and did a lot of research. My conclusions:
- as a combo with K20D this lens has tremendous less chances to be a bad focuser (compared to K10D). I really don't know why but the K10D+DA* is the bulk of troubles associated with this lens. Also the CA (PF) is way less on the new sensor;
- about the focus hunting in low light in my experience it happens especially when the target is a low contrast one (and I think most of the problem is from the AF module not the lens) and I saw it become more intense when the battery starts to deplete. I often use quick-shift (another great feature the Tamron don't have, btw) to roughly position the lens close to focus and it does the rest from there;
- the noise as you've been told already is almost not-existent and I suggest you keep the "confirmation beep" to realise when the focus is achieved;
- in good light my lens focuses "normal" that means not instantaneous but fairly quick. I don't think there are any speed benefits resulting from SDM compared to screw drive or at least not visible ones. The lens has a lot of glass in it and probably a ring motor with more torque would of speed things up more significantly;
- the esential part is the optical quality. I honnestly say that this is my most versatile lens and the last I would part away but of course it's a matter of taste. It constantly underexposes a bit so you may want to keep that in mind when shooting in low light. IMO it is very, very sharp and renders colors beautifuly with superb microcontrast. You can make your own opinion about it from the pictures.
Anyway I have absolutely no regrets for buying this lens whatsoever.
Hope it helps,
Radu