Andre Langevin <[EMAIL PROTECTED]> wrote: > I already have a 24-90mm and rarely go to 90mm so performance from > 24mm to 75mm is what interests me. Portability is not a key feature. > Only optical performance (including flare control). > > Thanks,
Hi Andre, I own both and a couple of weeks ago I did perform a side by side comparison (just to be nitpicking, since I already do prefer the 28-75 overall, mostly because I need the extra speed and do prefer the fixed f/ throughout the zoom range). I did test them at f/4.5 and f/9.5 (even if I do usually avoid shooting at stops smaller than 6.7, 8 on the *istD, to avoid to make the dust on the sensor too visible); the description comes from judging the results at 100% magnification on the monitor (subject: buildings from 200m to 1km circa). At 28mm and 50mm (f/4.5): the Tamron is the winner wrt sharpness; the difference is small in the centre but definitely big in the corners (softness of the 24-90 starting from circa 1/2 frame). At f/9.5 the situation is reversed, with the Tamron that doesn't seem to gain much (it was good already, though) while the Pentax lens gets a lot better, surpassing by a small but visible margin the Tamron (better definition of small details). At 75mm f/4.5, the 24-90 performs marginally better closer to infinity (but I suspect that the focusing was set differently - the lenses were both focused by the camera and there is a certain amount of difference in depth of field, with closer objects better defined on the Tamron either at 4.5 and 9.5). At f/9.5 there is almost no difference and becomes difficult to say which one is better, probably more a different rendition of the details more than a question of lpm. About the flare: the 24-90 handles flare quite well, but it is one of the worst Pentax lenses I used wrt reflections (at 24mm it shows a lot of aperture-shaped reflections when pointed to the sun - for example, the 28-70/4 is way better, it never suffered from this kind of behaviour, and so is the 20-35). The Tamron performs really well for a non SMC lens, but shows a strange kind of reflections, as it sometimes duplicates small, strong lights on the scene (and it is not predictable in the finder, so I guess it is a problem of reflections of light hitting the sensor and then duplicating on the rear element of the lens - there is an example in the portrait of Stan at http://www.photo.net/photodb/photo?photo_id=2784631 - look at the shirt). The Tamron is so good overall that I can live with that. HTH. Ciao, Gianfranco PS: If you want to, I can upload small portions of the pictures in a photo.net folder, hoping that they do not resize them, to show you the differences. ===== _ __________________________________ Do you Yahoo!? Yahoo! Mail Address AutoComplete - You start. We finish. http://promotions.yahoo.com/new_mail
