Well, there has to be some trade-off, doesn't there?
Even if we take Pal's original statement as true ("today's best zooms are every bit as good as primes"), a zoom is going to exact some penalty on it's user.
They're bigger, heavier, slower, more complicated, take more time to use (since you have one more control to fiddle with), and more expensive than a prime.
I'm not saying zooms are bad - I have a couple that I use quite often - I'm just saying that optical performance is only one thing to consider in a lens (albeit, a pretty damned important thing! <vbg>).
ciao, frank
That's very true indeed, but we started out discussing sharpness only. In fact, I found a lot of zooms which perform well stopped down at infinity. Many of these are weak at close range and/or wide open, though. If a manufacturer wants to look good on a lens test report, they just optimize for infinity performance. That way, they will get a high MTF score at photodo and get outstanding SQF from Pop Photo. (They have a sentence or two stating close range performance but in their wording everything is always good.) I use zooms indoor with bounce flash, so I really need good close range performance and wide open performance.
Really, I wish the A35-105/3.5, maybe a modern version which is as sharp as primes like Paal said, is available in AF. Tamron makes a 35-105/2.8 but the AF version is only available for N/M/C, and its reviews from real users seem a lot more mixed than the good magazine reviews it got. I don't care about their 28-105/2.8 as size is a very important consideration. Their new 28-75/2.8 is small but I like the reach of 105 more. Furthermore I would rather wait and see more real users' comments before I decide I will buy it.
But, replacing a Pentax lens with a third party lens ? That makes me feel sad.
Maybe I should change a bit of my thinking. I am not looking for a film lens which works also on digital, but rather a digital lens which also works on film. A 1.5x multiplier on a 28-75 is just right for me in that regard. For film I will stick with my Contax G2 with prime lenses for a long while. It is the Pentax *ist D which I plan to get down the road.
Bo-Ming Tong
