Boris Liberman wrote:
Hi!
Recent talk about 28/3.5 and 16-45 zoom performance got me confused.
My (probably very much Boris-the-average) belief was that most lenses are optimized at 3 or so stops from their widest aperture. So, for most f/2.8 lenses it would be f/8 or thereabouts.
Is it right thing to assume? Or there is something quite basic that escapes me?
Unconfuse me, will you please? :)
Hi Boris...
Just my 2�, but...every lens test of acuity or resolving power I've seen has shown that observation to be true.
Just yesterday I was talking about my 35/3.5 Super Tak; the chart from which I took my data shows it's sweet spot to be f/8, and in this lens, that acuity extends down to f/5.6 and up to 11.0. Across that range of f-stops, the numbers stay high, and fall off to the max aperture of f/3.5 and min. of f/16. In this lens, the sweet spot is almost perfectly centered.
With lenses, there are always exceptions, and even different testers come up with different numbers!
It's all frustrating, but if 1) you only compare lens performance within a single tester's data sheets, you'll get good comparisons, but never expect any of that data to spill out and agree with some other tester's data on the very same lens. Therein lies disappointment!
And 2) everything I read from the "experts" leads me to believe there are no absolutes.
It seems that like most things, there are examples of any given lens that perform exceptionally well ~ who knows why ~ and compared with other owners of the same lens, that person says it's a mediocre lens. Go figure!
For what that's worth...
keith whaley
