Originally posted by Pål Jensen Again price estimates are far too low
. A 560/4 ED IF lens will cost $8000. A 25/4 for the 645 system cost $5000......
My take is that your numbers are close. The competition seems to have 600 f/4's price at around 10k. Making them
a little slower and a little shorter, and maybe skimping on the quality a little will let them undersell the competition
by some but not a whole lot.
I have a 600 f/5.6 which is sort of a bench mark for me as to what it takes for a lens of this magnitude. When you
consider that the 600 f5.6 required a 112mm front element, and the 600 f/4 took a 150mm front element, while
the 400 f/5.6 got by with a 77mm front end. (I used screw in filter sizes as approximation of the front element size)
and the 400/f2.8 has a 145mm front element, it isn't that hard to see that there is a well out there when you try
to make long/fast lenses that is very expensive.
another ugly fact--if you look at the historical pentax glass the only long lense with a 'simple construction (4 elements)
was the Pentax K-500/f4.5.---but it had a downside---it wouldn't focus closer than 10 meters. Design parameters
of today's lenses are that they need focusing methodology that is light enough to be movable with camera supplied power.
Glass such as my A*600 f5.6 has double helicoids in it and focusing involves moving 2 elements---one in each direction.
It makes for quite a stiff twist for manually focusing and it isn't even clear to me whether the Petax AF system
can produce the horsepower to move that much glass.