Originally posted by aurele you are quoting only what arrange you, don't you ?
why don't you take in consideration the 3kg of glass that represente at least $3,000 just in raw materials ?
First, I stated that simpler lens designs (meaning those with fewer element
or less exotic materials) should be less expensive. You then disagreed with me, and stated that designs with many elements are more expensive. That's what I quoted. And what put my face squarely in my palm. Yes, I quoted only those parts of the post that were pertinent. I don't think that's sneaky or underhanded in any way.
As far as the weight of glass:
The Nikon 500mm weighs about the same, but with twice as many elements. From that, the glass weight seems to be a small portion of the weight of a lens. You are correct that the glass needs to be polished from raw, but so it does for other manufacturers--this does not change the fact that the amount and size of glass in the 560 represent terrible value compared to Nikon or Canon's offerings. But the main reason I cannot believe your theory is that I wonder how Pentax can market a similar optic and call it a telescope,
for a fraction of the price. I will allow some room for variation in the name of tighter tolerances, or anything along those lines, but that is egregious.
I was hoping that Pentax had imagined that a telescope conversion would allow them to price themselves under the rest of the super-tele market with a lens that has a few compromises that distinguish it from the so-called pro-grade, but also a sizable market in place who is willing to put up with some idiosyncracies in the name of saving thousands of dollars. Instead, the compromises are all in place, yet they want to compete with the tools that --on paper-- beat the Pentax in every category save reach? Even if this lens is optically remarkable, finding its niche will be a major struggle.
Or maybe Pentax was thinking "the Nikon and Canon are just 500mm lenses. Since we
still don't have a full-frame digital, ours is an 890mm! F5.6 is quite fast and $7000 is very affordable for an 890mm!"
I kid. (Sort of.)