Why did Pentax choose to make a f/4 constant zoom using the diaphragm to maintain
that, rather than
making a f/2.8 - f/4 zoom on this lens.
Am I making sense? :-)
Yep sure. One answer is that the constant relative aperture makes it much easier to
use with non-ttl flash. Another answer is
All this discussion is based on assuming that the lens would open to
F2.8 to begin with, which may not be the case at all. Sure, you can see
the aperture mechanism reduce itself as you zoom toward the short end,
but how do you know it would go to F2.8? What if it only went to F3.5?
In that
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