> I wait for ***documented*** evidence of same.:-)
Chuck, I don't know what it is exactly that you want me to "document"
because I'm stating the obvious. These are well-known traits and an
undeniable fact of life with some aspherical lenses. To be fair, it
isn't just aspherical lenses, but highly corrected optics tend to do
these things too. You are asking me to document that some roses are
red while others are yellow. Life is too short for me to go diving off
the plank on this one. Two minutes on Google or in Flickr will reveal
all you need to know.
The fact is that whatever is in focus is going to be more in focus
with a heavily corrected lens assembly whether aspherical elements are
used or not. The advantage of an aspherical lens is that you can
usually do with one piece of glass what it takes three to five to do
with conventional elements. However, the curse of an aspherical lens
is that the element treats out-of-focus light rays in a manner that
looks not unlike a mirror lens. Not all lenses do this, but that's
where the genius of the engineers comes in. (Olympus engineers are
better than Canon engineers in this regard).
A couple of years ago, we did a lens test. We took every lens we had
that did 50mm at F4.0. Here are the results. You can see how much
things vary from one to another. You'll also see how one lens in
particular folded the edges of the OOF highlights back in on itself
forming rings. There are other traits of some of the lenses which
aren't as pleasing, but at least this test proves that different lens
formulas result in different types of images when at exactly the same
settings. The camera did not move and we focused on the same point for
every lens.
http://zone-10.com/tope2/main.php?g2_itemId=12622
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|