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[OM] Re: Sharp, but wierd

Subject: [OM] Re: Sharp, but wierd
From: "Jamie Costello" <jcostello@xxxxxxxxxx>
Date: Mon, 14 May 2007 14:40:31 -0400
Thanks, Schnozz - great, as usual ;-)  This is why I subscribe to this list
...

-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On Behalf
Of AG Schnozz
Sent: Monday, May 14, 2007 2:32 PM
To: olympus@xxxxxxxxxx
Subject: [OM] Sharp, but wierd


I was testing a new lens purchase last night and found a very strange
artifact.

The lens is the outstanding Tokina AT-X 100-300 F4. I took out my
testing chart, placed it on the wall and proceeded to test the lens
at the common focal lengths (100, 135, 200, 300) and all apertures.

What I found was predictable--loss of contrast at the extreme
apertures and excellent contrast and sharpness in the middle.  What
wasn't so predictable was an "incompatibility" with RSE.  I'm
suspecting that I have a setting screwed up someplace, but here goes.

The outside edge-sharpness of the converging lines in the test chart
(same as DPReviews) is maintained all the way.  Very sharp.  However,
within the lines, there is a total blocking of the detail within the
converging lines at 1400 LPH.  At F5.6 to F11, the LPH tops out at
about 1650 with tremendous apparant sharpness throughout.  In fact, I
almost think that at 200mm and F8, this produces the sharpest image
I've ever seen from the E-1.  I wonder if the extreme telecentricity
of the telephoto design (thre rear-most element is a long ways from
the sensor) breaks through whatever blurring the AA filter is
providing.

So, when I get outside of the 5.6-11 range, there is excellent
edge-sharpness (except for F4 and F32), but the detail within is
mushed up.

However,

When opening up the files in Olympus Viewer, my LPH tops out at about
1600, but the blocking up is reduced some.  There is still a great
loss of edge contrast at F4.

How does this manifest itself in real pictures?  I shot pictures of
bison Saturday.  Those that were taken wide open had a "painterly
effect" in the details--like the NR was cranked up too high.  F8
yielded fur-details so tight that you could almost see the flees.

Wierd.  I'll be posting samples of this on my website tonight.

AG


       
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