----- Original Message -----
From: "Moose" <olymoose@xxxxxxxxx>
You are certainly correct that Oly is cropping the post correction image
(and ACR is obviously using the same exact
algorithms). However, I don't see where they would be up-sampling.
I suspect the whole image is enlarged in the
correction process (why?), then simply cropped to size.
At the long end of 12-40 Olympus RAW gives similar AOV as RawTherapee
so there must be different cropping on different focal length in Olympus
RAW. If different cropping is using on different focal length and Olympus
has to keep same pixel dimension on its files then they has to up-sample
the image.
At the same PPI, the objects on the image of Olympus one is bigger. As I
don't think RawTherapee will down-sample the image then it must be Olympus
up-sample it. No matter the up-sample is done during distortion correction
process or after, it has the same effect.
Comparing the angle of view of my old 11-22 at 11mm and the 12-24 at
12mm, I believe the 12mm is much narrower than quoted on a E-P5 with
Olympus Viewer. As you know even half a millimeter counted at wide angle,
it is too bad to see the result like that.
This is a tricky business. There is sample variation, and as you point out,
even small variations have a big effect on AOV. Modern Photo allowed FL
variation of ±5% in their tests. Here are the results for some OM lenses:
FL Spec. FL Meas. Var.
Zuiko 18/3.5 18.76 4.2%
Zuiko 21/2 20.15 -4.0%
Zuiko 40/2 41.33 3.3%
Zuiko 50/1.2 52.48 5.0%
Zuiko 50.1.4 50.94 1.9%
Zuiko 50/1.8 51.87 3.7%
Zuiko 90/2 90.44 0.5%
Zuiko 100/2 100.65 0.6%
Zuiko 180/2 180.57 0.3%
I didn't complain the 12-40mm lens even it may be slightly off (actually, I
found it slightly wider than 12mm when using RawTherapee and my old
11-22mm as a reference point) I just don't like Olympus cropped it so much.
Comparing the spec. 11 mm of one zoom to the 12 mm of another can't be
generalized; it only applies to those particular samples.
Yes, you are right but I just miss the 11-22 :-)
On the other hand I think you are talking about different lenses (11-22 vs
12-40...etc) not samples. AOV variation will not happen in lens production
but resolution and other aberration may do.
C.H.Ling
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