Hi,
I wonder why lensfun uses a set parameters - in case of my Panasonic DMC-FZ1000
<distortion model="ptlens" focal="9.1" a="0.01858" b="-0.05809"
c="-0.06581" />
<distortion model="ptlens" focal="10.1" a="0.01914" b="-0.06488"
c="-0.03567" />
<distortion model="ptlens" focal="12.6" a="0.01159" b="-0.0477"
c="-0.00043" />
<distortion model="ptlens" focal="18.2" a="0" b="-0.00914" c="0" />
<distortion model="ptlens" focal="26.3" a="0" b="-0.00224" c="0" />
<distortion model="ptlens" focal="65.8" a="0" b="0.00035" c="0" />
<distortion model="ptlens" focal="109.3" a="0" b="0.00049" c="0" />
<distortion model="ptlens" focal="146" a="0" b="-0.00305" c="0" />
<tca model="poly3" focal="9.1" vr="1.0004262" vb="1.0003030" />
<tca model="poly3" focal="9.1" vr="1.0004371" vb="1.0003172" />
<tca model="poly3" focal="10.1" vr="1.0003178" vb="1.0001682" />
<tca model="poly3" focal="12.6" vr="1.0003066" vb="1.0001788" />
<tca model="poly3" focal="18.2" vr="1.0002344" vb="1.0002283" />
<tca model="poly3" focal="18.2" vr="1.0002353" vb="1.0002221" />
<tca model="poly3" focal="18.2" vr="1.0002476" vb="1.0002138" />
<tca model="poly3" focal="26.3" vr="1.0001965" vb="1.0001175" />
<tca model="poly3" focal="65.8" vr="1.0000103" vb="0.9999799" />
<tca model="poly3" focal="109.3" vr="0.9999002" vb="0.9999031" />
<tca model="poly3" focal="146" vr="0.9997527" vb="0.9998454" />
Aren't the lens correction data recorded in the .rw2 raw file suffucient for
lens correction?
Following http://syscall.eu and applying the data extracted from an image of
mine,
I get, e.g., for an image with focal="9.1"
scale = 1.0/(1.0+(data[5]/32768.0)); 1.0
a = data[8]/32768.0; 0.19561767578125
b = data[4]/32768.0; 0.145965576171875
c = data[11]/32768.0; -0.14434814453125
Ru = scale*(Rd + a*Rd^3 + b*Rd^5 + c*Rd^7)
How are these releated to the parameters for focal 9.1 above?
In this case the image processed by Silkypix differs significantly from that
produced by darktable which uses lensfun.
If I crop the image produced by darktable to pixels 173 .. 5299 x 115 ..
3533 and rescale the image to 5472 x 3648 pixels
I get a very similar result to that produced by Silkypix.
(The image produced by darktable had some deficiencies in comparison to
Silkypix)
Many thanks for some explanation.
Helmut
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