C.H.Ling wrote:
> PTLens looks interesting but I see some problem for shots at different focus
> distance, like the Zuiko 18/3.5, it has very slight pincushion distortion
> for distance object but high barrel distortion at close distance.
>
Huh! Who knew. Gary's test showed no linear distortion at 1:40. I've not
noticed any at infinity, but then I don't usually shoot subjects where
slight pincushion would show.
I don't think I've ever shot anything really close with the 18 or
21/3.5s. I know some images posted here some time ago showed the 21/3.5
to have high field curvature close-up, So I wouldn't tend to use them
for that purpose.
I'll admit to cheating with PTLens on occasion. IF your image doesn't
have an EXIF, which is easy enough to erase in a copy, you may choose
any camera/lens combo you like. I've simply shopped for a lens with
similar distortion to the image I have and used it.
It's pretty quick, as the preview shows the effect immediately. Not
necessary for straightforward pincushion or barrel, which many apps
handle nicely. But with what Chuck calls moustache distortion, finding a
match can be better.
Another option is a plug-in that lets you select three points on a
horizontal line to correct the line - but I have for the moment lost
track of it.
> Distortion may not be very critical for 4/3 system. Most 4/3 lenses have
> very low distortion. ...
I was making no comment about 4/3 lenses. I was replying to a specific
request in a post for distortion correction software that covers 4/3 lenses.
Moose
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