For copying anything, 0 distortion is preferable, just as fine grain and
the best sharpness is.
Copying a rectilinear painting with barrel or pincushion distortion will
result in either a visible artifact around the edge or part of all the
edges being left out. 1 0istortion would mean a 1 inch variation in a 100"
painting and many paintings are larger.
It would also curve straight lines inside the painting and result in
mismatches with other images taken with xrays, MRI, or other imaging
techniques or equipment.
tOM
On Friday, March 29, 2002 at 20:53, John A. Lind <olympus@xxxxxxxxxxxxxxx>
wrote re "Re: [OM] Shooting paintings" saying:
> At 20:12 3/29/02, you wrote:
> >All 50mm non macro I have seen has barrel distortion, three 50/1.4 SC and
> >MC, 50/1.8 MC. 50/1.2, 55/1.2. May be I'm a bit exaggerated about the
> >distortion, but all the reports I have seen also shown about 1 0istortion.
> >For normal shooting it is fine, but for copy works, you need a very low
> >distortion lens unless you don't care about the quality.
...
> What might also be a fact is it's below detection threshold, even on an
> optical lab bench, which brings it back around to the need for it to be
> detectable in practical application. Paintings with strong, exceptionally
> precise rectilinear lines are very, very rare. I would look at the frame
> and its straight inside edges around the painting to see if there's
> anything detectable in the image by a human using eyesight alone without
> any aids.
>
> If this sounds strident, it admittedly is. While it's worthwhile to ask
> questions about aberrations and distortions detectable in a lab, the most
> important question is whether the magnitude of it is detectable in
> practical use, making practical photographs.
--------------- http://groups.yahoo.com/group/Olympus-Documentation
tOM Trottier, ICQ:57647974 http://abacurial.com
758 Albert St, Ottawa ON Canada K1R 7V8
+1 613 860-6633 fax:231-6115 N45.412 W75.714
"The moment one gives close attention to anything,
even a blade of grass, it becomes a mysterious,
awesome, indescribably magnificent world in itself --
Henry Miller, 1891-1980
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