On 12/26/2015 8:37 AM, Bill Barber via olympus wrote:
Perhaps I should have provided a bit more explanation about what I am doing. I
, along with 7 others, have recently opened a gallery in the tourist town of
Gruene, TX. Most of the art work is two dimensional. Several of the artist
would like to make smaller copies of their original art pieces and need digital
files of there work.
Anything small enough to fit on a scanner bed should be scanned. Eliminates all the distortion and lighting problems.
I've even scanned larger work in two passes, stitched together.
Briefly, the set up I use is Tota lights at 45 degrees from the art work, with
polarizing filters in front of the lights, lights and cameras at mid-point of
of art work with everything level and polarizing filter on camera.
I never needed all that polarizing stuff for the stuff I copied. I could see where original oils might. There comes a
point where four lights are needed for even illumination. Where that size may be with your particular lights, I don't
know. The inverse square math is unforgiving.
Capture in raw and converted to tiff. White balance corrected.
I had a friend who made the copies for reproduction, promos, etc. for his wife's oil paintings using an RB67 and film. I
don't recall seeing any polarizing material involved in his set-up.
Color accuracy was his big problem. As with so many artists, his wife was obsessive about the colors. I would be
shooting color targets and creating profiles for camera/lens/light combinations. Tungsten lights age, too ...
Currently using e-5 and could use Sony NEX 7. Although I have a variety of
lenses native to the digital cameras, it occurs to me perhaps an OM prime might
offer better results without the compromises of a zoom lens. Yes, I know I can
test the various OM options and thought perhaps others might have some specific
suggestions. My choices in the OM line might include the 50mm f2 macro, 50mm
f3.5 macro, 85mm f2, 100mm f2, 100mm f2.8. Also could use the Tamron SP 90mm
f2.5. As noted by Moose, there is an issue with the set up causing problems.
My concern is with lens distortion rather than the mechanical set up.
AG notes:
"... The issue with the 50/3.5 is the much longer effective focal length for copy work. What I've found is that when you
can keep the 50/3.5 within 18 inches of the subject, all is well with the world. But beyond that distance, you'll get a
bit of distortion. While it remains flat-fielded, the image will just start to pucker up like Donald Trump's sucking
lemons face."
I've not noted that in the many, many copy shots I've made with 50/3.5. But - perhaps he exaggerates the distance a bit,
and my copy set-up could only get maybe 30" from the subjects. Perhaps the 50/2 doesn't have that problem. And it won't
be obvious on anything without long straight lines. All the testing I referred to that I did was FF.
If I had this project, I'd be looking at the M.Z 45/1.8. A very sharp lens with very low distortion in the glass. As far
as I can see, ACR/LR don't apply any correction at all, and DxO correction is almost a mixed bag.
This example should be on point. Taken hand held of a painting about head height, so slight perspective/sensor-subject
alignment distortion(s), but the painting frame and the wallpaper will show up any non linearity in the lens.
<http://www.moosemystic.net/Gallery/tech/Lenses/M.Z%2045%20F1.8/45f18.htm>
The ACR/Lightroom conversion (and thus also Viewer 3) and both uncorrected conversions have each pixel in the identical
location*. The DxO correction doesn't seem to me a real improvement, but in any case is so minor it doesn't affect image
detail negatively.
So the M.Z 45/1.8 meets the criterion of low/nonexistent distortion, has the advantages over old OM lenses of AF and AE
and is much lighter and smaller. I also expect it to be higher resolution, as the designers didn't have to cover as
large an image circle and have better glass and aspheric elements to assist them.
The 60/2.8 is another v. high resolution, low distortion lens with flat field at macro distances. I just don't know how
it would compare to the 45/1.8 at what sound like more moderately close distances.
The 75/1.8 would also perform flawlessly, but is almost certainly too long for this sort of work. I don't as yet have a
50 mm eq. prime for µ4/3. I took B&H up on their one day offer of $100 for the new Panny 25/1.7, but don't expect to see
it for a while, as it appears they haven't actually shipped to retailers yet. But hey, I don't have one for $150 less
than those who ordered one any other day, and also don't have it. :-)
Contemporary Moose
* The Rawtherapee is displaced by one pixel in each direction from the others,
but once moved, identical.
--
What if the Hokey Pokey *IS* what it's all about?
--
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