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. 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. Capture in raw and
converted to tiff. White balance corrected. 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. Bill
Barber
-----Original Message-----
From: Moose <olymoose@xxxxxxxxx>
To: Olympus Camera Discussion <olympus@xxxxxxxxxxxxxxxxx>
Sent: Sun, Dec 20, 2015 1:05 pm
Subject: Re: [OM] Legacy lens for copy work
On 12/20/2015 9:40 AM, Jim Nichols wrote:
Bill,
I'm certainly no expert, but I have done a little of this type of work,
strictly for my own use.
I have done quite a lot, most recently helping a friend prepare slides for
University art classes he taught. Longer ago,
I actually had a huge, custom designed/made camera built and a room built
around it to make 4x5 slides from flat
originals from tiny to maybe 8x10 feet. I also conceived of, helped
design, had built and installed custom projectors to
rear project these slides on 6x7' screens at several magnifications. I
mention this to give my credentials for knowing
that centering and film/subject/projection alignment is THE KEY!
I think any lens 50mm or longer will work.
Yup. The reason not to go shorter is that one enters retrofocus optical
design territory, which is always less suited to
this use. In particular, a lot of them have field curvature at closer
distances. The 21 mm OMZs, for example, have quite
a lot of that.
But, more important than the lens is the alignment of the subject matter
and the plane of the sensor, or film, as the
case may be. To minimize distortion, the subject and the sensor must be
perfectly parallel, and the lens should be
level with, and centered on, the center of the subject.
Yes! Bill, it may be just the way you wrote the question, but it sounds
like you are confabulating two quite different
types and causes of distortion. Unsquareness, or perspective distortion,
is near 100% caused by centering and alignment
failure in the taking. Other lens non-linearity is solved by using lenses
specifically designed for flat copy work.
The OMZ 50/3.5 is just excellent in this regard, as is the Tamron 90/2.5
macro lens. I used these two extensively.
I find that small errors in alignment can be corrected in most photo
editing software, but at the expense of slightly
distorting the subject. It is better to get the alignment right when
taking the photograph.
True today, and I do a lot of that. Near perfection may be reached even
with pretty bad originals. This,
<
http://galleries.moosemystic.net/Brooklyn/Things/All%20Things/slides/_MG_3244corcr.html>
for example, is the skylight
over this stairwell. <
http://galleries.moosemystic.net/Brooklyn/Things/All%20Things/slides/_MG_3243.html>
Absent
board(s) to put across the railings at the top, and permission from the
guards, there is no way to take it straight on.
But when I was making lots of slides, it had to be right in the camera. I
used an enlarger base and upright, converted
to hold cameras, checked with levels for alignment. A wide range of
original sizes and limited travel are why I used two
lenses regularly.
With originals too large for that kind of set-up, I found the floor and a
tripod with lateral extension useful. For
something on the wall, levels and tape measures are your friends. Getting
the camera/lens right vertically is fairly
easy with them. Horizontal is trickier, and most often depends on a good
eye.Even the slight lean forward from the
vertical of a hung picture can make a difference, so watch that, too.
Then again, if this is digital, or to be scanned, small errors are easily
corrected without noticeable image IQ
deterioration.
Lighting is the other big issue. Unless working to enhance surface
texture, lights on both sides at 45° to the subject
seem to work best.
I know little about 4/3 lenses. For µ4/3, the 80/2.8 Macro is da bomb, but
at 160 mm eq. may not work for all
situations. In any case, most all µ4/3 lenses (except the 80/2.8?) depend
on correction of optical distortion in
firm/software*, so you are never looking at the actual lens output unless
using a converter such as DxO, with correction
turned off, RAWTherapee, DCRaw, etc.
Been there, Done Moose
* This is an intentional part of the overall design, letting linear
distortion go a bit to allow better correction of
other things that can't be corrected later.
--
What if the Hokey Pokey *IS* what it's all about?
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