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.