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Re: [OM] Legacy lens for copy work

Subject: Re: [OM] Legacy lens for copy work
From: Rick Beckrich <rbeckrich@xxxxxxxxx>
Date: Sun, 20 Dec 2015 14:59:39 -0500
+3 for the 50/3.5 macro.

On Dec 20, 2015 2:05 PM, "Moose" <olymoose@xxxxxxxxx> wrote:
>
> 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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>
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