From: King Sardon on
On Thu, 14 Jun 2007 02:35:39 +0300, Nick Fotis <nfotis(a)otenet.gr>
wrote:

>King Sardon wrote:
>
>> The slide is much higher contrast than the original scene. Digital
>> cameras are also high contrast imagers. So after rephotographing it on
>> a digital camera, the contrast will be very high. That may be a good
>> thing or a bad thing depending on the image and your objectives. But
>> if your objective is to make a close reproduction of the original,
>> then the objective will not be achieved.
>
>First, some background information:
>My slide duplicator is labeled "Ohnar", has metal construction and no zoom
>control. I suspect the optics are from Bush&Meissner, judging from a label
>on the box.
>
>It's essentially a fixed 1:1 reproduction system, with a holder and a white
>rectangular plastic diffuser that can make lighting more uniform.
>It contains also a fixed lens in the middle of the barrel.
>It has a screw-mount T2, added a T2-mount to Canon EF.
>If you don't have natural light available, you can use a lightbox or a flash
>facing the slide.
>
>Regarding contrast, I haven't seen raised levels of it, contrary to your
>assertion.
>Note that dSLR RAW files (even JPEG files) have LOW contrast, and often need
>sharpening in Photoshop or a similar application.
>Slide projection raises contrast, as far as I know, in order to heighten the
>impact to the viewer.
>
>In the Canon 1Ds MkII, the results were VERY good, and I suppose with the
>EOS 5D would be nearly the same.
>The pros:
>- low cost (got mine from Ebay), if you own already a full-frame dSLR
>- very high speed (scan at 1/60 of the second per slide or so)
>The cons:
>- you cannot automagically remove hairs and dust specks like in modern
>scanners
>- you can only scan 1 photo each time
>
>Another way (if you have a macro lens suitable for 1:1 shooting) is to use a
>light box under the slide, on a copy stand, and you put your camera on a
>fixed height.
>This method needs a lens which doesn't suffer from 'focus creep' (ie., it
>retains focus while it points down).
>
>At any case, you may need some experimenting before settling on a particular
>method.

By contrast, I mean differences in tone. High contrast images have
more dark areas and more light areas, at the expense of mid-tone
areas. Contrast has nothing to do with sharpening.

Slides typically have a gamma of 1.6, and that is high contrast. They
look great projected that way. But it can be tough to get good prints
from them unless you deal with the contrast by using low contrast
printing paper or contrast masks.

Normal contrast would be a gamma of 1.0.

Digital pictures are usually viewed on a monitor, and this gives a
similar effect to how slides used to be viewed. Pictures look better
on a monitor when the contrast is higher than natural, the same way as
with slides. Since the appearance on the monitor is the overall result
of the digital image and the monitor characteristics, it is hard to
talk about the gamma of a digital image.

If you shoot RAW, then you can post-process your shots to the gamma
you want and probably end up with nice results. The real test would be
to have them printed; then look at the shadows and highlights. If they
preserved the detail that was present in the slide, then you were
successful.

I recall that copying at 1:1 can be technically very hard because the
lens can be difficult to focus at that magnification. There could be
an advantage to copying slides on a smaller frame so that you would be
shooting at around 1:1.6.

KS
From: David J. Littleboy on

"King Sardon" <KSardon(a)fake.com> wrote:
>
> By contrast, I mean differences in tone. High contrast images have
> more dark areas and more light areas, at the expense of mid-tone
> areas. Contrast has nothing to do with sharpening.
>
> Slides typically have a gamma of 1.6, and that is high contrast. They
> look great projected that way. But it can be tough to get good prints
> from them unless you deal with the contrast by using low contrast
> printing paper or contrast masks.

FWIW, slides scanned on a quality slide scanner and printed on a decent
inkjet make drop-dead knockout gorgeous prints. Doing the scanning (and
printing) well requires skill and patience and experience (and a decent
scanner), but it's quite possible. (I find it a lot easier than scanning
negatives, since I know what I should be getting and grain aliasing isn't a
problem.) Lots of people do landscape and other "art photography" work that
way, although that class of work is better with medium (or large) format
than 35mm.

My guess is that a slide duplicator on a digital camera wouldn't be quite as
good as using a dedicated film scanner, but I'd think it'd be better than
Kodak "Picture CD" scans or Fuji Frontier scans.

David J. Littleboy
Tokyo, Japan


From: Nick Fotis on
King Sardon wrote:

> If you shoot RAW, then you can post-process your shots to the gamma
> you want and probably end up with nice results. The real test would be
> to have them printed; then look at the shadows and highlights. If they
> preserved the detail that was present in the slide, then you were
> successful.

The photos were reproduced in a railfan magazine from Fuji Sensia 35mm.
As far as I recall, there wasn't a big difference compared to the original
slide, at least compared to an A4 print (the full-page vertical opening was
larger than A4).

> I recall that copying at 1:1 can be technically very hard because the
> lens can be difficult to focus at that magnification. There could be
> an advantage to copying slides on a smaller frame so that you would be
> shooting at around 1:1.6.

If you mean the case of using a macro lens for copying over a light-table
(e.g. with an 100mm/2.8), the slide is essentially flat (at least in
theory :-) ), so you won't have a serious depth-of-field problem.
If you say about a slide duplicator, there is no focus alignment - the focus
is fixed.

Agreed, using a APS-C camera with a 1:1 zoom lens would give you some more
distance from the slide (and presumably would be easier to focus).
But if you focus the first time, easy or hard, you can keep this set-up and
shoot slides one after another (the light table and the distance would be
constant, at least in theory :-) ). A 90 degrees eyepiece would be very
helpful, I think, but not necessary.

Cheers,
N.F.
From: Chris Malcolm on
King Sardon <KSardon(a)fake.com> wrote:
> On Thu, 14 Jun 2007 02:35:39 +0300, Nick Fotis <nfotis(a)otenet.gr>
> wrote:

>>King Sardon wrote:
>>
>>> The slide is much higher contrast than the original scene. Digital
>>> cameras are also high contrast imagers. So after rephotographing it on
>>> a digital camera, the contrast will be very high. That may be a good
>>> thing or a bad thing depending on the image and your objectives. But
>>> if your objective is to make a close reproduction of the original,
>>> then the objective will not be achieved.

> By contrast, I mean differences in tone. High contrast images have
> more dark areas and more light areas, at the expense of mid-tone
> areas. Contrast has nothing to do with sharpening.

> Slides typically have a gamma of 1.6, and that is high contrast. They
> look great projected that way. But it can be tough to get good prints
> from them unless you deal with the contrast by using low contrast
> printing paper or contrast masks.

> Normal contrast would be a gamma of 1.0.

If the problem with the slide-photographing method is too high a
contrast, then could not contrast be lessened by optical means, such
as by using a large close and highly diffuse light source? It only has
to be lessened enough to bring it within the dynamic range of the
camera sensor, since after that the problems cam be dealt with by
software.

--
Chris Malcolm cam(a)infirmatics.ed.ac.uk DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

First  |  Prev  | 
Pages: 1 2 3 4 5 6
Prev: Bayer filter removal
Next: Battery woes