Dias Duplication with a Digital Camera




"Dias-duplication is easy compared to negative film copying, because positive film does not have that infamous orange mask to cope with. It's almost just like photographing any ordinary scene with natural colours" - or, so the common wisdom often say.


I do not agree.


I do not agree, because, while the orange mask has to be compensated out - and it is still just a single, monochrome filter - once, that is done we have all the virtues of the (well developed) negative, that is: Very high dynamic range, and generally very good resolution and detail. Even if the negative film isn't too properly exposed, we normally have lots of dynamic range and detail to work with in the further processing of our negative.


Diapositive film, on the other hand, has quite different charateristics, it is dramatically more contrast, dynamic range is low, and once exposed in the camera and properly developed, we essentially only have what we see. There are very few "hidden levels" that we may bring forward in further copying and processing.


Furthermore, it is my experience that diapositives are much more sensitive with the light source used (colour temperature and spectral lines). You may get so-so decent results with an artifical light source, but the resulting digital copies rarely look too convincing or natural. Your best light source will be the blue sky (away from the sun) or a slightly but uniformly and bright overcast sky.


Finally, although this is a problem of an entirely different nature, the dyes used in diapositives tend to be much less durable than those of negative film. Ectachrome will be known as particularly sensitive: Old Ectachromes are often more like gray scale pictures - only with the grey shades replaced by something reddish-purplelish! I have mostly used Agfachrome and later Kodachrome that both seem to withstand the tooth of time somewhat better - but still, they are ever so slowly fading and changing colour a bit as I see it: They are getting a kind of cyanish tint over time, (but my color sight is not the best, as I am somewhat red-green colour blind).


Anyway, having found aproper light source, you stand a fair chance of succes with diapositives also. You may use a set-up as the one shown in the negative-film section, but if possible I would then recommed that you replace the lamp with a mirror and do your work during day-time. If you have a full-frame DSLR, you may still use one of the various dias- and negative adapters (optical or based upon bellows) that were quite popular in the 60'ies thorugh the 80'ies and which can be found fairly frequently on the market for used gear. The same requirements in regards of the light source/colour temperature apply with this technique.


If you have an APS-C camera the used adapters will not work adequately because of the crop factor, and you will need to modify or construct an adapter of your own. The basics for a standard macro set-up will often do, the "core" being an extension ring (about 35 mm) and a normal 50 mm lens ("normal" as seen from the days of 35 mm film format).


Components: 1) Camera House (Pentax *ist DL); 2)Auto Extension Ring (Soligor for Pentax K); 3) Pentax SMC-M 50mm f/2.0, 4) Sunshade (Takumar Ř49 mm);  5)Home made Slideholder (Cardboard & Wood); 6) Cover plate from Slide Viewer (Agfa Gucki)

Now, just to close the circle you might want to construct some simple kind of negative holder to use with this set-up also for negative film copying.
As said, light from the bright sky is excellent for dias duplication, but for me this time of the day is usually not good for this type of activity and thus, I have to revert to artificial light. I have found that an old flash works very well for this kind of work. You cannot fire the flash directly against the slide, but bouncing the flash light from a bright wall will work.

 Experiment a bit, and you will have a set of values for distance to the wall and f-number, that will give you good exporsures with flash syncronization for most of your (properly exposed) slides.


With the above in place, let's take a look at some slides. First, we shall naturally try out the set-up with a well balnced, properly exposed diapositive taken on a sunny day:

Here we have the garden of my childhood. I took that picture when I was 12 years old in the summer of 1961. This duplicate is actually a fair rendition of, what the slide really looks like today. But isn't it a bit dull? Whether it is the fading over time or not, here is where the trouble with slide duplication begins: There is no single textbook solution as to how to improve upon the result. You have to try out the tools availiable in your software and gather experiences that way. Anyway....   ....doesn't this look much better? Isn't the grass nuch more "lawn-as-should-be"?? Here, the operation was fairly straightforward: Apart from a bit of clean-up with cloning, this image was enhanced using curves - although, more specifically by means of a special Camera Curve Profile, that I have developed for my Pentax *ist DL for this type of work. This time, it worked, but that will not always be so, and one has to try out other tools such as White Balance, Colour Cast, Contrast and more.

( click on images to see larger versions)

I said in the beginning that once you had set the exposure, pressed the shutter and developed you diapositve slide, you had come to a point of no return - with no further improvements possible. Well, as with all eternal truths, this may not be entirely true after all. Once you have digitized your slide, there may in certain instances be room for a bit of improvements:

0. Here we have a scene from my home town in the winter of 1960/61. Again, this is a fairly decent renditon of, what the slide actually looks like today and again, coulours have changed over all those years, but first of all, it is and always was overexposed. Anything we can do about it?   1. After a bit of initial clean up (alignment, cropping, clonig) we try darkening mid-tones. Hmmm....and buildings are still quite pale.....

2. Try darken midtone once more. Well, buildings are beginning to look a bit better. Now, what to do next?   3. How about a camera curve profile? No, too yellow. Equalize? No, much too yellow! Stretching levels then? Ah, that looks better.

4. Now is the time to try some white balace adjusments, (you should always try that at some point in the process - it may not always work, but it is worth the try).   5.A. Did the picture turn out a bit too pale? Try darken midtone (or adjust brightness and contrast in levels) once again. Add a finishing touch in focus or sharpening. Note that now the dust and dirt that have accumulated over all those years behind the glass have also been "developed" - for "serious work" I should have dismounted the slide and cleaned it!
  5.B. Now, in 5.A above we have a rather reddish colour cast (the sun was very low) and probaly a bit too much. So, one might try some fine-tuning in White Balance and/or Colur Balance. As said before, there is no straightforward text-book solutions for those pictures, where colours in the orginal have degraded. From here, tial-and-error and growing experience is the way forward.

What I do (hope to) have shown here is, that it IS possible to brings such pictures into a more "manageable" state, where they can be improved. I trust, most will agree that 5.A and 5.B are, after all, better than the 0 starting point?

Step 5. above really would conclude our litte journey into the realm of old, faded slides salvaging. We have a decent (considering the starting point) duplicate of the original diapostive slide and what would remain could be some conventional touch up in regards of dirt/dust and scratches.

However, I cannot resist the tempation to throw yet another ball into the game:


6. Addtional enhancement of 5.A using a camera-sensor/scene specific Camera Curve Profile.

Granted, this may certainly be overdoing things "a bit", severely enhancing colour cast, but I have included this example to demonstrate a) the power of the tools that you may have in your digital imaging toolbox (here: PhtoImpact X3) and above all b) to illustrate that the sequence of operations can by no means  be applied at random. As said above, had I applied my Camera Curve Profile at step 3, before the balancing and streching of levels, I would have had a rather yellowish image from which I would have had to take an entirely different route in order to reach a result similar to 5. above - and I suspect that I would have a hard time in reaching the same balance in red, blue and yellow as I have accomplished above.
A Few Concluding Remarks
Prices on digital dias- and film scanners have come down as have prices for everything digital in recent years. They are (can be) very good and offer resolutions easily around 7200 dpi. So, why bother with an old-fashioned set-up with roots in the ages of analogue film? Well, film scanners may be very good (unless you buy junk at dicount prices), but they are also very slow and the resulting files are very large.
You may need to give extra care to your best slidest - but honestly, how many are you going to print in A3 or even A4 size??? Chances are, you would like to compress a lot of your files to web- and/or screen display sizes anyway - and then perhaps print a few of the better ones in the normal 4 x 6 inch / 10 x 15 cm format.
And most importantly, you might simply want - like I did - to establish a digital archive of all your slides (and negatíves) in a hurry  - and if not your own, then perhaps inherited from older relatives and aquaintancies. You want that for quick reference and you don't want to spend hours feeding and watching a digital high-resolution scanner at work for that. Many have hundreds of slides and hundreds of negatives; many have even thousands!
Feeding your slide holder and capturing your slides with a set-up like the above is extremely fast and usually the results turn out good enough for on-screen viewing and small prints - and definitely good enough for archive- and overview purposes. If you then take your time and care in both preparation (cleaning, set-up, focus, test-shots etc.) and in post-processing you may even get really satifactory results with your better and most valuable slides.
And just maybe, it is NOW that you should act, before time and age takes its toll on those precious old photographic memories..........




Copyright © 2011 - Steen G. Bruun