Personally I have a whole heap of slides sitting in boxes, which I really want in digital format. Plus I have acquired the “life’s work” of several other photographers. Here’s the whole adventure ...
There is basically two ways to digitise slides, with sub-variations: scanning and photographing.
Nearly every forumite will tell you to scan the slides with a drum scanner. Sure, this might yield excellent results, but I do not have physical or financial access to such a scanner. Next in order of desirability is a dedicated film scanner. Unfortunately both Nikon and Minolta have discontinued the crème de la crème of this category, leaving us with a few others of (sometimes) dubious quality. I tried a Plustek OpticFilm 7200 and quickly sold it on again. The Reflecta range appears of good quality, but are very expensive here in the outpost of the colonies. At the bottom of this list is the flatbed scanners. My Epson Perfection 2400 Photo produces acceptable results and apparently the latest models from Epson and Canon are quite good. Drawbacks, however, are price and speed — or rather the ration between these two aspects. However, no matter how you cut it, a flatbed is time-consuming and the glass is a horror to keep clean.
The second option, which every forumite will tell you doesn’t work, is the traditional method of duplicating slides — with another camera. Some people have taken the quick & dirty route of projecting the slides (with a slide projector and a screen) and then photographing the image on the screen. But I’m going the truly traditional way of using a slide duplicator. Although this sounds rather easy — attach duplicator to camera, insert slide, press shutter button, edit — I am not quite satisfied with this process.
I have one goal with this project: create an accurate digital version of the slide as it exists now, which includes dye failure, with the absolute minimum of fuss. As stated on other pages of this website, I hate post-processing. As it stands, I already have a back-log of my own photographs, so do I really want to add several tens of thousands of slides to the queue? Nope. This means that the camera must produce as-is and on its own an accurate duplication of the slide. The only post-processing I’ll be doing is rotate, crop, rename and file.
The full auto method produces terrible results, so let’s dig out those old photography books and read up on silde duplication. In The Asahi Pentax Way (8th edition) is a whole chapter on slide copying (of which I’ve also included the chapter introduction, as it is very applicable to this whole page):
[...]
While there are commercial services available that will make duplicate slides for you, the cost is high and, perhaps more important, the quality is rather low. Only a few processors can guarantee first-class duplicates. It isn’t surprising, therefore, that the word “dupe” has come to mean second rate in terms of quality. Most dupes bear only a slight resemblance to the excellence of the original picture. The dupes usually are much more contrasty, lacking the great tonal and colour gradations of the original. Colour is often washed out. Highlights and shadows don’t have the detail in the original picture.
If you learn to duplicate your own slides, however, you can do far better. Not only can you duplicate your original transparency in colour, contrast and sharpness, you can quickly learn to improve transparencies whose original colour didn’t quite suit you. You can even recrop your transparency and enlarge portions of it. The cost of such a duplicate is no more than the cost of an original picture made on transparency film-usually less than one-fifth of the cost of a commercially made dupe which isn’t one-tenth as good.
Light Sources
The most satisfactory slide duplication is generally made using a light source similar to daylight. While daylight itself is certainly the least expensive and the most widely available light source, it varies greatly in quality depending on sky, time and weather conditions. Electronic flash or floodlights balanced for daylight probably make the best illumination sources. Daylight balanced floodlights work quite well with the Spotmatic camera since the continuous light source makes it possible to determine the correct exposure for slide duplication by using the behind the lens meter. For other copying, one of the modern small, inexpensive electronic flash units probably makes the most convenient light source. However, we will cover both types of lighting in conjunction with slide duplication.
Which Film?
Daylight balanced film is the only proper choice if you intend to use daylight or a daylight-balanced light source for duplication. There are more types of daylight films available than tungsten films so the choice of daylight illumination with a daylight balanced film would seem a logical one.
Which of the many brands and types of daylight films is best for slide duplication? High-speed colour films should be eliminated immediately. While these are excellent as prime films to take photographs under difficult lighting conditions, they tend to show excessive graininess and have less colour saturation. The slower, brighter, more fine-grained films are far superior for duplicating purposes.
Still there are many different brands and types of slow colour film. How do you choose the best? Actually you cannot. While some colour films generally will give you good duplicates, the very characteristics of some — more or less contrast, softer colours, finer grain can often help you with specific problem slides.
Generally speaking, a slide duplicate tends to pick up additional contrast and lose in-between tones. Therefore for pictures of average contrast with good range of middle tones, a duplicating film of relatively low contrast but bright colour is preferable.
The same type of duplicating film is also recommended for original slides having low contrast although a duplicating film of average contrast might also do. For original pictures having very high contrast, a very low contrast film should be used. The fact that a film makes excellent colour pictures in a camera is no guarantee that it makes good duplicates. Agfacolor (Agfachrome in the U.S.) produces fine slides yet makes a very poor duplicating film. Some film manufacturing companies make film designed specifically for slide duplication. Your photo dealer can tell you what is available in this line.
Exposure
Once you have loaded your camera and have the slide to be duplicated in place, your big problem with daylight or any continuous light source such as floodlight is exposure. First position your light. With a small flood, place the reflector about three feet in front of and facing the diffuser plate of the slide copier.
Certainly the most convenient and simplest method of determining proper exposure is with a through lens metering Pentax camera. Basically all you need do is to make a reading through the lens as you would for any close-up and shoot the picture. [...] In addition we’ve noted that with dense slides additional exposure is often required, while very light slides sometimes need only half the recommended exposure.
[...]
In all slide copying it’s advisable to use the optimum lens opening, between f/4 and f/5·6, varying the exposure by changing shutter speeds when needed. The 50mm f/4 SMC Takumar is the best lens for copying.
[...]
When you are copying slides which have more density and shadow detail than the test slide, double your exposure. If the slide is rather light without density, halve your exposure. At all times if possible, take a few shots under and over the estimated proper exposure for insurance.
The foregoing procedure was based on maintaining an exact control of the duplication procedure. Once you have established the strength and distance of the illumination source, do not change it or your exposure calculations will be different. Measure the light to copier distance carefully, note the lamp designation and type of reflector. Make sure when duplicating slides that you reproduce the lighting situation exactly.
Using Daylight
You can probably understand by now why daylight is rather unsuitable for duplication. Not only does the strength of the illmnination vary considerably day by day and hour by hour, but the colour of the light and the quality also change. If you do duplicate by daylight some slides may be too blue, some too warm, depending upon the quality of the daylight when you make the duplicates.
[...]
Using Electronic Flash
Perhaps the best illumination source for slide duplication is the light from a small electronic flash unit. Electronic flash is adequately balanced for daylight illumination. The quality is virtually constant. The light is easy to control. You just hold the electronic flash about a foot in front of the slide copier diffuser, and release the shutter. Since many small electronic flash units today have short connecting cords for the camera which are non-detachable, you may have to obtain an extension cord which allows you to remove the flash sufficiently from the camera. A coiled cord extending up to two or more feet is most practical.
In using electronic flash for copying, you must again establish an ideal exposure for a properly exposed transparency. Although it is possible to fix the flash at a non-changeable distance and then change aperture to vary the exposure, it’s best to shift the illumination itself to maintain the same most critical lens aperture. You can then vary exposure by establishing a series of different flash-to-copier distances between one foot and three feet.
Again you must make a series of test exposures to establish a norm for your own flash unit. Once you have found the proper illumination placement and aperture, make sure that you jot down all the data so you can duplicate the set-up again whenever you wish to dupe slides.
In duplicating well-exposed slides, you will find that some slides are more difficult to duplicate than others. This is usually caused by the varying characteristics of the slide subjects. If facial tones are of primary importance, you may find that some films used for duplication are not as ideal for facial tones as others. On the other hand, a film which does not reproduce facial tones well, may be extremely good with foliage or some other specific colour. The more experience that you have in duplication, the more films you use for the purpose, the more expert you will become on choosing the right film for each slide.
Correction During Copying
Duplicating slides which you consider excellent is but one copying possibility. Slides which are slightly off colour can not only be duplicated but can be corrected as well.
In duplicating under- or over-exposed slides, vast improvement can be made. However, it is not possible to put back detail in either washed out highlights or unrelieved shadows. You can alter the colour, the contrast and the overall density but you cannot create in the duplicate any detail that was not in the original.
When making a duplicate to correct exposure error, allow less than the “correct” exposure time for an over-exposed original and more for an under-exposed original. The amount of exposure increase or decrease of course, depends upon the error in the original slide. When possible try a number of different corrective measures varying each slightly. To get the perfect dupe make use of the half stops on the Takumar lens.
Colour correction is a fascinating area of slide duplication. Quite often original slides will be off colour. If taken on sunless days or even on a bright day at the beach, a slide may appear bluish. Slides made early in the morning or late in the afternoon may be too warm. The same types of filters used to correct the original picture-taking situations will also work nicely here. We recommend a full set of nine: CC10Y, CC20Y, CC40Y, CC10M, CC20M, CC40M, CC10C, CC20C, CC40C. The filters, incidentally, are available as gelatin squares which can be held in front of the copier diffuser plate. Gelatin squares cost only a fraction of the price of glass mounted filters. Therefore a full set of nine will be less expensive than it might appear at first.
There are no hard and fast rules as to which strength filter will work best. Obviously, if the picture is too warm a bluish filter should be used in copying while a yellow or magenta filter will cut down on the blue in an original.
The chapter on duplication in Colour Transparencies says the following:
[...]
Where only same-size 35 mm duplicates are required, the [method of using a camera to take a photograph of the transparency, suitably held and illuminated] is distictly simpler to manipulate, but requires special apparatus: preferably, a 1:1 copying device, which automatically gives the correct plane and position for the original, as well as extending the lens for exact focus. With this all that is required to complete the equipment is diffused illumination of the correct colour temperature. A piece of flashed-opal glass, and the appropriate filter, interposed between the light-source and the transparency, are the essentials. [...]
The thickness of the protective glass over the transparency is not sufficient to upset the focusing — particularly since a small aperture is used, normally f/11 or f/16.
[...]
It might be thought that daylight would be the illuminant most likely to give correct colour-balance in duplication, but the intensity and colour-temperature of the daylight falling on any fixed surface vary continually, hence it is quite impossible to rely on these factors.
The alternatives are to use either daylight film with a compensating filter over an artificial light source, or to use artificial-light type film with a lamp of the appropriate colour-temperature. Of the two, the first is usually to be preferred, since daylight emulsions give a more even balance between the three components. Artificial-light types tend to have a restricted colour range. (Kodak have recently developed a special material for the duplication of Kodachrome, [...].)
No ordinary material will give the best possible colour-balance without a further compensating filter. For duplicating Agfa or Ansco Color transparencies, a pale pink or lavender filter is usually required. For duplicating Kodachrome a pale green tint is most useful. But the correct shade for any particular set-up of lamp and diffuser must be found by trial. Such matters as this make preliminary experiment essential.
[...]
In the first trial it is well to make three exposures, twice, four times and eight times the indicated exposure respectively. After processing, it will be obvious which exposure is the most nearly correct, and future meter readings can be modified accordingly.
The diaphragm setting should be small — f/11 or f/16 — not only to ensure maximum sharpness, but also so that the exposure lasts several seconds. Too short an exposure is difficult to time accurately, and is more likely to give trouble with vibration of the camera.
[...]
[...] The transparency must be closely masked in the holder. The light should be diffused, as non-diffused [...] illumination will give excessively harsh duplicates.
Colour-correcting filters should be placed between the light-source and the transparency.
[...]
From these sources I have gathered the following points:
- A 1:1, or in the case of most DSLR cameras, a 1:1·6 copying device is required.
- An artificial, constant, diffused light-source of a specific temperature is required.
- Duplicating a negative increases contrast.
- The exposure should be in the range of seconds, which mean a low ISO rating, weakish light-source and a small aperture.
- For some films the use of colour-shifting filters are essential.
- Although everything (aperture, exposure, light-source, etc.) must be kept constant throughout, exposure and light-source may be adjusted according to the particular slide being duplicated.
I am using a Canon EOS 30D camera, which has a 1·6 field of view crop factor. This means that an out-of-the-box slide duplicator with a 1:1 ratio doesn’t work. The solution is a seperate lens and extension tubes. For this I am using a Minolta MD MACRO 50mm 1:3.5 lens, with the MD-to-EF adapter also functioning as an extension tube. The slide holder is a heavily modified Panagor duplicator.
The Panagor slide duplicator has been modified by replacing the barrel with a piece of plastic pipe coupler, in order to slightly increase the length thereof. I calculated (empirically) the focus distance of the lens so that a 36×24 image projected on the sensor is reduced by the required amount, then fixed the slide holder in place. Basically, with the lens focussed at xx metres the camera photographs the whole slide. I also added a stop to the slide holder, which greatly eases the positioning of slides.
A suitable light-source proved to be rather more difficult than I originally thought, especially since natural daylight is obviously out. Yes, you can purchase special daylight-balanced photographic lamps, but let’s face it — I’m a real Scrooge McDuck. So let’s explore the cheap options.
The option of using a flash is not viable, as I later found out that exposures of several seconds (as also stated above) produce the best result. Short exposures tend to be harsh and blow the highlights; simply because the light required is more intense.
This leaves a lamp as the only practical option, either incandescent or fluorescent. Both work, with the big distinction being the actual colour temperature of the light itself. In theory this is not a problem, as the in-camera white balance (WB) can be used to correct the colour temperature. Whether this works in the real world will be tested below.
Another option which I want to test, is using LED’s, either the “white” type or a Bayer-grid of red, green and blue.