Saturday, February 12, 2011

Hybrid copy - British Journal of Photography

Hybrid copy | Jan 4th 2011
It is getting difficult to find transparency scanners in the affordable bracket between entry-level, five-megapixel frame grabbers and the few surviving higher-end desktop machines such as the Nikon Coolscan 9000. Epson’s V600P is one solution, but most flatbed scanners do not offer anything close to the basic quality required for 35mm slide and negative digitising, or for higher-grade rollfilm conversion.
With some DSLR cameras now matching or exceeding the resolution of most 35mm scanners, and medium-format backs of up to 65 megapixels, the demand for forgotten optical duping systems has surged. Photographers are discovering that, if you have pristine film originals still in their lab sleeves, a device like the old Bowens Illumitran or Elinchrom Dia Duplicator can team up with a Nikon D3x, Canon 7D or similar higher-resolution body.
You can adapt old colour enlarger dichroic heads as light sources only, or complete units with focusing bellows, for the same purpose. The critical requirement is a perfectly even field of light, which means dense opal white acrylic between the source and the film to be copied. The new LED light sources used for video run so cool they can be placed very close to the opal diffuser, and they have the benefit of low infra-red emission with daylight colour temperature.
A copystand from Kaiser (one of the few remaining makers) or Firstcall Photographic, whose model 920 costs only £149.50 including twin tungsten lights for reflective originals, can be used with an opal diffused Litepanel or similar source and a good macro lens.
One problem I have found with the enlarger-type copy lenses originally sold with slide duplicators is that they often don’t work well with a digital body, producing reflection hotspots or very low contrast; all were also made for full frame, and make duping impractical with crop-factor DSLRs.
Modern macro lenses offer a wider range of focal lengths and working distances due to internal focus. The Sony 30mm f/2.8 1:1 macro, with its minimum focus barely 20mm from the lens front and its APS-C coverage, can be used with almost any copy stand or old duplicator chassis.
I’m using a 70mm Sigma macro on full-frame digital, and its working distance for 35mm to rollfilm formats is surprisingly close – much less than my Rodenstock 75mm Apo Rodagon 1:1 copy lens. It also gives much better contrast and colour rendering.
Compared to film scans, which take many minutes to complete and often have a combination of poor shadow detail and obtrusive aliased grain, a 24-megapixel copystand capture has greater dynamic range with smooth detail. The big issue is with dust and scratches. Where the film scanner might have Digital ICE to remove these perfectly, the camera capture needs careful manual retouching. Some well‑worn E6 originals are beyond hope with either.
ICE has never worked with silver negatives (it does to some extent with chromogenic negatives such as Ilford’s XP1). Scans from black-and-white film negatives are rarely good; it’s much better to return to the darkroom, make the best possible hand print in a reasonable size for copying such as 10×8-inch, and scan or re-photograph this. But a DSLR capture from a negative can work well if you are skilled enough to create good custom curves to map a raw conversion to a print-like positive result.
Creating a curve preset to handle copied C41 colour negatives is not easy, but it is possible. Again, making a perfect hand print and copying this is a far more accurate solution.
Testing a few alternatives for copying rollfilm originals, I found that a strong diffuser is needed; depth-of-field is not enough to remove any trace of uneven quality in the lighting. A local signmaker has quoted £25 for half a dozen 5×4‑inch cuts of 3mm opal acrylic. It cost the same for a single one as there is a minimum charge of £25, so a small stock of diffusers will be there for future use.
Colour and tone alike from the DSLR strike me as better than the results from my rollfilm scanner, discontinued and needing a new light source that can’t be found anywhere.
Sharpness is slightly less grain-perfect but looks natural, revealing detail and texture without visible grain. As for dust and scratches, big sky areas need retouching but a 1987 portrait shot (a test of new Fujifilm film at the time, chosen because scanners just don’t handle its red shades well) needed just four dust spots removing.
One surprise was that shots of negatives probably needed far less spotting than used to be the case in darkroom printing. Both black-and-white and colour, kept to the normal standards for more than 15 years, emerged clean. It was possible to use low-density (under-exposed) bracketed examples, compared to the density needed for similar scans or analogue prints.
The file sizes of around 48MB (16 megapixels) from square originals, and anything between that and 70MB (24 megapixels) for rectangular slides and negs are adequate for archiving and most editorial uses, or prints up to around 12×16.
Anything larger and the high-end route of drum scanning would be desirable.
But this costs very little to do, and it can be very fast indeed once everything is fixed down firmly, so film can be fed into a carrier without having to reframe or focus between copies. For strips of negatives a copy every few seconds would be practical, for single transparencies one every minute or so for a batch of matched sizes.
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