Is it correct that Kodachrome's colors after development are balanced for projection lamps with a 3200K color and by that produce neutral white and greys to our eyes when we see Kodachrome slides projected in that condition?
Is it correct that Ektachrome's colors after development are balanced for projection lamps with a 5000K color and by that produce neutral white and greys to our eyes when we see Ektachrome slides projected in that condition?
Any mix of both types of slides projected with one projector would be a challenge to the adaption of our eyes? A set containing both slide types on a 5000K viewing box can easily be sorted in two groups based on their overall color cast? Kodachrome slides having the blue cast.
We shouldn't make the mistake to interprete a color film description "daylight, tungsten balanced" as describing the above features, that description is for the exposure of said films.
If so the summary of Guyburns in the opther thread could be reduced to the following lines:
1. Kodachrome color, whatever film version, is balanced for viewing with 3200K projection light. Ektachrome film is (in general) balanced for 5000K light. "For the average human eye color receptors" is the other condition.
2 Desktop scanners, film and flatbed models, have an illumination that approaches 5000K with CCFL, FL or LED lamps. More or less continuous spectrum. The RGB filter dyes of (linear) CCD sensors will have slight differences in between but are very different to the human eye receptor.
3 Depending on the conditions described in 1 and 2, Kodachrome slides will show more color cast than Ektachrome slides when scanned as the light source suits Ektachrome better. Color inconstancy in changing light. Blue cast for Kodachrome slides the dominant effect. The difference between the human eye/brain and scanner sensor filtering producing color casts as well. Color inconstancy due to different observers. Differences between scanner lighting and sensor filtering per model and per scanner creating another color inconstancy.
4 Fading of Kodachrome slide due to projection time creating substantial loss of magenta in the slide and a shift to green. Dark fading of Kodachrome should so far be negligable but would create a yellow loss in time and a shift to blue. Fujichrome showing the best projection fade properties, Ektachrome better than Kodachrome, ratio 5: 2.5:1 in hours. All will fade with magenta loss on projection so a shift to green. Ektachrome and Fujichrome dark fading is faster and creates a cyan loss so a shift to red. Yellow staining of archived Ektachrome and Fujichrome slides, it doesn't happen with Kodachrome. A shift to yellow as a result of that. All types of aging will have an influence on scanning results.
5. A scanner can be profiled with an IT8 target + its reference data file (to counter any scanning inaccuracies) using software such as VueScan or Silverfast to correct for inaccuracies in scanning later on. Two Kodachrome IT8-7 slide types exist but they differ, Kodak's original made in 1999 is based on Kodachrome 25, the Lasersoft Kodachrome made in2009 is based on Kodachrome 64. Ektachrome target slides exist in many variations and shouldn't be used for Kodachrome scanning. More color management software exists for creating scanner/film profiles. Profiling is doing an average job in scanning, it can not correct color for slides that deviate from the average like due to exposure to other K values than tungsten or daylight, reciprocity color shifts, fading, etc. Each IT8 target also needs a IT8/CGATS file that contains the colormetric measurements for that target. This text file is required as part of the calibration process. The CGATS file for Kodachrome can be downloaded from FTP.Kodak.com/GASTDS/Q60DATA and is contained in a folder called K3-Data. Info about the colour coding of the IT8 targets is in the document TECHINFO.pdf.
7. In optimal conditions, fresh slide, correctly exposed, a profiled scanning workflow, will in the first place deliver a representation of the (Kodachrome) slide as it is, not of the original scene. With Kodachrome the results will have a mainly blue color cast due to the illumination change from the 3200K KCh is balanced for to the 5000K lighting of the average desktop scanner and differences between the RGB filter dyes/human eye-brain. Contrast in the tone range of Kodachrome film will be affected by the changes too, slide films have in general a wider dynamic range and desktop (film) scanners can not always cope with that, flatbeds even less. Correction for color, tone range, should be available in the Kodachrome settings of for example Vuescan and Silverfast and should be correct per scanner model. More or less as for example an insufficient dynamic range of a scanner can not be compensated that way. Any other experience? White, grey, balance on neutrals in the scanner and/or additional editing on 16 bit scans in editing software may still be needed or will be needed if the scan software doesn't know a Kodachrome setting. Similar RAW editing is another route. Whether one can avoid the per slide editing with Kodachrome batch scanning is open to debate.
I have some questions:
Is there information on how pro drumscan operators coped with Kodachrome slides? The use of 3200K lamps and altered, more Kodachrome friendly, filters on the PMTs? Must have been the solution in the infancy of drum scanner technology and not a bad approach. Later on solved with similar Kodachrome adaptions in software + profiling which may have been less effective but better adapted to demand. I checked some books on reprography here but couldn't find a clue.
I originally thought that there were Imacon models with a halogen tungsten lamp but I must have been wrong. There is a reference to replacing a 5000K fluorescent lamp with a 5400K lamp (repair) due to lamp production issues though. I wonder whether there have been DIY attempts to replace scanner lamps with 3200K lamps to suit Kodachrome scanning. In slide copying with a digital camera/slide copier that route should be easier. Did some searches but nothing substantial surfaced.
met vriendelijke groeten, Ernst Dinkla
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