How much scanning does it take?

[Stelios]

I got back some kodachromes today (actually 5 days earlier than expected!) and while trying to figure out how to scan the thing I was wondering how much scanning can the slide take before it gets a bit damaged. The scanners seem quite a source of light directed on the slide. What is the impact of each scanning? I feel reluctant in scanning it again and again in order to get it right (can't get the profiles to work right).
I have a Canoscan 4400F if it matters.. and I want to have some sort of web presentable jpgs from my slides.

oh..it looks wonderful under the loupe...

[Fredrik]

Why not find out? Take an (unimportant) shot two times, so as to get two identical slides. Put one away in dark storage, and scan the other one over and over. My guess is you'd need to scan it hundreds of times before you notice a difference. For practical purposes, don't worry about it!

However, it's tedious to scan the same slide over and over. In the professional version of Vuescan it is possible to save "raw" files, so once you get the very basic scanning parameters right (such as CCD exposure), you never need to rescan; just use the raw file, and you can apply profiles and adjust all settings just as if you were scanning the slide again.

Probably other software has this feature as well. It's incredibly useful.

[Stelios]

Now, I didn't know that. A raw file would be handy then. Thanks!

I did not mean that I'd forever scan the thing. I was only worried that the light source would be too strong and it would fade fast. I'm just being pedantic I guess.
I would try it out, but that'd mean I'd have to wait until I send it to Kansas and then have it back and... oh well. thanks anyway :)

[KenFretz]

You don't need to worry about it as your scanner will wear out long before you damage the slide. Remember Kodachrome was designed to handle hours and hours of light coming from projector lamps much more powerful than anything your scanner produces.

Ken

[wlodekmj]

You don't need to worry about it as your scanner will wear out long before you damage the slide. Remember Kodachrome was designed to handle hours and hours of light coming from projector lamps much more powerful than anything your scanner produces.

Unfortunately it is not that simple. Kodachrome was originally designed for movies, where a single frame is typically exposed for, roughly, 1/50 second at one showing. Kodak's technical specifications say that one Kodachrome frame is good for 60 seconds' exposure before it begins to downgrade. That is 3000 showings of a movie using a powerful projector lamp but only 6 showings or scans of a slide at 10 seconds each if an equally powerful slide projector, or scanner, lamp is used. KenFretz is right to say that most movie projector lamps are more powerful than scanner lamps, so in practice, you can expose a Kodachrome slide for much more than 1 minute before you notice any degradation, but the originator of this thread was right - this can be a concern.

[AndrewKirkby]

Unfortunately it is not that simple. Kodachrome was originally designed for movies, where a single frame is typically exposed for, roughly, 1/50 second at one showing. Kodak's technical specifications say that one Kodachrome frame is good for 60 seconds' exposure before it begins to downgrade. That is 3000 showings of a movie using a powerful projector lamp but only 6 showings or scans of a slide at 10 seconds each if an equally powerful slide projector, or scanner, lamp is used. KenFretz is right to say that most movie projector lamps are more powerful than scanner lamps, so in practice, you can expose a Kodachrome slide for much more than 1 minute before you notice any degradation, but the originator of this thread was right - this can be a concern.

Hi Wlodek :)
The Kodachrome specifications actually refer to the initial exposure of the film in the camera and reciprocity issues which come with long exposures (colour shift) - not the actual projection of the image after the processing is completed.

Kodachrome was designed as a cinema and still film - but for taking the photo initially, not for the projection and duplication.

It is quite surprising that while Kodachrome exhibits extremely long lasting colour and quality when stored in correct conditions (controlled temperature, humidity and NO light) it is also the worst film where projection is concerned. The dyes have extremely accelerated fading when they are exposed to bright light sources- compared to many E6 films which actually work far better under projection. Light appears to be the one key thing which does degrade Kodachrome severely and very quickly.
E6 films are more easily deteriorated by heat and moisture but not by exposure to light.

You can see the Wilhelm Imaging Research paper on slide films. I will track it down and post the link when i can find it. It details Ektachrome, Velvia, Kodachrome and a few others.

This all said i do not think short exposures of moderate intensity light from a scanner CCFL will cause any problems with your Kodachrome. If you were running them near a projection lamp of extremely high temperature and light intensity then you will probably be able to measure the fading of the image in a very short period of time...

You don't need to worry about it as your scanner will wear out long before you damage the slide. Remember Kodachrome was designed to handle hours and hours of light coming from projector lamps much more powerful than anything your scanner produces.

Ken

Kodachrome was never designed to be projected... In fact is the worst performing slide film when projected.
It is a widely documented and tested fact. The reason why Kodak continued to develop Ektachrome is because of this reason.

[wlodekmj]

Thank you Andrew, yes my mistake. I may be wrong in that Kodachrome is reported to be good for one hour of projection, not one minute. This is in a Kodak technical report; I'll add the reference when I find it. Their technical report E30 on storage and display only warns against long-term projection of Kodachrome.

[Stelios]

Having (briefly) read the Wilhelm Imaging Research paper it seemed to me an appraisal of Fujichromes. And I cannot remember talking about scanning, that's why I asked. Storage will always be a concern unfortunately. Until the day I print my own Ilfochromes. Oh some day...

[wlodekmj]

The Wilhelm book is excellent. Chapter 6 specifically covers fading due to projection: http://www.wilhelm-research.com/pdf/HW_Book_06_of_20_HiRes_v1a.pdf

On page 6 of the pdf file, near the end of Table 6.1 they recommend a maximum of 1 hour projection of Kodachrome for general users, or just 20 minutes for technical use. If slides are to be projected more, they recommend making and using duplicates. At the top of the table they say what projector lamp was used - the projector was set at high.

So, in reply to Stelios' question, this time should allow for several scans, but it is best to calibrate the scanner and then use that setting, rather than scan a slide repeatedly.

[uwphotoer]

Storage will always be a concern unfortunately. Until the day I print my own Ilfochromes. Oh some day...

Don't forget you have to put light through the slide to make ilfochromes too...... better make short exposures and focus fast.....

[Stelios]

hahaha I don't want to get that paranoid. If it goes, it goes I guess...