[rollei_list] Re: Old film
- From: Thor Legvold <tlegvold@xxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Mon, 30 May 2005 23:18:08 +0200
Richard, I don't know where you found all of this. You're a real gem :-)
Thor
On 30. mai. 2005, at 19.00, Richard Knoppow wrote:
>
> ----- Original Message -----
> From: "Thor Legvold" <tlegvold@xxxxxxx>
> To: <rollei_list@xxxxxxxxxxxxx>
> Sent: Monday, May 30, 2005 9:20 AM
> Subject: [rollei_list] Re: Old film
>
>
>> I still prefer Kodachrome for 35mm. A shame it's not
>> available anymore
>> for 120.
>>
>> Thor
>
> I don't know why Kodak has been trying to kill off
> Kodachrome but they have for a long time. Probably
> supporting the special processing is the problem. Kodachrome
> evidently has excellent dark storage properties while
> Ektachrome type films have better resistance to fading under
> projection. I've seen quite a lot of Kodachrome that still
> looks pristine after 60 years. I am not sure why the dyes
> are so stable. Kodachrome differs from more recent color
> films in that the substances which form the dyes are in the
> developing solutions rather than in the emulsion layers.
> This may offer a wider range of dyes that can be used or,
> perhaps its something to do with residues of some sort in
> the emulsion layers.
> Kodachrome has a curious history. From bits of history
> gotten from various sources it seems that George Eastman got
> interested in finding a practical color film for amateur
> photographers. Its hinted that this desire was one reason
> for the establishment of the Kodak Research Laboratories
> although I think Eastman's aquaintance with the Edison lab,
> which eventually became the famous General Electric research
> lab, may have inspired its creation. Kodak was not
> successful during Eastman's lifetime although it introduced
> at least two early color processes. One was an additive
> process using a reseau of colored particals similar to the
> Dufycolor process. Agfa also had a commercial process using
> a version of the same technique, as did others. Kodak called
> its material Kodachrome. I no longer remember the date of
> introduction but I think it was in the 1920's, perhaps even
> earlier. It was not a sucessful process. The other earlier
> Kodak system was called Kodacolor and was a lenticular
> system for 16mm motion pictures. This was introduced in the
> early 1930's. Lenticular color systems have some serious
> inherent problems. One of the worst is color fringing of out
> of focus areas of the image. The syetem also requires a lens
> with a large physical aperture causing a limited depth of
> field and an exageration of the above problem. A great deal
> of work by Kodak in cooperation with Paramount Pictures was
> put into adapting lenticular color for professional motion
> pictures. The system works pretty well for reversal where
> the camera original is projected but there are grave
> difficulties in printing and duplicating. These, along with
> the relatively poor image quality caused the system to be
> unsuccessful and it was withdrawn after a relatively short
> time.
> The later process known as Kodachrome was introduced
> about 1935 as a 16mm motion picture stock. The original
> processing method was very complex and very fussy. It
> depended on the conrolled penetration of a bleach into the
> emulsion. The film was first developed into a negative. It
> was then given a reversal development for the color nearest
> the support. After this it was bleached in a bleach solution
> that penetrated only the two top layers. Then it was again
> developed in a developer which produced the right color for
> the center layer. Again it was bleached, this time for the
> top layer only. Then it was developed a third time for the
> top layer. Joseph Friedman, in his book on the history of
> color processes, attributes this method to Mannes and
> Godowsky since other parts of the Kodachrome process dated
> from the turn of the century and were fairly well known
> technology. After about a year and half a better method of
> processing was found. This is the method still used. This
> still requires three separate reversal developments in
> developer containing the right couplers for the particular
> layers but eliminates the need for the differential
> bleaching. It makes use of the color sensitizing of the red
> layer, which remains after the first development so that
> selective re-exposure of the three layers is possible. The
> first reversal is of the bottom layer by fogging it with red
> light from the support side. Since none of the other layers
> is sensitive to red only the bottom layer becomes
> developable. Next the top layer is fogged using blue light.
> Because the yellow filter layer is intact the blue light
> does not fog the center (green recording) layer. After the
> top layer is developed the center layer is developed in a
> fogging developer. All this was necessitated by Kodak's lack
> of success in finding a way to keep dye couplers from
> wandering from layer to layer. Agfa did find a way and
> introduced a reversal color film at about the same time as
> Kodachrome that could be developed in a much simpler
> fashion. However, it was never sold in the US and was
> inferior to Kodachrome in image quality. The Agfa method of
> anchoring the dye is the one currently in use for all
> chromogenic color films. Kodak did eventually find another
> method of anchoring the couplers. This was introduced in
> Kodacolor film c.1941 and was the basis for Kodak color
> materials until probably the 1980's when they adopted the
> Agfa method. It is reported that Kodak made materials for
> the military using the Agfa technique during WW-2 when the
> Agfa patents were seized by the government.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
> ---
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