DufayColor, réseau layer

[MichaelG.]

Here's a little bit of nostalgia for some
... a bit of ancient history for others !!

small jpg version for previewing

2019-11-02-15.12.20 ZS PMax.jpg (209.85 KiB) Viewed 5360 times

Objective = Wild 40x 0.65
Eyepiece = Zeiss 8x Kpl
Camera Lens = 16mm f1.6
Camera = Toupcam UCMOS05100KPA

Transmitted illumination [dome LED under condenser]
Stack of nine frames, at 2 micron steps, in Zerene Stacker

The full resolution tiff file is here: https://www.dropbox.com/s/cv9t775tae7xm ... x.tif?dl=0

MichaelG.
.

Ref.https://en.wikipedia.org/wiki/Dufaycolor

Edit:
I note the rather different image on the wikipedia page, which shows a lot of fine structure.
The sample slide that I photographed may be a different version of the film
... either that, or mine is seriously lacking resolution !!
... perhaps I should have used epi-illumination [ ? ]

[MicroBob]

Hi Michael,
you roused my interest! This was apparently an early additive colour film method - can you tell more about the specimen?

Bob

[MichaelG.]

Bob,

The specimen came in a ‘mixed’ box of slides, doing the circuit of the Postal Microscopical Society.
Unfortunately there is little more to tell ...
The date 1908 is mentioned on the slide label, but I have no evidence that the sample itself is that age.
... As the Wikipedia page tells us, the material was in use for quite a while.
The slide is just a crudely mounted rectangle of [presumably fully processed] transparency, which looks neutral grey to the naked eye.

Like you, I’m intrigued by it ... I knew about the process, but had never previously had a specimen to look at: if I find anything more, I will post accordingly.

MichaelG.

[mrsonchus]

Looked it up Michael, my interest was pricked also! What a remarkable idea this was.
Judging by some of the images from searches, this worked really very well!
Quite amazing. Thanks for posting Michael, an intriguing post.

[MichaelG.]

I just found this page, which illustrates the steps in the manufacturing process:
http://www.brianpritchard.com/Dufay2.jpg
The referring page is http://www.brianpritchard.com/Dufay.htm

Also found this: https://filmcolors.org/timeline-entry/1257/

... But it’s time for bed now.

MichaelG.
.

Edit:
That last link is astonishingly good, and browsing around it will get you to three patents on this page:
https://filmcolors.org/timeline-entry/1343/

Edit:
Having just found this image: https://filmcolors.org/timeline-entry/1343/#/image/9246
I wonder if my specimen was a sample of this ‘loose screen’ material ?

... Much more research required !!

[MicroBob]

Hi Michael,
thank you for the interesting links!
Apparently the main advantage of this system was, that it was mainly used with existing b/w hardware. In a time when colour film was just in it's beginnings this was a useful property.

Bob

[photomicro]

A nice talking point Michael.

I am intrigued now to know when this box was put out on circuit, principally because in early 1993 I put a box out onto circuit that included a slide I had made of a small piece of Polarchrome film. As has been mentioned above, the great advantage of this technology is that the film is developed using essential the same chemicals as monochrome film, and hence is fairly easy to do. It really was quite ingenious technology to use this coloured 'mask' as a reverse filter during projection of the slide.

Later on in the journey of the box, some kind soul added an extra slide of the Dufay material. The notebook also describes an older French system from around 1900 that used dyed starch grains as the filter layer.

I seem to recall the polarchrome was a finer 'screen' than the dufay system.

Mike

[photomicro]

Just found some photos I took of various variants of this technology. I had totally forgotten about the Paget system.

Here it is.

IMG_6768.jpg (386.93 KiB) Viewed 5277 times

[MichaelG.]

Thanks for joining the conversation, Mike
... it's a fascinating subject.

For info. Here are a couple of scans of the slide, in its current condition.
It’s Slide #9 in PMS Box 95/8
According to the 'Damage Report' it had a broken coverslip in 1997, and was remounted and labelled in 2016.
.

DufayColor.jpeg (135.16 KiB) Viewed 5266 times

DufayColor_.jpeg (91.46 KiB) Viewed 5266 times

MichaelG