Very Interesting Discovery.....

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Jim Moore

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I finally had some time to do some BTZS testing tonight and found something very interesting.

I recently purchased 3 boxes of "Old" Zone VI Brilliant Grade #2 FB Paper (Pre-Calumet) that had been stored frozen.

I tested this paper along with fresh Zone VI Brilliant VC FB Paper.

The interesting thing is that the "Old" Grade #2 paper has the same curve as the VC paper exposed with NO filter.

Jim
 

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David A. Goldfarb

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That may be true, but not all no. 2 papers behave like each other, so I think Jim's observation is worth noting, for admirers of the old Zone VI Brilliant.
 

Donald Miller

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I agree with David. The contrast grade that a VC paper will exhibit is also affected by the color temperature of the light source that is exposing it without a filter. In other words an unfiltered cold light source will expose it totally different then an unfiltered tungsten or halogen light source. Graded papers do not exhibit this characteristic to the degree that VC materials exhibit.
 

NER

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Believe what you want. "Color temperature" is relevant only in discussions of color photography, namely in discussions of how different color films are balanced. Color of light and color temperature are not the same thing. VC papers are made with a combined coating of usually two batches of Ag-halide sensitized to different wavelengths of light (e.g., high contast sensitized to blue, and low contrast sensitized to green). When the paper is exposed to white light, it will show a normal or average contrast somewhere between the two extremes of its component emulsions. Obviously, two different no. 2 papers may differ in various ways.
 

Helen B

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I agree with Donald. 'Colour temperature' is a relationship between the proportions of light at different wavelengths. Its use is not restricted to colour film by any means.

Strictly speaking it should only be used for incandescent sources (those more-or-less obeying Planck's Law that relates the temperature of the source to its energy emission at any given wavelength), but it is commonly used to encompass other types of light source with varying degrees of accuracy and usefulness. Cold sources emit different relative amounts of blue and green wavelengths to incandescent sources even though they are both 'white', so there's reason enough for VC papers to behave differently.

Best,
Helen
 

Ian Grant

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I'll agree with Helen as I'm dumstruck by her knowledgeabilty :smile:

But for my tuppence: My old Johnsons 5x4 with it's mismatched grafted De Vere cold cathode head is a very green light. With Forte Polywarmtone my average Ilford filter is 1, before Les chips in with manufacturing inconsistencies :smile: my Durst is as normal around Grade 2.

And then I started life as a photographer / photographic chemist, but it's the making of images that counts !

Ian
 

Donald Miller

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NER said:
Believe what you want. "Color temperature" is relevant only in discussions of color photography, namely in discussions of how different color films are balanced. Color of light and color temperature are not the same thing. VC papers are made with a combined coating of usually two batches of Ag-halide sensitized to different wavelengths of light (e.g., high contast sensitized to blue, and low contrast sensitized to green). When the paper is exposed to white light, it will show a normal or average contrast somewhere between the two extremes of its component emulsions. Obviously, two different no. 2 papers may differ in various ways.

I respectfully disagree with you on the matter of color temperature as it relates to exposure of black and white variable contrast materials. I have before me the current catalog of Philips Lighting Company ( a major manufacturer and marketer of various types of light emitting lamps). This company lists the color temperature on a virtually every classification and specific lamp within a given classification of bulb that they manufacture.

The broad characterization of "white light" is simply that... a broad characterization. This so called "white light" can vary quite a lot insofar as the color temperature and consequently the percentages of blue vs red light that a given lamp will emit.
 
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Jim Moore

Jim Moore

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juan said:
I liked old Brilliant a lot for enlarging, so I'm interested in this. Donald has a very valid point - what light source did you use, Jim?
juan

The light source is a Beseler Universal 45 head using the V/C Controller in "Normal BW" (White Light) mode.

I have yet to do the test using my Zone VI V/C Cold Light Head, but I probably will just to see if the results are the same.

I am also going to make some prints on both papers tonight and compare the results.

I have never printed on "unfiltered" V/C paper before and I was really surprised to see that the 2 curves matched.

If in fact the prints "do" match it might be worth it for fans of the old Zone VI Brilliant paper to give it a try.

Jim
 
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