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Hue variations with BW400CN on RA-4
So now that I can print RA-4 at home, I decided to use my BW400CN for what they were made for, namely RA-4 printing. First reaction: blimey! they are nice, no grain, and smooth tones. It's weird to have an entire colour chain but to produce shades of gray in the end, but "toning" is much more simple 
Second reaction: why is it that certain areas of my print have a cooler tone than others? Anybody ever noticed something similar?
It's hard to tell whether it's related to densities. I would suspect that different shades of gray may vary in apparent hue. After all, color dyes are not perfect. But I'm wondering if that would be related to processing instead. I'm sorry I can't post a scan right now, but I'll try later if I can make it visible. I'm confused, and I wonder whether it's metamerism playing a trick on me.
I'm using Supra Endura in Kodak chems, processed in a Unicolor drum on a motor base. I use a stop bath between dev and blix.
Using film since before it was hip.
"One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11
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It just indeed might be a bit of metamarism from the dyes: What kind of light (sun, incandescent, fluorescent) are you viewing the print with?
Also, if you develop your own C-41, the orange contrast mask may be slightly "off."
A better workflow for you, if you like chromagenic film, is to try Ilford XP2 and use conventional B&W paper... It allows you to use fiber prints, too!
 Originally Posted by mhv
So now that I can print RA-4 at home, I decided to use my BW400CN for what they were made for, namely RA-4 printing. First reaction: blimey! they are nice, no grain, and smooth tones. It's weird to have an entire colour chain but to produce shades of gray in the end, but "toning" is much more simple
Second reaction: why is it that certain areas of my print have a cooler tone than others? Anybody ever noticed something similar?
It's hard to tell whether it's related to densities. I would suspect that different shades of gray may vary in apparent hue. After all, color dyes are not perfect. But I'm wondering if that would be related to processing instead. I'm sorry I can't post a scan right now, but I'll try later if I can make it visible. I'm confused, and I wonder whether it's metamerism playing a trick on me.
I'm using Supra Endura in Kodak chems, processed in a Unicolor drum on a motor base. I use a stop bath between dev and blix.
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this is something I noticed when working with bwcn on an optical minilab as well! I think there is crossover with this film. Also do your filter settings change with over/underexposure? Ours did at the minilab.
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Originally Posted by bob100684
this is something I noticed when working with bwcn on an optical minilab as well! I think there is crossover with this film. Also do your filter settings change with over/underexposure? Ours did at the minilab.
Yes, the colour balance is noticeably different with exposure. What is colour crossover?
Using film since before it was hip.
"One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11
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Originally Posted by mhv
Yes, the colour balance is noticeably different with exposure. What is colour crossover?
Film exposure, or exposure of the paper? -- Be specific.
Color crossover is where the three (red, green, blue) curves do not align, but instead "cross over" each other.
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Originally Posted by Discpad
Film exposure, or exposure of the paper? -- Be specific.
Color crossover is where the three (red, green, blue) curves do not align, but instead "cross over" each other.
Its been a few months since I worked at the lab, but it was the film's exposure that varied the color cast on the print. We were confused at first b/c we color corrected to make them neutral on the monitor, finally we turned off the accs which makes descisions on basline color corrections for how things will appear on the print processor's monitor and sure enough there were differences between under neutral and over film samples.
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Originally Posted by Discpad
Film exposure, or exposure of the paper? -- Be specific.
Color crossover is where the three (red, green, blue) curves do not align, but instead "cross over" each other.
OK, here's what I noticed: from the same negative, prints exposed at different times have different colour balance. For example, the one at 14secs @ f11 has a more cyan cast than the one at 9 secs @ f11. That part is not surprising to me.
What is surprising, on the other hand, is that on the same picture, the one I printed at 10secs @ f11, say, some parts thereof are more cyan, and other ones are more red.
Using film since before it was hip.
"One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11
My APUG Portfolio
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Well, there are two thoughts that come to my mind here. The film itself cannot have crossover per. se. It is a single layer film with a 'black' dye former.
The paper can have crossover or reciprocity. You may be seeing reciprocity, but that is an awfully short exposure time over which to see such a color shift. In any event, with color, you keep the time constant and vary f stop, not the other way around. This eliminates reciprocity.
Also, process variations can cause both crossover and color shifts. If you are not using a steady temp, time and a good enlarger with transformer, you can get shifts.
PE
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Michael
I would not worry too much re the crossover, It is natural occurance printing this way.
You will find the more contrast range on the original negative the more *cross over* you will see .
To get less *cross over* a flatter negative will be very helpful.
This is the same problem printing scala on Ciba material. the flatter the original image the better nuetral can be achieved.
I do not think you are doing anything wrong, just your negative may have too much contrast.
You can take advantage of this *cross over* problem with time and make negs to look a certain way on colour paper.
Trying to get a nuetral step wedge on colour paper from a silver step wedge is one of the most difficult tasks one can imagine.
If you do a colour ring around on paper from a negative, less exposure with identical colour balance will give you a more cyan cast, more exposure with identical colour balance will give you a more red cast.
Bob
Originally Posted by mhv
OK, here's what I noticed: from the same negative, prints exposed at different times have different colour balance. For example, the one at 14secs @ f11 has a more cyan cast than the one at 9 secs @ f11. That part is not surprising to me.
What is surprising, on the other hand, is that on the same picture, the one I printed at 10secs @ f11, say, some parts thereof are more cyan, and other ones are more red.
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