1. Coat an 8x10 paper with emulsion, allow to dry. Be consistent in the amounts of sensitiser you use, the method used to apply it and time between exposure and coating. There are many variables besides what I've just mentioned (e.g. humidity in some cases). The more consistent you are with your coating and processing the more predictable your finished results will be.
2. Expose a small cut strip of your paper using a Stouffer 31-step (or 21) wedge to determine exposure scale and "standard" print time. This should be when step two and step one (base material) are as black as each other. See also, How to Use a Step Wedge.
3. Expose one of the RGB, HSB or *HSL RNP-Arrays at the standard print time derived from step 2. Currently my thinking is the HSL Array is the best option, but it might be over-kill in some cases. (Adobe 98 Version of there RNP Array here HSL Array 98.)
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4. Locate a "white" square which is adjacent to a "gray" square. Write down the colour number (i.e. RGB 64,0,64). This will become your negative's colour. Note: you probably will have multiple choices for a white square. Try and pick the one that looks like it will print the smoothest. Remember that the tones directly above the tone you pick as your white point, at least ones which are above the "equator" will also be the path your negative uses to change from maximum to minimum density. Try and look for areas of smooth transition. For example, on the sample below I would avoid picking many of the colours on the left of centre side as the show a very uneven contrast response.
5. Use ChartThrob to create the 101-step wedge, invert to negative (Ctrl-I or Opt-I), create a new Layer (set the layer's "mode" to "screen")
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6. Fill the new layer with your RGB colour using the Paint Bucket tool and print this to OHP.
7. Contact print the ChartThrob wedge to your process/paper. You should see something similar to the picture below. Note: If you see a lot of white steps (more than four) you may need to "refine" your blocking colour choice a little. See an explanation of colour refinement here.
The highlights in the above print out of chart look pretty good. The blocking colour is doing its job correctly. The only problem that remains is to take some of the highlight and mid-tone density and move it down into the shadow area. Notice how the shadow area peters out after 70 percent. The curve will fix this.
8. Run the printed output from the ChartThrob 101-Step wedge back into Photoshop using your scanner. Turn off any "auto" settings in your scanner. I use the "Levels" command to set my white point to square 0 per cent and my black point to square 100 per cent on the first scanned print out. Reason: since I'm not going to ever change my standard print time or my negative colour I'm basically committing to the tone in the 0 per cent square as my "white" and the colour in my 100 per cent square as my "black".
Now use ChartThrob's "Analyze" command or read the section on creating curves by hand.
9. ChartThrob creates a curve layer in Photoshop. Save the ChartThrob curve layer.
Note: Sometimes I'll "smooth" the curve just a little bit by changing from "Curve" mode in the curve dialogue to "Free Hand" mode. This allows you to access the "Smooth" command. I might do two iterations or clicks of the "Smooth" command. Just remember to switch back to "Curve" mode or the curve file gets saved as an AMP file instead of a ACV file.
10. Create another ChartThrob wedge (Step 5). This time apply your newly minted curve to the "positive" image. (Note: if you apply the curve using an "Adjustment" layer you'll have to "Flatten" command the image before inverting to negative.)
Notice how the mid-tones look a little "washed-out" since the curve was applied. That's ok, what' really happening is that we're "adding" density to the negative by lightening mid-tone and dark areas of the positive.
11. Invert (Ctrl/Opt.-I), create new layer (set mode to screen), fill layer with density colour. Print to OHP at standard print time.
12 Now contact print the above curved wedge to your process.
Now notice how the step wedge prints now compared to last time. Nice, huh? A full range of tones from white to mid-tone to black. Might need a little tweaking but it's basically there. Congratulations with this colour and curve combinations you can now go and make some digital negatives.
Questions? 