The Monitor

When an image is digitized all the tones less than rgb 16 are so dark and the changes so small that the differences cannot be easily seen under normal viewing conditions. TruNeg takes RGB 16 as being “just black” and the first visible tone from black, it then prints the negative to reproduce RGB 16 as the last visible tone before black. 

To check that your monitor displays this properly open the TruNeg Step Wedge and set the background to Medium Gray, in reasonably subdued room light, set the monitor gamma to 1.8 and adjust the brightness and contrast so that step T14 is just but clearly distinguishable from RGB 0. The scale should get lighter in a smooth and regular pattern with each dark tone being clearly separated from the tone before. If T14 is a little too light it is better than being too dark.

Make a note of the monitor settings and make sure your images are edited under these conditions.

The Printer

The printer has a difficult job to do when printing a negative. In the positive, rgb 16 is taken as being black and all the tones less than rgb 16 only need to appear black and minor variations or bands of constant density are lost in the dark tones.  In the negative, input rgb 0 will always be just paper white in the print, and tones T1 to T5 in the correction curve will be the highlights and lighter print tones. The curve has a very low gradient in the negative highlights and minor changes in the highlight density will cause a significant change in the print.

It is therefore important to know how the printer prints these dark tones and to find the lowest rgb value, or highest density, the printer can smoothly separate single rgb differences.

The TruNeg Printer test strip included in the download is an 8x0.75 inch image with an rgb scale of rgb 6 to rgb 34. Rgb 6 is chosen as the darkest tone needed to be resolved because at lower values the correction curve gradient becomes too low to be workable. The file is borderless and different print settings can be ganged up beside each other on A4 film for comparison.

Above is a scan of two printer settings. In the top strip the printer managed the color and was unable to separate tones below rgb 14 and there are distinct bands through to rgb 26/27 which will prevent any possibility of having smooth highlights in the final print. It is not until rgb 27 that the printer starts to print smoothly. A negative curve can be made starting with rgb 27, however it will have to have enough density or UV opacity to make a clean white. In the bottom strip Photoshop managed the color. All the tones from rgb 6 to 30 appear separated and the gradation is smooth.  The zero tone, negative Dmax, at the left hand end was the same in each.

The printer does not have to resolve all the tones to rgb 1, what we are looking for is the darkest tone above which the single rgb steps are resolved and smooth. This should be the darkest negative tone to make “paper white” in the Control Negative test print.

Detailed step by step explanations on how to set up various printers is outside the scope of these instructions or the author’s experience, however there are a few things that seem obvious.

1.     From the above, using the Program Manages Color in the Print Settings would appear to be best but should not be assumed.

2.    Compare different Printer Profiles to see which gives the highest density and smoothest tones. Be wary of any profile that does not produce a consistent colour through the tones.

3.    Use a Grayscale or b&w printer option if available.

4.    Use Absolute Colorimetric to render negatives. Perceptual assumes that the image is positive so any changes it makes to make the positive better will be opposite to what is required.

5.    Do not tick “Black Point Compensation” or “Match Print Colors”.

6.    The printer driver has to be 16 bits per channel.

7.    Use the highest printer quality.

8.    Do not adjust any density or colour settings at this stage.

Remember the goal is to achieve the highest maximum density with an even separation of tones.