A note on the context of this document

This is the international version of an article published on the German ColorNeg web site. Some navigational elements will therefore take you to pages that are in German. Menu entries you do understand will usually take you to other English pages though. You're quite welcome to look around. You can always use your browser's back button should you go astray. Finally you may want to go to the international ColorNeg web site.

Virtual Grades

In the wet darkroom you would alter a black and white print’s gamma value by choosing between different paper grades to print your image on. When using ColorNeg on monochrome negatives it is also permissible to use gamma for artistic purposes. Please note that this is not true for color images where any significant artistic utilization of Gamma can destroy your image’s color integrity. To have a reference while working with your black and whites we provide you with certain predefined settings. We offer a *.negpos file with characterizations especially devised for black and white photography for you to download. In this context we will be referring to those characterizations as Virtual Grades.

Virtual Grades in ColorNeg will act similarly to actual paper grades in the darkroom. When working with graded black and white photographic paper the utilization of a grade that is too low would result in a dull print. This means that depending on exposure such a print would either contain no tonal values that are anywhere close to a pure white or anywhere close to a deep black. On top of that the mid tones would not be ideally distributed.

ColorNeg is always able to solve the first of these traditional problems for reasonably well-exposed negatives. The full tonal range from deep black to pure white will always be used independently of the Virtual Grade selected. Virtual Grades have an impact on contrast and on the mid tones without influencing highlights or deep shadows. When switching between different Virtual Grades you can be certain that no more clipping occurs at either end of the tonal range than was the case with the previously selected grade.

The Virtual Grades have been derived from actual RC photographic papers with fixed grades. To obtain the most natural rendition of a depicted scene as a grayscale the condition positive Gamma * negative Gamma = 1 must be met. This is unrelated to the gamma encoding used in digital images but is about the characteristics of the negative as such. Emanuel Goldberg described this fact in his 1922 book "Der Aufbau des photographisches Bildes" therefore the above condition is sometimes referred to as the Goldberg condition. This name is no longer widely in use but we will use it in the following anyway to refer to the above fact. We will discuss what that means for differently developed negatives further below. As in the traditional darkroom you may also choose any of the 13 Virtual Grades available grade for artistic merit. They range from 00 to 5 in half grade steps. Compare the effect of the individual Virtual Grades when inverting the same normally exposed and developed negative:
Virtual Grade 00, 00½, 0, 0½, 1, 1½, 2, 2½, 3, 3½, 4, 4½, 5.

For the example image the most natural representation is achieved by using Virtual Grade 2. This is where the Goldberg condition is met for a normally exposed negative. Since the ideal positive Gamma depends directly on the negative’s Gamma different Virtual Grades will produce the most natural rendition for negatives processed under different developing conditions according to the following list:

Virtual Grade 2 for normally processed negatives (Gamma 0.62)
Virtual Grade 1 for push 1 processed negatives (Gamma 0.70)
Virtual Grade 0 for push 2 processed negatives (Gamma 0.85)
Virtual Grade 00½ for push 3 processed negatives (Gamma 1.00)
Virtual Grade 2½ for hold 1 processed negatives (Gamma 0.55)
Virtual Grade 3½ for hold 2 processed negatives (Gamma 0.45)

Since all Virtual Grades have been derived from actual paper grades they are not equal to the exact point where the Goldberg condition is met for the gammas listed above but are rather values in the vicinity of the value you would get by calculating the inverse gamma. In practice you will also not always precisely meet the listed gammas dead on in processing your films either.
Some users have been asking whether using the slider setting of gamma = 1 in ColorNeg would not be the best choice for inverting all black and white negatives. The assumption that this leads to an unchanged grayscale is wrong insofar as that the film usually does not work linearly but has a film gamma below 1. While there is nothing to say against this from an artistic point of view as long as you get what you desire in converting your images please note that gamma = 1 equals the setting that would yield the most natural representation for a negative that has been push 3 processed, which is roughly about what Virtual Grade 00½ would do. It will become obvious when you try this virtual grade on the example image that this is not the ideal setting for a normally processed negative.

To use the Virtual Grades download them as a *.negpos file.

Save the downloaded *.negpos file in the location you use for your auxiliary files and load it into ColorNeg using the respective button. If you are using Mac OS and do not know where your auxiliary files should be put please refer to the manual. You can select the Virtual Grades from the user section of the manufacturer list afterwards. The user section is automatically activated when working with black and white material. Please take care to select a proper color film characterization the next time you are working on a color negative though.