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 below. 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 photographischen 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:
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.
Saving characterization files with ColorPerfect 2.15 and later or our legacy PC plug-ins
With ColorPerfect 2.15 and later you may simply save characterization files as plain text files under any (short) name you like. The only requirement is that you use a specific file extension instead of *.txt. For ColorNeg mode use *.negpos, for ColorPos mode use *.colorint and for PerfectRAW use *.pfraw. As soon as you have chosen the User entry from the Maker list you can conveniently deal with these files using file open and save dialogs from within the plug-in. For our legacy plug-ins that only worked this way for PC versions.
Here are the the virtual grades for download: VirtSWGrad.negpos
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Saving & loading characterization files with the legacy Mac 32 bit ColorNeg and ColorPos plug-ins
For our earlier 32 bit plug-ins for Mac OS X things were a bit less straight forward. We really recommend you to get the free upgrade to ColorPerfcet 2.15 which resolves these long standing issues and offers so much more.
Using Photoshop 7 and Photoshop CS with the legacy plug-ins you had to copy all auxiliary files you wanted to use into a specific folder. Using more recent Photoshop versions you could organize your files anywhere and specify the folder and filename to use on the Plug-in's user interface using a workaround.
For those not familiar with this workaround and still wanting to use an outdated plug-in for whatever reason the easiest way to get a *.negpos or *.colorint file to work is storing it under a default file name. If you have never edited the file name read-out on the original ColorNeg plug-in the default is ColorNeg.negpos, for the original ColorPos plug-in it is ColorPos.colorint.
Here is the Virtual Grades *.negpos file for download as: ColorNeg.negpos Put that file into the folder detailed for your version of Photoshop below and it will get loaded into the user section of the film maker list the next time you use the plug-in.
Keeping multiple files with different file names was also possible of course. After selecting the User entry from the Maker list and pressing the Load button the set up screen for the auxiliary file path showed. While it was active what's usually the read out for the name of the current characterization file the plug-in became an editable field where you could specify which file you intended to load (without the file's extension).
Auxiliary file locations for the legacy 32 bit plug-ins on the Mac
The following information is a shortened outtake from an old ReadMe.txt file. If you are familiar with that ReadMe.txt already you might want to stop reading here. Of necessity our 32 bit plug-ins for Mac OS X used an odd convention for the folder location of the auxiliary files. The location varies with the version of Photoshop. We would have preferred a better way of doing this, but at least this oddity does not come up that often in normal usage once it has been resolved.
Adobe Photoshop 7 and Adobe Photoshop CS
The location of auxiliary files for Adobe Photoshop 7 and Photoshop CS is very odd and very nearly the same. To get there, double-click Applications in Finder, then double-click Adobe Photoshop x, where x is either 7 or CS. Now locate the Adobe Photoshop x icon you might normally double-click to start Photoshop, but do not double-click. This icon may or may not have .App after the Adobe Photoshop x. Although it does not appear so, this icon is really a folder. Single click with the right mouse button (or control-click on a single button mouse) to bring up a menu of options. Click on the option Show Package Contents. This will open a new Finder window with a folder Contents (and possibly other items). Double-click Contents. That will disclose several other folders. For Photoshop 7 The folder you want is MacOS, while for Photoshop CS, the folder you want is MacOsClassic. That is the folder where the auxiliary files go, so double-click it and transfer in your *.negpos or *.colorint file(s). ColorPerfect and ColorNeg will always read and write their files to and from this folder, so this is where you will always find them. You can create aliases and place them in other folders for easier access if you often work with these files.
Adobe Photoshop CS2 through CS5
These versions of Adobe Photoshop do not write to a peculiar folder, but neither do they make it easy to control where files go. They pick the root folder instead of the hidden folders described for Photoshop 7 and CS. You can just let ColorPerfect put its files in the root folder if you wish, but as the root folder is not really a good place to put files, we provide a clumsy workaround. The root folder is the one with a path that is a single slash, "/" often shown in Finder as Macintosh HD. Put the file ColorPerfectPath.txt in the root folder, then edit that file to contain the path to where you really want the files. As delivered, the ColorPerfectPath.txt file contains the path /Users/MyUserName/Documents, so if you substitute your actual user name for MyUserName , ColorPerfect will put its files in your Documents folder. The path must be a valid path - that means that if you want to use a new folder, you must first create the new folder yourself (probably using Finder) before it will work. Now go to the target folder in your chosen path and transfer in your *.negpos or *.colorint file(s). ColorPerfect will always read and write its files to and from this folder. It is possible to change this path from within ColorPerfect whenever you load or save a file.