Innovations in Applied Mathematics relating to Sight and Sound
Innovations for Non-Profit Corporations relating to Financing and Housing

Go to C F Systems Home Page

Photoshop Tips for Advanced Users

Last Changed 3/31/8

The ColorNeg family of Photoshop plug-ins is available for both PC and Mac.

Version 1.02 of ColorNeg and ColorPos introduce a breakthrough in handling color in old films and problem photographic images. Version 1.02a introduces the ability to adjust color balance by directly scrolling CC (Color Compensation) filter values or even by typing in CC filter values. Version 1.02a of GamSat introduces a new refinement in color accuracy which we call Ambiance and GamSat now also will work as a Photoshop CS3 Smart Filter.

The tips presented here are for the advanced Photoshop user working with photographic images. There is a 16-Bits/Channel Highlight Detail Secret tip with a surprising demonstration of 16-Bits/Channel power. If you have been having trouble with blown highlights in digital images this may be the secret you've been looking for. We have become known for our Photoshop plug-ins, including ColorNeg and ColorPos, which deal with getting superior and more accurate color from color negatives, color slides, and digital camera images and we describe these just below. But if your main interest is the general Photoshop tips you may (Go directly to TIPS.)

ColorNeg and ColorPos plug-ins have an "Auto" color feature, gray-clicking, scrolling for unidentified color negative film types and much more. The ColorNeg plug-in for dealing with color negatives in Photoshop is now in version 1.02a and has built-in data for around 115 types of film from Kodak, Fuji, Agfa, Konica and Ferrania as well as a new technique for making those few films that you use easily accessible. For serious users it has advanced features for dealing with color balance, dealing with problem negatives and dealing with rolls of similar negatives and there are several ways to calibrate your system for the ultimate results. See our Color Negative FAQ for more information about digitizing color negative images.

The companion plug-in, ColorPos, is also in Version 1.02a and is intended to maintain color integrity while making the initial, largest corrections to a positive image, such as a scanned image of a color slide or a print, or an image from a digital camera. ColorPos is very similar to ColorNeg in its layout and functionality. The 1.01 versions of ColorNeg and ColorPos both have an improved Undo and easier handling of B&W negatives and version 1.02 introduces a breakthough method that makes dealing with old films and problem images very much easier. Our colleague in Germany has prepared a nice illustration of this, available in English. More recently he has done some interesting work showing the difference between the way GamSat handles saturation and hue and the way those adjustments are normally made using Photoshop tools. This work led to our collaborating on the concept of Ambiance, which gives even greater color accuracy in GamSat. Version 1.02a of ColorNeg and ColorPos introduces the ability to adjust color balance by directly scrolling CC (Color Compensation) filter values or even by typing in CC filter values. The CC concept is central to understanding three-primary color photography systems, which, after all, is what you are working with whether you use film or a digital camera. Your images may contain "millions of colors" but every single one of those millions of colors is a mixture of just red, green, and blue. (See notes regarding current versions of ColorNeg, ColorPos, and GamSat.)

If you downloaded ColorPos or ColorNeg between 4/1/8 and 4/3/8 there may have been a puzzling error in a table in the Addendum Manual. Please see Table Note.

We have worked with our colleague in Germany to produce German language versions of our plug-ins and manuals: Wir sind eine Kooperation mit einem deutschen Kollegen eingegangen, um eine deutsche Version unserer Plug-ins und Handbücher zu veröffentlichen. Diese sind von nun an auf der Webseite http://www.colorneg.de verfügbar. Dort finden Sie außerdem einige der Materialen dieser Webseite auf deutsch sowie interessante neue Artikel.

These PC-based plug-ins work with Photoshop 6, Photoshop 7, Photoshop CS, Photoshop CS2, Photoshop CS3, Photoshop Elements 3, and Photoshop Elements 4. The Mac versions of ColorNeg, ColorPos and GamSat work natively on both PowerPC and Intel Macs, with Photoshop versions 7 through CS3. The ColorNeg Mac Manual (700 KB PDF) is available and there is a Notes file for the Mac release. The ColorPos Mac manual is still not ready, but there is a Notes file. The GamSat Mac Manual (800 KB PDF) is now available and there is a Notes file for the Mac release.

For an overview of the what and why of color integrity, color negative inversion and these plug-ins click here.

The ColorNeg plug-in inverts color negatives - and B&W negatives - correctly (Photoshop and many scanner software packages do this completely incorrectly, resulting in warped color) and the ColorPos plug-in operates on photographic images from positive sources including scanned slides and digital camera images, preserving color integrity while making the initial, often large image adjustments - those major changes where the errors introduced by standard Photoshop adjustments cause the most distortion of color. We have very enthusiastic users of our plug-ins. These plug-ins compliment our tips Color Balancing Color Negatives and Color Integrity in Digital Images, using the physics and mathematics discussed our CFS-243 Color Integrity and CFS-244 Negative to Positive PDF documents.

The downloadable ColorNeg and ColorPos demo versions impose a fine gridwork pattern on the images they produce, unobtrusive enough to allow evaluation and in fact we expect there will be some people for whom the trial version is sufficient, gridwork and all. A thirty-day trial version of the GamSat plug-in is available for download. When you get a paid registration key, the same key is valid for ColorNeg, ColorPos and GamSat, removing the time limit or the gridwork of the trial versions. Different paid registration keys are required for the Mac and PC packages, however.

Download the ColorNeg for PC zip file -- View ColorNeg for PC ReadMe
The ColorNeg for PC Manual (1.7 MB PDF) has a Descriptive Table of Contents, merely descriptive here but within the PDF manual it is linked to give a guided tour.

Download the ColorNeg for Mac zip archive file -- View ColorNeg for Mac ReadMe
The ColorNeg Manual for Mac (700 KB PDF). This manual has a Descriptive Table of Contents similar to the one above for the PC version.

Download the ColorPos zip file for PC -- View ColorPos ReadMe
The ColorPos Manual (1.6 MB PDF) has a Descriptive Table of Contents, merely descriptive here but within the PDF manual it is linked to give a guided tour.

Download the ColorPos for Mac zip archive file -- View ColorPos for Mac ReadMe
The ColorNeg for Mac Manual is not ready yet.

Download the GamSat zip file for PC -- View GamSat ReadMe -- View GamSat for PC Manual (800 KB PDF).

Download the GamSat zip file for Mac -- View GamSat ReadMe -- View GamSat for Mac Manual (800 KB PDF).


Purchase ColorNeg, ColorPos and GamSat for PC from a secure website. When purchasing "ColorNeg family for PC" from our site which provides secure data entry, you will receive a Key via e-mail which will remove the time limit or gridwork from the demo versions downloaded from this site. This same registration Key is valid for the PC versions of ColorNeg, ColorPos and GamSat.

Purchase ColorNeg, ColorPos and GamSat for Mac from a secure website. When purchasing "ColorNeg family for Mac" from our site which provides secure data entry, you will receive a Key via e-mail which will remove the time limit or gridwork from the demo versions downloaded from this site. As well as ColorNeg for Mac, this same registration Key is valid for the Mac version of ColorPos and the Mac Version of GamSat.

Users confirm that ColorNeg and ColorPos work very well indeed when given a properly scanned negative or positive but that figuring out how to make a scanner deliver a good, clean 16-bit linear scan can be quite tricky to do. It appears that scanner software writers often feel it necessary to gild the lily, intentionally distorting color in hopes of impressing the user. Others misleadingly label settings or controls for reasons known only to themselves. Some users have volunteered helpful instructions on how to deal with this for various scanners and systems and we now have a web page devoted to Getting a Good Linear 16-bit Scan. Anyone having difficulty getting ColorNeg and ColorPos to perform well should visit this page.

Version Notes: The current download version of GamSat is 1.02a. This version introduces the concept of Ambiance, which gives even greater color accuracy in GamSat. This version also makes GamSat our first plug-in fully compatible with Photoshop CS3 Smart Filters. (We are evaluating how [and whether] to make ColorNeg and ColorPos compatible with Smart Filters, as we find Adobe's implementation of this concept to be weak.) The current download version for both ColorNeg and ColorPos is 1.02a. Version 1.02a introduces the ability to adjust color balance by directly scrolling CC (Color Compensation) filter values or even by typing in CC filter values, and also introduces an improved processing of feathered areas between selections. The Auto Color feature in ColorPos has been changed to be more consistent with the default initial color balance. The Mac version of ColorNeg had a serious bug in the handling of film types and film files, where some code was left out in adapting the PC version to the Mac. The Mac version of ColorPos had a serious bug relating to the adjustment of Shadow, also a problem in adapting the PC version to the Mac, although the default shadow setting behaved properly. Version 1.02a also fixed a bug in both ColorPos and ColorNeg where the color letter was left off the CC display. In version 1.02 we have made what we expected to be a minor improvement in the little-used FilmData scrollbar control. To our surprise, this has proven to be a major improvement - a real breakthrough in dealing with old films and films with other color problems. We also added the ability to recognize 8-bits/channel images and issue instructions for dealing with them. For use with ColorNeg we have have added a new plug-in, Scantique, intended to help users through some of the problems they encounter in dealing with scanners. Finally, in 1.02 we fixed a couple of bugs that were so obscure we doubt they bothered anyone and we think we more or less fixed the About boxes in the Mac versions. In the Mac ColorNeg version 1.01c the default initial value of "Gamma C" has been changed to 2.2 to better agree with typical Mac Photoshop usage - this change is so trivial the version is designated 1.01c2. The real changes are in the manual. Current users are advised to download the revised manual (PC users as well as Mac) and follow up on item 4 in the new notes file or read-me. We are aware that the "About" box in some Mac plug-in versions is odd. This will be fixed when we get an Intel Mac for our own testing. The primary changes in the PC 1.01c versions have been to maximize code compatibility between the PC and Mac versions and to provide for the possibility of languages other than English. There is one fix involving the fine control of the scrollbar which will be important to most users and ColorPos adds a button which allows starting with no CC correction. In Version 1.01b of both ColorNeg and ColorPos there were also some cosmetic changes, but the real reason for the release was to fix a bug in saving CC files that originated in version 1.01a. In Version 1.01a of both ColorNeg and ColorPos the Undo function was completely revised to work more as would be expected and the handling of B&W (grayscale) has been made easier to do. ColorNeg expanded the list of built-in film types from around 80 to around 115 including 4 films of Ferrania. The sheer number of choices has started to make selecting a film more annoying than it should be and to aid against this we included a "MyFilms" list, where the user can save the most frequently used films. ColorPos fixed a particularly embarassing bug, whereby the CC value for one of the color channels (R, G, B) would be displayed as zero rather than its correct value. We do not know how or when that bug crept in or how it escaped our attention. Version 1.00d removed possible confusion over which user grayscale is in use in Known calibrations. Version 1.00c of ColorNeg corrected a problem with repeating (Control-F) and scripting and further improved handling of highlight and shadow in selections. ColorPos version 1.00c corrected a problem with highlighting, a problem with extreme cases, and problems with the scrollbar control present in the earlier releases. The 1.00c versions of ColorPos and ColorNeg also corrected a problem in dealing with selections that resulted from my tacitly assuming something very logical which turned out not to be true.

Dialog Size: The preview image for ColorPos and ColorNeg is designed to fit within the constraints of Photoshop running on a system with a 1024 x 768 display. Users running higher resolutions have expressed a desire for a resizeable dialog box so the preview image could be larger, or an arrangement where the changes are shown in the original image window. Photoshop prohibits the latter for third-party plug-ins and makes the former either impossible or very difficult to achieve reliably. However, users with valid registration Key codes can e-mail us and request versions of ColorNeg or ColorPos (only these two) to fit higher resolutions. Specify the resolution desired and include the Key code in the e-mail. We will try to honor such requests but we cannot guarantee that we will be able to do so. In particular, we have not yet tried doing this for the Mac version.

Table Note: In the initial release of ColorNeg and ColorPos version 1.02a on 4/1/8 there was an error in the table of Silent General Controls in the Addendum Manual in which incorrect Control Values were given. The download was corrected on 4/3/8. The complete correct table is:

Control Value	Action	Signal
-1	Toggle CC Adjust or Old Color Adjust	CC Adjust mode will or will not appear when Color Adjust color is selected
-2	Toggle Old or New Auto Color	AUTO in caps for old version
-3	Toggle Enter action	Default: Enter means OK, Escape means Cancel Or: Neither Enter nor Escape do anything
8	Call up registration dialog box	Necessary to change a key code (rarely necessary).

The Control Values -1 and 8 apply to all versions of ColorPos and ColorNeg. The Control Value -2 applies only to ColorPos and the Control Value -3 applies only to Mac versions.

Photoshop Elements: These plug-ins will work with Photoshop Elements and have been tested with PC versions 3 and 4. They may work with later versions and with Mac versions but we have not tested them. Since Photoshop Elements is often sold as part of a package with a scanner, a digital camera, or a digitizer, this can be an inexpensive alternative for persons who do not already own a copy of Photoshop. On the downside, users should be aware that setting up to work with selections is not as convenient in Photoshop Elements as in full Photoshop. On the upside, the plug-ins provide Photoshop Elements with a lot of 16-bit/channel functionality that it does not have otherwise.

Tips

Our investigations into the problems of accurate digital color representation have led to several web pages on our site which we believe all serious photographers will find both revealing and helpful. The first and most central of these is a demonstration/explanation of the serious and pervasive problem of Color Integrity in Digital Images. Our Photo Documents web page covers this as one of our recent research projects into the principles of digital and film photography. For each project there is a non-mathematical, practical summary and an in depth mathematical analysis. The approach is largely original with us and we have not seen similar treatments elsewhere, either in print or on the web. These documents answer many of the mysteries of digital photography. Our Color Balance, White Balance, Calibration, and Color Temperature delves into the use of these often misused terms as they apply to digital and film imaging. And Dunthorn Calibration describes a method of testing your photographic image entry system for color integrity and helping you find out the source of any problems detected by this test. It will also determine the positive gammas for color negative films, required for optimum use of our ColorNeg color negative inverter. ColorNeg and ColorPos have all modes of Dunthorn calibration built in. See Above for details. For an overview of the what and why of color integrity, color negative inversion and these plug-ins click here.

We have some comments about Photoshop RAW image input and how to work around it to produce properly calibrated images, a novel method of sharpening photographic images, comments on precision and accuracy in digital photography, several answers to "Where are the color density filters?", a novel perspective on routine color balancing, a strange but effective way to rough color balance difficult cases, a method for coloring B&W photos, and avoiding loss of detail. There is a tip on color balancing color negatives that fully explains what is involved and why and another tip for B&W photographers who want to achieve an accurate tonal scale. These tips are original with us and are not likely to be found elsewhere. You are welcome to use these tips in articles, courses, or books, but please credit C F Systems and www.c-f-systems.com when you do. E-mail us (cfs.cfs@c-f-systems.com) if you wish. Please see NOTICE in the paragraph below.

It may be inspiring to know that these novel tips were developed by a member of the older generation. Having made my first color print at age fifteen, I have over fifty years experience in printing color photographs as a hobby. Adding to this is more than forty-five years experience dealing with computers, mathematics, and numerical methods. This gave me a unique perspective when I started using Photoshop several years ago. The tips on this page will mostly avoid the mathematics, to make them useful to more people. If you are curious about the origin of a tip and you indicate your level of understanding in mathematics when you e-mail us (cfs.cfs@c-f-systems.com) , we will try to respond accordingly. We try to respond to all legitimate e-mails that we receive. If you do not get a response, please see the NOTICE on our Privacy Policy Page.

A Better Method of Sharpening Pictures in Photoshop
A 16-Bits/Channel Highlight Detail Secret
Color Integrity in Digital Images
Color Balance, White Balance, Calibration, and Color Temperature
How to Work Around Photoshop RAW Image Input to get Color Integrity
Color Negative FAQ
Color Density Filters in Photoshop
Routine Color Balancing?
Color Balancing Difficult Cases
Color Balancing Color Negatives
Getting a Proper Tonal Scale in Black and White Photography
Dunthorn Calibration - Check and fix color integrity of image entry systems
Matching Colors in Photoshop
Preventing Banding and Stair-Step in Photoshop Images
Accuracy and Precision in Digital Photography
Coloring B&W Photos
Brightness, Contrast and Loss of Detail
Silver-Based Gamma, Video Gamma and Levels
Processing Old Color Films

Visit Our Photo Gallery
Our gallery is very small but changes often (much less often than we'd like, really, as we respond to the greater interest shown in our methods and plug-ins).

Although it has nothing to do with Photoshop, our monograph on the problem of highlight and shadow detail in digital photography may also be of interest. Go to Highlight/Shadow Page

As used in the context of this page, "Adobe" and "Photoshop" are registered trademarks of Adobe Systems Incorporated.

A 16-Bits/Channel Highlight Detail Secret

This tip would have been on our site earlier but we only recently learned that very few photographers seem to be aware of it. The tip includes a neat demonstration of the power of 16-Bits/Channel images. The basic idea is simply that if you are scanning in 16-Bits/Channel images or bringing in 16-Bits/Channel RAW digital image originals and you are losing highlight detail, just darken the image. Make the image quite dark if necessary to bring out the highlight detail. For reasons we will demonstrate, you do not lose shadow detail by doing this and it is not at all necessary to separately scan a light and dark image and combine them. Once you have the dark image in Photoshop you can use various tools to selectively lighten portions of the image, preserving the highlight detail as you brighten the too-dark parts of the image. With Photoshop RAW input, darken the image not with the brightness control (which is not brightness at all) but with the exposure control, moving it into its negative value range. The exposure control also doctors the image somewhat but generally will be acceptable in this usage. (Note: How well this works with Photoshop RAW may depend upon the type of camera. Fuji cameras with the SuperCCD sensor chip are designed to capture extra highlight detail and work well. However, if the camera does not capture the highlight detail in the first place, this tip will not work.)

Scanner software is all different, of course, and the controls are often misleading, so telling which control will darken the image without otherwise altering it can be tricky. You can test whether you have chosen the correct darkening tool in the scanner by first scanning an image normally and then, without moving the image source, scanning a darkened version. Use a moderate resolution (dpi) well below the scanner's maximum to avoid confusion from scanner variability. If you have chosen the correct tool it should be possible to use just the highlight slider on the Levels tool to adjust the darkened version so that it exactly matches the normal version. For a really precise test first Image→Adjustment→Invert the normal image. Now select all of the darkened image, copy and paste it over the inverted normal version. Then, operating always on the upper, darkened image layer select Layers in the Layers-Channels-Paths dialog and set the opacity to 50%. Now, using the Levels tool and sliding the highlight adjustment pointer to the left it should be possible to achieve an evenly gray image in which the underlying image becomes invisible. After you OK out of the levels tool, explore the image with the cursor so that the pixel values show up in the Info panel. The pixel values should all be the same. Variations of two or three counts are acceptable. This test works better in 16-Bits/Channel mode, which requires Photoshop CS. You can use this same test with Photoshop RAW to produce normal and dark images and see how much the "exposure" control deviates from what it should do.

If you were to darken an 8-Bits/Channel image in an effort to preserve a highlight detail you would lose a lot of shadow detail. It is natural to think that the same will happen with a 16-Bits/Channel image but that is not at all the case. Photoshop displays pixel values as 0 through 255 for both 8-Bits/Channel and 16-Bits/Channel images so it is not generally appreciated that the space between any two successive counts in a 16-Bits/Channel image can hold a full 8-Bits/Channel picture. That is, a fully detailed color 8-Bits/Channel image could reside between pixel values of 100 and 101. To illustrate this we have a sample image in 16-Bits/Channel: Colorkid2.tif (400 KB) (To download this file using IE, "wrong" click the mouse and select "Save Target As." Other browsers have similar tricks.) If you load this image into Photoshop and explore it with the cursor so that the pixel values show up in the Info panel you will find that all pixel values are given as either 0 or 1; nothing higher. Now use Image→Adjustment→Levels and slide the highlights slider to the left as far as you can. Normally this will reduce the highlight value from 255 to 2 - it will not continue to 1 or 0. OK out of levels and you will have a color image, but quite dark. Now call Levels again and again bring the highlights slider to the left, but go only to 128 this time. OK out of Levels and you will have a full color image, all of which originally showed pixel values of either 0 or 1. If it would have been possible to put the highlight slider all the way to 1 the first time, the second adjustment would not have been necessary. This illustrates that the detail you are shoving down into darkness by making the original scan dark is not lost and is easily recoverable.

If you were curious enough to look at the final histogram of Colorkid1.tif you probably noticed that it is a "comb" with every alternate cell having a value of zero. This is because Photoshop 16-Bits/Channel is really 15-Bits/Channel.

Once you have the darkened image, there are numerous ways to restore highlight detail, perhaps involving Levels adjustment layers applied with a gradient, or feathered selection of light and dark areas with different Levels adjustments applied. We will mention one here that we have seen less often. First put the image into Lab mode: Image→Mode→Lab Color. Then Image→Adjustment→Curves. Apply a curve something like:


Where the line is straight it preserves tonal values and where it curves over at the top it compresses tonal values, preserving highlight detail rather than blowing highlights. Because we are in Lab mode color integrity will be reasonably well preserved even for more elaborate curves. This is not true for the Curves tool in RGB mode. Of course it is possible to convert back to RGB mode after making this adjustment.

Return to Tips List

Coloring B&W Photos

This method of coloring B&W photographs in Photoshop can produce very convincing results. It also offers a lot of control, so the artistic possibilities are unlimited. There are Photoshop plug-ins and other programs that automate this same task to varying degrees, but here we will use just Photoshop.

The principle involved is the same one that has been used for a century or more, where B&W photographs have been colored by painting over areas of the photo with transparent media, usually special transparent oil paints. A wash of a single flesh tone over a monochrome image of a face or of green over the leaves of trees or red over a plaid shirt is normally very convincing even though the coloring carries no fine detail. As a personal historical note, the original reason I took up darkroom work was to make mat-finish prints so my sister could paint them; that starting a couple of years before the example photograph used here was taken.

Coloring photographs can be done most satisfactorily in Lab mode. Lab mode does not refer to "laboratory," but to the three components of its color system, with "L" being lightness-darkness, "a" being a measure of red versus green, and "b" being a measure of blue versus yellow. This system is designed to be perceptually even, as nearly so as is practicable, with the result that major color and density changes made under the Lab system are much less prone to producing color casts and odd color effects than the familiar RGB system. It is well worth learning about Lab just because it often offers a ready solution to otherwise difficult Photoshop color problems. Here, the grayscale image we start with is a reasonable approximation to the "L" lightness scale, with the "a" and "b" components each starting out as zero, or no color. We will select an area and change "a" and "b" to apply a color cast over that area in exactly the same way as applying a transparent wash of oil color would work on the same area of a paper print.

The example shown here is a "Portrait of the Artist as a Young Man" which has been colored by the method to be described. This was not chosen for its artistic merit, but serves well as an example.

This photograph is from a paper negative made around 1953. At that time I took a piece of print paper intended for making enlargements and taped it where the film would go in an old folding camera. Enlarger paper is very slow compared to camera film. Using available light coming in from windows, an exposure of a minute or more was necessary. Note that the image of myself and the less noticeable cat are both slightly blurred from motion in the long exposure, while the background is sharp. Like the "orthochromatic" films used for almost all amateur B&W photography until the 1960s, the enlarger paper was not sensitive to red light. That point will have importance later.

To color a B&W photo, start with a picture that you have already adjusted to be a good grayscale image. For best results scan a 16 Bit/channel mode image and remain in that mode at least until the Lab coloring has been completed. If that is not possible, 8 Bit/Channel mode can be used and will usually be satisfactory. Convert the adjusted grayscale image to Lab: Image > Mode, select Lab Color. Next make selections of the different areas that each will be given a uniform color, using any convenient method. The selections do not need to be exceedingly precise, but they do need to outline areas of uniform color. Working with a grayscale image it is often easiest to use the lasso to select, cleaning up the selection with the lasso Add to Selection and Subtract from Selection. After a selection has been made, save it using Select>Save Selection. If you are working in 16-Bit/Channel, the selections will have to be saved in a separate (New) image file.

While the area outlines do not have to be extremely precise, the different areas do need to meet at precise borders so that there are no gaps or overlaps. With the example photograph, I started by outlining the entire person and saving that selection as Person. For this process to work best, do not apply any feathering to the selections as you make them and save them – not yet. Next, with the Person selection loaded, I used the lasso subtract to remove everything below the head and then more carefully to remove everything below the hairline. The resulting selection was saved as Hair. Then Person was reloaded (Select>Load Selection), followed by reloading Hair with "Subtract from Selection" selected. This insures that the upper border of the next selection will exactly meet with Hair. As with the hair, the face was selected by lasso subtracting what remained below the face, and the hands were lasso-added to the selection, the resulting selection saved as Flesh. Next, Person was reloaded, and Flesh was reloaded with "Subtract from Selection." The result was lasso-subtract trimmed below and saved as Shirt. And so on. Later, the entire wicker sofa was outlined, the outline passing through the seated subject, and then Person was reloaded with "Subtract from Selection" on. The entire set of books was outlined and then groups of books selected out of that selection. The overall books selection was reloaded and the already selected groups of books subtracted out prior to making each successive selection of books. These groups of books were used to get different colors of books on the shelf.

In all the above, lasso select was used because I have found working with that quickest and easiest for me. By all means, use other selection options if you prefer. Of course, some powerful selection options do not work well with grayscale images, regrettable but unavoidable. Many powerful selection options and techniques do not work in 16 Bit/Channel mode, also regrettable, but in this case easily solvable. Change the mode to 8 Bits/Channel and save the picture as a separate file. Make and save all the selections in this file, using any of the methods available in 8 Bits/Channel mode, but avoid cropping or resizing the picture. When the selections have been made and the new file saved again, leave this file open and re-open the 16 Bits/Channel file. Now you can load the selections while editing the 16 Bits/Channel image by using Select>Load Selection and picking the name of the 8 Bits/Channel file from the upper pulldown list.

The example image is available in PSD form, as a reduced 800 x 499 Lab image (the original working version was 2001 x 3205) with each selection represented as a levels adjustment layer. This shows how the selections are arranged and what Lab adjustments were made to each selection, to give an idea of what to do with your own picture. The file will work only with Photoshop and is a little more than a megabyte in size. (Download Example Image.)

Working with your own picture file, next load the selections one by one and apply color. It is usually better to add some feathering – perhaps 3 or 4 pixels for a 2000 x 3000 photo – at this point unless the borders of the selection are truly sharp. To apply color, use Image>Adjustments>Levels. Since you are in Lab mode, the selections are "Lightness", "a", and "b" rather than "RGB", "R", "G", and "B". Select the "a" channel. Note that the profile is a vertical line at a=0, or very nearly so. Move the center slider to the left and the image will become more red – to the right more green. Try to pick a reasonable tone for the area – this will become easier with experience. Next, do the same with the "b" channel. Move the center slider to the left and the image will become more yellow – to the right more blue. Again, try to pick a reasonable tone. Alternately adjust a and b until you think you are close. Do this with each area selection until the photograph is completely colored. Then go back and readjust the areas that need improvement.

Particularly when you are first starting into this, it will be helpful to have a reference. Pick a region in the example photo and see what was done to achieve that color, then try that as a starting point for a similar area in your own picture. It may also be helpful to load an actual color picture of similar content into Photoshop and convert it to Lab mode. Then select that picture and hover the pointer over an area so the Lab coordinates will show up in the Info window (Window> check Info). Select the picture you wish to color and hover the pointer over a similar area to see its Lab coordinates. Alternately adjust the Levels for the selected area and hover the pointer over it until you approximately match the a and b coordinates to the reference picture.

In the above, we did not adjust Lightness. That seems reasonable because a and b are the color channels. However, Lightness really is an integral part of the color system and you will find that sometimes Lightness will have to be adjusted a little to get the color you want. Again, use the center slider to adjust lightness, then go back and tweak a and b. Before, we mentioned that older B&W photographs are likely to be orthochromatic, as is our example. For such images the Lightness is likely to be quite far off for some colors and may need fairly large adjustments to look reasonable. So, do not be afraid to adjust Lightness. In fact, Lab mode is the best place to make such overall density adjustments when they are necessary. In the example file, you will find that the Blanket and Wall Paper have curves adjustment layers in addition to the levels adjustment. For each of these I wanted the lighter portions to fade to white; the curves will show the strange adjustment necessary to achieve this while maintaining a consistent overall color.

When the photograph looks like it is close to correct, convert back to RGB mode and if you wish, make final adjustments in a mode which is probably more familiar. If you are in 16 Bits/Channel mode, you may wish to change to 8 Bits/Channel mode. Selections that were saved in a separate file will still work in 8 Bits/Channel mode and long as the image is not cropped or resized. Particularly the first few times you try this method, you may want to save your Lab mode working file and revisit it after a few days; very likely some areas that appeared OK previously will appear less so after the eyes have rested. It is particularly easy to misjudge the saturation of colors. Large errors in saturation are best handled in Lab mode, but if saturation errors are minor, you may find it easier to correct them in RGB mode, using the Hue-Saturation control.

It is likely that you can make significant improvements in the photograph using RGB mode, due not only the experience factor but also because any switch of mode always will make some adjustments easier. For example, by using Image>Adjustments>Curves to edit a colored selection, the endpoints of the R, G, and B curves can be adjusted to purposely add or remove color casts in the lighter or the darker parts of the selection. The PSD example file was tweaked in RGB mode to form the JPG version that appears above.

Return to Tips List

How to Work Around Photoshop RAW Image Input to get Color Integrity

The much-praised Photoshop RAW conversion is so poorly and strangely designed that we finally gave up trying to understand what it actually does. Do not depend on any of the names of the controls in RAW conversion to describe the action actually performed. In particular, "brightness" is definitely not brightness and, incredibly, is more nearly gamma! On the Dunthorn Calibration page there is a short description of what we thought RAW was doing when that document was written, but it is actually even more confused than that. The best hope is to get the image through the RAW process - which does a decent interpolation of the Bayer grid - as untouched as possible. We have found that setting:

Temperature 6050
Tint 0
Exposure 0.00
Shadows 0
Brightness 50
Contrast 0
Saturation 0

Appears to do this, or nearly so, for the few cameras we have tried. Be sure to use 16-bits/channel mode. Needless to say, anything on the Calibrate tab should be left set to zero if you ever expect to have an image with color integrity. Tint and Temperature serve to set the color balance and although the adjustments they perform are cumbersome, they do not appear to destroy color integrity, so they can be set anywhere reasonable and you can set the actual color balance later using the ColorIntegrity or ColorPos plug-in or the Levels control Highlights slider. Also - remarkably - "Shadows" appears to do a correct blackpoint adjustment, with minimal effect on color integrity. If you are not using the ColorIntegrity or ColorPos plug-in, this Shadows control is preferable to using the shadows slider on the Levels control. Adobe RAW also does introduce some minor distortion in the highlights, so we actually prefer to set Exposure to a value more like -1.0, producing a dark image, and then correct the result in ColorPos.

You can use these settings along with the approach described in Dunthorn Calibration to do a calibration for your digital camera "by hand" or alternatively the ColorIntegrity plug-in will do calibrations semi-automatically using the Dunthorn or other grayscale. Doing these calibrations is not a trivial task but in our opinion well worth the effort.

It has recently been brought to our attention that the newest Adobe Photoshop RAW converter has a "Curves" tab and under the Curves tab is a "Linear" option on the pulldown. The problem is that the result of using a "Linear" curve does not produce a linear image; the resulting image is gamma-encoded, just as before. You choose whether this represents Adobe arrogance in redefining "linear" to the polar opposite of its long recognized technical usage in this context or if it merely represents Adobe ignorance that this term already had a widely recognized use in imaging. In either case, do not be fooled by this.

Return to Tips List

Getting a Proper Tonal Scale in Black and White Photography

Photoshop does just as poor a job of inverting black and white negatives as it does with color negatives, the resulting tonal scale being extremely warped. While the ColorNeg plug-in was designed to work with color negatives, it does black and white negatives equally well, giving complete control over the image gamma in the process. By doing the inversion properly, ColorNeg produces an accurate tonal scale and in the process, provides the tools to manipulate the tonal scale in a manner very similar to what Ansel Adams did in the darkroom. The method of dealing with the tonal scale described in Color Balancing Color Negatives can be used in place of ColorNeg, although it is considerably more cumbersome to do so.

Return to Tips List

Silver-Based Gamma, Video Gamma and Levels


Photographers with much experience in silver-based methods know that gamma is a measure of the contrast shown by a photographic material. Many people know that the middle gray Levels tool in Photoshop really is a "gamma adjustment." Is this the same gamma that indicates contrast? I have not found much written about this and apparently the reason is that the answer is complicated and can be confusing. The practical answer is no, the two gammas are really quite different even though the mathematical form is nearly identical. Download the mathematical PDF (175KB) for a complete explanation. This document has been completely rewritten with more detail and we believe it will be easier to understand [2/1/4].

Although the two equations for gamma in silver-based photography and video work appear nearly the same, in practice the behavior and meaning of gamma is quite different in the two fields. A higher silver-based gamma always means increased image contrast and a lower silver-based gamma always means lower image contrast. This is never the case with video gamma, which is what is actually used by the "Levels" tool in Photoshop. In Levels, moving the midpoint to the right makes the overall image darker, but this is achieved by lowering the contrast in the darker tones of the picture while simultaneously raising the contrast in the lighter tones of the picture. This is easily seen once you know what to look for. Similarly, moving the Levels midpoint to the left makes the overall image lighter, and this is achieved by raising the contrast in the darker tones of the picture while simultaneously lowering the contrast in the lighter tones of the picture.

Despite the fact that gamma is a fairly straightforward mathematical concept, there is considerable confusion regarding gamma in digital photography. It can be rather fun to track down the exchanges between Timo Autiokari and Charles Poynton concerning gamma (try Google if you are interested). These are two obviously intelligent people. Both offer very useful information on the web, but each clearly believes his view is the only one possible and the other fellow hasn't a clue. But there are very few things in science and virtually none in technology that can't be viewed in more than one valid way.

Return to Tips List