Question 1.  A friend has a film scanner and uses color print film.  She wants to turn some of her images into black and white.  She has decided that she likes grayscale tonality the best.  So she scans her image with her scanner set to grayscale.  She opens the image in Photoshop.  But when she tries to add a Hue/Saturation adjustment layer, she sees that feature disabled.  Why?

1. Answer
   1. The Hue/Saturation adjustment layer can only be used with an image that is in a working space that recognizes color, such as RGB, CMYK or Lab.  Grayscale does not recognize color.  Since the scanner was set to grayscale, the image is in the grayscale working space.

Question 2.  What would you suggest to your friend in question 1 to fix her problem?

1. Convert the image to RGB by clicking Image > Mode > RGB Color.
2. Start over by rescanning the image with the scanner set to a RGB space.
3. Use a two step conversion process using Lab because Lab is a device independent color space.  Being device independent, it will override the scanner setting.  The two step process would first convert the image to Lab by clicking Image > Mode > Lab Color and then convert the image to RGB by clicking Image > Mode > RGB Color.

1. Answer
   1. B is the correct answer.  Answers A and C are incorrect because even though we could create a Hue/Saturation adjustment layer after the image were converted to RGB, there would still not be any color information to adjust.  The color was lost at the point of scanning and cannot be restored in Photoshop.  Therefore, the image would have to be rescanned.

Question 3.  Another friend has a film scanner and uses black and white print film.  He scans his images with the scanner set to a RGB color space.  He opens the image in Photoshop.  He can add a Hue/Saturation adjustment layer to his image.  However, regardless of which color range he chooses, none of the sliders seem to affect the image.  Why?

1. Answer
   1. Even though the black and white negative was scanned as RGB, there is no color in the negative for the scanner to capture.  Scanning a black and white negative in a RGB color space is done primarily to capture subtle differences in tone that is hard for a scanner to pick up when scanning in grayscale.

Question 4.  Figure 1 is a black and white version of the color chart.  The color chart was converted to black and white to retain Measured luminance.  No other tonal adjustments were applied.  Figure 2 contains the dialog boxes of a Curves adjustment, a Channel Mixer adjustment and a Gradient Fill adjustment.  The Curves dialog box in Figure 2A, shows a flat lined curve.  All input tones are mapped to a single output tone; 128.  The Channel Mixer dialog box in Figure 2B, has 0% for all three channels.  The Gradient Fill dialog box in Figure 2C, uses a linear gradient, ranging from solid black to solid white.

Using the dialog boxes in Figure 2, which of the following could have been used to convert the color chart to black and white as shown in Figure 1.

1. Curves adjustment layer with blending mode of Color with a flat lined curve as shown in Figure 2A.
2. A Channel Mixer adjustment layer with blending mode of Color with all color percentages set to 0 as shown in Figure 2B.
3. A Gradient Fill adjustment layer with blending mode of Color with a black to white linear gradient as shown in Figure 2C.
4. All of the above.
5. None of the above.

1. Answer
   1. All of the above.  A Curves adjustment layer with a flat lined curve and a blending mode of Color tells Photoshop to not change luminance, but map all colors to a single chroma, i.e. monochrome.  In fact, it does not matter where the flat line curve appears, at the bottom, middle, top or in between, as long as all input tones are mapped to a single output tone, the image will be monochrome.  Channel Mixer with the monochrome box checked and a blending mode of Color tells Photoshop to apply the color change (the monochrome check box) but to ignore any luminosity changes, which are the red, green and blue percentages.  In fact, we can change the percentages to any number we want, but as long as blending mode is Color, they will be ignored.  A Gradient Fill using a black to white gradient and blending mode of Color works the same.  Photoshop is being instructed to map all colors to black and white but to leave luminance unchanged.
      
      In addition, we can even use the Color Fill, Gradient Map, Photo Filter and Threshold adjustment layers to convert a color RGB image to a black and white RGB image as long as we use the correct settings and blending mode.

Question 5.  In the GCC method of converting a color RGB image to a black and white RGB image, the layers are arranged as follows (see Figure 3).  The topmost layer is a Channel Mixer adjustment layer to remove color.  Next there is a Curves adjustment layer with a blending mode of Luminosity to manage tone by color.  Then the Grayscale layer to give baseline luminance and then the Image layer.  The Curves adjustment layer is used to adjust luminance as desired.  However, if we move the Curves adjustment layer to below the Grayscale layer and above the Image layer (see red arrow in Figure 3), it will no longer have any effect whatsoever.  Why?

1. Answer
   1. As the image travels upward from the Image layer to the next layer, which is now the Curves adjustment layer, we can actually use the Curves adjustment layer to change the luminance of the image.  However, as it continues upward, the next layer is now the Grayscale layer.  Since the Grayscale layer's blending mode is Luminosity, we are telling Photoshop to discard the luminance of all previous layers, including any changes made by the Curves adjustment layer, and replace it with the luminance of the Grayscale layer.  Immediately after passing through the Grayscale layer the image consists of the color from the Image layer and the luminance of the Grayscale layer.  Since the Curves adjustment layer is only used to change luminance, then its effects were discarded by Photoshop when the Grayscale layer was applied.  Give yourself a pat on the back if you got this one right.