Meeting 10

Chi di spada colpisce di spada perisce

Topics: RGB Color Correction, Karl Kuntz toning methods, Color Replacement, Hue & saturation methods

Files needed from the server:

Toning RGB files in Photoshop
Still, there are times when toning RGB (or even CMYK) in Photoshop needs to be done. The following exercises show several approaches. Toning RGB pictures in Photoshop is usually "destructive" (except by using adjustment layers that avoid lossy toning). If a user takes too many attempts at toning an RGB picture, they may reach a point when it becomes impossible to adequately correct it. If this point is reached, then it is best to start from a fresh copy of the file - if it is still available.

Open 07begin.psd (Exercises 4). Also open 07final.psd file as a reference target for our adjustments.

Use Image>Adjustments>Curves command on 07begin.psd (Exercises 4)...

Image>Adjustments>Curves

To make adjustments in Curves, the best way to begin is to click near the center of the curve graphic to add a control point, then drag it at right angles to the curve itself. This "curves" the curve, and adjustments are immediately viewable. Most color correction is iterative - meaning that it's mostly trial and error adjusting the various channels to obtain pleasing color. An experienced operator will be able to identify the off-colors present in the picture, then quickly choose and adjust the appropriate curve to correct the picture.

When the dialog box first opens, the composite (RGB) curve is shown. Adjusting it affects only how light or dark the image is because all curves are adjusted equally. Unless the lightness/darkness is substantially wrong, I generally adjust the RGB channel for proper lightness/darkness last after I've corrected the other channels for color.

Different channels (Red, Green. Blue) can be selected in the Channel drop down list to adjust the corresponding curve.  If Red is chosen in the drop down list, only the red channel is affected by curve adjustments. Green and Blue channels are also adjusted individually once they are chosen. Remember the color wheel as you identify colors in your picture to correct so you can target the proper channel for adjustment.

*(Optional) Use the Black point eyedropper to set the black point.

*(Optional & very dangerous) Use the White point eyedropper to set the white point.

*(Optional) Use the gray eyedropper on a neutral toned object to set the overall color balance for the photo.

Note that there is a "Save Preset..." selection in the Curves dialog box to save a set of corrections to be used on future pictures. It's nested behind the small dialog icon (horizontal lines) at the top. This is useful if a device or circumstance imparts a repeatable color cast to images -- the same correction can be applied to all photos once one is corrected. Use the "Load Preset..." button to load a previously saved set of corrections.

TIP: LAB color model advantage - extreme toning changes can produce unwanted shifts in color saturation and contrast. For example, greatly lightening an  underexposed picture can make faces very red, and affect shadow colors adversely. To better maintain color and contrast, try changing the picture's Mode to LAB color temporarily. Run curves and make changes to the Lightness channel (the L in Lab), while leaving a and b channels untouched. Convert back to RGB when you are finished.

Sometimes Saturation is the problem...

Open the file redhead.jpg in Exercises 4.

Try to adjust color using curves... it will be difficult. The problem with this picture is mostly excessive color saturation. Over-saturated color is often perceived to be "brilliant" and manufacturers of film offer some film varieties that have more saturation than normal. These films also tend to be high in contrast, and some scanners tend to amplify the already high-contrast tones.

For the redhead.jpg picture, use Image>Adjustments>Hue/Saturation to desaturate the orange color that is the problem in this picture using the following steps:

After opening the dialog box, change the Edit field from Master to Reds.

Click on the eyedropper in the dialog box and then click on the saturated orange cheek of the girl.

Move the Saturation slider to the left to reduce saturation.

Adjust the color selection slider at the bottom to pick up some yellows that are too saturated too.

The picture should now look more life-like.

Karl Kuntz Method 1:
The Columbus Dispatch has used a process devised by Karl Kuntz to correct color in some off-color photographs. It won't work for all photos, but it's fast to try. To try it, open the file tree-lined big.jpg (Exercises 4). The steps are listed below:

Crop the border. Since what follows is for a "semi-automated" way to correct color, the border of this picture must be cropped away. It represents tones that are not in the photograph itself, and the presence of these artificial tones will defeat the process.

In the Image>Adjustments>Levels dialog box, Click on the Channel drop down box, and choose the Red channel.

Slide the black point triangle for the Red channel to the beginning of the picture histogram data on the left side. Side the white point at the beginning of histogram data on the right side.

Now choose the Green channel and the Blue channel and do the same thing to their black points. Adjusting the black points of each channel individually should get color close.

Go to the RGB Channel and adjust the overall black point and gray point.

Click OK to accept the Levels changes.

This may be enough to completely correct the picture. But if not,

Open the Curves dialog box: Image>Adjustments>Curves.

Now adjust the Red, Green, and Blue curves individually to fine-tune the color correction needed for a good photo. Click OK when done.

Try these steps on the file called tree-lined big.jpg (Exercises 4), then fine-tune using curves.

I have found that a picture that has been adjusted first using Curves can be fine-tuned by the above method (a bit of a reverse of Karl's method). For example, a color cast in the darker tones of an otherwise good correction may be eliminated by choosing Levels and then moving just the black point triangles in each channel to the beginning of the data in the histogram.

Be especially careful of moving the white point to histogram data to force some parts of a picture to white. Some pictures shouldn't have a white, and forcing some data to white will blow-out highlights. For example, using this technique on the Bale Hop toning assignment will make the hay bales excessively high in contrast with white highlights where there shouldn't be any.

I have also found that this method works better with some pictures than with others. The Food at Hadrian's toning exercise given at the end of this lecture responds nicely to this technique. The careful toner will still need to have a good eye for color to judge whether this method solves the color problems.

Karl Kuntz Method #2 Using the Curves White-Point Eyedropper:
Sometimes you wish to neutralize a color cast in a photo. If it has a very light neutral tone in it (white shirt, snow, etc.) you can try this method. It works very well with some pictures, but won't correct 100% of them. However, it may provide a very close solution that can be further tweaked with many images.

Open costumed_skater.jpg from Exercises 4.

Begin by setting your Eyedropper tool to a 5x5 sample area on the Options bar.

Open the Curves dialog box (Command-M).

Double click the white-point eyedropper in Curves to open the Color Picker window. You should see the dialog box as shown below.

Next click in the picture itself on an area that you wish to make neutral white (white shirt, ice, snow, white wall, etc.) In our example, find a highlight on the ice.

The color of the spot you sampled in the picture is displayed in the "Select target highlight color" dialogue box and that color numbers are shown for it. The Lab color settings for Luminance, a, and b are displayed together with other color methods. L is the luminance channel and varies from 0 (black) to 100 (pure white). Don't change luminance, but do change the a and b numbers to zero. This makes the color neutral - no color cast.

Click Ok to return to the Curves dialog box.

Click again in the SAME SPOT using the newly reconfigured white-point eyedropper in the Curves dialog box. The color you clicked will now become neutral gray, and other colors will shift with it. With Curves still open, you may further tweak the tones as desired.

Click OK in the Curves dialog box, and choose NO to the prompt to save the new target color as the default for the white-point eyedropper.

This method works with pictures that contain neutral tones - white snow, white shirts, Kodak gray cards, etc. If there is nothing in your picture that contains a neutral tone, don't waste your time with this method.

Big Tip

Adobe Bridge CS3 introduced the ability to use the Camera RAW interface to tone JPGs and TIF files, and it continues in the Creative Cloud version. To change handling of TIF and JPG files, start Adobe Bridge, go to Camera RAW Preferences (under the Adobe Bridge CC menu item at the top left), go to the JPEG and TIFF Handling section, and choose "Automatically open all supported JPEGs". Do the same for the TIFF format. (Do the reverse if you do not want to use Camera RAW for TIF and JPG files.)

Toning problem pictures may be easier with the two color sliders at the top of the Camera Raw converter compared to using Curves in Photoshop. However, some of the usual advantages that you have when toning Camera RAW will not be available when toning JPGs or TIFs. For example, blown highlights will remain blown out, and you can't fix them like you can with a true RAW file.

If you don't want Camera RAW to open your JPGs or TIFs, choose "Disable JPEG support" and "Disable TIFF support".

To experiment with toning JPGs in Camera RAW, set the Camera Raw preferences in Bridge to "Automatically open all supported JPEGS". Then open in Camera Raw an untoned JPG file.

Bigger Tip

Photoshop CC has integrated the camera raw toning interface as a filter. Use the familiar controls without having to go back out to the Camera Raw stand-alone program. Choose Filter > Camera RAW filter. It does not change the original camera raw file, nor does it appear to change the raw file's thumbnail in Bridge. It is just another way to tone a photo in Photoshop using alternative tools, but doesn't fully work like the stand alone Camera RAW program.

Another Tip:
Use Image>Adjustments>Replace Color to select and de-saturate residual color casts in a picture. This is most useful when there is a stubborn cast remaining after other color adjustments are used to get close. One use is removing residual green in some pictures made under fluorescent lighting.

Replacing Colors in an Image with Other Colors

There are a variety of ways to change colors in an image. They include:

1) Use a brush with Color mode selected in the Options bar. This is useful for local touch-up of color or small replacement jobs. The steps are:

Open a file (use 07final.psd in Exercises 4).

Select the brush tool.

Check the Options bar and select Color in the Mode drop down list. (By default it will indicate "Normal")

Select an appropriated brush size.

Choose the color you wish to use -- it must be selected as the foreground color.

Paint over the area that you want to change.

(NOTE: If you have adjustment layers above the original image, you must select the layer that contains the original image to replace color. Adjustment layers will be discussed in a future class meeting)

If you have an advanced need for color replacement, there is a Color Replacement Tool in the toolbox that already has the Mode on the options bar set to Color as above. It has more finesse, especially in the ability to "stay within the lines" through sampling . Its use is otherwise identical to the previous steps, i.e. brush on the desired color.

2a) Use Image>Adjustments>Replace color. This method is useful if the image contains a multitude of scattered detail that is comprised of a similar color. Using the Paintbrush tool on this type of image would be possible but tedious.

Open (or Revert to) 07final.psd

Choose the Eyedropper tool and select a color you wish to change throughout the image (in 07final, click on one of the red peppers).

Image> Adjustments> Replace Color

Adjust the Fuzziness slider to select more or less colors that you want to change. Notice how the chef's lips (also red) are also selected if fuzziness is set to a high number. That can be prevented if preliminary steps are taken (detailed later).

Change the Hue slider to affect the color of the image. Saturation and Lightness sliders can also be adjusted to achieve a desired effect.

Click OK

Done

2b) If you wish to change the reds in the peppers but not anywhere else in the image (for example if you wanted to exclude the lips from a hue change), first lasso around the region of the image you wish to affect before performing the steps given above. Here are the steps needed to change instances of a color in just a small region of the picture:

File>Revert the 07final image to its original form.

Choose the Lasso tool and roughly select the bowl of peppers.

Choose the Eyedropper tool and select a color you wish to change throughout the selected part of the image (in 07final, click on one of the red peppers).

Image>Adjustments>Replace Color

Adjust the Fuzziness slider to select more or less of the similar colors you want to change. Notice how the Fuzziness preview is restricted to approximately the region defined by the lassoed selection. It does not display the full image as before.

Change the Hue slider to affect the color of the image. Saturation and Lightness sliders can also be adjusted to achieve a desired effect.

Because the lassoed area does not include the lips, they remain unaffected by the changes made in the Replace Color dialog box.

Click OK

Done

3) Use Hue/Saturation to apply a color cast to the picture.

File> Open >trees n snow.jpg (Exercises 4)

Choose Image> Adjustments> Hue/Saturation

To colorize overall, click the Colorize check box. Adjust the Hue slider to choose a desired color cast. Saturation usually should range from 15-40 for pleasing tones that aren't overly saturated.

Click OK

Done

This resembles a Duotone mode picture, but it is still an RGB mode picture and NOT a duotone. This method is the way to colorize pictures for the web (an RGB world). Duotones are for print ONLY and will be discussed in a later meeting.

If you don't wish to completely colorize a photo, you can still shift the overall image color by not clicking on the Colorize button in the dialog box. For example, Saturation can be greatly reduced to give a tinted B/W photograph appearance to a color photo.

Tip: Nikon scanners and Fuji color negative film often produce super-saturated reds. They are unrealistic. To make the red more natural, use Hue/Saturation, click on the Reds button, and slide Saturation to something less than zero.

Stump the Chump Invitational Toning Challenge
In the class meetings that follow, I invite the submission of pictures you'd like to see toned. I will pick one, tone it, and show the steps in future meetings. I hope to do this once per week.

If you have pictures you want to submit to me for toning, drop them into the Stump the Chump folder on the server. I will pick one picture from the submissions, tone it, and present the toned picture in class with steps for toning it.

If you wish to also tone the picture yourself to see if you can do better (Stump the Chump!), help yourself! We can project the comparison onscreen in class, but please document your toning steps to share with the rest of the class.

Tech Exercises 4:

Turn-in_04 folder - Due by Friday Feb 17

Start toning these in class if there's time left. Color correct the xmas_tungsten.tif file. (The following files can be found in Exercises 4) Color correct the allen green1.psd image by whatever means you desire. Color correct the food at hadrians_sm.jpg file Selectively color-correct different regions of the bale-hop.psd image (Exercises 4) to make a pleasing picture overall. Be sure that the tilt of your LCD screen is correct before making judgments about tone. Remember also that notebook computer screens are often poorer choices for toning than fixed monitors because of the design tradeoffs involved in reducing laptop size, weight, and power requirements. Some models can't be calibrated or trusted for critical toning at all. Please save files in the JPG file format to save space (non-JPG files will be discarded without a grade!). Place all files in Turn -In #4. Be sure to add your last name as part of the file name! Do NOT submit your files together in a folder that you make! Please submit the files individually. Thumbnails of the corrected files appear here to aid your own work.                 © 1998 Wm Schneider All Rights Reserved © 1997 Wm Schneider All Rights Reserved © Jimi Allen All Rights Reserved © 2001 Wm Schneider All Rights Reserved