Resolution, digital correction
Just stick with the basics

By Bradley Wilson ©2006

Original photo of Technician Editor Tyler Dukes performing a tasting during the Anheuser-Busch Brewery Tour in St. Louis	1. Crop. Don’t perform any color correction until the image has been sensibly cropped.	2. Ensure that there is a true black and white. (SEE FIGURES BELOW)

Finding a true white and black
RED In the Image > Adjustments > Levels dialog box adjust the shadow (black) slider below the left side of the histogram in to where there is data in the image.	GREEN Repeat this for the green channel. In this picture notice that both the highlight slider and shadow slider need to be moved in this channel.	BLUE Finally, move the highlight and shadow sliders in on the blue channel. Then click OK.

4. Based on data obtained using the Info palette, three modifications were made. First, the midtones were adjusted to be lighter using the Image > Adjustments > Levels dialog box. Then his shirt was brought back in using the History Brush. Finally, his eyes were lightened using the Dodge tool.	Notice how the Info palette indicates that the image has an abundance of yellow in the normally white ceiling tiles.	5. Filter. Because the background still had such a strong yellow cast from the tungsten lights, I applied a Cooling Filter to the entire image. Then, using the History Brush, I brought back in some of the color into his skin tones.

Our procedure

Do all color correction in RGB mode (after all, your monitor can only display RGB). Try to do all the color correction for a given issue or spread at one time for consistency. Working in an evenly sit room on a monitor with a neutral background will help maintain consistency. Consistency is the key to quality color correction.

FOR: All images
RESPONSIBILITY: Photographer
FILE LOCATION: Photo Server

For ALL images before being saved on the Photo Server. All such images must also be captioned. Do NOT adjust the resolution of these images. Resolution is media dependent. Adjustments in resolution will be made after the photos are copied to the appropriate media's server.

1. Crop the image for how it should appear on the page. Don't crop the image so tight that the page designer doesn't have any play room. Leave a little breathing room, but crop out the useless information.
2. Find white and black points. In each separate channel of the image/adjustment/levels dialog box, pull the white point in until there is data on the histogram. Repeat with your black point. Do not adjust the midtone point.
3. Adjust midtones. A majority of the time, the subject’s skintones will be a reference point for midtones. When using the Info palette, use the grayscale measure Well-exposed skintones should be at 30-40 percent. In the Levels palette, drag the midpoint in the RGB channel to adjust the brightness or darkness of your midtones. To ensure there is detail in the highlights and shadows. Do not go by what you see on the screen. Use the Info palette and Eyedropper tool to see what the actual hue, saturation and brightness values are for the actual pixels.
4. Adjust for details in shadows and highlights.
   1. Using the Eyedropper tool and Info palette, make sure that there is detail in your shadows and highlights. If the shadows are too black (>90 percent in grayscale) without any detail, adjust the midtone slider so there is detail in the shadows
   2. If necessary, adjust the midtones using the History brush. Set the history state to when the midtones were correct. Set the opacity to 15-30 percent and brush your midtones back into the correct range.
5. Correct for color imbalance.
   1. First, using the Eyedropper tool and Info palette, see if there is a color cast to the picture. Extremely high Y (yellow) values in CMYK indicate a yellow color cast, for example. This is where experience is a good teacher. Use the CMYK values of past images that printed with good color correction to use as a reference for skin tones. Make sure to compare similar skin tones. Neutral colors, grays, that are known to be truly gray, can also be used to check for color imbalances.
   2. If you find a color cast, there are many ways to remove it. All depend on using the Eyedropper tool and Info palette to determine when you've added or removed enough color. Image > Adjustments > Levels, Selective color, or Photo Filter.
      • Levels. Use this to adjust the color channels, lightening or darkening the channels as needed.
      • Selective Color. Use this to add or remove colors from specific color ranges. For example, to adjust for cyan in skin tones, can pull down the individual color ranges of the skin tones and add cyan. The only drawback to this is that when adjusting for cyan in the red, don’t inadvertently change the color of the reds elsewhere in the photo.
      • Photo filter. This works just the same as a filter on the lens. Adjust colors using a specific filter type, such as a warming filter to increase yellows and oranges, or a cooling filter to increase blues.

NEXT: COPY the image to the appropriate media's server for use in an individual media. Leave the original image on the Photo Server for use in other media and archiving. Copying the image may be the job of the nightly photo editor.

FOR: Images selected from Photo Server for use
RESPONSIBILITY: Photo editor
FILE LOCATION: Individual media server

1. Convert to grayscale if necessary. If the image is going to be used in black-and-white, go to Image > Adjustments > Desaturate then Image > Mode > Grayscale. Going through the desaturation step generally results in a better quality reduction to black-and-white (but not always).
   All correction work should be done in RGB mode.
   To grayscale and image, first desaturate, then change the color mode to grayscale.
2. Change resolution for the publication according to the resolution the printer reqires. To find the maximum size an image can be used in the publication, turn OFF resampling in the Image > Image Size dialog box. Then type in the appropriate number in the resolution field.
   • Agromeck 150 LPI = 300ppi
   • Technician 85 LPI = 170ppi
   • Nubian Message 85 LPI = 170ppi
   • Online = 72ppi
3. After finalizing the photo’s size on the page with the designer, change the dimensions of the photo to fit. Make sure the resampling option is turned on in the Image Size dialog box. Do not change the height/width ratio.
4. Save as RGB JPEG (quality = 12) into the appropriate edited folder. Leave the original, unchanged photo on the Photo Server.

Naming Files

To get your pictures published, people have to be able to find them. Quickly. To make this easy, we’ve developed a file directory structure and naming convention that will help designers find images not only now but a year from now when they need an image for the annual year in review or whatever. The date and other information are contained in the system’s file information.

description_IN.ext

• “description” is a one- or two-word description of the contents of the photo. Be specific. Don’t just say “band.” Give a name or a section or an instrument or something. Be sure to include “Photo by <YOUR NAME>.”
• “IN” is the photographer’s initials.
• “ext” is the appropriate file format assignmed by Photoshop, probably .PSD or .JPG. Do NOT change the extension.
• Notice that there are no spaces or funky characters in the file name.

The Eyedropper tool and Info palette are two of the photographer's best resources when color correcting. This value, for example, indicates a slightly yellow flesh tone for a caucasian individual. While it's slightly yellow, the K-only value of 14% indicates it's neither too light nor too dark. Between 10% and 30% would be about right.

A few color tips

From Austin Dowd

• Properly exposed images using the right white balance require less correction.
• All photos will be different. Practice and learn from mistakes.
• Do not trust your monitor. Your printer and your computer screen are two completely different outputs. Correct for the printer and not the monitor.
• LCD (liquid crystal display) monitors will have different colors and brightness at different angles of view.
• Keep consistent. Correcting on the same machine with the same lighting conditions in the room will help to create a consistent correction process
• Learn from your mistakes. Always go back to images you have corrected in the past. What worked well? What didn’t? How could that image have been improved?
• Don’t color correct on a machine with a colorful background image. Keep it neutral gray.

LPI, DPI and PPI
Learn what all those number mean

At the time a photographer clicks the shutter on a digital camera, the amount of digital information in that image is fixed, based on the settings at the time of the camera. It will never contain any more information than at the time of capture. Still, time after time, page designers try to enlarge photos beyond the original size resulting in a loss of quality. When a photo is enlarged in a page-layout program, the pixelation (“jaggies”) becomes evident.

Here's the original, cropped, image. It's 43.722 inches x 32.444 inches at 72ppi. It contains 21.0 megabytes of information. Photo by Bradley Wilson.	The Image > Image Size dialog box shows that resampling has been turned off. So any change in the resolution of the image will also change the width and height in proportion.

Digital information

When shot, an image has a set number of pixels per inch. For example, let’s say a one-inch square “photo” has 72 pixels per inch. Half of the pixels are white, and half are black. If this photo is simply enlarged, all that the pagination software can do is enlarge the pixels making the photo look “pixelated.” If the photo is made smaller, the pixels move closer together, and the output device throws the extra information away.

The best procedure to follow is the same one page designers followed in the “old days.” Sketch out the page and decide the approximate size of the photograph and then digitize the image at that size with enough information to reproduce it clearly.

For example, if you know a photograph is going to be printed in a newspaper (such as the Technician) that uses a line screen of 85 lines per inch (information that you’ll have to obtain from your printer) and you know it’s going to be about 4 x 6 inches in size, you can scan it or resize it with that information in mind. Entering the appropriate size and resolution (85 * 2 = 170 PPI) into the image size dialog box.
Of course, programs such as Photoshop will allow a user to resample an image – adding information where necessary to fill inthe gaps. The software will take the information that is available and extrapolate the necessary data. However, this data will only be a rough approximation of what was really there, and the photograph will look blurry at best.

To expedite production when the final size is not known, it is always better to have more information than not enough. For example, if you know that a photo is going to be used on the news page but do not know the exact size, it is better to save it a little larger than necesssary perhaps even at a higher resolution than necessary. Then, when the final size is determined, resample the image (down) in Photoshop.

For example, take a 4 x 6 inch grayscale photograph at actual size (100%) for output at 150 LPI (300 PPI) and it will occupy 2.06 MB. If you later decide that this same photo is going to be reproduced at 2 x 3 inches, go into Photoshop and, under Image/Image Size, make sure Constrain Proportions and Resample are turned on. This will keep the dimensions of the photo in proportion. The photo won’t look stretched. It will also force Photoshop to discard the unneeded data. Then type 3 inches in for width, and you will notice that the height changes proportionally. And the final size (at the top) changes from 2.06MB to 527KB, substantially smaller and more efficient.

One pearl of wisdom. Because the amount of information in a digital image is set at the time of capture, the file size in megabytes (indicated at the top of the Image Size dialog box) should NEVER go up.

Raw images

Because photos may be used in high-resolution publications (such as the yearbook), medium-resolution publications (such as the newspaper) or low-resolution publications (such as online), don’t change the resolution of an original image before saving it on the Photo Server. Leave it at the same size and resolution as it was when it was taken. The page designer or photo editor will copy the image and change the size, resolution and mode of the copy AFTER the image is moved from the Photo Server to the appropriate media server and folder for the page on which the photo will be used. All original images should be storied on the photo server with only the basic color correction completed. Photo editors and designers may need to complete additional editing/cropping.

For reference, the Technician and Nubian Message are printed at 85LPI and the Agromeck and Windhover are printed at 150LPI.

Here's the same image but with the resolution set for yearbook quality reproduction. So, the largest size this photo can appear in the yearbook without any loss of quality is 10.493 x 7.787 inches at 300ppi.	Notice how the bracket on the right of the Document Size portion of the dialog box indicates that width, height and resolution are all linked together.

LPI
Lines per inch; reserved for the number of lines in a screen of a printed image; determined by the maximum resolution of the press on which the page is being printed;
photocopy 65 LPI
newspaper 85 LPI
yearbook 133 LPI

DPI
Dots per inch; reserved for the number of dots available in output of a laser printer or other output device
laser printer 600 DPI
imagesetter 2400 DPI

PPI
Pixels per inch; the number of “picture elements” in an image as it appears on the screen
Web page 72 PPI
photocopy 130 PPI
newspaper 170 PPI
yearbook 300 PPI

FORMULAS
The maximum resolution of a printer
10% * DPI = LPI
Example:
A 600 DPI printer can output a maximum of 60 LPI (600 * 10%) and still retain all 256 levels of gray

Number of pixels needed in an image at actual size
LPI * 2 = PPI
Example:
A photograph to be reproduced at 85 LPI must be scanned at 170 PPI (85 * 2) to avoid pixelation.

Enlargement/Reduction
LPI * % enlargement/reduction * 2 = PPI
Example:
A photograph to be reproduced at 85 LPI and enlarged 150% must be scanned at 255 PPI (85 * 150% * 2) to avoid pixelation

If, for example, the yearbook staff, working with the designer, knew the photo was only going to be reproduced 5 inches wide, the photographer could resize the image to make it more efficient.	Because all 21MB of information aren't needed, turn on resampling to fix that resolution. Then change the width to be 5". Notice that the file now occupies only 4.78MB of disk space.

CLICK HERE for more information on resolution.