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April
2004




 

 

 

 













 

 

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Digital image reproduction


Editor’s note: Newspapers & Technology continues publishing the most recent version of the Specifications for Newsprint Advertising Production (SNAP) guidelines. The first installment appeared in October. The series will continue as an occasional feature over the next several issues. To obtain additional copies of SNAP, contact the WPA, the Graphic Arts Technical Foundation (GATF) or the Newspaper Association of America (NAA). More information can also be found on GATF’s Web site at www.gain.net.

An established workflow, with standard operating procedures, should be in place in the photo department to ensure consistency.

While it’s unreasonable to assume that all news images can be staged and set up exactly the same, some basic guidelines for capturing and balancing the image at the camera will help the overall reproduction quality of the images.

Consider the following factors for correct reproduction of a digital camera image on newsprint.

Digital camera images require proper exposure. A correctly exposed image will have good contrast and will reproduce well on newsprint. If the image is over-exposed, important highlight detail is lost.

Underexposures will only enhance the noise in the blue channel.

Make sure that essential highlight and shadow detail fits within a five-stop range.

(Editor’s note: A real world tip from Rob Galbraith and his “The Digital Photojournalists Guide:” Use fill flash in every lighting situation because it dramatically improves the quality of the printed image.)

When flesh tones are involved in the subject matter, make sure that they fall at the optimum point on the tone curve. The LCD display on the later digital cameras, coupled with the histogram and the saturated highlights indicator, make it easier to determine where tones are falling on the curve.

 

Light matters

Remember that the color of light is critical to the color of the image. That’s why it’s important to plan on having a portable lighting kit.

When it isn’t possible to control the light source, make sure that the resulting color cast is fixed during the “acquire” step, before it ever reaches Adobe Photoshop.

Proper setup during a “acquire” will ensure accurate image quality. The camera’s color settings must suit the lighting situation at hand to produce accurate color. If no consideration is given to the color of the light at the time the picture is shot, then unsatisfactory color will result even with the latest digital camera technology.

Set the neutral point before the assignment is shot. Use a neutral gray card shot under the same lighting conditions and the same exposure that will be used for the subject.

If the neutral point is set correctly, then neutral areas of the subject will remain cast-free. Following the above steps will ensure correct color before the assignment is shot.

Since digital cameras produce small files that will be enlarged, be sure to keep the ISO as low as possible. Take pictures at ISO 200 whenever possible.

When the ISO increases, so does the blue channel noise. Frame and tightly crop the image with your camera.

Shooting the subject tight ensures that you’re capturing every important pixel needed for enlargement of the image.

 

Sharper images

Make sure that the picture is sharp.

Acquire the pictures correctly. The key points previously mentioned, contrast, tones and color, are obtained during the “acquire” function.

During “acquire” the proprietary format used in the camera is being converted to an editable document. Using the “click balance” function, in the acquire software, is another way of eliminating severe casts. But be aware that an incorrect “click balance” will create partial color casts that will create major problems in Adobe Photoshop.

Focus on getting the color right during the “acquire.”

Some of the basic recommendations for workflow include:

- Choose the correct illuminant/neutral point. Shoot a gray card and expose properly every time the light changes. Balance should be set when shooting before “acquire” so that it will not affect the raw data.

This helps to apply the correct color matrix (daylight, tungsten, flash, etc.). If an incorrect color matrix is applied, that setting can be changed in the thumbnails. The white and black points should be set by the imaging operator, not the photo.

- Crop the image. Turn off the fixed target size during res-up.

- Analyze the image with the info palette. Analyze the red-green-blue (RGB) data. Check the shadow and highlight areas for detail. Do not make adjustments of more than two points.

- Adjustments with levels and curves should only target neutrals.

- Dodge/burn using the lasso and feather tools (three pixels).

- Correct noise. In the LAB mode check B channel for noise. Go to dust and scratches and set the radius at 9 and threshold at 0.

- Sharpen using the fade USM feature only (100 percent setting). This only affects the luminosity or detail channel and will not sharpen the color.  Regular USM settings should be done by the imaging operator.

- Capture/save as highest quality JPEG.

- All numbers should be shared between photo and prepress to preserve the integrity of the tone curve on newsprint. There should also be open dialog between the two departments to ensure accurate reproduction of the digital camera images.

Some of the numbers recommended in “The Digital Photojournalists Guide”:

Skin color and density values - All values referenced with the info palette, first reading set to grayscale (K), subjects front lit, reading the brightest area of the face, not specular highlight:

White skin. Ideal is 35 percent; 20 percent to 60 percent is usable. If the skin tones are lower than 20 percent they will become contrasty and over-saturated when corrected. Skin tones darker than 60 percent may become flat and noisy.

Asian/South Indian. Ideal is 45 percent; 25 percent to 60 percent is usable. Skin tones lighter than 25 percent become contrasty and over-saturated when corrected. Darker than 60 percent may become flat and noisy.

Black skin. Ideal is 60 percent, but varies because of the reflective qualities of black skin; 30 percent to 75 percent is a usable range. Skin tones lighter than 30 percent become contrasty and over-saturated when corrected. Tones darker than 75 percent creates noise and loses detail.

Skin color and density values when using Photo Mechanic/AP Viewer - All values referenced with the info palette, first reading set to grayscale (K), subjects front lit, reading the brightest area of the face, not specular highlight:

White skin. Ideal is 40 percent to 45 percent; 40 percent to 55 percent is usable. If the skin tones are lower than 40 percent they will become pasty and over-saturated. Skin tones darker than 44 percent may become dark and noisy.

Asian/South Indian. Ideal is 50 percent to 60 percent. Skin tones lighter than 40 percent become pasty and over-saturated. Darker than 65 percent may become dark and noisy.

Black skin. The ideal is difficult to recommend because of the reflective qualities of black skin. Somewhere between 40 percent and 70 percent is the usable range. Skin tones lighter than 35 percent to 40 percent indicate that image quality throughout is marginal. Darker than 70 percent creates noise and loses detail.

Skin color and density values when using Kodak v5.63 Acquire software - All values referenced with the info palette, first reading set to grayscale (K), subjects front lit, reading the brightest area of the face, not specular highlight:

White skin. The ideal is 35 percent, but 35 percent to 55 percent is usable. If the skin tones are lower than 30 percent to 35 percent they will become pasty and over-saturated. Skin tones darker than 55 percent may become dark and noisy.

Asian/South Indian.  Ideal is 45 percent to 55 percent. Skin tones lighter than 35 percent become pasty and over-saturated. Tones darker than 65 percent may become dark and noisy.

Black skin. Again, the ideal is difficult to recommend but 35 percent to 70 percent is the usable range. Skin tones lighter than 30 percent to 35 percent indicate that image quality throughout is marginal. Darker than 70 percent creates noise and loses detail.

 

Prepress toning tips

Always make use of the histogram to evaluate the distribution of pixels throughout the tonal scale. Because it plots the brightness values and the proportion of pixels at each level, the histogram is a good tool for helping an operator judge the brightness and contrast of an image.

The pixel distribution in the histogram will allow the operator to determine the location of important detail in the image (high key, low key or normal key).

Photographers should also make use of the camera’s histogram by acquiring a series of images shot at different settings.

Choosing an image that has the best histogram for a specific situation or event will give the imaging operator more information. This will help ensure accurate use of the full tonal range and limit detail loss.

 

Use levels, curves

All highlight and shadow adjustments should be made using levels or curves, or a combination of the two. Digital images tend to develop heavy midtone areas after highlight and shadow placement. Adjusting the midtones using the curve will offer accuracy.

Photoshop also helps the operator target the location of the midtone.

By selecting a midtone area in the image, placing the cursor in that area and holding down the mouse button, Photoshop will display the location of that tone on the curve. This will help the operator to adjust the image accordingly.

 

Color casts

Casts should be neutralized first to detect other problem areas. Images with a light cast can be neutralized using the gray eyedropper tool in the curves dialog box.

Double-click on the eyedropper tool to display the color picker. Enter 40C, 30M, 30Y, 0K in the CMYK value boxes.

Click OK, remaining in the curves dialog box. Take readings in the areas that you know should be neutral. Click the gray eyedropper tool in one of those neutral areas to bring the values to 40 percent, 30 percent and 30 percent.

If the image becomes darker, then lighten the midtones while still in curves (1.35 gamma).

If the neutral highlight needs additional adjustment, go to selective color and choose whites. Take out the color or colors responsible for the contamination. Once the cast is removed continue toning.

The gray eyedropper will only work on certain originals and only in neutral areas. Evaluate the image carefully and be sure to measure a variety of areas before choosing this method to neutralize.

You may also find that using a different combination (lighter or darker) of neutral percentages will yield better results. In some instances, individual curve adjustment works best.

Editor’s note: The next SNAP installment will continue the discussion of digital photography and also cover prepress technologies.