Digital Photography Technical Tips

To take quality photos with a digital camera, you need the correct format, ISO (International Standards Organization) setting, and resolution. Most digital cameras display common symbols for exposure modes and offer basic file formats for creating and saving your digital photos. Taking the photo on the highest setting will maximize both the quality of the image as well as the range of sizes at which you will be able to use it in printing projects.


Formats Defined

Camera Raw: A format offered by some digital cameras. Stores raw, unprocessed data without applying normal adjustments to sharpness, color, and exposure. Gives photographers ultimate control over images and editing flexibility, but files must be converted to a standard format before sharing online, printing, or viewing in most photo programs.

JPEG: The most popular digital photography image format. JPEG compresses images to make files significantly smaller, but too much compression reduces image quality. Used for print, the web, and email.

TIFF: The leading format for files that will be used in print publications such as newsletters and magazines. Preserves all image data but usually results in larger file sizes than JPEG and can’t be displayed by web browsers and email programs.

ISO Settings Defined

ISO (International Standards Organization) Settings: On digital cameras, ISO settings control how sensitive an image sensor is to light. The higher the ISO, the less light you need to capture a photo. Beware: an ISO set too high may result in an image with “noise,” or a speckled defect.

Image Resolution Defined

Pixels: Pictures are made up of little squares called pixels. Pixel stands for PICture ELement.

Megapixel = One million pixels: A megapixel is one million pixels. A camera with a small megapixel rating (say 1 or 2 mp) will produce photos that lack detail. Photos from a 6- or 7-mp camera are generally considered acceptable for large prints.

PPI (Pixels Per Square Inch): The number of pixels per inch in your image. Pixel count is simply multiplying the number of horizontal pixels by the number of vertical pixels. If you do not have enough pixels per inch (ppi) in your image, it will appear blurry. See the chart below for pixel counts needed for quality photos.

Max Print Size Minimum Pixels Needed
4" X 6" 2 megapixels
5" X 7" 3 megapixels
8" X 10" 5 megapixels
11" X 14" 6 megapixels
16" X 20" 8+ megapixels

DPI (Dots Per Square Inch): Color photographs are printed using four inks: cyan (blue), magenta, yellow, and black (CMYK), and four separate dot patterns, one for each ink. Dots per square inch (dpi) refers to printed dots and the space between them. Digital cameras primarily use the RGB (red, green, blue) color space but four-color printing presses use CMYK. So to print on a four-color printing press, all RGB images need to be converted to CMYK. For digital production, RGB is used.

Frequently Asked Questions

Why Is a 300 dpi Image Needed for Print Publications? When a digital image is prepared for reproduction on a printing press, pixels are converted to dots. Dots have spaces between them. 300 pixels become 150 dots and spaces, so 300 dpi becomes roughly 150 dpi. 150 dpi is the accepted standard for printing photographic quality images. Digital images with a dpi lower than 300 will print as poor quality, jagged, pixelated images.

Why Is a 72 ppi Image Used for Web and Email? A computer monitor outputs at 72 ppi. Using a higher-sized ppi image will not look any better and will take longer to download.

How Do You Determine the Resolution of an Image and How Well It Will Print? The term “image resolution” refers to how many of your image’s pixels will fit inside each inch of paper when printed. Image resolution pertains to printing your image but has nothing to do with how your image appears on your computer screen. This is why images you download off the internet usually appear much larger and of higher quality on your screen than they do when you print them.

Images should have a print resolution of 300 ppi at their final size in the file. Resolution and image size are inversely proportional to each other. In other words, enlarging an image will decrease the resolution, and shrinking an image will increase the resolution. To determine resolution from pixel dimensions, divide pixel width and height by 300 to determine the maximum size at which you will be able to use the image, while maintaining a quality resolution of 300 dpi.

Example:
If an image is 1200 pixels x 1600 pixels, 1200/300 = 4, and 1600/300 = 5.33.
The maximum usable dimension for the image is 4" x 5.33". It will print crisply and clearly at this size or smaller.

To view your pixel count, open the image in:

  • (Mac and PC) Photoshop
  • (Mac) iphoto, Preview
  • (PC) Windows Picture Viewer

Photoshop Example:
Open the image in Photoshop. Go to the Image menu at the top of the screen and choose Image Size, which brings up the Image Size dialog box (see below). The Image Size dialog box is divided into two main sections, Pixel Dimensions at the top and Document Size directly below. The Pixel Dimensions section tells you how many pixels are in the image. The Document Size section with resolution set to 300 tells you how large the image will appear on paper if printed.

Image size window sample