Picture Perfect

Understanding digital image files is the key to producing high-quality photos.

By David C. Mayo, CCIM

In today's electronic world, commercial real estate professionals are exposed to digital photography daily, and many of us frequently use digital images in our businesses. Understanding digital photo production is the first step to creating visually appealing marketing materials and Web sites.

Digital image production involves capturing the original image via scanner or camera, storing images in picture file formats, and outputting images either for Internet or print use. To produce images successfully, you must use the correct resolution and file format for the photo's ultimate use.

These guidelines can help you create professional-looking digital images, whether you place them on your Web site or print them on photo-quality paper.

Deciphering the Lingo
A digital image is a file comprising hundreds and even thousands of pixels. A pixel is the smallest picture element of a digital image, and image resolution is the number of pixels per inch, or PPI. Larger PPI numbers indicate more detail, which correlates to better image quality. Simply put, to have crisp, clear images, set your camera or scanner to the highest-possible resolution because you always can reduce a digital image's size to match the intended use, but you cannot increase its resolution without losing clarity.

Most digital cameras automatically save images in the joint photographic experts group, or JPEG, file format. Widely used for images and illustrations with complex shading and coloration, JPEG is the optimal format for the Internet because every Web browser recognizes and supports it.

The JPEG file format compresses images after they are taken, which allows faster downloads and saves storage space. When opened, a JPEG file returns to the image's original dimensions. However, each time a JPEG image is opened and closed it loses varying amounts of data, thus reducing image quality over time.

On the other hand, when tagged image file format, or TIFF, images are opened and closed, they are mathematically and visually identical to the originals. TIFF files commonly are used in print publishing, Internet-based faxing services, 3-D applications, and medical-imaging applications.

Most professional photographers prefer the raw file format because it stores only the raw image data, allowing later color processing, tonal and exposure correction, and image sharpening without compression's constraints. Raw files are the digital equivalent of undeveloped film negatives. However, raw files are not universally supported on the Internet, and each camera manufacturer's raw format is different.

Digital Image Production
You must consider the resolution when capturing and outputting digital image files. The two resolution aspects to consider are spatial and brightness.

Spatial resolution refers to the number of pixels in an image file. You would have to magnify a high-resolution image to see its pixels; however, it may be possible to see individual pixels in low-resolution images, which appear jagged or grainy.

Brightness resolution refers to the number of brightness levels that can be recorded in a pixel; a higher brightness resolution means a greater number of levels. When you print a photo, the brightness information is used to determine the number, size, and color of the inkjet printers' dots of ink or the color and amount of laser printers' toner that is laid down on the paper.

All digital images, regardless of format, ultimately are resolution dependent, and the number of pixels limits an image's quality, as well as the printed image size. A relationship also exists between the captured image's resolution and the output device's resolution. For instance, a computer screen can display far fewer dots per inch, or DPI, than a photo-quality inkjet or laser printer can print.

So how do you know the resolution at which to capture your original image to achieve quality output results? Let's use a photo-quality inkjet printer as an example. The table shows two output resolution ranges and the associated DPI. You do not need the same resolution in your original digital image as the resolution of your printed photo. The table assumes that 200 PPI is adequate for good quality and 300 PPI is required for high quality. Using these figures, the table shows the total number of pixels required for four standard-size printed photos.

Your camera's specifications come into play here. With a 2-megapixel camera, a photo taken at maximum resolution is about 2 million pixels, or about 1,200 pixels by 1,600 pixels, which enables you to print a good-quality photo at 5 inches by 7 inches or a high-quality photo at 4 inches by 5 inches maximum. If you intend to print good-quality 8-by-10 photos, you would need a 3-megapixel camera with about 1,536 pixels by 2,048 pixels. A 5-megapixel camera at 1,944 pixels by 2,592 pixels can produce high-quality 8-by-10 photos.

It is nearly impossible to preserve an image's quality when increasing it beyond a pixel-imposed size limitation. A good rule of thumb is to always capture photos at your camera or scanner's highest available resolution.

If you are looking for a new digital camera, evaluate models that will achieve high-quality images for your various marketing needs. Many new point-and-shoot digital cameras have 5 megapixels; professional digital SLR models offer as many as 18 megapixels. However, most commercial real estate professionals can produce excellent photo-based materials with a 3-megapixel digital camera.

For more information on digital photos, visit Hewlett-Packard's Digital Photography Center at h30015.www3.hp. com/hp_dpc/home/home.asp or Kodak's Digital Learning Center at www.kodak.com/US/en/digital/dlc/index.

David C. Mayo, CCIM, is principal of Vector Realty Advisors, a national real estate consulting company in Louisville, Ky. Contact him at (502) 657-6444 or dmayo@ccim.net.