Whether you are creating a brochure, a fine-art print on watercolor paper, a web page or a PowerPoint presentation, a variety of image display options are available to you as a digital photographer. Yet before your image is ready for display, there are many technical considerations to understand to make sure that the intended audience views the intended image.

Digital cameras capture images in RAW, TIFF, JPEG and a variety of other proprietary formats that determine an image’s quality and file size. So-called “lossless” formats compress files without the loss of data, while “lossy” formats discard redundant data. Images that are destined for digital display are typically saved at 72 pixels per inch and sized to fit within a computer monitor’s average screen resolution, which is now 600 x 800 pixels. Images destined for print are saved at up to 300 pixels per inch, or 1.5 times the final printed screen resolution (133-line screen x 1.5 = 200 pixels per inch).

TIFFs, JPEGs & RAWs

TIFF (lossless) and JPEG (lossy) are two of the most common formats and typically are displayed through different media. TIFF is used in print, a high-resolution medium, and JPEG in digital, a screen-resolution medium. TIFF and JPEG can be quickly formatted in image editors for a specific output, while RAW and proprietary image formats need to be processed before they reach the editing stage.

Digital image display has always been a balancing act of image quality vs. image size vs. the bandwidth needed to deliver the image to the intended audience. Consideration of the viewing audience is addressed by choosing the right image size or image format and optimizing the image for the intended medium.

The type of network connection and related bandwidth dictate the type, size and quality of digitally displayed images. Within a network, bandwidth is defined as the capacity (measured in bits per second) of a network medium, such as copper wire, cable, fiber-optic or wireless transmitters.

Before the advent of broadband Internet connections, such as DSL and cable modems, superior image quality had always meant larger image size and slower image transfer. An upside to this dilemma has been that low-resolution images are hard to reproduce in print and can be easily watermarked to thwart image pirates. The downside is that photographers and their audiences are usually interested in image detail, which is an inherent feature of high-resolution photography.

The JPEG image format is ubiquitous when it comes to digital image display for any Internet bandwidth connection. Created as a standard for digital image transport, JPEG can be compressed to the desired size and degree of image quality needed. JPEGs are created within image editing software, such as Adobe Photoshop or Microsoft Paint, and displayed within any Internet browser or multimedia presentation program.

Not all of the data within the JPEG format is actually needed to display the image, which is why JPEG is called a lossy format. Recurring information, such as similar tones in a blue sky, is discarded during the compression process. When creating images for the web, JPEG is the lowest common denominator and is usually considered first because the majority of Internet connections are made through a 56 Kb modem. Higher-resolution images can be offered via additional links for those with larger bandwidth connections.

Next generation

While high-resolution image capture is the preferable method for shooting digital photographs, historically it has not always been the best method for printing a digital image — until now. New alternatives to the JPEG format are entering the market in the form of high-resolution image viewing modules.

Both the MGI Zoom Server and LizardTech MrSid require specific server software to function and really are geared toward large organizations, such as stock agencies or content providers who operate their own web servers and the accompanying high-res server software. Zoomifyer Pro, however, can function on any web server and does not need specific server software to display its images. It is used by photographers and larger content providers alike. Each technology offers both image-authoring and image-viewing technology. (See “Web Links” below.)

The photographer who understands and knows how to manipulate image file size, file type and image resolution can now consider a variety of methods for the display of digital images. The proliferation of high-speed network connectivity has expedited the production process and opened up new opportunities to studio and location photographers. Further technological advances will only increase transmission speeds through greater bandwidth and expand the geographical range of network connectivity, which will speed the images to their intended audiences even faster.

When an image is being transferred over a network, the file size is directly related to the elapsed time needed to deliver the image. Depending on the network media, transfer rates vary in speed and availability. The transfer rate is described in either kilobits per second (Kbs = 1,000 bits per second) or megabits per second (Mbs = 1 million bits per second). Remember that there are 8 bits in a byte, 1,024 bytes in a kilobyte and 1,048,576 bytes in a megabyte. Additional factors that slow the transfer rate include latency or delay in the network and slow processor speed of the CPU on either the sending or receiving end.

Dial-up: The original method of connecting to the Internet with a modem. Still very popular and used extensively where broadband connectivity is not available. Transfer rates of 9-56 Kbs.

Satellite: For rural or remote internet connectivity. 500 Kbs download with 56 Kbs upload.

Dedicated Service Line (DSL): Installed over existing copper telephone lines with the addition (by your local phone company) of a voice/data splitter. This “always-on” dedicated network must be located within two miles of a telephone company switch. Data transfer of 128 Kbs up to 1.5 Mbs.

Cable Modem: Cable modems share bandwidth with other local users, and transfer rates can vary depending on other local usage. Download speeds are between 500 Kbs and 2 Mbs.

T-1: Used in corporate environments; can be configured to carry voice or data and support a 1.54 Mbs data rate.

Wireless networks: Based on the 802.11 network standard, 802.11b or WiFi, this is an increasingly popular high-data-rate standard used in homes, businesses and shared public networks. 802.11b network broadcasts transmit up to 11 Mbs, but are limited to a 100-meter range.

Web Links

Roxio/MGI Software (MGI Zoom Server) www.mgisoft.com

The Minneapolis Institute of Art www.artsmia.org/modernism/eintro.html

LizardTech MrSid Software www.lizardtech.com

Library of Congress lcweb2.loc.gov/ammem/pmhtml/panhome.html

Zoomifyer Pro www.zoomify.com