Before you transmit that digital image, are you using the right file format?
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.
Products like the MGI Zoom Server, LizardTech MrSid Image Server and Zoomify Zoomifyer Pro offer the ability to view high-res images through practically any Internet connection. These display technologies offer features including zoom in and out, pan throughout the image and, above all, image detail. Images can range in size from a few megabytes to several gigabytes in size. This is made possible by proprietary technologies within each product that send only the requested distinct groups of pixels to the viewer requesting the image through a web page.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”)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.
