So What are Megapixels?

Start shopping for a digital still camera and you'll be bombarded with megapixels. If you listen to most salespeople, you'll be misled as to what megapixels really are and just how many are needed. You'll need to understand megapixels so you can make smart shooting decisions or instruct those that are acquiring images for your project. A megapixel is a unit of storage and describes the total number of pixels in an image.

In the strictest sense, a megapixel is one million pixels. This is a very common term used to desribe just how many pixels a particular camera can capture with its sensors. For example, if a camera can capture pictures at 3872x2584, it is referred to having 10 megapixels (3872 x 2584 = 10,005,248). If you were to print that picture on paper at 300 ppi (pixels per inch), it would roughly be a 13" x 8.5" print.

How many megapixels do you need for video? It all depends on how the pixels are meant to be used. If you plan to do a large zoom or just reposition the photo, all 10 megapixels may be needed. On the other hand, a 1920x1080 HD video frame needs only a 2.1-megapixel camera to capture the minimum required pixels.

Looking for an easy-to-use megapixel calculator? I highly recommend

Print Resolution

In print, using too low of a resolution results in pixelization— output with large, rough-looking pixels. Using too high a resolution image increases processing time and storage requirements and slows the output. Video and print pros have very different definitions of full size and high quality.

If you translate a 648X486 television screen into inches, it would be approximately 9X6.75 inches. At 72 ppi, the file size is approximately 900 kilobytes. If you asked a print professional for the same size image at high quality, you would likely get a file in the range of 4 to 60 megabytes. This is because print professionals often use resolutions of 150 to 600 ppi, depending upon output requirements.

Be sure to specify image resolution when working with outside artists and clients, or you will spend a lot of wasted time down-sampling images. Print-ready images will quickly eat up your disk space and are difficult to transport electronically due to their large size. Filters and image adjustments take longer on large images, especially if you are used to video or Web work. The only advantage to this extra information is that you can have more control over cropping and scaling of the final photo. Unless I plan on doing dramatic moves on an image in After Effects, I request outside artists to provide me with images at 200 ppi for standard-definition video; this involves the least work for all parties.

Copyright: Jami Garrison/iStockphoto

Copyright: Guy Erwood/iStockphoto

To access the PNG-24 format, choose File> Save for Web. This great format can store transparency with no need to manually create an alpha channel. Check your NLE or compositing application to see if a PNG file will work.

Web Formats are Great...

i^—. Web formats are great... 1 * \ for the Internet! Don't use

JPEG, GIF, or PNG in your video projects. If you have to use a Web format, choose PNG-24. It is the most versatile of all the Web formats and even supports transparency.

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Web Resolution

High-resolution images won't always be your problem, though. With the proliferation of image-rich Web sites, clients are often providing artwork directly from Web sites. While this is a convenient way to find things, it offers many problems. Web images are a low-resolution medium. While Photoshop builds Web and video images at 72 ppi by default, it is rare to find full-screen Web graphics, due to download times. Larger images tend to be sliced up as well, making it difficult to reformat them for video. The worst problem, however, is compression. Web graphics generally employ three file types: GIF, JPEG, and PNG. These compression schemes discard information; especially color detail, to achieve smaller file size. The Graphics Interchange Format (GIF) is most commonly used to display indexed-color graphics. Indexed color supports only 256 colors and should never be used for video source material.

The Joint Photographic Experts Group (JPEG) format is extremely common. It can be found in Web pages and digital cameras. Most Web images are highly compressed and do not hold up well when reformatted for video. Digital cameras that use at least a 2.1-megapixel system and are set to high or fine quality can produce acceptable results. Be careful when working with JPEGs; they may be set to CMYK or grayscale color modes. It is necessary to convert these to RGB before using them in a video program, or unpredictable color changes may occur.

The least likely format you may encounter on the Web is PNG. The Portable Network Graphics (PNG) format can be used for lossless compression and for display of images on the World Wide Web. There are two varieties of PNG, 8-bit (PNG-8) and 24-bit (PNG-24). These two formats support RGB, indexed color, and grayscale modes, as well as interlacing. Of all the Web formats, the PNG-24 is most desirable (least awful) for video purposes. The file size of a PNG file is significantly larger than GIF or JPEG. This will give you more information to work with. PNG files are very uncommon because older Web browsers do not support them and the large file size deters many Web designers.

Avoid Web graphics at all costs. Both you and the client will be very disappointed with the results when using a Web-ready graphic. If clients insist that the Web-ready format is all that's available, dig deeper. Ask them for a business card. If their logo is on that card, then it must exist in a print-ready format (somewhere). Ask who designs the cards or how they get additional cards at work. After a phone call or two, you will have the appropriate .eps or .ai file.

Digital Cameras For Beginners

Digital Cameras For Beginners

Although we usually tend to think of the digital camera as the best thing since sliced bread, there are both pros and cons with its use. Nothing is available on the market that does not have both a good and a bad side, but the key is to weigh the good against the bad in order to come up with the best of both worlds.

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