What's a Megapixel_

So many people have been asking which digital camera to buy, how many "megapixels" do I need, and "What's a megapixel_"
      You would need to read an entire book to get the real, in-depth answers to these questions, and after that you'd still be in a quandary about which camera to buy. I'm going to share some quick, simplified, rules of thumb for making your own decisions.

What's a pixel_

A megapixel is simply one million pixels. What's a pixel_ The technical definition takes several pages, so let's suffice to say a pixel is the single, square "picture element" among a grid of many others which captures and then represents that particular point of light the camera saw when you clicked the 'shutter' button. (Of course, digital cameras really don't have shutters in the traditional sense.)
      So, the megapixel measurement a camera obtains is calculated by the largest photo the camera can take -- calculated by taking number of pixels of photo width times the number of pixels of photo height. So, a 640 x 480 pixel photo is about a third of a megapixel. My Olympus camera is calculated at 2,240-by-1,680 resolution, racking up a whopping 3,763,200 pixels or 3.7 megapixels.

Pixels into perspective

I can see from the looks on faces that you're wondering what the heck is he talking about. Okay, we need just a little more math, then I'll bring this down to street level. As a reliable rule of thumb, there are roughly 72 pixels in an inch. (Don't believe what Microsoft tells you!) So if you were to lay that 3.7 megapixel photo out on a table it would measure to around 31 inches by 22 inches.
      In all manner of speaking the human eye begins to smooth out and disregard actual pixels in an image when seen at half size or smaller. So, now let's put these two factors together.
      A 3.3-megapixel digital (capture) photo camera should produce an 8 x 10-inch print that to the eye looks like continuous tone. (Photo prints from negatives are referred to as "Continuous tone" because you don't 'see' the grain that composes the image.) If the printer is good, and well tuned, then most likely you could print an acceptable 11 x 14-inch print as well. Under very close scrutiny, or with a magnifying glass you would be able to see the pixels, but generally you don't view 11 x 14 prints that close up.
      So the rule of thumb: divide the capture size by 50% for an "acceptable" print, and by 30% for a "near continuous tone" print, and by 25% for an exquisite continuous tone photo.

How do you want it_

The most important thing to remember is what you will most likely be using the camera for. Match the resolution of the camera to how the image will be reproduced.

Home and Hobby

For home and hobby use 2mpx cameras will produce wonderful 3 x 5 snapshots, and acceptable 5 x 7s. If you're handy at photoshop, and have a reasonably good ink jet printer using the highest quality photo papger you can squeeze and 8 x 10 out of 2mpx. 2mpx is fine for web use or an occasional on-screen (computer or TV) slide show.

Semi-Pro

For semi-pro use, a 3mpx would be required for producing 8 x 10 on up to 11 x 14 images on paper.

Professionals

The pro needs a minimum of 3mpx, and should get 4 to 5mpx for any larger work. 5mpx images will reproduce well at 20 x 24 size, and perhaps larger with the right image processing.

Calculate the required size

The key to making your images look good is matching the image size to how large it will be when it's output.
      Let's say you're working on a brochure and you want great looking photos. If the photo is to be 3 x 4 inches in the brochure, then a 2mpx digital shot is more than enough. Even if you wanted the full front cover 4 x 9 inches, the 2mpx would squeak by, where a 3mpx would be better.

The bottom line is what you like.

If you and your family enjoys looking at photo albums on the computer, or TV and aren't that worried about printing beyond special occassions, then a 2mpx camera should do just fine. A 3mpx camera will give that extra margin for those times when you do want a larger print, or you want to print a small cropped area of the photo.
      Most importantly, read your camera's documentation. There you'll learn how to capture jpg "snap shot" quality photos, or high-end professional quality "tif" files. The cameras are versatile, and in today's marketplace very capable and reasonably priced.
 

Until next time, happy mousing.
 

 

If you have tips, tricks or questions you'd like to add to "This Old Mouse" just let me know.   Macintosh User Groups are invited to use this column in their newsletters, but Please read the "Read Me" first, okay!

About the Author:
      Fred Showker is Editor in Chief of "MUG" the AACUG Mac User Guide, and the User Group Network News service, and a founding Apple User Group Advisory Board (UGAB) member. He was an original founder of the User Group Forum on AppleLink Personal Edition, and America Online where he was AFA for eight years. Many MUG (Mac User Group) members know him for his work with the Mug News Service (MNS), National Home & School Mac (NHSM), or his many speaking appearances at NAUG, NAUGSAW and Macworld Expo and others. Today, he's a familiar name in many user group newsletters around the world for his 60-Second Window, now in its 13th year of syndication... read more

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