Having A Hard Time Trying to Define Megapixels?

The Answer is Just Around the Corner

Let me help you out: I'm going to define megapixels in a way that should clear up a lot of confusion.

Since the very first digital camera, this one term has been shrouded in mystery. It has been the defining feature on digital cameras for years and has been built up and hyped to no end.

The megapixel race has boiled down to a catch phrase: "more is better".

It makes sense why camera makers and retailers aren't falling over themselves to clearly define megapixels to consumers: a megapixel number makes it easy to compare two different cameras.

"Our camera has 10 megapixels while our competitor's only has 8. I'm sure you can tell which one is better."

And - surprise, surprise - the more megapixels it has, the more a camera costs. Of course a salesperson is going to tell you that a camera with more megapixels is going to take better photos.

But what are these megapixels really good for? In the following paragraphs, you'll find out.

In The Beginning

The foundation of megapixels is the lowly pixel.

A pixel is one dot of information in a digital photograph. Digital photos today are made up of millions of tiny dots (Mega = Million).

This means that a 3 megapixel image contains approximately 3 million pixels, while a 5 megapixel image contains 5 million pixels.

Here's some more math to help explain this: let's say that you've taken a landscape photo with a 3 and 8 megapixel camera.

The 3 megapixel photo is 2048 pixels wide and 1536 pixels high
The 8 megapixel photo is 3504 pixels wide and 2336 pixels high

If you take these numbers and multiply them, that is where the megapixel number comes from:

2048 x 1536 = 3,145,728 (3 million pixels or 3 megapixels)
3504 x 2336 = 8,185,344 (8 million pixels or 8 megapixels)

This is just the tip of the iceberg - there's a lot more information required to define megapixels.

Is More Better?

So a camera with more megapixels takes clearer photos right?

After all, if one camera is capturing 5 million pixels and another is only getting 3, then the photo with 5 million pixels should look better.

Not exactly.

While a digital photo that contains 5 million pixels is larger than one with only 3 million, at small sizes they are hard to tell apart.

Take a look at the two sample photos to the right. Can you tell which one is 3 megapixels and which one is 8?

I doubt it - if you can then you are one of the few who absolutely needs a camera with more megapixels.

If you're like most folks, you won't be able to tell the difference until you click on these photos and view the full-size images.

You'll notice two things: one, the 8 megapixel photo is significantly larger than the one with only 3.

Second, the 8 megapixel photo takes longer to download - it contains more information that the 3 megapixel photo, which results in a larger file size.

This means the following for photos that contain a lot of pixels:

It takes longer to transfer them from camera to computer
You need more hard drive space to store them
You need a more powerful computer to view and edit them

If more megapixels take up so much more space and there is no difference in image quality then what's the point of mega-megapixel cameras?

Large Print Sizes

First, the most obvious advantage: you can print photos with more megapixels at large sizes.

Let me define this another way: if you print an 8 megapixel photo and a 3 megapixel photo at 4x6 inches (standard print size) you'll be hard-pressed to tell which one is which (just like when you compared the small images above).

But if you print both photos at 12x18, you will see a difference in quality.

The 3 megapixel photo won't look as clear and as sharp as the 8 megapixel photo when printed at this large size.

This table shows you the most common acceptable print sizes based on the number of megapixels your camera has.

Number of Megapixels	Acceptable Print Size (Inches)
2.0	4 x 6 [standard]
3.0	5 x 7
4.0	8 x 10
5.0	9 x 12
6.0	11 x 14
8.0	12 x 16
10.0	16 x 20
12.0	18 x 24

Here's how to read the megapixel print size table: if you have an 8 megapixel camera, any print that you make that is 12x16 or smaller will look fantastic.

If you have a 4 megapixel camera, you can make high-quality prints at 8x10 or smaller.

Now, there is nothing stopping you from printing your 4 megapixel photos at 20x30. You could even print your photos billboard size if you wanted to.

As you increase the print size more and more above the acceptable print size, the image deteriorates further and further.

A 4 megapixel photo printed at 4x6 will be perfectly clear. It will also be clear at 8x10. But a 4 megapixel photo printed at 12x18 will show a loss of image quality.The same image printed at 40x60 will show considerable loss of image quality.

If your goal in life is to make really large prints, then you want to get a camera with the most megapixels you're able to afford.

If you enjoy using your digital camera to send photos to friends and to print 4x6 photos, then spending a lot of money on a 10 megapixel camera is just a waste.

More Image Cropping Options

You can now define megapixels in one way: more of them lets you make larger prints.

There is a second benefit to having a lot of megapixels in your photos: it gives you freedom to crop.

Let's say that you've taken a photo with a 4 megapixel camera - you're able to make nice 8x10 prints with this.

You take a photo of an egret, but you're too far away from the bird, and you don't have enough of a zoom lens to get up close and personal.

The primary subject of your photo is tiny. You decide to crop the shot so that the egret is larger.

No problem...except that you can no longer print at 8x10.

You need 4 megapixels to print at 8x10 before the image starts to deteriorate. When you crop the image, you are eliminating pixels - let's say that you crop out 1.5 megapixels from your photo.

You wind up with a 2.5 megapixel photo - you can make a nice 4x6 print, but that's about it.

Now imagine that you take the same shot with an 8 megapixel camera.

With this shot, you can crop out a full 50% of the image (4 megapixels) and still make a high-quality 8x10 print.

But be aware that cropping and adjusting your photos takes time. In fact, it takes a lot longer to edit photos than to take them in the first place.

If you're not inclined to spend a lot of time sitting in front of the computer cropping and adjusting your photos, then a camera with a huge number of megapixels doesn't provide you with a lot of advantage.

Summary

Let's finish up and conclusively define megapixels with a quick summary of the pros and cons of cameras chock-full of them.

Pros	Cons
Large size prints Cropping flexibility	Large file sizes Requires memory cards with high capacity Takes more time to transfer from camera to computer Fills up your hard drive faster Requires a more powerful computer to view and edit