Digital Picture Perfect

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Digital Picture Perfect

Have you ever wondered how to optimize your digital pictures for emailing? In this article Juan explains the ins and outs of the digital picture mysteries and shows you how to avoid common pitfalls when sharing your photos via email. This three part article takes you through the theory behind picture sizes, transfer methods, and creating manageable attachments.

Visual Size Vs. File Size

When emailing a picture, one must consider the size of the picture. Monitors render pictures on screen with a resolution of about 72 dots per inch (dpi). Pixels are the smallest visual representation of a dot. If an emailed picture will be viewed primarily on a monitor, and the acceptable viewing area of a picture is 4 by 6 inches, then the pixel size of the picture will be 4 x 72 by 6 x 72. Pardon the math but it's a must in order to understand this concept.

(4x72) x (6x72) = 288 x 432 which equals 124,416 pixels.

Now that we know how many pixels it takes to makeup our picture we are going to define the weight of each pixel. Are you still with me? In computers a bit is the smallest unit of information. A byte is composed of 8 bits. Each character (letter or number) is represented by a byte.

If you were to write a letter to your grandmother and spent 1000 alphanumerical characters (telling her how much you miss her and that you are looking forward to that special package at Christmas) your letter will consist of 1000 bytes or 1K. (At this point, this article has about 1500 characters or 1.5K - to give you an idea how much information 1K is.)

A Picture is Worth a Thousand Words

The 4x6 picture, on-the-other-hand, is made up of 124,416 pixels. If this picture is in gray scale, each pixel is be represented by one byte. So the picture will be a total of 124,416 bytes or 124.4K. That is one hundred and twenty-four thousand characters and the picture is not even in full color.

Lucky for us gray scale is only represented in 256 different shades of gray. Wait until we learn about full color. On a color picture, each pixel (new info) is composed of three different colors - red, blue, and green. Each color has a brightness level of 256 different shades. It takes one byte to represent each shade of red, blue and green. So our one-byte pixel is now three bytes big.

Back to the math:

(4x72) x (6x72) = 288 x 432 = 124,416 pixels TIMES 3 = 373,248.

The picture is now 373,248 bytes big or about 373K rounded to the nearest thousand. By now, you could have described the picture to your grandma 373 times in each of your 1000 word emails.

Review:

1000 Character email = 1K (approximately 250 words); one 4X6 Digital Photo in Black and White = 124K; and one 4X6 Digital Photo in Full Color = 373K