Megapixels

Intro

• When you are going to purchase a camera, two very important questions should be asked:

First Question• First will it be a point and shoot or an SLR?

What the heck are megapixels?• Second how many megapixels is this

camera?

Objectives• Learn what Megapixels are.

• How Megapixels relate to maximum print sizes.

• What DPI and PPI are.

• How to figure out the maximum print size based on the pictures resolution.

• What is resolution and how is it calculated.

• How to calculate an area.

Why is this useful?• A Camera is a tool; use the right tool for the

job.

• Making an educated decision about what camera to purchase.

• If you have a picture you will know exactly how large you can print it without losing quality.

What is a Megapixel?• A Megapixel is 1 million pixels• Pictures are made up of little dots

called pixels.• Pixel stands for PICture Element• They are arranged horizontally and

vertically

How are megapixels calculated?

• Multiply the number of horizontal pixels by the number of vertical pixels. It is exactly like calculating area.

• A 3MP ( megapixel) camera has 2,048 horizontal pixels and 1,536 vertical pixels, for a total of 3,145,728 pixels. We would simply call this a 3 MP camera.

Find an unknown dimension• Example 35=7Y

• 7 X 5 is 35 so we divide 35 by 7 which equals 5.

• 24=8Y

• 32=Y – 4

• 12=Y + 9

• Bonus 3Y + 8=20

Answers to examples

• 24=8Y Y=6

• 32=Y – 4 Y=36

• 12=Y + 9 Y=4

• Bonus 3Y + 8=20 Y=4

Find the Megapixels• Find the Megapixels for the following pictures:• 4300X2600• 3228X2300• 2300X1800

A Picture is 12 MP, it’s length is 5300 what is it’s width?

• Remember to round the number to the nearest million.

Answers

• 4300 X 2600= 11,180,000 or 11MP

• 3228 X 2300= 7,424,400 or 7MP

• 2300 X 1800= 4,140,000 or 4MP

• 5300 X 2,264 for 12MP

Bonus• You can use this same idea to find the total

square footage of an area.53’

26’

Find the total square footage

Bonus• Answer

53’

26’ 1378’

Part 2

Resolution• Resolution is basically your total

pixel count• If the pixel count ( or resolution) is

small, the image quality is poor.•

What is the difference between dots per inch and pixels per inch????

• PPI refers to the square pixels in a digital image, with NO spaces between them.

• DPI refers to printed dots AND the spaces between them.

PPI DPI

Printing• When printing on paper, resolution is

also how many pixels you have per inch.

• This is the image resolution and has nothing to do with the technology by which the print is made. (Inkjet, Laser)

• Adding or taking away pixels is called resampling, and can cause loss of quality

Printing• 150 DPI ( 300 PPI) is the accepted

standard for printing photographic quality images.

• Printers usually refer to the number of rows or lines per inch (LPI)

• 150 LPI is simply 150 rows of 150 Dots Per Inch

• When a digital image is prepared to print, pixels are converted to dots.

• Dots have spaces between them. 300 pixels becomes 150 dots AND spaces, so 300 PPI becomes roughly 150 DPI.

More Pixels = Better Quality

• 72-ppi and 300-ppi images; inset zoom 200%

• PPI is used to describe how densely the pixels that make up an image are packed within a span of an inch.

Are all cameras equal?• Even if two cameras have the same

number of pixels, it does not always mean that the size of their pixels are also equal.

• If an SLR camera has a greater “digital Sensor area” than a compact camera, then each pixel from the SLR will be larger in size than each pixel from the compact camera

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So Why do we care how big the pixels are in size?

• A larger pixel has more light-gathering area, causing the individual pixels to be further apart, making it easier to control image noise and tonal distribution. 

• The image will be smoother and more detailed

How do you know how large you can print your photo for maximum

quality?• You take photos of your sister’s wedding. You

have an 8 megapixel camera. This is 8,000,000 pixels

• Your resolution is 3264 x 2488• If you have 300 PPI, you will divide 3264 by 300

and 2488 by 300 • You get 10.88 x 8.29. So the biggest photo you

would want to print for maximum quality is 10 x 8

Here is a chart to help you

(numbers inside colored boxes are megapixels)

                                                                                                             Inches @ 300 DPI ( numbers inside colored boxes are megapixels)

Megapixels Pixel Resolution*Print Size @ 300ppi

Print size @ 200ppi

Print size @ 150ppi**

3 2048 x 1536 6.82" x 5.12" 10.24" x 7.68" 13.65" x 10.24"

4 2464 x 1632 8.21" x 5.44" 12.32" x 8.16" 16.42" x 10.88"

6 3008 x 2000 10.02" x 6.67" 15.04" x 10.00" 20.05" x 13.34"

8 3264 x 2448 10.88" x 8.16" 16.32" x 12.24" 21.76" x 16.32"

10 3872 x 2592 12.91" x 8.64" 19.36" x 12.96" 25.81" x 17.28"

12 4290 x 2800 14.30" x 9.34" 21.45" x 14.00" 28.60" x 18.67"

16 4920 x 3264 16.40" x 10.88" 24.60" x 16.32" 32.80" x 21.76"

Megapixels vs. Maximum Print Size Chart