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
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
Inches @ 300 DPI ( numbers inside colored boxes are megapixels)
Megapixels vs. Maximum Print Size Chart
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"