Resizing Images - Basic
A few things you need to know
Pixel (picture element)
– A pixel (px) is a single
point in a raster image,
or the smallest addressable
screen element in a display
device; it is the smallest unit
of a picture that can be
represented or controlled
– 1,000,000 pixels = 1 Megapixel (MP)
(A raster graphics image, or bitmap, is a data structure
representing a generally rectangular grid of pixels. Raster
images are stored in image files with varying formats,
i.e. JPEG, TIFF )
Resolution Resolution
• Resolution properly, refers to the pixel density. “Display
resolution” is something else – it is the digital dimensions,
the actual number of distinct pixels your screen can display,
from left to right and from top to bottom.
• Pixel density (resolution) affects only one thing - the size of
the image when it's printed. By setting the resolution we
tell the printer, not the screen, how many of the pixels in
the image to squeeze into an inch of paper. It is noted in
pixels per inch (ppi).
• By setting the “image dimensions” we set the size of the
image. For web or screen, usually in pixels i.e. 1024px wide
by 680px high.
Viewing Images on a screen
• The size at which an image appears on your screen depends only on two
things - the pixel dimensions of the image and the display resolution of
your screen.
• The native or display resolution of a display device is the number of
distinct pixels in each dimension that can be displayed. Typical sizes are
2560 x 1440, 1920x1080, 1366x768, 1280x1024, 1280x800, 1024x768 and
800x600
• Images will be displayed pixel-for-pixel. In other words, each pixel in the
image will take up exactly one pixel on your screen. For example, a
640x480 pixel image would fill a 640x480 pixel area of your screen. No
more, no less. No matter what you set the image's (pixel density)
resolution to, whether it's 72 ppi, 300 ppi or 3000 ppi, it will have no effect
at all on how large or small the image appears on the screen.
• For best results, set your computer's display (monitor) “Properties”
(settings) to the native resolution of your monitor.
Viewer Programs
• When you open an image, in most cases, the program
(viewer program) automatically scales the image down
to fit the screen or window.
• As an example, 3000px by 2000px could size down to
something like 800px by 530px to fit the window on
the screen.
• The image will still look great because it is still being
displayed pixel by pixel.
• Viewing images this way may give you the impression
that the image is the correct size (pixel dimensions) for
displaying on a projector or on a web page. This may
not be the case.
Viewer Programs
Default Viewer Program
•
Windows Picture and Fax Viewer
• Usually, automatically “fits to
screen”
• Options to;
– View full size
– Rotate
• Will not necessarily open RAW files
– Web browsers
• Usually displays full size
•
•
MAC I Photo
MAC Preview
– Will open just about anything
– Preferences will set “scale to
window” and other options
•
Numerous free viewers
–
–
–
–
–
–
Gimp (Mac)
Seashore (Mac)
IfranView (PC)
ViewNX2 (Nikon)
RAW Viewer – CR-2 (Canon)
Windows RAW Viewer
Resizing for Digital Competition
Generally
You have selected an image that you want to submit.
You will need at least two versions, one for screen
(projector) one for print.
You should process the print version first. Keep in mind
that if you intend to mount it in a ‘standard’ picture
frame (i.e. 5x7, 8x10, 11x17) the aspect ratio
(height/width) will probably change from how it came
out of the camera and you may not want this same
aspect ratio for the competition entry.
You may need 2 or 3 versions of the same image.
Resizing for Digital Competition
• Workflow (from a copy of your original image which has been
processed for print) using any program you are comfortable with.
• Crop for best aspect ratio (club projector has been set to a 3:2 aspect
ratio – this is recommended, but not mandatory)
• Most digital SLR cameras are a 3:2 ratio and compact cameras
are 4:3. Many cameras now have the option to change the
aspect ratio before shooting)
• Set resolution (pixel density) to 100 ppi
• Resize (change the pixel dimensions) to 1920px by 1080px for landscape
and 1080px x 810px for portrait.
• Save as JPEG, if need be, compress to 1MB or less (usually one of the
‘save’ options)
Hints & Tips
Q
I have an image that is 640px x 580px. How big a print
can I make?
A True answer, as big as you want.
But, very quickly you will start to see "blocks"
(pixelization) and the quality will drop off
For printing you need at least 200ppi (pixel density
resolution), so the best print size for this image is 640÷
200 = 3.2inches by 580÷ 200= 2.4 inches
However, it will look great on the screen, a full 640px
wide by 580px high, likely 7 inches by 4.5 inches
Hints & Tips
Express workflow for PhotoShop
• Crop image to 3000px x 2000px (3:2 aspect ratio).
• Adjust as required, sharpen at end.
• Save as jpeg, set compression to give a file size of 8MB or
less.
• Then, click “Save for web and devices”, select jpeg, high
quality, size 1920px by 1080px, save with new file name
• This will give you two images, one suitable for printing (4x6,
or 8x12 or 12x18) and uploading for printing, and another
image suitable for digital competition submission and
email.
Hints & Tips
• If you want to Email a picture for someone to print, here is a rule of
thumb for the image size
Image Resolution (pixels)
Maximum Print Size (inches)
less than 640X480
Wallet size only
640X480
absolute largest, 4X6
1024X768
4X6
1152X864
5X7
1600X1200
8X10
• By doing the math, you can see that we have a minimum of 150200 pixels per inch (300 is better as long as you don’t have
upsample)
• Note that a lot of Internet providers will bounce emails with large
attachments, especially 10MB or larger
Hints & Tips
Best size for digital competitions, slide shows,
websites and presentations.
• These images do not need the same resolution (pixel density)
that is required for printing. 100ppi will suffice.
• Older monitors, projectors and the default for PowerPoint and
ProShow etc. is usually a 4:3 aspect ratio. (i.e. 1024px by
768px)
• Modern screens and projectors have an aspect ratio of 12:9
(i.e. 1366px768px)
• The club projector has a native (display) resolution 1600px by
1200px (12:9 aspect ratio), however the aspect ratio is
adjustable and is set at 3:2 (1920px by 1080px)
Hints & Tips
Upload to Costco and the Like for Printing
Costco now allows 8MB per image. Process your image
normally, simply make a JPEG compression of the file to
get to 8MB or less
FTP
Companies like PrintPartner who do things like 40”x30”
prints on canvas, need lots of pixels. They provide an FTP
(File Transfer Protocol) site and will take up to 40MB size
files (best to use .tif or .psd). You will need an FTP
program, user name and password for the site. (In
essence you upload directly to their hard drive)
Hints & Tips
• Good (free) Image Sizing Software
– Ifranview
– Fastone
– ViewNX (Nikon)
– Picasa