Work flow, why JPG, why resize ?
Printing digital photos for high quality, the
original size should be retained from the source (camera, scan, video
capture) and only image corrections applied. However, to view on the
web or email friends, the ‘raw’ image size is not needed and slows down
download time (it also makes people on dial up mad).
JPG files are a lossy compressed format. The image
has a built in compression scheme and every time you edit and re-save a
JPG you loose quality to the compression algorithm. It is best to always
keep your original JPG image and save the edits as a new file.
Here’s a good read:
Digital Image File Types Explained
Resizing photos for web use :
Using the image ‘RAW.JPG’ as an example, without
modifications. The physical file size is 1.6MB. This is pretty big to
email and unacceptable for viewing on the web. This is a great image to
print, as it will print a beautiful 11x17 natively (from a 6.4 mega
Note the dimensions in pixels and resolution (Dots
Per Inch - DPI) below. This is a screen shot of
Photoshop 7.0, I think all image editors have an option to resize
and will look similar.
Photoshop Elements 2.0 is a great tool for less then $100 and easy
Three things to make this a better (faster, smaller)
image to view on the computer or email friends.
Change resolution (pixels/inch or DPI) to 72
Change height and width (size)
Save as a JPG and choose a higher compression
(or not, to keep the compression artifacts less noticeable).
A good size for images to email is 800x600 or
1024x768 *max*. For use in a document (Word article) you can go with an
even smaller size. The images on the
Pictures link are
468x312 pixels and most of the image links on the
http://archive.downeastsoaring.org site are 1000 pixels wide (example).
Resizing the original RAW.JPG
1.6MB image to 800x533 pixels (533 tall to keep the aspect ratio) and
changing the resolution (or DPI) to 72, this new image,
800x533.jpg, is 185kb. This will never print a
quality 11x17 but is a great size to email or view on the web. Still too
big for a Word document however.
Saving the resized 800x533 image using a higher (I
used twice as much as ‘normal’ in this example) JPG compression results
in the image 800x533_hcompress.jpg
and a file size of 74kb! Wow, however looking at the new image, the
quality has suffered too much for my taste. How much compression to
apply to the final image depends on personal preference, and the
intended use of the image. Compression is usually an option when
choosing to save the image (File > Save As).
The image pasted below has been resized to
300x200pixels @ 72dpi is 37kb in size. Not super quality, but fast to
load and sufficient for this purpose.
Remember if you paste a picture in Word and resize it
inside of Word, you are not changing the physical size of the image,
only the scale the you have told Word to display it. Thus, you paste a
1MB JPG into Word, and resize it %75 to look good, you still have a 1MB
file embedded inside the Word document.