Tutorial - What happens when you edit a jpeg:
Why it's best to start with
a format that the compression does not effect the images quality, and save in more than one format
In the following table, the image was saved as a jpeg. Then one area (shown
in the green box) was used to illustrate what happens. Always remember, that
a picture/image saved in jpeg losses quality, and won't give the best results.
When the image was later reloaded and re-saved as a jpeg, it got less and
less clear. This is a problem that you can avoid by starting with an image that
has not been jpeg compressed and by saving your work in a format that is a
does not lose image quality when saved--such as-bitmap or tif--
(though you may want to save a second way, as a jpeg, if you are going to need a
smaller file size, a copy for a website or to send via email).
Note that every time the section in green was copied and resaved the jpeg
compression blurs the pixels that are near any change of color.
Orginal Image
|
Orginal Image saved as jpeg0
|
Jpeg0 loaded and saved as jpeg1
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Jpeg1 loaded and saved as jpeg2
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Jpeg2 loaded and saved as jpeg3
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Jpeg3 loaded and saved as jpeg4
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Jpeg4 loaded and saved as jpeg5
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Jpeg5 loaded and saved as jpeg6
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Another way to say this is: When using/editing an image, alway start with an
image that is in a format that does not lose image quality
when the image is saved. Only save the final result as a jpeg, but always save a
copy of the image as a bitmap, tif or other image format that does not drop
pixels before saving as a jpeg.
If starting with a jpeg do not save back to the orginal jpeg, as then you
have reduced the quality of your orginal if you have to go back and edit again.
Printing images/pictures
When printing images, the minimum resolution should be 150 dpi, for example
a digital photo that is 1280x960 will usually print with acceptable results
up to 8.5x6.4 inches. I personally try to have a resolution of 200 dpi or
more, which for the 1280x960 would print a nice 4x6 inch image.
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