PNG ten times as big as JPG

Asked by Michaël Van Dorpe on 2009-12-19

When scanning a picture and saving, simple-scan defaults to jpegs.

However, in the file picker dialog, one can also enter for example "foo.png" as filename.

The result with my scanner is that the resuling file is about 10MB, ie about 10 times as big as saving to JPG.

I don't know much about these file types, and what type I should use, and what file sizes to expect, but this looks odd to me.

Question information

Language:
English Edit question
Status:
Solved
For:
Simple Scan Edit question
Assignee:
No assignee Edit question
Solved by:
Robert Ancell
Solved:
2009-12-20
Last query:
2009-12-20
Last reply:
2009-12-20

This question was originally filed as bug #498438.

Robert Ancell (robert-ancell) said : #1

This is completely expected - JPEG achieves small sizes by throwing away data that you wouldn't notice (like an MP3 file). In contrast PNG contains all the image data, the noise from the sensors, the grain of the paper, ... - this is a lot of data!

As you wont notice the missing data it defaults to JPEG (as does your camera).

If you want the raw scan data then you would save as PNG (this is like a photographer using the RAW format from their camera).

Best Robert Ancell (robert-ancell) said : #2

This is completely expected - JPEG achieves small sizes by throwing away data that you wouldn't notice (like an MP3 file). In contrast PNG contains all the image data, the noise from the sensors, the grain of the paper, ... - this is a lot of data!

As you wont notice the missing data it defaults to JPEG (as does your camera).

If you want the raw scan data then you would save as PNG (this is like a photographer using the RAW format from their camera).

Thanks Robert Ancell, that solved my question.

Bryce Nesbitt (bryce2) said : #4

For a line drawing, the PNG may well be smaller than the JPG.
For a photo the JPG wins hands-down in most cases.