Re: What format for save-as on a scanned photo?

[Scott Klement <pctech@xxxxxxxxxxxxxxxx>]

> What format for save-as on a scanned photo?
>
> What format gives the best quality of scanned & saved image?

A few considerations related to image quality:

WHY NOT JPEG?

The JPEG format has a "lossy" compression scheme.  That means that it 
actually drops details from the picture as part of it's compression of the 
data, causing poorer image quality.

The lossy compression in JPEG is designed for photographs (as opposed to 
line art, or cartoons, or other image types where you might have 
relatively few colors and crisp, well-defined lines.)  So it's not as bad 
with photographs as it could be with other types of scans.

This lossy compression can be turned off (it's an optional feature of the 
format) if your software supports the disabling of it.  However, most 
graphic design people prefer to use a different format for their master 
copies to avoid the potential for the loss.

Then, when deploying to a web site or other means of distribution where a 
smaller-sized image is preferred, the master picture would simply be 
converted to JPEG.  That way, the compression is only done once.


KEEP THE COLORS HIGH

A few older image formats (Grayscale BMP, GIF format, etc) are limited in 
the number of colors they support. Reducing the number of colors will 
drastically reduce the quality of your picture, but will make them take up 
less space.

For the master copy of your images, it's best to use a format that allows 
a high number of colors.  Modern BMP/DIB format allows for 24bit colors, 
as do PNG, TIFF, and JPEG.   However, some people will avoid DIB/BMP 
because of the historical 8-bit (256 color) limitation.


My experience is that the main two formats to avoid are GIF and JPEG 
(JPG). Other than those, all of the raster image formats basically work 
the same.  There's really no advantage to GIF anymore, anyway... PNG has 
all but replaced it.

JPEG is still great when you need lossy compression to get a very small 
image size without reducing the number of colors.  But shouldn't be used 
for the "master" copy, only for the finished product.