Small file size when savinga an image as JPEG

[idomanu]

Hi.
I tried scanning the same 35mm slide using SilverFast and Epson Scan, the software that came with my Epson V750 Pro scanner. I scanned them at the same resolution and size, but when i saved them as JPEG, the Epson Scan image file was twice as big as the SilverFast.
What is the reason for that? i played with the diferent settings in SilverFast(Q Factor and different JPEG formats), but the file was still dramatically smaller then the one i got using Epson Scan.

is there less data in the file from SilverFast then in the one using Epson Scan? why is that?

i'll be very happy if someone could help me understand what's happening...
thanks!

[LSI_Ketelhohn]

Dear idomanu,

JPG is a compressed file format.
Size depends on the chosen settings for this file format and mainly depends on the chosen compression algorithm and quality.
Uncompressed files are only possible using the TIFF format.

kind regards,
Arne Ketelhohn.

[toddinpal]

Is there any way to increase the quality of JPEG files? Using other tools, I can convert a hires TIFF 349MB file into JPEG files ranging from 50KB to 18MB. I would think for a starting raw file size of 44MB I ought to be able to save that as a 8MB JPEG.

Regards,
Todd

[LSI_Ketelhohn]

Dear Todd,

If you want high quality compressed images you need to use a lossless compression like jp2 (JPG2000).
This however is a professional file format which can not be read by all applications.

Otherwise smaller files always means lower quality.
The final compression rate also greatly depends on the image content.
Some images (with a lot of homogenous areas) can be compressed better than other images.

kind regards,
Arne Ketelhohn.