Saving jpgs

[Daz]

If I open a jpg, that I have downloaded from my camera, using Photo Editor
(or Paint Shop Pro or Aftershot), and then save it at best quality, to give
a photo with the original quality, the resulting file size is about four
times the original jpg size.

If I increase the compression, so that the file size is the same as the
original, then the quality is reduced.

Can anyone explain this phenomenon?

Daz

 

[Yves Alarie]

1. What kind of camera do you have?
2. What level of jpg compression do you use in your camera?

 

[Daz]

1. I have a Fuji S304.
2. All that I can find, from the manual, is that the picture format is JPEG,
Exif Ver.2.2. Does this tell you what compression my camera is using?

 

[Michael J. Mahon]

If I open a jpg, that I have downloaded from my camera, using Photo Editor
(or Paint Shop Pro or Aftershot), and then save it at best quality, to give
a photo with the original quality, the resulting file size is about four
times the original jpg size.

If I increase the compression, so that the file size is the same as the
original, then the quality is reduced.

Can anyone explain this phenomenon?

It sounds like PSP's JPEG compressor is not doing as good a job as
your camera's compressor.

This is a little peculiar, since JPEG is defined by particular
compression and decompression algorithms.

Maybe someone is taking shortcuts...or you are selecting different
levels of optimization or interlaced/progressive when compressing.

Try some more experiments and try to find what PSP compression
degree is just indistinguishable from the camera's version.

FWIW, I use Photoshop, and I find that I can usually preserve all
the quality of a photo at about half the camera's "HQ" compression
file size.

-michael

Home page: http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."

 

[Daz]

Thank you for your advice Michael. I will experiment a bit more, as you
suggest.

Vic

 

[Yves Alarie]

Your camera has two level of compression: fine and normal. Obviously fine is
better.
I have Paint Shop Pro X.
When you open a photo with it and you Save As, the default compression is
set at 20. If you use this, the file size will be about the same as the
original. If you set this down to 1, less compression, the file size will be
about 4 to 5 times the original. However, there is nothing to gain by doing
this.

 

[Yves Alarie]

Your camera has two level of compression: fine and normal. Obviously fine is
better.
I have Paint Shop Pro X.
When you open a photo with it and you Save As, the default compression is
set at 20. If you use this, the file size will be about the same as the
original. If you set this down to 1, less compression, the file size will be
about 4 to 5 times the original. However, there is nothing to gain by doing
this.

 

[Yves Alarie]

Sorry. Wrong person!

Your camera has two level of compression: fine and normal. Obviously fine is
better.
I have Paint Shop Pro X.
When you open a photo with it and you Save As, the default compression is
set at 20. If you use this, the file size will be about the same as the
original. If you set this down to 1, less compression, the file size will be
about 4 to 5 times the original. However, there is nothing to gain by doing
this.

 

[Daz]

Thanks alot. I think that I am now starting to understand the JPEG
compression process.

Vic