JPEG compression level

[Doug Kerr]

Most of our cameras, with respect to the JPEG output, provide for a choice of two or more compression ("quality") levels.

Of course, the typical file size may differ substantially among these (that is of course the point of having a choice).

For example, for my Canon PowerShot G16, the estimated file size for the "superfine" JPEG compression choice is about 1.6 times that for the "fine" compression choice (the estimated file size does not vary witg ISO setting).

What has the experience of the members been with regard to the choice of a JPEG compression level and its impact on image quality?

Thanks.

Best regards,

Doug

 

[Andrew Stannard]

Hi Doug,

You might find the following articles of interest, although I have to confess I didn't get all the way through at full attention:

http://www.impulseadventure.com/photo/jpeg-compression.html

http://www.impulseadventure.com/photo/jpeg-quantization.html




It's a little out of date now, in terms of camera's discussed, but the underlying ideas are obviously still relevant.


My own practice has always been to leave JPG settings on the highest quality available. The number of images that will fit on a decent sized memory card always seems to be more than enough, so haven't really felt the need to experiment with other compression settings.


Kind Regards,
Andrew.

 

[Bart_van_der_Wolf]

Hi Doug,

You might find the following articles of interest, although I have to confess I didn't get all the way through at full attention:

http://www.impulseadventure.com/photo/jpeg-compression.html

http://www.impulseadventure.com/photo/jpeg-quantization.html

It's a little out of date now, in terms of camera's discussed, but the underlying ideas are obviously still relevant.

Hi Andrew,

I agree, that is a very useful resource, and I've been using the JPEGsnoop utility for some time (e.g. when I needed to check compression quality of different versions of the same file from the web). I rarely shoot Camera JPEGs, Raws are my usual image files because they allow to achieve much higher image quality, with larger gamut and more room for tonality adjustments. JPEGs can be used as output files for off-site printing, in which case it can be useful to find a balance between upload size and image compression losses.

For producing relatively high quality image content on the web that takes up a minimum of file-size space (=faster page loading, especially on mobile devices) I regularly use the Radical Image Optimization Tool application (Win), which also has a plugin for IrfanView. RIOT allows to flip between pre/post compression versions to visually judge if the compression generates visually relevant losses, and one can set a target file size for which it then figures out the required compression setting.

Cheers,
Bart

 

[Doug Kerr]

Hi, Andrew,

You might find the following articles of interest, although I have to confess I didn't get all the way through at full attention:

http://www.impulseadventure.com/photo/jpeg-compression.html

http://www.impulseadventure.com/photo/jpeg-quantization.html

Yes, interestingly enough, just yesterday I ran into those (in connection with updating my JPEGsnoop utility).

My own practice has always been to leave JPG settings on the highest quality available. The number of images that will fit on a decent sized memory card always seems to be more than enough, so haven't really felt the need to experiment with other compression settings.

For me, the file size issue is more than a memory card matter, since I keep every camera shot (maybe not if I have taken 500 test shots to look for some obscure thing, but otherwise!) on my hard drive, and they migrate into my hard drive backup system.

Thanks.

Best regards,

Doug

 

[Andrew Stannard]

That's understandable Doug - although as storage gets bigger and cheaper I suspect it will become less of a problem.

Regards, Andrew