Technical Canon question about compression?

[av8er23]

I shoot with a Canon SD550. I have taken thousands of pictures with it. There is a setting that has to do with compression.

There are three settings:
Superfine
Fine
Normal

I always shoot in the max resolution which is 3072 x 2304. I find that you can crop a picture quite a bit before you start to get pixilization or blurriness. Could some one please explain the compression a little more?

I use photoshop 7.0 for editing and i compress most of my pictures to about 1 meg after editing them. Is this generally a good pratice? I may one day come back and was a big blow up of some pictures. Thanks for the help!:14:

I would also like to learn more about shutter, exposure, and speed if you guys know of any good articles.

 

[KrisB]

Here's a whole article on JPEG format: http://en.wikipedia.org/wiki/JPEG

Basically, my view on it is that storage is basically limitless now. I mean, a 120GB portable hard drive is only $150... fill it up, toss it in a safety deposit box and move on to the next one.

So... I shoot all my images at full-res, "superfine" compression, and keep the originals that way. If I edit an image, it doesn't get saved over top... it gets an "a" appended to the filename (e.g. IMG_1033a.jpg).

JPEG Compression isn't usually noticed as blurriness or pixelation. It's more often noticed as a solid colour no longer appearing solid (you'd understand if you took an image in Photoshop and saved it with the absolute lowest compression).

 

[bladephotog]

The image resolution settings on your camera determine how large of a file the camera is saving. The smaller the file the less information - and less information you have to upsize a photo.

So shoot everything at full resolution. You can always downsize a photo but you can't upsize without a loss of image quality. And when you work on a photo always resave it using a different name. Keep the original file unaltered as each time you resave a photo as a JPEG it's re-compressing it. Every time you re-compress a JPEG you lose information.

I always download my disks and burn them to a CD or DVD. Then I work on copies of the photos. That way I can always return to the original if needed.

 

[av8er23]

Those are good points guys. I have developed a bad habit of editing all the orginals commonly using autolevels, croping, and compressing. I guess i should take the advice of kris b and get an external HD. Thanks

 

[CompuDude]

Yes, always save as. Never save over your original.

On the other hand, I used to own an SD550 and loved it, and I shot at the max size, but used the middle (fine) compression level. Hard drive space may be cheap, but the difference between the two was so subtle it really didn't seem worth it to me to nearly double the file size. The bigger your files, the longer everything takes, from file write time, to copying the pictures off the chip, to backing it up... you name it. If I could really see a difference, I'd have gone superfine in a heartbeat, but I really didn't see enough to make it worthwhile to me.

 

[av8er23]

Thanks for the imput Compudude, I do not really see a difference neither but I am thinking down the road when I might have some of my collection blown up in a frame size. I assume that it will make a difference then. Maybe not though.