how much quality is lost when i save in jpg rather than png format

I believe none if your saving from the web because you are not modifing the picture your only copying it.

Except for certain internal processes involving metadata changes, every edit and save as a JPEG file will have a detrimental effect on image quality. If you wish to retain quality of an image that requires editing, save in a lossless format, TIFF, PNG, etc, and only convert to JPEG at the final stage before uploading.

Saving a file from the snipping tool to JPEG, which you are not going to edit is OK as the JPEG compression process is only performed once, thogh it will degrade to some extent, set the snipping tool JPEG settings to highest to retain as much detail as possible.

Many images from the net will only save in either .bmp or .jpg format directly. You need to first save the pic you want then as said right click the image, Open With, select Paint. Once it's opened in Paint, click the icon shown below and then choose Save as .png and delete the original.

manhunter2826 said:

, every edit and save as a JPEG file will have a detrimental effect on image quality.

wow, thanks barman, that i never knew. any reason why this happens -- short explanation ? lol

a Jpeg image discards information that is deemed to be un-necessary for the human eye to "see the image", this reduces the size, but also removes subtle detail. As this process is repeated every time a file is saved, the image quality is reduced each time.

An interesting experiment is to take an image, and save to a new name, and compare the quality of the images, (setting the compression to high will speed up the process).

When the jpeg system was developed the web was young and image quality was low so this loss was not really an issue, but today with high bandwidth, and HD screens the compression can be noticeable with "artefacts", (stray pixels and blocky images).

If you wish to retain quality for the web, the PNG image which has a better lossless compression is the way to go.

I do keep Jpeg images from my own camera but the system I use keeps a master copy, and a list of changes and "publishes" a copy for upload as required. A lot of my original images are stored as digital negatives (Raw), format which creates huge files but can be edited continuously without detail loss.

Hope that's short & simple enough, unfortunately image compression is a complex subject