What happens when I open a JPEG image (say something I've already processed, resized and saved for the web) and make a change to it -- convert it to black and white, clone something out, whatever. Then I save it and close it. Is there a loss of quality? Does it "compress" it again? Just curious. Hopefully my question makes sense. I'm using PSP X2, but I imagine PS and the others work more or less the same way given this scenario.
There should be more compression and loss of quality, especially when using save for web. If you were using the highest quality jpeg I would venture to say that there isn't any real noticeable loss, but save for web I would think yes.
There should be more compression and loss of quality, especially when using save for web. If you were using the highest quality jpeg I would venture to say that there isn't any real noticeable loss, but save for web I would think yes.
Thanks. Actually I meant just opening the image, making some change, doing a CTRL+S (or File|Save) and getting out.
From what I understand it does, so I go back to the original photo and do the changes I want to see. The jpeg will lose detail everytime it is opened then saved. I am sure we'll get more info from more knowledgeable people as this goes on to confirm this.
If you were to do a file save at highest setting then probably nothing. If it is a save for web as long as it looks good on the screen then I wouldn't worry about it, it's really just for viewing at screen resolution.
Jpeg is a lossy compression format. To use an extreme example, if you were do each step of your editing work flow one step at a time, saving and then reopening the new file before each new step, the end product would not look very good.
From what I understand it does, so I go back to the original photo and do the changes I want to see. The jpeg will lose detail everytime it is opened then saved. I am sure we'll more info from more knowledgeable people as this goes on to confirm this.
Good feedback. Thanks to all. I ask as I'm looking at some orginals that I already (painstakingly) processed, and I see a flaw or two. I'd like to be able to fix those without starting from the original -- i.e. get in and out real fast.
If I know it's a pic I will be editing again I will save it as a tif. (I almost always shoot jpeg) Tif is a lossless format and I can pick up where I left off without worry of losing more detail.
For images that I've processed a lot (more than two or three steps) then I always saves the .psd file (before resizing it)! It makes it easy to go back without ever loosing image quality and you still have a high res version of the finished picture instead of just a web sized one without having to have two .jpgs laying around of the same picture.
But in this case, if it's just for the web, then make the changes and say 'save as...' and choose the highest quality.
