Maybe it’s been this way all along, but here’s what I have:
I have a 4MB jpeg that I uploaded to photoshop express.
When I click the edit option it, it says 4MB.
I then do nothing but save it to another file name, and it saves it as a 1.6 MB file.
Somehow I was under the impression that photoshop express didn’t ‘scale down’ the size of your file when you uploaded it. Any ideas???
The compression used in JPEG can trade off image quality for file size fairly readily. Most programs that write JPEGs have something like a “quality” slider for the encoding that varies from “high quality/big file” to “low quality/small file”. Likely when you re-save it, it’s getting re-encoded with a lower quality setting.
Hmmm. . . looks like they’ve pulled a bait and switch. My old bookmark did not have ‘mobile’ in it, but the new url does. Looks like they’ve changed it to assume you’re going mobile.
Every single time you save a JPEG it will go through its compression routine and degrade the file quality. This happens over and over until the file reaches its minimum size (and also worst quality). Photoshop and other quality programs will let you choose how much compression to apply.
Regardless, it’s recommended that you edit the file in its native (lossless) format and only export to JPEG when the project is complete.
solosam has a lock on best practice, but conditions aren’t always perfect. If you are starting with a JPEG: if you think you may need to edit that JPEG again, save a PNG or PSD before saving it as a JPEG. And then try for a slightly larger JPEG than the original to minimize quality loss. Any time you want to edit the image, edit the PNG again, and then save as a JPEG again. That way your JPEG will never be worse than after your first save.
That’s assuming the OP wasn’t just trying to make a copy, and just used a no-edit save as an example. If you are trying to make a copy, look for a method to do that directly. Only use the “save as PNG/PSD and convert to JPEG” workaround if you have to. I personally would rather reupload the file under a different name if I had to.
Well, if I wasn’t stuck on dialup for the time being.
That’s not true for every program. Some (notably IrfanView) allow some basic operations (90-180-270 degree rotations and cropping) without recompressing, and therefore with zero JPEG quality loss.
Still, your advice is good. Only compress to JPG at the end of a long string of edits.