Q: So, I understand the generational degradation of JPG and other similar formats when editing and re-saving. What I don’t know is… When moving a JPG from folder to folder does that decrease it? When moving an entire folder of JPGs, does that decease all the individual files within? Does simply renaming the file decrease it? When saving a copy would decrease the original, or just the copy? Am I missing any other kinds of changes that do or don’t degrade the quality? And how much degradation occurs? Significant, minimal? Can’t tell till the 20th edit? ~ Terri R., Aurora
Tech+ No degradation. Moving or copying a digital image makes an exact duplicate of the image.
But as you mentioned, it’s the editing and re-saving of images that may cause some quality degradation.
For the 411 on this, head over to Adobe, makers of the aged and prolific Photoshop software that artists have used for years to turn creations digital.
We shrink digital images because a raw 10-megapixel beauty from a smartphone can gobble up a lot of storage space, not to mention cause websites to load slower. And compression techniques allow for the image to still look good online, for example, though if you print it out at the store, you may see some fuzziness, slightly off colors and just an overall smaller image.
Digital image compression is essentially divided into two categories: Lossy, which means a loss of detail during compression; and Lossless, which compresses but does not remove detail.
The most common image formats:
JPEG or JPG (Joint Photographic Experts Group): Lossy, so a lot of data is lost in the final image. But it’s a sliding scale of quality, meaning it’s up to the user. Sharper lines? The larger the image. Increasing compression means the photo will probably look a little blurry and pixelated.
PNG (Portable Network Graphics): Lossless compression, so images keep their details. Good for screenshots since it keeps a representation of nearly every pixel. Digital Trends has a good write-up: “JPEG vs. PNG: Which image-saving format is the better one to use?”
GIF (Graphics Interchange Format): Limits the number of colors to 256, which alone cuts down in its size and means major limitations for image quality. But gather up a bunch of them and link them to create short animations — animated GIFs.
TIFF (Tagged Image File Format): Lossless format, and popular among professionals because it offers flexible compression quality yet retains color and information. But the files tend to be quite large. Better for print-outs but not so friendly for websites.
The experts can tell you more. Some useful sites I tapped for this answer:
- 99designs.com: Image file formats: everything you’ve ever wanted to know at bit.ly/picformat1
- Adobe: Choosing a file format, at bit.ly/picformat2
- University of Michigan Library research guide: All About Images at bit.ly/picformat3
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