Basically, images which shows a distinctive lack of quality in regards to properly adjusted brightness/contrast along the whole image, along with usually lower actual image quality. Something like post #188697

I'd say leave it for the mods to decide.

Poor tagging, yes, but not a poor scan. Of course it's not 4000px X 3000px but it's still viewable, not blurry and almost non-existant JPEG compression artifacts

That post isn't even a scan, it's a photo.
I figured I would add this passage from the rules page:
"Make an effort to post quality, finished, non- repost images. Avoid crap-quality things like tiny images, grainy images, motivational poster memes, screenshots, image macros, images with absurdly huge and extremely annoying watermarks, etc."
So it's fine to flag if it's overly grainy.

help:flag for deletion states:

Do not flag images because you don't like them. Do not flag images because you think there's too much of it. Please refrain from flagging images because of questionable relevancy or quality. These things are at the moderators' discretion.

Furthermore, it lists the acceptable reasons to flag for deletion. Grainy images, poor quality, and photographs of paper are NOT among them.

since my picture was used as example can I say that I have no access to a scanner and my ability to take pictures is highly limited due to the annoying controls and camera's 3 picture size saving quality, making the largest striped that size grainy and the smallest being thumbnail sized; and I was unable to tag the picture due to some kind of error that updated the tags when I attempted to start editing the tag field with my phone.

null0010 said:
help:flag for deletion states:

Furthermore, it lists the acceptable reasons to flag for deletion. Grainy images, poor quality, and photographs of paper are NOT among them.

Then why did you give that as a reason for deleting the picture in the OP?

?:I

Kclub said:
Then why did you give that as a reason for deleting the picture in the OP?

?:I

Well, that is not covered in the flag for deletion wiki, but it is in the rules one. I don't know who added the bit about not flagging based on relevancy or quality, but I'm not so sure it should be there.

Un-deleted this particular picture, as after a closer inspection, it isn't "Heavily grainy" nor is it substandard quality on a whole. We are not art snots here folks, remember that. We do allow some grain, or sketchwork images. So long as the picture can still clearly convey whatever its subject matter might be.

I'm gonna assume this means quality is going to have to be looked at by caseand lots of floating,"What is too low quality?" when it comes to scans and photos.

Rarborman said:
I'm gonna assume this means quality is going to have to be looked at by caseand lots of floating,"What is too low quality?" when it comes to scans and photos.

The general rule of thumb is, is it on clean paper {non line paper}. Is it so grainy you cant make it out, or "Is it blurry, heavily distorted, or full of uncleaned lines" that make it hard to determine what your looking at. But most of it will be taken on a case by case basis