saved images gritty

[Maddman]

Hey everyone, as you can see here all these images look fairly low in quality but they were all saved in as high a quality as photoshop would allow (this happens with. jpeg and .png files) to be honest I have no idea why this is happening and I don’t think I’ve seen it on other artists works
photoshop is on RGB and image sizes are 10.567 x 15.767 inches (1585 x 2365 pixels) at 150 ppi and I've tried at 300 and 75 ppi with the same results
I'm using photoshop cs6 on the creative cloud
Thanks in advance
(the screen caps of the image size previews are a bit gritty because of the capture program they look nice and smooth in photoshop)

 

[Tom Mann]

If you are referring to the more-or-less vertical darker lines running through your "Why?" comment in the left image, and the more-or-less horizontal lines running through the right image in that pair, that phenomena is called, "banding". There are a few common reasons for this.

The most common is that you are working at 8 bits per channel (aka, bpc), and you are seeing changes of a single unit in one of the color channels, eg, R going from R=50 to R=51 in the next band in the sequence and either to 52 or back to 50 in the next band. This problem is fixed by working entirely, start-to-finish in your workflow at 16 bpc, except for one final conversion to 8bpc at the very end, when you are preparing a file for the web or for printing. Such banding has almost nothing to do with the JPG quality setting. JPG compression artifacts look like blocks, not bands. (There are good examples in Wikipedia on the difference between the two.)

The second most common reason for seeing such banding on your monitor is that it doesn't really exist in your file, but somewhere in your video chain, the bit depth is low or lowered from what it could be. The most common reason is a low quality monitor (eg, a laptop screen), but video chain induced banding can also occur when extreme monitor calibration profiles are needed to bring your monitor into compliance with, say, sRGB standards. The easiest way to check this is to post these parts of your PSD file, I'll check them on my monitor and tell you whether I see any banding or not.

HTH,

Tom M