You file is 30 by 30 what? Pixels, inches, feet? 30 x 30 inches at 300ppi is HUGE!! How much RAM do you have? Pretty sure that will bring PS to it's knees...
You can probably separate the two issues.
The banding is likely to be caused by working in 8 bit. With low opacity/flow and soft brushes you really need every step in the gradient you can get. So you do need to work in 16 bit. If you are already in 16 bit then it is likely that the banding is only on your screen and not in the actual image.
For the slow brushes - a 9000 x 9000 pixel image is large but not massive. However, how big (in pixels) is the brush? Sometimes on large images we end up using larger brushes. I have a reasonably fast system here with 64GB memory and I can still see slight delays with very large brushes (e.g. 5000px brush). If you are using very large brushes, you may have to live with it until you can upgrade your system.
Thank you both Melissapiccone and Dave here hope is more helpfull info
I am using Photoshop CS6 Extended on a Mac Pro , 3.5 Ghz 6 core- intel Xeon ES Memory 32 GB 1866 Mhz DDR3. Graphics AMD FirePro D500 3072 MB running OS X 10.9.5 Mavericks. More information I created the same file on Macbook Pro and I am not encountering this issue. So why then is it happing on my Mac Pro? I do not understand why I am encountering the time delays and banding what I can do to resolve the issue? As for the file size yes it big but I have used this size before with multi layers in PSB format without problems. As for the pixel size of my brush its on the large size around 2100. I also have and
HP Pavilion 27xi 27-Inch Screen LED-lit Monitor
Any help you can provide would be greatly appreciated Thank you,
The issues of banding and slow draw are likely to be separate.
You did not confirm whether you are experiencing this when working in 16 bit mode?
One other thought. Have you tried changing the GPU settings in Preferences -Performance (e.g. Advanced/Normal/Basic etc)? It is just possible that a driver update has caused some issues.
Do you have plenty of scratch disk space (even with large RAM - Photoshop still builds up the scratchdisk)
I am sorry Dave I was using 8 bit and have the GPU set at basic. I also did try 16 bit and still encountered problems.
Do you any more ideas of what I can do to resolve this issue?
Thank you for your help,
Dave, I think I may have to reinstall Photoshop and related software. Is there a correct procedure for uninstalling and reinstalling software non CC based?
Thank you for your help,
Some banding is unavoidable with such a shallow gradient. This has nothing to do with Photoshop.
Even if the file is 16 bit depth, the display system is still working at 8 bit color depth - so you still see the 256 discrete steps from black to white. A 10 bit display path is possible, but is only supported in some expensive monitors and video cards, yours not among them.
IOW the banding is not in the file, but your display system. If the banding is very irregular the problem is most likely a bad monitor profile, or calibration tables in the video card with extensive curve adjustments.
The standard way to deal with banding in synthetic gradients is to add a tiny amount of noise. It doesn't take much. Even the most fine-grained photographs always have just enough noise to conceal any banding, so it's never a problem there.