What are these brush stroke circles?

[Erin36580199gw9s]

When I select the brush tool and set the softness to zero, on my previous pc it would allow me to put on a lovely, hazy colour with no definitively visible outline, enabling me to give a glow effect. With my new pc, I've installed photoshop onto it but, when trying to add an image of the sun on a sky, I get this grey circle. It disappears if I remove the blue layer(or at least appears to) but when experimenting with other soft brush colours and backgrounds, I still get a weird outline, which I really don't want as it ruins the effect! Never had this before! 

Tried changing blend mode, brush settings and can't find any solution. Please could someone assist me here?  Attached an example - did multiples with different settings to see if anything worked and it did not!

(Yes I asked Gary Google but he doesn't know what I'm talking about!)

Any help would be great.  Thanks.

[kglad]

what app?

[Erin36580199gw9s]

Photoshop

[kglad]

in the future, to find the best place to post your message, use the list here, https://community.adobe.com/

p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post (like this one has already been moved) if it helps you get responses.

<"moved from cc desktop">

[Trevor.Dennis]

What are your brush settings?
What size is the image document, and what size the brush?

Are You clicking once with the mouse, or using a tablet?

Try checking Build Up in Brush Settings, and hold the button down for a few seconds.

How good is your monitor? Is it prone to showing banding? What profile are you using?  Paging @D Fosse 

[D Fosse]

Yep, this can be summed up very simply:

As long as you work in 16 bit depth, any banding you see on screen is in your display system.

Banding is caused by insufficient bit depth. In 8 bit depth, there's only 256 discrete steps from top to bottom. Most displays are 8 bit, most office and gaming displays are 6 bit + dithering.

[NB, colourmanagement]

Reads like a banding issue to me too, I agree with @D Fosse 

are you viewing the image at 100%

How have you calibrated and profiled the display system?
What monitor display screen are you using? 

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management
Help others by clicking "Correct Answer" if the question is answered.
Found the answer elsewhere? Share it here. "Upvote" is for useful posts.

[Trevor.Dennis]

@Erin36580199gw9s  You need to answer the questions asked of you.  You'll much better advice if we have moreinformation.