I using blender 2.76b or older (2.75, 2.76). I painting model 1k face, 1024x1024. my PC corei3, ram 8gb, win 10, gigabyte r7 250 2gb. I use brush radial 1>3 pixel and > 50 pixel no lag. But brush radial 3 > 50 pixel very lag and slow. My setting i use default. Help me. Thank so much.