I notice a slightly blur when activate convolution bloom on all the viewport, whenever pixel are affected by bloom or not.
This is very subtle, but there is!
To see if it 's related to the texture used (the default one provided by Epic), I did a simple test with a custom texture. I followed the guidelines from the doc, specially the part of the image that should be the considerably brighter than the rest of the image. My texture test is a background with a luminosity value = -20 stops and just a pixel point in the middle with a value of +20 stops. I get the same slightly blur in the viewport.
Is there an explanation about this drawback, and is someone know if there is a workaround to avoid it? (For now, I reduce the convolution scale from 1 to 0.7. By doing this, the blur effect disappear, but bloom result is not so good as it was at 1).