srcdir="C:\\drorbn\\BBS\\shots\\"

shot=ColorConvert[Import[srcdir<>"Dror-170927-204747.jpg"], "Grayscale"]

Blur[shot, 20]

ImageApply[Abs[#1-#2]&, {shot, Blur[shot, 20]}]

ImageApply[Abs[#1-#2]&, {shot, Blur[shot, 20]}] // ColorNegate // ImageAdjust

ImageApply[Max[#1-#2,0]&, {shot, Blur[shot, 20]}]

ImageAdjust[ ImageApply[Max[#1-#2,0]&, {shot, Blur[shot, 20]}] ]

ImageAdjust[ ImageApply[Max[#1-#2,0]&, {shot, Blur[shot, 20]}] ] // ColorNegate

ImageAdjust[ColorQuantize[
ImageApply[Max[#1-#2,0]&, {shot, Blur[shot, 20]}],
2]] // ColorNegate