In 1.8.1, a single block of TNT would blast an area about 3x3x4, but since the update to 1.8.2 and above, the blast radius is slightly smaller. The attached screen shots show a test using the exact same section of rock in 1.8.1. and 1.8.3. I dug a hole four blocks deep and placed one block of TNT at the end.
After-TNT-1.8.3.jpeg shows fewer damaged blocks on the side closest to me than in After-TNT-1.8.1.jpeg, including two complete rows of block on the floor.
(I've seen reports similar to this affecting earlier Minecraft versions, but I'm not sure if this is a new issue or a continuation of those earlier ones. Moderators, please move if necessary)
Is this still an issue in the current Minecraft Snapshot 15w47c or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.