Torch flame particles for torches put on the side of a block with a block directly above the torch causes the flame to initially be dark as the flame clips into the ceiling, then the flame image brightens as the 'flame' image scales down.

What I expected to happen was...:
Put a torch on a wall with the ceiling directly above it, and the torch flame particles burn bright as the flame sprite associated with the particle scales down from initial size to nothing.

What actually happened was...:
Put a torch on a wall with the ceiling directly above it, and the torch flame particles are dark when the particle first spawns, then gradually brightens to normal brightness as the particle scales down to nothing.

Steps to Reproduce:
1 - Build a room that is 3 blocks high, and give it a ceiling.
2 - Put a torch on the wall close to the floor. Observe the flame, the 'flame' sprite stays bright through the particle's lifetime (from the time it spawns to the moment it 'shrinks to nothing'). Compare this torch to the one in the next step.
3 - Put a torch on the wall close to the ceiling. Observe the flame, the 'flame' sprite goes dark when it clips into the ceiling, and gradually brightens as the flame sprite scales down to the point where it no longer clips into the ceiling.

Observations:
I first noticed this today in snapshot 14w10c, but upon further testing it apparently has been going since 14w06b. The torch flame sprite burns with a consistent brightness on snapshot 14w05b and previous builds. At first I thought it was an addition to the 'torch flame' animation, where the sprite starts bright and then goes dim as the flame sprite scales down, except that the fade effect was going in reverse (dark when the particle spawned, and got brighter as the particle aged and scaled down). So I played around with torch locations and found that torches burn bright until I put a torch on the wall with the ceiling directly above it, then the flame clips into the ceiling and appears to be dim while the upper half of the flame is in the solid block directly above it. Is it possible that the flame sprite is being vertex lit, and the flame sprite image is going dim when the upper half of the flame clips into a solid block?

CEILING

CEILING