Who applies censorship on an ecchi anime? In my few years of watching anime, I have noticed varied amounts of ecchi-ness portrayed and the corresponding censorship it generates. I mentioned "varied" because I have noted differences in censorship techniques (black/white bars, excessive lighting) and the amount dealt to the scene. For instance most non-ecchi anime have the breasts censored, some only have the nipples removed, and a quite a few bare them completely. The quite few who go the extremes may even be classified as hentai already.

Points in case (I wanted to include pics but then decided against it):


Partial covers: Gokukoku no Brynhildr, Infinite Stratos, Trinity Seven
Bared completely: HighSchool DxD, Yosuga no Sora, Elfen Lied


My question: How does Japan implement various levels of content ratings (G, PG, R18+)?  Is it the production studio who applies these varying amount of censorship or is there a committee assigned that does it? Does the same apply for violence/gore censorship?
Japan does not have any rating system for normal television.
Some satellite television requires an 18+ age check to contract some channels.

DVD/BD and movies have a rating system similar to North America (G/PG12/R15+/R18+).

Most such censorship in anime is "self-censorship".
Each TV station has a different code, and the code is different for different airing time slots.
Morning anime and evening anime have more restrictions. Late night anime have less restrictions.

TV stations do not explicitly state what the code is, but the director of Bokurano wrote a blog post that says that he was asked not to show blood in the anime.

They have restrictions on blinking the screen (which can cause epileptic seizures), drinking alcohol, tobacco, violence and fanservice (ecchi) scenes.

One important group about censorship is BPO (Broadcasting Ethics &amp; Program Improvement Organization).
BPO is an organization concerned with ethics of broadcasting for all TV stations.
Sometimes, they ask TV stations to remove shows which were deemed bad for children.

Another reason is the shift in animation business models.
The old model got most of its profit from commercials.
In that time, anime production removed entire non-compliant scenes instead of adding lighting.
But recently, anime production gets more profit from DVD/BD than from commercials.
They find that broadcasting a censored version and selling an uncensored version on DVD/BD is a better strategy to increase sales.