I've noticed that between HDMI and component there are different brightness levels on my tv, I know this because I tested both cables in my ps3 and noticed I had to calibrate differently to hdmi, so the settings were different, why is this?
All analog (and for that matter digital) video signals have a terminal load. This is stated in ohms and for video is 75 Ohms. This allows an source of a given output voltage, impedance and current drive to deliver the correct levels to the source. Video is nominally 1V peak to peak with the video information delivered in the lower 0.7V portion. (Please check me on this, it's from memory!)
If a TV has a termination value either too high or too low, the voltage level will also be incorrect. The voltage level is directly related to the brightness of the signal, so if it is wrong, the brightness will also be wrong.
The PS3 or cable could also be to blame. If the PS3 drive is a bit high, then even if the line termination is correct, the signal will be too bright. A failing cable could make the signal darker, but with the colour and black and white info coming of different cores (B/W on one, colour on two), this would be unlikely.
I see, I reckon it's my ps2 component cable as it was a cheap brand one, I don't think it would be the ps3 because it also does it with the ps2 and all other older consoles. It could also be my ahem, cheap alba tv doing it as well.
It probably will be your PS2 cable I would have thought as I've used 3 different ones in the past (plugged into the same TV) and they were all different, the cheapest one actually was the best picture, it's not always about the price but if the spec is correct then all should be good.