I read the article here by Bob Atkins concerning APS-C vs full frame, and I became curious. I went into a couple of sites specifically dedicated to the 4 thirds, and they make it seem like that is the largest sensor, although they don't actually say its size "The Four Thirds type sensor is twice the size of the two thirds type sensor, which is commonly used in many digital cameras" According to the Atkins article, APS-C is 22x15mm (and I think this is a "two thirds" aspect ratio. He also states that the 4 thirds sensor is 18x13.5mm, clearly smaller than APS-C. What am I missing in translation between the article and the website. Because of their vagueness, and never having mentioned the size of the sensor, I tend to distrust the 4 thirds website. It seemed to me to be a lot of hype, with very little factual information. So, here I am, at the only place I know I will get the real information. Thank you in advance for any input you may have.