Got a good question from one reader- Can you explain for us ignoramuses what you mean when you say Full Frame Sensor? I'm not clear why say the Canon 5DMk2 is 'Full Frame' and the 7D isn't, and why some lenses suit the Full Frame well (e.g. 15mm) but not others? Thanks Professor. These are great tutorials....
The difference comes with what's known as 'crop' sensors (Canon are 1.6x, Nikon 1.5x- the factor refers to the width ratio compared to full frame so the 40/50/7D sensor is 36mm/1.6= 22.5mm across). They are so called as they are smaller in area than full frame (hence cropped) and images shot with the same lens will also be cropped compared to a full frame. This comes down physics as the sensor is closer to the lens to get full coverage from the light coming in. So your 100mm lens behaves equivalent to a 160mm lens. It also means angle of view is restricted as your lenses are behaving like longer lenses- fine for shooting long lens action (as a 500mm becomes a 800mm) not good at the wide end as a 20mm behaves like a 32mm on a crop body. So to achieve the same wide angle the manufacturers have built 10mm lenses which then act like 16mm lenses on crop bodies... Make sense?
It's been a good thing for surf shooters as you can get great reach on long lenses with crop bodies, but it's sucked at the wide end cos the Canon 10mm blows. Thankfully Tokina's 10-17mm fisheye zoom has saved the day. A proper Canon 10mm fisheye like Nikon make would be velly nice.
I won't go into the debate of how many megapixels in sensible on a crop sensor... suffice to say I've just got a 7D and I'm more than happy with the 18MP they've crammed in there (I'm also equally happy with the 10MP on my 40D)...
