I shoot with a A99 Sony full frame camera and have a couple of wide angle lenses. One Sony 16-35mm (full frame), which I use 70% -80% of the time and a Sigma 10-20mm APS-C lens which I rarely use. Although the camera has an Auto change setting when switching from a full frame lens to an APS-C lens it doesn't work with Sigma lenses. You need to manually it set to "ON". Last night I was trying some star shots using wide angle lenses. Just for the hell of it I thought I'd give the Sigma a run. I went to change the APS-C setting to "ON" and it was already set on it. Apparently I hadn't changed it back to "Auto" last time I used the lens, which was months ago. The upshot of this is that for months I have been shooting cropped images with my Sony lens with out realizing it, which is not great, especially when you do a bit of real estate photography on the side. Ah well, hopefully lesson learned. Sorry if I have bored you with this post but I thought I'd share anyway.