I just got the NX1 so I am trying to learn a bit here and there. I have a NX lens on order, but just using the NX1 manually with my EF lenses so far. It was my understanding that when using a NX to EF adapter, the EF lens will be wide open at the lowest aperture for that particular lens. So i have a few EF lenses. 1. Sigma 18-35 F1.8, Canon 24-105 F4, and a Tokina 11-16 F2.8. I have been doing some low light tests and with the Sigma, the shots are just turning out way to dark and just don't seem right for a F1.8, ISO 400, 1/60 setting in a typical living room type setting. It seems as though my Sigma is sort of stuck at F4.0. Again, sorry if i am just confused, but if I was to first put my Canon 24-105 F4 on and then put my Sigma F1.8 on, does the NX1 think the Canon is still on and using the F4 of the Canon? I did a quick test with a Sony RX100 point and shoot. Sony RX100, F4.0, ISO 400, Shutter 1/60 and the photo turns out the same as my NX1 with ISO 400 and 1/60th, but since i am using the Sigma F1.8, it should be 3 stops different. Not sure what the deal is, if someone could point me in the right direction. I unfortunately do not have a Canon DSLR to put the Canon lenses on right now. Only my NX1 and Sony RX100. Thanks.