Hi all, I have a little problem. I just bought a 15mm lens Bodycap and now want to get a Sigma prime because very affordable. Haven't shot with the 15mm yet but just wondering: which one to get as I already have the 15mm even if it is not top notch IQ? I do landscapes and church interiors and general travel photography as I'm not a pro but an amateur. For portraits (that I don't do much) I have my D700 and Nikon 85mm 1.8 on the way. Could you please help on decision?