I'm considering buying the EF 85/1.8 or EF 100/2 for portrait photography indoors. Since I'm not sure whether 100mm may be too long for indoors, I decided to try these 2 focal lengths using my EF 70- 200/4L. My body is Elan 7, by the way. The problem is that I'm not sure whether I can trust the focal length scale on the lens, because I found something strange: it seems like the short focal length of the 70-200 (supposed to be 70) is similar to the long focal length of my EF 24-85/3.5-4.5 (supposed to be 85). They give the same picture when the camera is mounted on a tripod. I compared the picture I get with the 24-85 at 50mm to my EF 50/1.8 and they're the same, so it looks like the 24-85 is "ok". Did anybody notice this issue? Can it be true? How can I really know what the 85 and 100 mm focal lengths will look like?