When I was testing my Rokinon 85mm for my last post I wanted to do a comparison of bokeh or how the lens blurs the background with other lenses I have. I decided to use some flowers in a flower bed, but they moved a little too much. I then decided to use a wrought iron fence, with my camera on a tripod to keep things the same. Using Live View I focused on a specific finial then proceeded to take pictures with the only change being closing the aperture in full stops from f1.4 to f11 and lengthening the exposure time to keep the exposure even. Then not moving the camera I switched to my DFA 28-105 and zoomed to frame the scene as closely as possible to the framing of the 85mm. The exif notes the focal length at 95mm, which I found curious, you can see the photo below and compare it. I then put the DFA 70-210 on the camera, again being careful to not move the camera. To match the framing with that lens it was at 70mm. You can see that photo below as well. 

At similar apertures the lenses are very similar, the 28-105 is wide open at f5.6 at the focal length, the 70-210 is a constant f4 throughout it's zoom range, but is nearly identical to the others at f5.6. I am postulating that the physical length of the lenses and having the front element be closer to the subject is the reason for the focal lengths reading as so significantly different.

What do you think?