I have a Takaumar 1.4/50 and newly acquired Konica 1.8/40 pancake lens for my GH2. My results with the Takumar have been mixed. I have a lot of shots that are very soft which could be due to a number of issues; high iso, poor focusing (on my part), moving subjects, etc. I decided to try some side by side shots in a semi-controlled environment with the Konica lens and see if I got different results. Long story short, I didn't see much difference though I seem to get the focus wrong with the Takumar more frequently. However I got an unexpected result I can't quite explain. My methodolgy was to take two groups seven photos, one with the Takumar and one with the Konica. I used aperture priority mode and fixed the ISO at 320 and used aperture f4 for both lenses and all photos. When I reviewed the photos I discovered that in every case the shutter speed was twice as fast with the Konica as with the Takumar. The historgams for the images were very similar indicating that the exposures were equal and correct. I'm at a loss to explain why one lens would be a full EV faster than another given the same aperture and ISO. The Takumar lens is somewhat yellowed and it is a 20% longer focal length. Would these explain a 1EV difference in their performance?