Until we get several repeated measurements for each sensor-stack, take them as a suggestion, not an absolute fact. For right now, please remember most the physical thickness measurements are single measurements (if there are two confirming measurements, I’ve made the number bold). Hopefully we’ll have some more contributors soon. Thanks to Shane Elen at for all of the Nikon physical measurements. The actual physical measurements may be a little different depending upon what types of glass were actually used. The sensor optical measurements are made by Brian Caldwell and measure the optical equivalent as if the sensor stack was made of glass with a 1.52 refractile index. Right now it’s pretty limited but we’ll continue to expand it as we get more information. ![]() Since it’s really hard to find that kind of information I’ve started a database here. The bottom line is if we want to predict what lens-camera combinations will have problems, we need to know something about sensor-stack thickness and exit pupil distances. This is calculated at 40 line pairs/mm and a 50mm exit pupil distance is fairly close, but you can see even a 0.5 mm difference in filter stack size could have an effect. Here’s a theoretical example that Brian Caldwell published on almost 7 years ago. A 24mm f/1.4 rangefinder lens can be hugely affected. So in theory, a 135mm f/4 SLR lens isn’t going to care much about the sensor stack thickness. Reverse-telephoto design wide-angle lenses (SLR lenses basically) have the exit pupil more forward than Rangefinder wide-angle lenses, generally. Wide-angle lenses may have very close exit pupil distances. In general more telephoto lenses have very forward exit pupils and aren’t affected by sensor stack thickness very much. It can be measured, but those measurements aren’t readily available. The exit pupil is an optical phenomenon – the exit pupil is not the physical location of the rear aperture or the rear element. A lens with the exit pupil very close to the sensor is affected a lot. ![]() (More specifically, how far forward the exit pupil of the lens is.) A lens with the exit pupil far away from the sensor is not affected by the thickness of the sensor stack very much. Wide-aperture lenses are going to be more sensitive than narrow aperture lenses. The difference in sensor-stack thickness between the camera the lens was designed for and the camera actually being used.(I’m assuming the adapter contains no optics itself.) Several factors come into play here. The practical importance comes when we want to use a lens designed for one camera on a different camera. The results might be totally different on another camera, or if each was shot on the camera it was made for. But it’s completely false to use those test results and say the Leica lens is better than the Canon-mount lens. That is good, practical data for any A7r owner to have. If a tester tests a Leica lens and a Canon-mount lens by mounting both to an A7r, he has created a valid test showing how those lenses perform on that camera.
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