I think the notion of FF = heavier lens may not be true

Started Nov 8, 2013 | Discussions thread
TrapperJohn Forum Pro • Posts: 16,488
Understand why the earlier 4/3 lenses were so large, and the current ones aren't

The ZD 4/3 lenses have a telecentric light path, which is to say the light coming out of the back of the sensor is perpendicular to the sensor, at a 90 degree angle. That was done specifically to address the vignetting and soft edges caused by the early deep light well sensors. Light at extreme angles wasn't a problem for film, which has no real depth, but it was a problem for the digital sensors of the day, that had fairly deep light wells, which meant light at angles was lost on the way down the well to the actual sensor.

It's why the first DSLR's were APS and not 24x36 - the film lenses available at that time were not telecentric (didn't need to be) but when used on early digital sensors, the image lost definition and intensity the further from the center of the sensor. Easy solution was to make a smaller sensor to crop out the troublesome edges. Hence, the 'crop sensor', that cropped a 35mm image circle to get an acceptable photograph.

Some companies, particularly Canon and Leica, addressed this with microlenses on the sensor to straighten the light out, Oly addressed it by making a lens that straightened out the light. Oly got what they wanted, excellent rendering and razor sharp wide open, but the lenses were larger and heavier, from the thicker barrel and larger internal elements that were required to straighten out the light path.

This isn't needed any more. The latest sensors have shallow light wells that can take light at more extreme angles, which makes the short focal length mirrorless systems possible at all.

For a more accurate size comparison, use the µ43 size optimized lenses like the 45 1.8, 75 1.8, 12-40 constant F2.8, 12-35 constant F2.8, 20 1.7, 17 1.8, etc... they are very small for what they can do.

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