Why is FE 70-200 bigger and heavier than Canon's

Started Feb 13, 2014 | Discussions thread
viking79 Forum Pro • Posts: 14,151
Re: Because you cannot defy physics + shallow mount

bigley Ling wrote:

Timbukto wrote:

Shallow mount is great and all for adapters, but that means for most lenses the extra chassis you remove from the body, ends up on each tele lens.

really?? can you verify this theory please.

Given a simple single element lens its focal length at infinity is going to be the distance the lens must be from the sensor.  A 200mm lens needs to be 200mm from the sensor to focus at infinity.  So if your flange distance is 45mm from the sensor vs 18mm from the sensor, it means your lens is 27mm longer in the case of the short flange camera.

Now a complex design can have a built in teleconverter or telecompressor, high refractive elements, etc to make it a telephoto ratio of something other than 1.  Pentax FA 300mm f/4.5 for example is much shorter than 300mm, or the DO optics from Canon are even more so.  Obviously there are always tradeoffs.

My Samsung 85mm f/1.4 for NX mount mirrorles (25.5mm flange distance) is notably longer than a DSLR 85mm f/1.4 lens with 45mm flange distance, but the overall camera system length is going to be comparable.


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