|
|
As we all know, older lenses were designed for film cameras. The ray path of each lens is designed to "hit" precisely on the plane of the film. But unlike film cameras, digital cameras must have a piece of optical glass, known as IR-filter, installed in front of the sensor. Its function is to protect the sensor and filter out invisbile IR-light. The result is: when we use legacy lenses on digital sensors, the optical path, which originally designed for film, would inevitably be changed due to the existence of IR filter in front of the sensor that leads to degradation of optical performance. Since the degradation is related to the ray angle, the larger the incident angle, the more severe the degradation will become. Roger Ciacala of Lensrentals first discussed this issue in 2014 (http://www.lensrentals.com/blog/ ... -and-adapted-lenses). Also Lloyd Chamber of Diglloyd (http://diglloyd.com/blog/2015/20 ... d-lensBehavior.html)
For rangefinder cameras, since the flange distance is significantly shorter than the SLR's, the ray angle, especially for wide lenses, would be even more extreme, resulting in particularly bad result in corner performance, which commonly known as "smearing." Leica solved (or at least alleviated) this problem by installing particularly thin IR-filters in their cameras, particularly the M8 and M9. This is why many have argued that Leica cameras yield better result than Sony cameras even with the same lens.
If the question is related to the filter thickness, what if we replace the filter of an 36MP A7R with a thin one in order to maximize its resolution power with legacy lenses?
Roger Ciacala also ran some tests here:
http://www.lensrentals.com/blog/2015/01/a-thinner-sensor-stack
|
|
發表於 2015-8-25 18:19:27
發表於 2015-8-25 21:04:19
樓主
