Originally posted by filmamigo Not to abandon my love of the leaf shutter ... but I was perplexed that the lowly Nikon D70 used a hybrid shutter with mechanical first curtain and electronic final curtain shutter. It had an official flash sync speed of 1/500 and with manual flashes could sync up to 1/8000.
Not sure why this is no longer possible? Presumably the move from CCD to CMOS prevented using a hybrid shutter like this?
Yes, there was a CCD architecture called "interline transfer CCD" in which each pixel consisted of a separate photodiode that connected to a CCD bucket brigade column via a gate. The CCD part of the chip was covered by an opaque material. Thus, the sensor could capture the image in the photodiode array and then instantly dump it into the CCD where it could be slowly transferred off the chip for read-out. The design offered a true global shutter for video applications but image quality was lower than that of a sensor optimized for use with a mechanical shutter.
In theory, one could create an interline-transfer architecture in CMOS by creating a separate photodiode & charge storage/read-out array but it would add probably 1 or 2 EV to the base ISO, take away 1 or 2 EV in dynamic range, increase the noise in the image, and add cost.
The fundamental fact that a silicon sensor is ALWAYS light sensitive means that the best way to get the cleanest possible image is to put a shutter in front of it.