Re: Good article
There are a very few systems cameras with a fully electronic shutter, like the Sony A7S and the Panasonic GH4. Unfortunately, the problem is that they take a long time to scan the sensor as they lack what's called a "global shutter". On the latter, the senor can, in effect, take an instantaneous "snapshot" of scene. However, on a CMOS sensor, the photosites have to be read sequentially, and row-by-row. On even relatively low resolution sensors with 12-14MP, this process takes, perhaps, 30ms. In consequence, for even modestly fast shutter speeds, the sensor rows have to be cleared and read as a sort of rolling strip that passes up the sensor. Of course, this is essentially what a focal plane shutter does, by exposing a narrow strip for higher shutter speeds. The difference is, electronic shutters take about 1/30th second, whilst a half-decent focal plane shutter traverse the sensor in about 1/250th sec or less. What this means is the top of the image is exposed before the bottom, so you get "leaning verticals" on moving objects. That's called "rolling shutter". You still get it on focal plane shutters, but it's about an order magnitude worse on electronic ones. Also, this problem is worse the higher resolution the sensor, which is why you don't see the option on sensors of 16MP upwards. (A lot of cameras do have an option for something called "EFCS", or electronic first curtain shutter. That's a partially electronic shutter which uses electronics to clear the photosites (which can be done faster than reading), and this runs ahead of a physical second curtain which shuts of the exposure. It's quieter than a fully mechanical shutter, but far from silent.
You see the problem with "rolling shutter" on a lot of video cameras with CMOS sensors as you get weird effects like twisted aeroplane propeller blades. It';s technically possible to create a CMOS sensor with a global shutter, but (currently at least), only by creating a temporary charge storage area for each pixel, which means giving over silicon real-estate which, in turn, means compromising other aspects of sensor performance, like dynamic range and noise performance.
Having taken more than a few photos at gigs myself, I know the problem of noisy shutters. Of course it depends on the circumstances. In a full-on rock performance, especially if it's outdoors and you are in the pit in front of the stage, not problem. If it's a folk singer or a string quartet in a quiet concert hall, it's nasty (not to mention at wedding ceremonies).
Biting the hand that feeds IT
