Originally posted by biz-engineer I don't see much advantage to mirrorless cameras until CMOS sensors are full designed for mirrorless, continuously capturing images at a quick frame rate.
SmartPhones drive the largest volume of image sensors (millions of sensors sold per month), and that has an impact, which propagates to the other larger sensors.
I see where you're going with this, and although I agree with your point that quick frame rate will give new capabilities, there's other things going on here that I have a slightly different perspective on it.
In my experience, Mirrorless vs DSLR isn't so much considered in sensor design; the shutter operation is a factor - electromechanical and/or electronic global shutter or rolling shutter. But this has been around with CCDs since the '90s and CMOS Active Pixel sensors since perhaps 2005. CMOS is finally getting to be good enough to replace CCD in science applications; mirrorless has almost nothing to do with it.
Originally posted by biz-engineer Then, obviously, faster sensor readout open up more functionalities, such as in camera stacking, video recording , slow motion.
Faster sensor readout was always a constraint of CCD sensor, which have been around for 50 years now, and right now they are at their state-of-the-art, although they are still limited to typically 1-4 simultaneous readouts.
The shift to CMOS fabrication for Active Pixel Sensors allowed lots of logic to be put on the same chip - including many hundreds or thousands of parallel analog-to-digital converters.
Noise is the counterpart.
Stacking isn't really as necessary if you get rid of noise on long exposures. Cooled CCDs can shoot 20min to hour long exposures, with a bit of amplifier glow in the corners where the chips are read out.
CMOS suffers from glow along the edges of the chip, especially where the logic and ADCs are. And there are thousands of transistors involved in doing that to get fast readout.
The other thing is the sheer number of pixels is driving the need for (a) more ADCs on board the CMOS sensor; (b) higher memory bandwidth to temporarily store the pixel data streams, (c) faster storage devices to save the final image, (d) faster onboard FPGAs and processors, (e) faster interfaces to get the data out of the camera - to displays, computers, storage.
So, frame rate isn't just constrained by the sensor readout speed. If you can't move all the data around, manipulate it, and store it in realtime, then the fastest sensor readout is constrained by the slowest part of the system.
Originally posted by biz-engineer But so far, most mirrorless models use sensors that were designed for DSLR, performance is not (not yet) revolutionary.
I don't agree that the issue is "designed for DSLR". Right now we can get big CMOS sensors with 24fps-30fps; the issue is how fast you can move the data, manage the data, process it, and present it, in a device that has to run off a couple lithium cells, and not need a massive heatsink and cooling fans. There is a huge amount of processor power, fast memory, and custom logic to keep up with the frame rates that are technically possible, with a pretty small power pack and limited ability to get the heat out. Heat of course is the cause of thermal noise - and that impacts image quality.
My issue with most mirrorless is the lag between photon in and photon displayed on the electronic viewfinder. And the pipe from sensor to display is quite constrainted when you get to large pixel counts.
Originally posted by biz-engineer In medium format, the mirrorless versions of the 645z are not that impressive with their contrast detect AF, about as slow as focusing in live view. Bodies are smaller , but autofocus on those cameras is far from impressive.
Agree completely. I find them disappointing.
Originally posted by biz-engineer When mirrorless models will have sensors capturing 50 images per second, then mirrorless will be a game changer.
High frame frame sensors, with enough computing horsepower and memory bandwidth would give most of the same game-changing capabilities to a DSLR.
The DSLR constraint would be moving the mirror and firing the shutter; Live view has already shown that it's not that different to mirrorless.