On 24/09/2015 22:19, DJC wrote:
On 24/09/15 15:44, NY wrote:

I'm not sure about your autofocus reason though. The speed of autofocus
response will be a function of the camera's AF detector and (for an
interchangeable lens) the speed of the AF motor in the lens. Digital
cameras may have faster AF, but that may because they are newer rather
than because they are digital rather than film. Unless anyone knows
differently in which case I might be about to learn something!

As far as I can remember, my film SLR took about the same time to focus
as the digital SLR which replaced it, using the same lens, which
suggests that, for my setup, most of the time is taken by the motor in
the lens rather than by the AF sensor and logic in the camera. That's
for like-for-like focussing rules - eg single-shot rather than
continuous and similar sizes of focus zone.


For a SLR the time is limited by the speed of the mirror. Both digital
and film SLRs have mirrors and shutters so there is no difference. The
autofocus sensors are separate from the digital image sensor.



The latest "SLR" don't have mirrors but do have shutters and use the
same sensor for autofocus (some of the time). They do this because its
cheaper as the alignment of the autofocus is guaranteed if its on the
same chip. They also don't suffer from mirror shake and are quicker to
react to the shutter button. You can easily spot mirror less ones, they
are thinner as they don't need space for the mirror.

Professional photographers use them to do movies where they don't want
to put an expensive camera like under cooling towers you are blowing up
or on drones. Something you can't do with film cameras.