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Phase detection autofocus (what you're describing) is still used in cameras today, and hasn't changed significantly since the 90's. DSLRs are essentially just a

Phase detection autofocus (what you're describing) is still used in cameras today, and hasn't changed significantly since the 90's. DSLRs are essentially just a film camera, but with a CMOS sensor replacing film. One of the reasons why they still exist, despite the obvious inconvenience of not having a big screen to look at, is because until recently it wasn't possible to build a mirrorless camera with phase detection autofocus. I have a Canon EOS 55 from the late 90's, and in many situations it has better autofocus performance than my Fujifilm mirrorless from 2017.

ohazi 5y ago
Yeah, I remember when the first CMOS sensors with phase detection elements started showing up. This is what I meant by "conceptually similar" although I probably should have clarified, since we've had massive sensors without these elements for longer. I guess contrast-based autofocus is what really needs the DSP, since you need to do edge detection / FFTs on more patches of image for the technique to work well, as well as PSF analysis if you want to guess the lens defocus direction. With phase it's just a few cheap 1D correlations, and you get accurate lens direction information for free, which explains why it feels so much faster. Unfortunately we didn't have access to an electron microscope, so a modern mirrorless camera would have made for a rather less interesting teardown.
- sudosysgen 5y ago
  Contrast based autofocus just doesn't compete either. New, higher end mirrorless cameras still use phase detection just like the DSLRs of old. Sony still uses old-style sensors but mounted directly on the chip, while Canon uses pixels that only accept light from some directions to calculate phase information. Both of these tactics end up with very similar results. Though it is augmented with DSP.
sudosysgen 5y ago
Mirrorless cameras with phase detection have actually existed for a long time - actually since 2010 - before they became practical with EVFs and better batteries. Something that really slowed it down is that Canon filed a patent for Dual Pixel AF which was the first on sensor pdaf system to outperform previous systems, and then proceeded to not make any serious mirrorless camera using it. All the worse is that DPAF was a fairly minor invention that other companies didn't do first mostly because they didn't have the manufacturing capabilities yet - basically using a microlens to split the light instead of a divider to obscure it. So Sony had to find ways to make it work without infringing on the patents and without artifacts.
- toomanybeersies 5y ago
  As a disclaimer: I haven't bought a camera (or looked at new models) since 2018 > Mirrorless cameras with phase detection have actually existed for a long time - actually since 2010 I guess that depends on your timescale. The first SLR camera was 62 years ago, with the Nikon F (1959-1973, 14 years span). The first [SLR] camera with phase detection autofocus, the Canon EOS 650 (incidentally my first SLR [1]) was released in 34 years ago, in 1987. It wasn't until 2002 (Canon EOS-1Ds, 19 years ago) that there was a DSLR that could capture images on par with film. Even if Canon deliberately suppressed mirrorless PDAF (which I don't dispute), phase detection autofocus has been around much longer than digital cameras, and at least until recently DSLRs have had better autofocus performance than mirrorless. To be clear, I'm not cargo culting DSLRs here. My point is that beyond the change from film to CMOS sensor, DSLRs are not significantly different from the film cameras they replaced. [1] I mentioned to a coworker that I was thinking picking up photography; the next day she gave me a bunch of film photography gear that had been sitting in her attic for the past 20+ years. Unfortunately, the EOS 650 ended up getting stolen.
  - sudosysgen 5y ago
    I definitely agree that 11 years for cameras in general isn't that much - I personally use us 60+ year old lenses on my A7ii so I can certainly empathize. Mostly my point is that mirrorless cameras adopted PDAF as soon as making a useful pro-level mirrorless camera was possible. Also, I'd argue that mirrorless cameras are basically a digital version of rangefinder cameras - they make a lot of the same tradeoffs optically and indeed there is a continuous history from digital rangefinders to modern mirorrless cameras.
  - brudgers 5y ago
    SLR cameras go back well over one hundred years. For example the early Graflex models. http://camera-wiki.org/wiki/Auto_Graflex http://camera-wiki.org/wiki/Auto_Graflex

ohazi 5y ago

Yeah, I remember when the first CMOS sensors with phase detection elements started showing up. This is what I meant by "conceptually similar" although I probably should have clarified, since we've had massive sensors without these elements for longer. I guess contrast-based autofocus is what really needs the DSP, since you need to do edge detection / FFTs on more patches of image for the technique to work well, as well as PSF analysis if you want to guess the lens defocus direction. With phase it's just a few cheap 1D correlations, and you get accurate lens direction information for free, which explains why it feels so much faster. Unfortunately we didn't have access to an electron microscope, so a modern mirrorless camera would have made for a rather less interesting teardown.

sudosysgen 5y ago
Contrast based autofocus just doesn't compete either. New, higher end mirrorless cameras still use phase detection just like the DSLRs of old. Sony still uses old-style sensors but mounted directly on the chip, while Canon uses pixels that only accept light from some directions to calculate phase information. Both of these tactics end up with very similar results. Though it is augmented with DSP.

sudosysgen 5y ago

Mirrorless cameras with phase detection have actually existed for a long time - actually since 2010 - before they became practical with EVFs and better batteries. Something that really slowed it down is that Canon filed a patent for Dual Pixel AF which was the first on sensor pdaf system to outperform previous systems, and then proceeded to not make any serious mirrorless camera using it. All the worse is that DPAF was a fairly minor invention that other companies didn't do first mostly because they didn't have the manufacturing capabilities yet - basically using a microlens to split the light instead of a divider to obscure it. So Sony had to find ways to make it work without infringing on the patents and without artifacts.

toomanybeersies 5y ago
As a disclaimer: I haven't bought a camera (or looked at new models) since 2018 > Mirrorless cameras with phase detection have actually existed for a long time - actually since 2010 I guess that depends on your timescale. The first SLR camera was 62 years ago, with the Nikon F (1959-1973, 14 years span). The first [SLR] camera with phase detection autofocus, the Canon EOS 650 (incidentally my first SLR [1]) was released in 34 years ago, in 1987. It wasn't until 2002 (Canon EOS-1Ds, 19 years ago) that there was a DSLR that could capture images on par with film. Even if Canon deliberately suppressed mirrorless PDAF (which I don't dispute), phase detection autofocus has been around much longer than digital cameras, and at least until recently DSLRs have had better autofocus performance than mirrorless. To be clear, I'm not cargo culting DSLRs here. My point is that beyond the change from film to CMOS sensor, DSLRs are not significantly different from the film cameras they replaced. [1] I mentioned to a coworker that I was thinking picking up photography; the next day she gave me a bunch of film photography gear that had been sitting in her attic for the past 20+ years. Unfortunately, the EOS 650 ended up getting stolen.
- sudosysgen 5y ago
  I definitely agree that 11 years for cameras in general isn't that much - I personally use us 60+ year old lenses on my A7ii so I can certainly empathize. Mostly my point is that mirrorless cameras adopted PDAF as soon as making a useful pro-level mirrorless camera was possible. Also, I'd argue that mirrorless cameras are basically a digital version of rangefinder cameras - they make a lot of the same tradeoffs optically and indeed there is a continuous history from digital rangefinders to modern mirorrless cameras.
- brudgers 5y ago
  SLR cameras go back well over one hundred years. For example the early Graflex models. http://camera-wiki.org/wiki/Auto_Graflex http://camera-wiki.org/wiki/Auto_Graflex