Phase Detection vs. Contrast Detection Autofocus | Hacker News Reader

Phase Detection vs. Contrast Detection Autofocus

creative-photographer.com

30 pointsdosshell10 comments

The article is probably from 2018 as the newest DSLRs like Nikon's D780 has about the same sensor PDAF capabilities as their Z-series mirrorless bodies.

It's funny, how in the beginning mirrorless cameras (and DSLRs in the liveview mode9 had really slow contrast based AF but nowadays the best models have already catched the DSLR PDAF systems and in some cases are better and more intelligent (like Sony's A7Riv, A6400 and A9* subject tracking which understands subject disappearing from the frame and reappearing etc).

Also, it's funnily telling which photographers have really gotten used to bad DSLR PDAF as they are using only the middle focus point with mirrorless cameras which have the same or better AF-capabilities even in the frame corners. They don't trust the mirrorless sensor PDAF and try to use it like the older DSLRs worked.

I used to shoot with a Nikon D70s and a D300 and I didn't feel limited but all of a sudden with my Sony a7m2 the "small" PDAF area feels super limiting, even though I think nothing has changed.

Though the AF algorithm seems to have a hard time focusing to infinity at times... I'm saving my bucks for an a7r4.

Also not mentioned often is the fact that many cameras have back focus/front focus problems, whereas the combination of PDAF and contrast AF that mirrorless cameras have basically eliminates this problem.

Sounds awfully familiar. Sony A7ii was really frustrating camera. Used it for for few years or so. The A7rII was a lot better and A7iii is already really good. In many cases I'm just using continuous focus and reframing the picture whenever I want without any stress about missing the focus. Tthis means I can concentrate on more important aspects of the portraits than the focus. Ofc difficult lighting situations requires more care but it's still easy compared to previous models. A7r4 feels even better.

Currently it looks like Sony is leading the mirrorless AF-race by 1-2 generations unless Canon manages to bring new flag ship model with something better as the rumors suggest but let's see how that really goes.

My camera is fairly old at this point, but has both methods. Unfortunately, when doing contrast detection AF, it may stop down the aperture if it's too bright. This extends your depth of field, and your camera will then tell you parts of the image are in focus when they will not be when you take the shot.

Really frustrating.

I’ve moved from a 5D mkIII to an R5. The autofocus is extremely impressive, the biggest win however is not the focusing performance but the coverage. The 5D, and most SLRs, cluster the PDAF points in the middle of the frame where as the mirrorless focuses anywhere.

I'd be interested how the iPhone 12 LiDAR compares to these now, especially in low light

If it is comparable to laser focus in other phones, it should be very fast for close up objects and useless for further ones.

and coincidentally focusing close is harder and focusing further away is easier.

You are comparing Focus assist light with LiDAR, not the phase based or contrast based focus.

I don't think so. The focus assist light is (as the name implies) just a light that gives more visisibility and thus assistance to the existing (constrast/phase) autofocus. Not different than opening a window or switching on a light at the location.

Whereas LiDAR can be used to focus all on its own (without even engaging phase/contrast focus). Of course it can be combined too.

In other words, the difference is focus assist is just a light (which doesn't do anything else), where lidar actually measures focus distance.

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