contrast based af vs phase detect af in real world

[eatstoomuchjam]

1 hour ago, kye said:

Those examples are just how I described..  PDAF knows where to go and CDAF doesn't..  No new information here 🙂

Right, but they're why your conclusion of "PDAF vs CDAF is a small portion of the AF system on a modern camera" is absolute nonsense.  One of them is able to consistently and smoothly track moving subjects and one of them is not.  If the subject is completely still, then continuous autofocus isn't needed.

Your list of things that you don't understand has nothing to do with the discussion.

As far as shooting interviews/close-ups with an intensely fast lens, if that's what people want, that's totally fine.  It probably won't be my thing, but maybe their client or audience will like it.  I've also personally used extremely shallow DOF on eyes or similar to show that a character is feeling isolated in that moment.  The directors of those shorts seemed to like the result and I felt like it was effective in the final product.
Anyway, the failings of CDAF have been more than evident to me in the past when using the FF equivalent of a 50mm lens at f/2.8 (such as a 25/1.4 on M43) - no need to bust out the 85/1.2.  Just as there is a middle ground between coke bottle and clinically sharp lens, there is also a middle ground between "the irises are in focus, but the nose is fully blurred" and "there's almost no sense of subject/background separation, as everything from foreground to background is in in focus and autofocus is effectively meaningless now anyway."

[Al Dolega]

15 hours ago, kye said:

 I wonder if maybe we need a pressure sensor to press on where the harder you press the faster it moves the focus towards where you're looking.  

That way you could lift off for no focus changes, press slightly to really ease in, or press lightly-firmly-lightly to ease out of focus and then ease in again at the destination, capturing the need for focus adjustments that are not only smooth but faster or slower depending on context, and with all the precision of the computer in focusing on the eye and not eyelashes or nose.

That is a really cool idea! Limited of course to situations where you can use an EVF, but if the EVF tilts and extends, or is a separate rig-able unit... and has the ability to lock its position so your eye-pumping can be accurate... that would create a lot more of those situations. And for shooting from the screen you could implement some type of pressure-sensitive button on the grip, used in the same manner, for the speed adjustment at least.

[kye]

3 hours ago, eatstoomuchjam said:

Right, but they're why your conclusion of "PDAF vs CDAF is a small portion of the AF system on a modern camera" is absolute nonsense.  One of them is able to consistently and smoothly track moving subjects and one of them is not.  If the subject is completely still, then continuous autofocus isn't needed.

This is true, but you're forgetting the bigger picture.

One of them:

• has intermittent subject-recognition failures
• occasionally focuses on the background instead of the subject
• focuses on the wrong part of the subject
• focuses on the wrong subject
• can be blinded by flares
• can be completely clueless when a new subject is introduced and is meant to be the new focus, etc
• and can track a subject for AF-C in the right conditions.

The other:

• has intermittent subject-recognition failures
• occasionally focuses on the background instead of the subject
• focuses on the wrong part of the subject
• focuses on the wrong subject
• can be blinded by flares
• can be completely clueless when a new subject is introduced and is meant to be the new focus, etc
• and can't track a subject for AF-C in the right conditions

Like I said several posts ago.  Apart from the pulsing of DFD, by far the most common focus issues I see have nothing to do with that last bullet point, and are a variety of examples of PDAF systems having issues from the other bullet points.  

Only the other day did I see a beautiful slow-motion follow-shot of a model running and turning to smile at the camera and the golden light from the sunset behind her bathing the whole scene and then she just slightly went to one side and the AF-C quickly racked focus to the background and then back again when she moved closer to the middle of frame again.

Shot ruined.

A long conversation ensued about how to use it in the edit and cover up the AF failure.

PDAF not for the win...  not even slightly.

1 minute ago, Al Dolega said:

That is a really cool idea! Limited of course to situations where you can use an EVF, but if the EVF tilts and extends, or is a separate rig-able unit... and has the ability to lock its position so your eye-pumping can be accurate... that would create a lot more of those situations. And for shooting from the screen you could implement some type of pressure-sensitive button on the grip, used in the same manner, for the speed adjustment at least.

I wonder if future devices will have a little fisheye camera on the back that does a facial recognition on the operator and detects a variety of facial movements and can map them to controls.  This isn't about to happen any time soon, but maybe.

In IT systems design the general idea is that you work out all the things that need to happen and then work out how to make the humans do the things that humans are better at, and the machine do the things that machines are better at.

It might take a completely different approach, like having a button next to the focal ring of the lens that will engage AF and you can manually focus and when you're almost there just press the button in and it will do the rest to fine-tune and hold the focus.  Maybe the button just finds the part of the frame closest to being in focus and chooses that, so no issues with it choosing the wrong thing.

[BTM_Pix]

43 minutes ago, kye said:

I wonder if future devices will have a little fisheye camera on the back that does a facial recognition on the operator and detects a variety of facial movements and can map them to controls.  This isn't about to happen any time soon, but maybe.

There are some tiny (and cheap) 3D gesture scanners available that could achieve this mapping movements to controls. They generally recognise up to 9 different hand/finger gestures so there is a lot of scope.

Similarly, but at the expense of more power and increased size (though not massive and still hot shoe mountable) there are a lot of cheap single AI unit cameras that can be used if you want to do the same with facial recognition.

If they were powered by the camera then the form factor could be reduced further.

The advantage of the AI camera route is that it can be turned facing the scene and do other things too....

This is a rough and ready demo of a face detect AF system that I made for the BM cameras that demonstrates how they can be harnessed to not only detect a face but specific individual people's faces if you train the AI.

The video shows the face recognition in single AF-S mode, AF-C mode and the wide AF-C mode.

With wide AF-C mode, with it being an outboard system with a much wider view of the scene it can detect the subject even when they are out of the frame and be ready for when they step into it.

I left it off the main AFX development as it wasn't quite there at that point for a couple of practical reasons but I'm going to look at it again as things have moved on a little bit in the subsequent four years since I made it.

Being able to decide who's face amongst a crowd of many would satisfy a lot of AF uses as, after all, what YouTuber would't want full on Narcissist AF mode 😉 

It has practical implications for narrative to though as it can easily switch between specific performers in scenes.

[kye]

37 minutes ago, BTM_Pix said:

There are some tiny (and cheap) 3D gesture scanners available that could achieve this mapping movements to controls. They generally recognise up to 9 different hand/finger gestures so there is a lot of scope.

Similarly, but at the expense of more power and increased size (though not massive and still hot shoe mountable) there are a lot of cheap single AI unit cameras that can be used if you want to do the same with facial recognition.

If they were powered by the camera then the form factor could be reduced further.

The advantage of the AI camera route is that it can be turned facing the scene and do other things too....

This is a rough and ready demo of a face detect AF system that I made for the BM cameras that demonstrates how they can be harnessed to not only detect a face but specific individual people's faces if you train the AI.

The video shows the face recognition in single AF-S mode, AF-C mode and the wide AF-C mode.

With wide AF-C mode, with it being an outboard system with a much wider view of the scene it can detect the subject even when they are out of the frame and be ready for when they step into it.

I left it off the main AFX development as it wasn't quite there at that point for a couple of practical reasons but I'm going to look at it again as things have moved on a little bit in the subsequent four years since I made it.

Seriously impressive stuff..  I wish the camera manufacturers were even remotely interested in incorporating this kind of stuff.

Unfortunately, online all these bozos reduce the discussion to PDAF = GOOD / DFD = CDAF = BAD and so there is no knowledge or demand for it from consumers.

[ac6000cw]

1 hour ago, kye said:

It might take a completely different approach, like having a button next to the focal ring of the lens that will engage AF and you can manually focus and when you're almost there just press the button in and it will do the rest to fine-tune and hold the focus.  Maybe the button just finds the part of the frame closest to being in focus and chooses that, so no issues with it choosing the wrong thing.

Oly/OMDS cameras I've used have an 'MF' function you can assign to a button - it stops C-AF and enables the lens focus ring. After you've done the manual focus, press it again and AF takes over again. When going from MF to AF it doesn't force the AF to re-focus so basically (if C-AF is enabled and the in-focus part of the image is within the AF area) the C-AF will hold your focus. Also in MF mode you can push the AF-ON button to force an S-AF re-focus.

On my OM-1 I normally have video AF set to C-AF, then using the MF and AF-ON buttons I can switch between C-AF, MF and MF+S-AF while recording if I want to.

(Oly/OMDS cameras don't have an AF-lock function, so the MF function is the next best thing - you just have to be careful not to touch the focus ring accidentally...)

[Davide DB]

Are these manual focus shots? 😉

 

 

 

[zlfan]

pdaf may pulse too. my c300 og is upgraded to dpaf. I used it for continuous af. at infinity for landscape, I can see it pulse. I have to use one shot af to force the lens to stay at infinity, then pan or tilt. for subjects 3-5 meters away during an event, c300 og dpaf works fine, I have not seen significant pulse. c100 mk ii dpaf is much more reliable. at infinity, I don't see pulse on c100 mk ii.