Autofocus For Video: What's Your Take?

[Davide DB]

The autofocus technology used in the latest generations of mirrorless cameras has made great strides. Established technologies such as PDAF (Phase Detect Auto Focus) have been joined by the ever-present A.I. (it's so cool today to have this acronym even on breakfast corn flakes) with algorithms that actually exploit huge amounts of data through machine learning. It is therefore possible to speed-up sensor's data analysis and recognize people, faces, eyes, dogs, cats, birds, cars, trains and who knows what else in the future.

 

As for underwater photography, there are countless tutorials on the best autofocus settings for both WA and macro. Even here the topic has been addressed several times for the now very popular Sony A7Rs.

 

As far as underwater video is concerned there is practically nothing on the Internet, and I do not think the photography tips are always directly applicable.

 

I was discussing this on Youtube and was told that typically those who make videos are less technical (users are more casual), all on automatic or they know their camera well and don't need tutorials.

 

Will this be true?

 

Let's use this thread to tell how you use autofocus in video, what is your use case, camera and how do you find it.

 

[Davide DB]

I am an old filmmaker who "still" uses a GH5M2 with CDAF. 

Never had problems in WA or medium close shots but I only use single AF configured on the AF-Lock button. I lock the focus on the subject or, on moving subjects, I lock the focus at an intermediate value and try to stay as hyperfocal as possible.

In all mirrorless housings it is impossible to operate the manual focus ring to follow the subject: the gear is so tenfold that one turn moves the focus by very little.

Only on cinema housings is there a more "humane" relationship between turns of the housing ring and the focus barrel on the lens. 

In practice the focus ring is dedicated exclusively to macro shooting and even there it is necessary to have a basic focus with AF and only then to work in manual for micro adjustments.

I must say that in static macro conditions with good lighting I can also work only in Single AF by using a small area and moving it to the relevant point with the slider and then use Lock-AF. 

 

What is different with modern intelligent PDAF systems?

 

Could we work in CAF by following the eye of a fish, a nudibranch or the eye of a hermit crab as it moves in macro?

 

Could we reliably track the face of a diver swimming from the blue toward us?

 

[SwiftFF5]

Interesting topic @Davide DB, thanks for starting it.  I shoot with a GH5, and try to use autofocus as much as possible, to be able to track small moving critters.  However, it sometimes won't focus, or focuses on the wrong things, which gets very frustrating.  I switch between MF and both autofocus modes, depending on what I am doing at the time, but it doesn't always work well, and I have missed some really good clips because of that.  I am very interested in seeing what the PDAF autofocus on the GH7 will do, but I am waiting until someone gets one in the water and sees what it will do, especially with white balance, before I spend the money on a new body and new housing.

Edited July 7 by SwiftFF5

[Davide DB]

1 hour ago, SwiftFF5 said:

I switch between MF and both autofocus modes, depending on what I am doing at the time, but it doesn't always work well, and I have missed some really good clips because of that.  I am very interested in seeing what the PDAF autofocus on the GH7 will do...

 

Yes, I'm at the window too 😉

 

Given that Sony AF is often considered as a reference I'm curious to read/see what's possible to achieve in a real scenario. Plenty of Sony/Canon uw shooters out there but it's not clear if they are really exploiting their camera AF capabilities or just working in a traditional way like me. 

As I wrote in another post, it is considered rude to ask a photographer/filmmaker what he/she shot with and how he/she did it 🙂

 

Discussing autofocus with some professional underwater filmmakers, their reaction was a mixture of disgust and wonder. 
They all work exclusively in manual focus. But cinema cameras often do not have evolved AF or you simply cannot rely on AF for important shots.

[Davide DB]

As example this is a rare video showing as Canon R5 animal eye AF works on fish (but on photography)

 

IDK What the result would be on a 30" clip...

 

 

 

 

Here it works but on a single static animal

 

 

 

[Davide DB]

Digging the net I found another example, always from the same user.

 

 

 

[humu9679]

@Davide DB I've been a still photographer for more than 40 years, and only recently began dabbling in video. I am very surprised to see so much manual focusing going on with serious videographers. My supposition is that AF in video is akin to point and shoot in stills, considered amateurish and certainly hit or miss. I figure videographers will come around when AF performance improves. I'm curious to see what videographers think of AF performance now.

[Davide DB]

3 hours ago, humu9679 said:

@Davide DB I've been a still photographer for more than 40 years, and only recently began dabbling in video. I am very surprised to see so much manual focusing going on with serious videographers. My supposition is that AF in video is akin to point and shoot in stills, considered amateurish and certainly hit or miss. I figure videographers will come around when AF performance improves. I'm curious to see what videographers think of AF performance now.

 

In land shooting the issue is debated. In film, the problem doesn't really exist: you have a team, manual focus is handled by a professional focus puller. Conversely, automatic focus is particularly felt in all those run & gun situations or for one man bands in weddings and events in general. Then youtubers and the v-logging craze did the rest.

Of course, footage like this without an Animal Eye AF would be exclusive to the BBC or a few other camera operators and instead...

 

 

 

 

 

All the underwater videographers I know work more or less as I described above but the danger of living in a bubble is always lurking 😉

 

That is why I am curious for feedback here.

 

 

[humu9679]

2 hours ago, Davide DB said:

 

In land shooting the issue is debated. In film, the problem doesn't really exist: you have a team, manual focus is handled by a professional focus puller. Conversely, automatic focus is particularly felt in all those run & gun situations or for one man bands in weddings and events in general. Then youtubers and the v-logging craze did the rest.

Of course, footage like this without an Animal Eye AF would be exclusive to the BBC or a few other camera operators and instead..

 

 

 

 

 

 

 

 

I've seen Mark Smith's images of birds in flight. Pretty amazing. I'll be following with interest the exploits of videographers on this site, and I would hope you would divulge any technical details to the newbies here.

[bghazzal]

Very interesting subject indeed, looking forward to reading more real life feedback, especially from Sony-AF users!

 

I don't have much experience/feedback to contribute, as while not being professional nor having a cinema rig I also shoot in manual focus both for wide and macro.
 

This is not because I think using AF is amateurish in any way, but because in my case AF just doesn't work underwater.
Lumix LX10 autofocus is slow, and CAF tracking uses up way too much of the cam's very limited battery power.
Other major issue is particules in the water, water movement, there are simply too many things leading AF to tracking in the void and missing shots.

 

What works best for me is manual with back-button focus AF (AF/AE lock, set to single area AF) and focus peaking for visual feedback.

 

- For wide angle, it's mostly hyperfocal and not an issue at f/8 to f/11 with the Inon UWL-H100, just back-button lock and good to go, reefs, sharks, mantas etc...

I shoot wide in ambient light with a filter, so peaking info is more limited, but there's usually enough feedback to judge how much is in focus.
 

- For macro/supermacro, there's more going on on the focusing front, and getting small critters both in focus and properly lit is critical -  I acquire general focus, and then use peaking to see where I'm at.

I was using the focus knob at first, but while it's very useful for fine-tuning the focus point on an already acquired focus, it doesn't really work for acquiring focus for tiny critters - backbutton AF and nudging the camera (on its quadripod) really works best.
So it's usually nudge/backbutton acquire> nudge > fine tune

In macro shooting's full artificial light, focus peaking is generally wonderful, and once the focus point is acquired you can really adjust to your liking.
For tiny critters, DoF is super shallow already, so aperture considerations tend veer to the artistic (the how-shallow-can-you-go focus-limbo dance 😁)...
If there's a little surge, most tiny critters will swing in and out of focus and DoF is so shallow CAF wouldn't make much of a difference...

 

- Focusing is, however, much more tricky for closeups/portraits of medium-sized critters in movement - but I find this is also very much size/behaviour dependent.
This crab clip was in constant fast motion, roughly 10cm wide critters, but there was use sufficient leeway to keep things in focus, following the show and reaquiring critical focus with backbutton AF when needed, and while this wasn't really macro, it was sufficiently artificial-dominant lighting for peaking to work great and see when I was nailing it.

Even if playing with aperture and depth of field, UW action is usually slow enough to reaquire focus and get a decent clip, especially with larger to medium subjects like turtles, octopuses etc
 

- The trickiest bit, and one where I would love a super-fast autofocus, is tracking fast-moving small critters, say in the 5cm range, especially of the free-swimming variety...
This is hellish, as it's combining shallow DoF with fast movement, and this is where I'm missing the most number of shots.

I haven't found a good solution, and if the critter doesn't slow down it's very difficult to get usuable footage - and even if it's in focus and stable, on my cam zoomed-in shallow dof + movement makes for some very sea-sickness inducing clips, as the sharp/stable critter is moving in front of a blurry fast moving background, and quite the roller-coaster ride....
Fun watch (weeee!), but I've never used those shots, as it's just too much...
Would probably need a lens with more depth of field to shoot something less psychedelic and useable...
 

Classic free-swimming critters like ghostpipefish (usually in the 5 to 10 cm range) can be tricky, as while they don't move around too much, staying close to their camouflaged habitat, they can have a tendency to move in and out of focus - partial hand-held, ie using one or to legs for support but allowing follow movement works well (or fully handheld if stable).

But then it also depends on conditions and the subject itself -  some are also nice and cooperative and stay in one place to allow for multiple shots with different focus areas (eye closeup, mouth closeup, shallow dof...), nice and easy.

 

I'm also concerned about black-water video shooting scenarios, which combine hand-held, small moving, critters and lighting considerations (critical with transluscent critters).
This is where efficient AF definitely sounds like a good idea (so you can focus-pun intended - on lighting), and I'm not sure how things will go IRL.
I do have a hunch that a "light-box" type config might be good enough - if you know that the central part of your "light box" square is in focus, then it's mostly a question of keeping the critter in there as you follow the movement.
But this is just a theoretical projection for now, never-try-never-know as they say...

 

All this to say that MF + backbutton AF works for me, and tracking animal eyes hasn't been much of an issue - if it's big enough, you can follow peaking points handheld, and if smaller then a semi-handheld solution allows for the small movement required to do so...

Then again, I've also never been in more cinematographic shooting scenarios where I had to track the face of diver swimming towards me for instance, for which a good autofocus or solid manual tracking option would be absolutely necessary....

 

***

 

I'd like to add that while the video forum clearly has a really limited reach, it's really refreshing to take part in this type of concrete, practical technical discussion!
I really wish there was more of that (along with more aesthetic/artistic discussions to even things out, of course...).

I've been reading into WeP archives recently, digging for historical info on a filter, and there was a bit more of this going on 20 years ago, when you had a lot of users experimenting with video rigs and sharing practical, technical info with their peers.

Then it all seems to have died out a few years back, with video discussion flatlining, paradoxically exactly when sharing video was finally becoming possible...

I have a feeling this is linked to the rise of bandwidth-enabled commercial video content, where semi-professional video-shooters started working as "content creators" sharing their content online (liveaboard-based videos, for instance, were no longer limited to trip-recap videos sold to customers, but became promotional content actively shared online, like professional advertising content for resorts or locales), and were thus much less inclined to share information (maybe not so much out of pride as out of protectionism?)
This dying-out of practical discussion also happened at the same time as the rise of social-mediable clips of vloggers and YTubers, which probably accounts for 80% or more of video content found online, and mostly 1-shot-stand affairs.

Industry, truly professional UW cinematographers have always been more secretive, and working in a world of their own, with techniques closely linked to the equipment (and teams...) they have access to - inspiring, but a little out-of-reach...

 

Edited July 8 by bghazzal

[Davide DB]

7 hours ago, bghazzal said:

I'd like to add that while the video forum clearly has a really limited reach, it's really refreshing to take part in this type of concrete, practical technical discussion!
I really wish there was more of that (along with more aesthetic/artistic discussions to even things out, of course...).

I've been reading into WeP archives recently, digging for historical info on a filter, and there was a bit more of this going on 20 years ago, when you had a lot of users experimenting with video rigs and sharing practical, technical info with their peers.

Then it all seems to have died out a few years back, with video discussion flatlining, paradoxically exactly when sharing video was finally becoming possible...

I have a feeling this is linked to the rise of bandwidth-enabled commercial video content, where semi-professional video-shooters started working as "content creators" sharing their content online (liveaboard-based videos, for instance, were no longer limited to trip-recap videos sold to customers, but became promotional content actively shared online, like professional advertising content for resorts or locales), and were thus much less inclined to share information (maybe not so much out of pride as out of protectionism?)
This dying-out of practical discussion also happened at the same time as the rise of social-mediable clips of vloggers and YTubers, which probably accounts for 80% or more of video content found online, and mostly 1-shot-stand affairs.

Industry, truly professional UW cinematographers have always been more secretive, and working in a world of their own, with techniques closely linked to the equipment (and teams...) they have access to - inspiring, but a little out-of-reach...

 

It is a general phenomenon that has almost wiped out the forums. But videomakers have been swallowed up by YouTube and the social media mania more than others.
I know several professional videographers and they are actually more jealous than photographers about their methods and tricks of the trade.

 

let's see if we are lucky

[humu9679]

16 hours ago, bghazzal said:

Very interesting subject indeed, looking forward to reading more real life feedback, especially from Sony-AF users!

 

I don't have much experience/feedback to contribute, as while not being professional nor having a cinema rig I also shoot in manual focus both for wide and macro.
 

This is not because I think using AF is amateurish in any way, but because in my case AF just doesn't work underwater.
Lumix LX10 autofocus is slow, and CAF tracking uses up way too much of the cam's very limited battery power.
Other major issue is particules in the water, water movement, there are simply too many things leading AF to tracking in the void and missing shots.

 

What works best for me is manual with back-button focus AF (AF/AE lock, set to single area AF) and focus peaking for visual feedback.

 

- The trickiest bit, and one where I would love a super-fast autofocus, is tracking fast-moving small critters, say in the 5cm range, especially of the free-swimming variety...
This is hellish, as it's combining shallow DoF with fast movement, and this is where I'm missing the most number of shots.

 

All this to say that MF + backbutton AF works for me, and tracking animal eyes hasn't been much of an issue - if it's big enough, you can follow peaking points handheld, and if smaller then a semi-handheld solution allows for the small movement required to do so...

 

 

 

 Your focusing in the crab video seemed to work out okay. I think you might like Sony's latest AF. It will allow for tracking of small critters once you've locked focus. The hard thing would be keeping them in the frame.

[Davide DB]

38 minutes ago, humu9679 said:

 Your focusing in the crab video seemed to work out okay. I think you might like Sony's latest AF. It will allow for tracking of small critters once you've locked focus. The hard thing would be keeping them in the frame.

 

Probably yes but...

 

I'm still waiting for someone to show up saying "hey I used animal eye AF on this clip, here are the results!" 😁

[bghazzal]

18 hours ago, humu9679 said:

 Your focusing in the crab video seemed to work out okay. I think you might like Sony's latest AF. It will allow for tracking of small critters once you've locked focus. The hard thing would be keeping them in the frame.

Perhaps – in this type of scenario, where you’re following fast moving medium-sized action, not having to worry about focusing would certainly be a relief, but I’m also not convinced results would be that different.

It would for sure make life easier if it works, but I think there might also be a risk of AF loss and tracking when the subject is out of the frame / lighting - which is bound to happen at some point -  in which case staying focus-locked-in might actually be easier.
Hard to tell – I know on my cam it wouldn’t work, but if Sony AF is as good for video as it is for stills, it could be very nice indeed in some cases!

I chose this specific example as it was technically more challenging because of the fast moving of medium sized subjects, with little time to adjust. This might sound a little paradoxical, but for smaller macro to supermacro subjects I find it somewhat easier (MF examples of all sizes here or here). Based on my experience and the setup I use, but in the 10mm to 5mm critter size-range and below, depth of field gets so shallow that AF  doesn't have much to offer.
You basically have to move (nudge) the camera if the critter moves out, there’s just not enough range to focus-follow.
 

But for fast-moving middle-range subjects (which are not that common actually), and also more tricky applications like small subjects free-swimming in the water column (black-water beckons...), I can definitely see the appeal of fast and efficient AF tracking.
Tricky enough following the show and being stable! 😅
 

17 hours ago, Davide DB said:

 

Probably yes but...

 

I'm still waiting for someone to show up saying "hey I used animal eye AF on this clip, here are the results!" 😁

Bring back 80s home-video zoom-shots! 😁
Joke aside, I agree, it would be great to have some illustrations of latest AF tracking-technology being put to good use for underwater video.

Animal-eye AF on the eye of fish moving in a school would be amazing, and I would love to have access to the extended-range / helping hand an efficient Sony AF system could give if it works as it's rumored to.

AF seems like a no-brainer for stills, since you are effectively freezing the movement, but for video nailing the 10-seconds-minimum of focused, stable footage required for moving pictures ofen requires a different type of control over the camera.
Really curious as to how others approach the issue and what works best for them.
 

Edited July 9 by bghazzal

[SwiftFF5]

@bghazzal wrote "for video nailing the 10-seconds-minimum of focused, stable footage required for moving pictures often requires a different type of control over the camera."

 

Amen to that, getting the subject in focus is one thing, but keeping it in focus long enough to be useful is the hard part.  Something that we all, probably, struggle with.

[wydeangle]

Here's an example of the use autofocus from 5 years ago using an AX700 Sony:

 

It's in 4K so view it that way if you can.

No lights - no post processing.

 

Tom

Edited July 9 by wydeangle
revise link

[bghazzal]

Thanks for sharing this, really interesting.
 

 AF is doing a great job at staying on the crab and ignoring the smaller shrimps and bigger clownfish.

However at 53 seconds in it loses focus as the crab is moving to top left of the frame, and regains focus when the camera moves in.
Same at 1:56, would you know what is going on here?
 

In the first instance, it looked a bit like the crab has reached the dof limit, but seems too shallow for this critter size - for the last one I'm wondering if AF is confused by camera movement?

It almost looks like there's a weak artificial light source at the begining (I'm guessing it's sunlight), so I'm wondering if it's actually changes in illumination angles that throw it off balance twice.

Do you think using a video light would have helped the AF lock-in on the crab by increasing contrast data?
 

Anyway, it’s very interesting to see AF in action, doing a good job 5 years ago already.


 

 

Edited July 10 by bghazzal

[Davide DB]

Thanks @wydeangleYes, same questions as @bghazzal.

Do you remember which AF did you use? It seems a center frame CAF and it loses focus when the crab moves on the frame borders.

 

[Nikolausz]

I'm relatively new to this, so I don't have that much experience with AF cameras. I currently use a Sony A6400 and my approach depends on the lens. I use AF with wide lenses without problem. I tested SEL 10-18mm F4 and SEL 11mm F1.8 under low light low visibility conditions without any problem. Another lens I used with mixed results is the SEL 30mm f3.5 macro. In AF mode it often shift focus, especially if something appears in the foreground. Another issue is that even when used on a tripod, it applies some micro adjustment, which makes the whole footage bad. I have an example here:

 

So in such case it's better to adjust focus with AF and then switch to MF. Sometimes, with larger high contracts subjects it works well:

 

 

I have recently tried the 90mm macro lens and I concluded that the AF was quite OK but it's not a lens for hand held videos.

[Davide DB]

9 minutes ago, Nikolausz said:

In AF mode it often shift focus, especially if something appears in the foreground. Another issue is that even when used on a tripod, it applies some micro adjustment, which makes the whole footage bad.

 

IDK Sony A6xxx AF. Which settings do you use?

[Nikolausz]

2 hours ago, Davide DB said:

 

IDK Sony A6xxx AF. Which settings do you use?

Sony A6400, AF-C as I remember focus area was center.