Today we're gonna be looking at three cameras
with three different autofocus systems.
We've got the Sony a7 III with the hybrid system,
the Panasonic G9 with the contrast based system
with the twist, and the Canon EOS R which uses
Canon's famous Dual Pixel CMOS autofocus.
Now I have a few goals for this video based on
a few misconceptions I wanna tackle.
First, I wanna reduce some of the perceived disparity between
phase detect and contrast detect based autofocus systems.
Everyone seems to think that phase detect is awesome
and the way of the future,
and contrast detection is terrible and is a dinosaur.
And that simply isn't true.
Two, I wanna explain what makes Canon's Dual Pixel autofocus
so special and how the new EOS R has improved upon it.
And three, I wanna tell you why the Panasonic G9
is the fastest focusing consumer camera out there.
Four, I'm gonna answer a subscriber question
about autofocusing points
and if having a lot of them is important.
And lastly, number five, I want you to leave this video
feeling like you know which autofocusing system
is the right fit for you and how to best use it.
And I hope to do all this in under 15 minutes.
Let's get Undone.
[offbeat music]
♪ Gerald Undone ♪
♪ He's crazy ♪
What is happening, everybody?
I'm Gerald Undone and let's talk autofocus.
But before we do that, let's just take a quick minute
to thank Camera Canada for hooking us up
with the EOS R so I can show you tangible results
when it comes to the Dual Pixel autofocus.
They have the EOS Rs in stock now so if you're Canadian
like me and you wanna get your filthy mitts on the new Canon,
make sure you check out Camera Canada.
Links will be in the description below.
Alright, so let's talk about what I keep hearing
when I watch camera reviews or read blogs and forums,
which is that contrast detections sucks
and phase detect autofocus is where it's at.
In fact, when the new Panasonic full frames
were announced at Photokina, one of the most repeated lines
I heard was how they were disappointed that they opted
for contrast detection instead of upgrading to phase detection.
But the first thought that always enters my head
when I hear things like that is,
"You know the Panasonic G9, a contrast based system
is the fastest focusing camera out there, right?"
It's also the most accurate focusing camera I've ever used
and these sentiments can be extended
to all of the new modern Panasonic models.
There are some things that it's not that great at,
such as tracking fast moving subjects,
and locking on after a transition.
And this is logical if you know how contrast detection works,
and it's also where phase detection beats it.
But that doesn't mean we should be immediately disappointed
when we hear that a camera uses contrast detection.
And to prove that, let's quickly talk about
how these two different systems work.
So, phase detection is all about bringing two slightly
different perspectives into alignment at the right time.
Similar to what we talked about in previous videos
about raise converging.
Phase detection is a method of achieving focus
by shifting the overlap until it starts to line up
perfectly or comes back into phase.
And this is how most DSLRs work in photo mode.
And they actually have a separate sensor
dedicated to this task.
Because the mirror is blocking this from being done
on the actual image sensor, a secondary reflection
is taking place that bounces this down onto the AF sensors
so that you can focus before you actually
take the picture and lift the mirror.
And this system was the standard for action,
sports, and wildlife photographers because of
its innate advantages when it comes to speed.
And the reason why phase detection is quick in this way,
is because knowing how something is out of phase,
allows for two other variables to be known as well.
Which way the focus is out, as in-- is it too far forward,
or too far back, and how far out of focus is it?
And knowing these two things allows the camera to make
a rapid movement in the right direction and with conviction.
This was much different than contrast detection
which also existed on those DSLRs but only
when live view was enabled and the mirror was locked up.
If the mirror is up, and you're reporting directly
to the image sensor, then there's no way
to bounce a duplicate image down to the AF sensor.
So, those cameras had to use a different on sensor solution
called contrast detection.
The idea behind contrast detection
is the camera analyzes the image as it sees it,
and moves the focus back and forth
until it achieves the best contrast.
This is more like how you edit your photos
and videos when it comes to sliders.
You probably start out with a bit too much,
then you pull it back a bit, then you add a little bit more
until you find that that sweet spot that you like the best.
But contrast detection was very dependant
on the quality and the power of the cameras processors,
and in earlier models this meant much worse performance
when compared to the dedicated phase detect AF sensor.
This lead to a pretty obvious disparity where you'd be using
your DSLR in photo mode and you could track a flying bird,
but when you switch it over to video or live view,
you'd get a much different experience.
So, this lead to the conclusion that contrast detection sucks
and phase detection rules. Right? Well, no.
There's serious pros and cons to both.
And we already talked about the pros of phase detection.
So, what are some of its cons? Well, it's less accurate.
Especially when it came to DSLRs.
Because the focusing wasn't being done on the image sensor,
it was much more vulnerable to lens inconsistencies
and micro-shifting of the hardware.
This is why many camera and lens combinations
needed to be calibrated and have focus adjustments stored
in order to prevent front or back focusing.
These errors aren't possible with contrast detection
because the analysis takes place on the image sensor itself,
and the calculations are based on the final image.
Also, because of the requirement for incoming light
to be reflected down through a translucent mirror component
to hit the dedicated AF sensor, phase detection
that hard limits on what f-stops it could work under.
If your lens was too slow or you used the wrong combinations
of adapters and teleconverters,
autofocus would be laboured, if not, impossible.
Now, while light is important in all autofocusing systems,
contrast detection is based more upon visible contrast
and it doesn't really care how narrow your aperture is.
So, this makes contrast AF a more versatile system
when it comes to various shooting conditions.
But, contrast detection has its limitations as well.
It doesn't have the ability to know
how far from correct focus it is, or in what direction
it needs to move, like phase detection does.
It's a bit more of a guessing game.
It goes in one direction and sees if it's better or worse.
And if it's better, it goes more and more,
getting better and better until it starts to get worse,
and then it backs off a bit
until it finds that perfect position.
This is what creates that pulsing
when contrast detection is hunting, or when using
certain detection modes in video shooting.
It can't lock on to good focus as easily as phase detection,
because it's never quite sure.
Phase detection can just go and say,
"yep, I'm in focus, stop doing things now."
Where, contrast detection has to constantly check
to make sure it's in the best position possible
because it doesn't know if the focus is better,
unless it compared it to something worse,
over and over and over again.
But at that time, contrast detection
was the only option for video, even if phase detection
could potentially give a more pleasing result
by transitioning correctly and then stopping.
But the cool features like face tracking and the other
detection modes generally only worked in contrast detection
because they too, were based on calculations being done
on the actual image sensor and didn't integrate well
with that separate phase detection sensor.
Now, this is where mirrorless differ.
Because there's no mirror box, there's obviously no way
to bounce the image down to a dedicated AF sensor,
so manufacturers started putting
the phase detection components right on the image sensor.
And this improved one of the major problems
of phase detection by reducing the likelihood
of having a focus misalignment
from having that separate autofocusing sensor,
and that lens variance that we were talking about earlier.
The calculations were being done right on the image sensor
just like with contrast detection.
And this opened up the door for other computational modes
like face detection and tracking to be used
with phase detection and not just contrast detection anymore.
But the early incarnations of this weren't the greatest
due to the less than stellar implementation and the missing
horsepower needed to drive such a system.
Because the camera processors
just weren't as good as they are now.
It also continued to highlight a fact about autofocus
which is that you can do it quickly
or you can do it accurately, and despite all the advances,
while phase detection was definitely faster,
contrast detection was still more accurate.
Despite all the hate that contrast detection receives,
if you're subject isn't moving, contrast detection
will produce a better focus. Period.
If you shoot products and stage scenes like me,
phase detection is irrelevant and somewhat undesired.
Those were the facts of life up until not that long ago.
But these three cameras that I mentioned in the beginning
of the video, show the different approaches that
the manufacturers have taken to overcome those limitations.
The first solution was a hybrid system,
and I'm sure you've heard the term,
"hybrid AF" before but basically all it means is that
it incorporates both autofocus systems.
Hybrid systems are around even in DSLRs,
but of course they were only engaged when in live view,
and still used regular contrast detection.
But some of the image capture pixels on the sensor
were replaced with autofocus ones
that would make phase detection calculations.
The idea was to let the initial focus happen
with phase detection so we get moving in the right direction,
and know approximately how far to go,
and then fine tune it with contrast detection.
That way, it wouldn't be as slow as normal
contrast detection because it wouldn't have to do
its hunting all the way up, just at the very end.
But we could get some of that accuracy
from contrast detection at the end,
where it fine tuned it and found
the best possible focusing position.
It seemed like the best of both worlds.
The Canon, however, does seem like a waste of sensor
real estate for something that they couldn't use in photo mode,
that didn't perform as well as their dedicated AF sensor,
and still required contrast detection
in order to complete the focus.
Their solution, of course, was their Dual Pixel autofocus,
which incorporates phase detection
into nearly every pixel.
Each one of these pixels has two photo diodes
which create the phase difference data.
It's as if each pixel has two mathematical perspectives,
thus, dual pixel.
This allowed for much more efficient results
than the sporadically placed AF pixels in the hybrid systems,
without giving up any image capture pixels in the process.
It also allowed for much more computational data
for the phase detection to work with,
similar to what you would get
from a full contrast detection sensor read out.
This meant full implementation of features like face tracking,
using the data range of contrast detection
but at the speed of phase detection.
This made Canon comfortable enough to move forward
with a completely phase detection based system
with no reliance on contrast detection.
Dual pixel also provided
a more balanced experience in low light
by adjusting some of the tougher scenarios for contrast detection
like bright lights in a night environment.
So, overall Dual Pixel autofocus is an important
and impressively balanced development from Canon.
But, it's not perfect.
First, it's not quite as accurate as the dedicated
contrast detection systems, and it's also not quite as fast
as the hybrid systems out today that have less data to crunch,
and better processors to crunch it with.
Because the processor department is something
that Canon is lagging further and further behind in.
But the new EOS R does address one of the issues from
the DSLR days by enabling dual pixel autofocus in photo mode.
Canon moving the mirrorless means you no longer
have to use the dedicated AF sensor and thus,
miss out on those extra features
when not using live view, it's Dual Pixel all the time.
Now, this'll mean some adapting and probably
some kinks that will need to be worked out for the sports
and wildlife shooters moving over from DSLRs
because the systems do feel a little bit different.
But, I think this is definitely a step in the right direction.
Dual pixel AF is fantastic for video because of the gorgeous
focus transitions that make for really natural racks and pulls.
Plus it has stability in focus once the transition
is complete without any pulsing
because it doesn't rely on contrast detection.
And it's here where the hybrid AF systems suffer
a little bit, despite Sony and more recently Fuji
offering autofocus systems with great capabilities.
Their video AF while quick and reliable,
still has a bit of harshness to it.
Almost as if you can see the hybrid action occurring.
It's like you get a fast bit and then a slow bit.
And the fast bit is really fast.
Faster than Canon, and that's pretty impressive.
But then it's almost two fast for its own good
if you want a more natural look.
Outside of that though, these modern hybrid systems
are fantastic and they're my favourite of the three,
with Sony being the path maker for innovation in that area.
Because of their better processors,
and their more manageable data range
which is created by combining the two AF systems.
These hybrid cameras are the only ones that are able
to do both, reliable continuous eye detection,
and near perfect lock-on tracking.
Their video autofocus, as I said, is fast,
and locks on well, and their high burst rate photo modes
provide more keepers than the other two systems.
But the Panasonic G9, a contrast-only system
is still faster and more accurate when it comes
to low movement, single shot focusing,
because of something called Depth from Defocus.
Panasonic's Depth from Defocus, or DFD,
is like the reverse of Canon's Dual Pixel.
Canon found a way to make a fast system more accurate
and generate more data where Panasonic found a way
to make an accurate system faster.
If we look at speed graphs demonstrating the way
that AF systems work, a phase detection system
would be a straight line that goes from out of focus,
to in focus over time, with a slightly larger range of error.
But a contrast based system would be more of a wiggly line
that might even go the wrong way to start and then,
kind of wiggle its way up and it would take longer,
but it would have a smaller range of error,
and it might even have to over shoot a little bit,
before coming back to find the perfect line of focus.
Panasonic's depth from defocus system, however,
would graph more like this, which is much closer
to what you'd see from a hybrid AF system.
It'd be a straight line,
and then a little wiggle at the top.
Now, on the hybrid systems, the straight line is generated
by the phase detection getting you most of the way there,
and a little contrast detection to finish it off.
But, in the Panasonic Depth from Defocus,
this straight line is generated differently.
It's instead generated by having stored computational
data of the paired lens, allowing the system to skip
the initial hunting and jump straight to the finish line.
Basically, the Panasonic cameras quickly examine
the near and far focusing data, and compare it against
the known qualities of that lens,
to determine which direction, and how far to move the focus.
And because Panasonic cameras have a track record
of hosting impressive processors,
it can make these calculations very quickly,
faster than phase detection systems
can figure out phase differences.
There's one major limitation with DFD though,
which is that it only works with Panasonic's own lenses,
because of that requirement of having that focusing database.
That doesn't mean, however, that if you put on a lens
that isn't made by Panasonic, that the focusing speed
just goes right in the toilet, make no mistake,
this is not your grand-pappy's contrast detection.
It's improved dramatically over the years.
It just means you're not the fastest gun in the west anymore
if you take out that Panasonic glass.
Unfortunately though, Depth from Defocus
does not completely fixed two of the most
common limitations of contrast detection.
It's better, but still not the best
at tracking fast moving subjects,
because it still needs to do that back and forth
assurance test at the end which can mean missed shots.
That being said, though, I have seen significant improvement
in this area over the years and I think that right now,
it's a lot better than people are giving it credit for.
The second thing that DFD hasn't completely fixed is that
pulsing in video recording, because it doesn't have
that one and done approach that phase detection has.
It does, however, have nice tap to focus transitions
when recording video, in my opinion.
A quick side note for curious people, yes, this does
actually address some of the variance you see
in autofocus performance when you're using different lenses.
Because these different systems have
different techniques for achieving focus,
some lenses are gonna perform better than others.
For instance, for a full on sports-style
phase detection technique, you'd want a lens
that can move glass quickly and with a single movement.
But for supreme accuracy in a classic
contrast detection scenario, you want a lens that can
sweep through the focal range smoothly and with finer
adjustments to find that perfect sweet spot of focus.
The final under-appreciated trait for contract detection
which has only started to be matched recently
is the greater coverage you get for autofocus points.
With DSLRs using a dedicated AF sensor, you'd often be
limited in the amount of points and placement.
Unless you got a pro or prosumer body,
and even then, they didn't match anywhere near
the 100% coverage of a contrast detection system.
And in order to explain why this is important,
I'm going to answer a question I had from a viewer here
named Ruben who asked if having more autofocus points
really did anything, and if it made for a sharper image,
or if it was just wasteful to have more than,
say, 50 points. So, the short answer is no.
Having many autofocus points does not affect sharpness,
but if your image is out of focus,
then obviously it won't be sharp.
Basically all an autofocus point does is provide
a point in the frame that can be focused on.
And the more points that you have, the more flexibility
you have in choosing where you want to focus.
This has some obvious advantages.
For instance, say you wanted to track a moving subject
and you didn't want to move the camera,
or you physically couldn't keep up with
or predict the movement of that subject.
Having more focus points would allow you to better
track the subject through the frame, than if you had fewer.
If you imagine that you had a small group of points
in the center, and your subject moved back and to the left,
you'd have no way of focusing on them unless you recompose.
So, when it comes to the marketing component
of your question, Ruben, I think what companies
are trying to say when they advertise
having hundreds of focus points,
is, "look how much of the frame we can cover!
You can track an object all the way through the frame,
and you can focus on any element you want to."
And this is great even if you're not shooting action
because of the weaknesses of the focus recompose technique.
Focus recompose, for those that don't know,
is when you focus on something, say, using the center point,
and then you change the position of your camera
because you want to frame it up differently,
but you keep the focus where it was when you focused
on that subject when it was in the center of the frame.
And this was the only way to really do it
when you only had a couple of focus points.
But this has always been a bit of a problem
because lens elements aren't flat
like the final image, they're spherical.
And because of this, focusing and recomposing
in the modern era with cameras that have
hundreds of focus points, is a pretty silly practice.
It might seem minor, but the variance in distances
between the center and the corners of your frame
to the curvature of your lens can have a larger
than expected impact on your subject's sharpness.
So, this is one instance where having more focus points
could actually affect the sharpness of your final image.
So, it's best to compose first, and then select
the focus point that falls best on your subject.
And the more focus points that you have, and the more
coverage that those points have across the sensor,
the better capability you'll have to do this.
So, I hope that answers your question, Ruben.
In my opinion, having more focusing points
and more coverage is not marketing BS,
but a better tool to be able to achieve the focus
you want using the composition that you prefer.
And this, like I said, was an area that
contrast detection has been best at for many years.
Dual Pixel was definitely a step up for Canon, but again,
was limited to only being able to use in the live view,
and was limited to about 80% of the frame.
Hybrid systems have since closed the gap,
however, with many models this year reaching numbers
in the 90s and up to 100% coverage.
But this is another issue that the EOS R has addressed
for Canon, because not only does it have coverage
up to 88% in one dimension and 100% in the other,
but this coverage is available in photo and video.
Something that was lacking in the DSLRs.
In conclusion, we've come a long way in terms of autofocus.
And much of the old information
on autofocus systems is just that, old.
Contrast detection is actually a fantastic option
if high speed, movement, and tracking are not a concern.
And it's the preferred method for accuracy which is why
it's still used in the most advanced hybrid systems.
Hybrid systems which offer incredible features
and functionality like continuous eyeAF and record high
keeper rates for action photography.
So, it's gonna be easier to address my fifth goal
for this video by excluding all of the scenarios
where the focusing type doesn't really matter.
If you're into landscapes, still life, staged portraits,
or product photography, etc., I believe that
any of these modern systems will give you
surprisingly fast and reliable AF performance.
So, I'd concern myself more with the other features
on that camera and make sure
they're giving you what you need instead.
Because contrast detection will not be a limitation
to you in anyway for that type of photography.
And in many ways, will actually be an advantage.
If you're into action with erratic subjects:
birds, sports, etc., a modern hybrid system
wins in my opinion hands down.
The Sony a7 III, the a9, and the newer Fujis
like the X-T3 are gonna give you incredible results.
You'll have the speed and accuracy you need to have
the best keeper rate money can buy.
And after that, it's on you.
I'd also recommend a good hybrid system
if you're a video shooter or vlogger who wants to be
in front of the camera and wants instant focus
when they point it around at things.
If you're behind the camera and you want top quality
video processing, you'll often find that these cameras come
with contrast detection, but that should be fine
because you're probably going for maximum control anyway.
Lastly, if you want a really easy all-rounder
that performs well in most scenarios,
whether it be photo or video, I'd go with Canon's Dual Pixel.
While not as accurate as some,
and while not the absolute fastest,
it's probably the best balanced AF system out there,
and has plenty of potential for any type of shooting.
It gives the smoothest and the most pleasing results
when it comes to video and the EOS R represents Canon's
best implementation of this system to date.
But honestly, we're in great times here when it comes to autofocus.
There's so many great systems, and so much innovation,
that I think a lot of unnecessary
hyper criticism is put on autofocus.
Especially when it doesn't affect our bottom lines like it
would for, say, a professional sports or wedding photographer.
Cameras aren't perfect. Autofocus isn't perfect.
And we can't demand perfection from them
because of the very way that they function.
What we can do, is use them like tools.
Understand how they work, and try and find the best tool
for the job and the best way to use it in that situation.
Anyway, that's gonna be it for me.
I hope you found this video helpful
or at least entertaining, and if you did,
make sure you leave it the old thumbs up
and consider subscribing if you haven't already.
But if you did not find this video helpful or entertaining,
feel free to hit the dislike button twice.
Alright! I'm done.