Hi John Hess from FilmmakerIQ.com.
Do you like the creamy look of a shallow depth of field?
Well this is the wrong video for you because today’s lab we’re putting everything into
focus by getting the fattest thickest juiciest depth of field using the hyperfocal distance
In recent years getting a shallow depth of field has been seen as a sort of style du
jour - that’s because consumer equipment had smaller sensors which combined with the
necessary wider lens resulted in very deep focus.
But now sensor sizes are getting bigger, shallow depth of field is relatively easy to accomplish.
With 4K resolution and beyond, getting sharpness and detail may be start to becoming the new
hot style.
Consider these classic deep focus shots from Citizen Kane - a film every teacher reaches
for when discussing deep focus… as we should as it was a technical achievement by cinematographer
Gregg Toland.
By keeping everything in focus from the foreground all the way to the background we can allow
for Orson Welles’ intricate blocking to take shape.
But everyone talks about Citizen Kane and deep focus.
Check out this shot lensed Tonino Delli Colli from the beginning of Sergio Leone’s Once
Upon a Time in The West when Frank’s henchmen first meet James’ Bronson’s Harmonica
playing character.
Notice the staging where we can see every detail in the foreground and the background
at the same time.
Or even step it up to modern films with these breath taking landscape shots from The Revenant
lensed by Emmanuel “Chivo” Lubezki that allow the personal drama in the foreground
to be in focus as well as keeping the natural drama in the background sharp.
To be fair, they do pull focus closer than the hyperfocal distance in that shot.
But you see hyperfocal distance in many of these landscape shots.
There’s Beauty is in the details: How do we accomplish that look?
If you think the answer is to just stop down the aperture - well yes but there is a limit.
At high apertures your lens will begin to suffer from diffraction and get blurry.
You still need a higher aperture, but we can utilize a powerful trick of landscape photographers
known as the hyperfocal distance.
WHAT IS HYPERFOCAL DISTANCE?
Simply put, the hyperfocal distance is the distance where everything from half that distance
all the way to infinity will be sharp.
In other words - it’s the distance you focus at to get the deepest possible depth of field
for your lens setting.
How does this work?
Let’s use a thin lens diagram.
Much of these basic concepts we covered in our courses on lenses so if you don’t know
the terminology, you’ll want to check those out - but we’ll give you a brief refresher
here.
Here you see collimated light rays - or basically light from infinity - converge at the focal
point.
That is the basic property of a lens.
Now as we move the source of light closer to the lens, the focus point will retreat
away from the original focal point.
Now our imaging plane has to be here to see this object in focus.
Let’s introduce the concept of circle of confusion.
The Circle of confusion is how big a spot of light can be on a sensor or film to still
be considered a single point of light.
In other words, how out of focus can a point of light be to still be considered a point
of light or “acceptably sharp”
The hyperfocal distance is the point of focus where the cone generated by the light rays
from infinity create a blur that just matches the size of the circle of confusion.
So as you see in this animation - the lights rays from the hyperfocal distance is in perfect
focus, the light rays from infinity fall inside the circle of confusion therefore it is still
considered in focus.
Now the cone generated by half of the hyperfocal distance is also inside our circle of confusion.
Here is the equation which you derive using basic geometry and algebra.
Notice the three variables: F is the focal length of the lens, N is the Fstop which can
be written as F/Diameter of the aperture and C is the circle of confusion.
So there are three players involved.
The smaller the focal length, the closer the hyperfocal distance - wide angle lenses will
have a closer hyperfocal than telephoto.
The higher the fstop value, the closer the hyperfocal distance.
That makes perfect sense, the more stopped down you are the wider your depht of field.
Finally the larger the circle of confusion - which is tied to sensor size, the closer
the hyperfocal distance.
In other words, the bigger the sensor, the closer the hyperfocal distance.
That last one might feel odd but it’s because smaller sensors have shallower depth of field
given identical lenses and focusing distances without considering field of view.
But if we want to hold field of view constant we have to divide the focal length by the
crop factor - but notice that the top part of the equation is squared - that’s key.
The Circle of confusion is also divided by the crop factor if we don’t change the f-stop
we’ll find, using a little algebra, that equivalent field of view from a smaller sensor
will have a hyperfocal distance that is closer by a factor of one over the crop factor.
Let's walk through an example using real numbers which might be easier to understand than all
this algebra.
Let's image a 50mm lens on a Full Frame stills camera and compare it to a Micro four thirds
sensor which has a crop factor of two.
On the full frame camera, the hyperfocal distance when shooting at f8 is 34.34 feet whereas
on the same lens shooting on the Micro Four Thirds camera the hyperfocal distance is
68.51 feet - twice as far away.
Therefor the smaller sensor has a shallower depth of field - an object at say 20 feet
would have been in focus to the large sensor - but out of focus to the Micro 4/3rds camera.
But I hear you say, the field of view will be different.
You're absolutely right.
Let's use the field of view equivalent lens on the Micro 4/3rds camera.
Since it's crop factor is 2 we take 50mm and divide by two to get the equivalent lens - a
25mm lens.
Now both cameras will be taking the same field of view but when we redo the math we find
that the hyperfocal distance on the Micro 4/3rds camera is now 17.17 feet exactly 1/2
or 1 divided by the crop factor of the hyperfocal distance on the larger sensor.
So that’s one of the reasons why smaller sensors seem to have deeper focus despite
the fact that one to one they actually have a shallower depth of field.
If none of that made sense - you may need to visit our course on depth of field or just
dig through the comments below, I’m sure it’ll rage a big discussion.
But that’s all I will really say on that matter and it’s not really important unless
you’re jumping around between cameras with different sensor sizes…
Enough theory let’s put this concept to use.
So that’s one of the reasons why smaller sensors seem to have deeper focus despite
the fact that one to one they actually have a shallower depth of field.
If none of that made sense - you may need to visit our course on depth of field or just
dig through the comments below, I’m sure it’ll rage a big discussion.
But that’s all I will really say on that matter and it’s not really important unless
you’re jumping around between cameras with different sensor sizes…
Enough theory let’s put this concept to use.
You could do the math every time you want to figure out your hyperfocal distance but
if you have a smartphone, there are really useful free apps that can tell you not only
your hyperfocal distance but also you depth field for any given distance, aperture and
sensor size.
You can use the values given to you by the calculators and just try to find the appropriate
focus distance on your lens - but I’ll give you a few other techniques that might be more
practical in the field.
Now on these vintage manual lenses you may see these hash marks around focus indicator
- this gives you an approximation of the depth of field.
To get the hyperfocal distance, all you have to do is turn the focus ring so that the far
hash mark just touches the infinity symbol for your given aperture.
Since these vintages lenses are built for 35mm stills film, you may not get perfect
results on crop sensors and keep in mind this is just an approximation.
Modern lenses generally don’t have these markings.
It should be obvious but if you are using a camera with autofocus - turn it off and
go into manual mode.
To visually estimate the hyperfocal distance, start by picking a point far off in the distance.
Set your focus to infinity and then pull focus closer until that far away point just begins
to blur.
Now just walk it back a bit and you’re set.
Use any screen magnification features on your camera to help you find this distance.
Here are a few walkabouts shots I took on my Canon 5D Mk II with a 35mm shooting somewhere
between f11 and f16.
Notice in this first shot that the rocks which are maybe 20 feet away are just as sharp as
the building in about 500 yards away.
Or this shot of some sandstone on the cove which are about 15 feet away which are just
as sharp as the homes on the cliffs maybe a good 10 miles across the bay.
Now you may not always need to shoot all the way to infinity - using this technique you
can try to set your far edge of your depth of field to the far subject - an example is
this deep focus shot.
Here I’m using that same 35mm lens with the full frame Canon 5D.
Since we’re indoors, I want try to have as wide an aperture as I can so I don’t
have to pump a lot of light or add grain by boosting the ISO.
I know my wall is about 20 feet away from the camera and my chair is about 4 feet from
the camera.
Using my depth of field calculator and trying out different apertures and distance values,
I was able to arrive at a subject focusing distance where both the back wall and the
foreground are in focus - a focusing distance of 7 feet at F13.
I really do recommend picking up the depth of field app for your phone and playing with
it to see what different values give you as it really does help give you at least an intuitive
sense in how focusing works.
With deep focus and high resolution, there’s a lot of cool things you can do - so when
you get tired of the bokeh, give the hyperfocal distance a try.
It will certainly force you to think about composition andl be another tool in your journey
to making something great.
I’m John Hess and I’ll see you at Filmmaker IQ.com.