Maxwell Smart had a telephone in his shoe. Many people today have a camera in their (cellular) telephone. :-)

Miniaturization is all the rage--and not just in cellphone cameras. Even "camera cameras" are getting smaller.
For example, small size seems to be one of the big selling points of mirrorless cameras over DSLRs.

Pity the poor fool who is still using a large format view camera! He will never know the pleasure of snapping
a "selfie" in a bar or restaurant. :-)

But consider: f/64 was reasonably sharp on a large format (film) camera. (Remember the "f/64 Group"?)
That was some serious depth-of-focus! But now f/22 has disappeared from cellphone cameras---because
on thee small cameras, it's too fuzzy.

Alas, not everything can be minauturized without loss of quality. For example: a minature loudspeaker will
not do a very good job of reproducing bass (low frequency) tones. Very clever technical tricks can be used,
but they all take a toll on quality. For the best bass reproduction, you need big speakers.

That's because sound waves have a certain size. Concert A (440.00 Hz) has a wavelenth of 2.5 feet. But low A
on the 88-key grand piano (55.00 Hz.) has a wavelength of 20.5 feet. It's hard to get a big wave out of mall
box!

Similarly, light has a wavelength. Even though light is a transverse wave and the wavelength of visible light
is measured in nanometers (400 to 700 nanometers, roughly), it still has a fixed size. You can minaturize a
camera, but you can't minaturized a light wave unless you want to take photos by ultraviolet light or X-rays.

Why should photographers care? Because f/22 on a "full frame" (we used to call that "miniature format")
camera is a bigger hole (aperature) than f/22 on a dinky APS-C sensor.

As most here will know, f-number is defined as the ratio of lens focal length to the diamter of the aperture.
Small format (or sensor) cameras must use shorter focal lengths for each type of lens: wide, standard or
telephoto. Therefore, the aperture is smaller for a given f-stop.

And when you try to push light though a too small hole, something awful happens: it splits (defracts) into its
composite wavelenths! Each is defracted at a differnt angle. So a dot of light becomes a blob of light
on the sensor or film, which gives you a fuzzy image.

There is absolutely nothing one can do about defraction, except to use a bigger aperature. (It's a fact
of quantum physics: built into the universe.)

This is why large and medium-format pinhole cameras are much shaper than 35-mm pinhole cameras.
It's easy to make a 35-mm pinhole camera: drill a hole in the center of a body cap, and mount the correct
size pinhole over it. But the resulting image will be fuzzy (but still kinda nice): the usual pinhole
fuzziness plus diffraction.

Few of us want to produce fuzzy images. So if minaturizatoin continues to conquer the camera market,
will depth-of-focus soon be a thing of the past?

I hope not. I don't want to have to use a camera whose smallest aperature is f/16 or f/11. But that's
"progress": in the electronic gizmo world, "smaller and cheaper" has totally replaced "bigger and better".

Maxwell Smart had a telephone in his shoe. Many people today have a camera in their (cellular) telephone. :-)

Miniaturization is all the rage--and not just in cellphone cameras. Even "camera cameras" are getting smaller.
For example, small size seems to be one of the big selling points of mirrorless cameras over DSLRs.

Pity the poor fool who is still using a large format view camera! He will never know the pleasure of snapping
a "selfie" in a bar or restaurant. :-)

But consider: f/64 was reasonably sharp on a large format (film) camera. (Remember the "f/64 Group"?)
That was some serious depth-of-focus! But now f/22 has disappeared from cellphone cameras---because
on thee small cameras, it's too fuzzy.

Alas, not everything can be minauturized without loss of quality. For example: a minature loudspeaker will
not do a very good job of reproducing bass (low frequency) tones. Very clever technical tricks can be used,
but they all take a toll on quality. For the best bass reproduction, you need big speakers.

That's because sound waves have a certain size. Concert A (440.00 Hz) has a wavelenth of 2.5 feet. But low A
on the 88-key grand piano (55.00 Hz.) has a wavelength of 20.5 feet. It's hard to get a big wave out of mall
box!

Similarly, light has a wavelength. Even though light is a transverse wave and the wavelength of visible light
is measured in nanometers (400 to 700 nanometers, roughly), it still has a fixed size. You can minaturize a
camera, but you can't minaturized a light wave unless you want to take photos by ultraviolet light or X-rays.

Why should photographers care? Because f/22 on a "full frame" (we used to call that "miniature format")
camera is a bigger hole (aperature) than f/22 on a dinky APS-C sensor.

As most here will know, f-number is defined as the ratio of lens focal length to the diamter of the aperture.
Small format (or sensor) cameras must use shorter focal lengths for each type of lens: wide, standard or
telephoto. Therefore, the aperture is smaller for a given f-stop.

And when you try to push light though a too small hole, something awful happens: it splits (defracts) into its
composite wavelenths! Each is defracted at a differnt angle. So a dot of light becomes a blob of light
on the sensor or film, which gives you a fuzzy image.

There is absolutely nothing one can do about defraction, except to use a bigger aperature. (It's a fact
of quantum physics: built into the universe.)

This is why large and medium-format pinhole cameras are much shaper than 35-mm pinhole cameras.
It's easy to make a 35-mm pinhole camera: drill a hole in the center of a body cap, and mount the correct
size pinhole over it. But the resulting image will be fuzzy (but still kinda nice): the usual pinhole
fuzziness plus diffraction.

Few of us want to produce fuzzy images. So if minaturizatoin continues to conquer the camera market,
will depth-of-focus soon be a thing of the past?

I hope not. I don't want to have to use a camera whose smallest aperature is f/16 or f/11. But that's
"progress": in the electronic gizmo world, "smaller and cheaper" has totally replaced "bigger and better".

You need to read the comments in order to see that the comment was referring to "depth of focus" and then the OP replied that he meant "depth of field" rather than "depth of focus."
Although they are two different terms, they often are used interchangeably, kind of like "pixels per inch" and "dots per inch" when printing pictures.

More on the two "depth of" terms:
https://www.edmundoptics.com/resources/application-notes/imaging/depth-of-field-and-depth-of-focus/

Smaller sensors use shorter lenses for similar angles of view, so while a M4/3 sensor is tiny, some interesting things happen when you compare the two. A 10mm lens on a M4/3 has an angle of view similar to a 20 mm on a full frame camera.

At the same subject to sensor plane distances, the M4/3 camera with a 10mm lens will have less depth of field than a 10mm lens on a full frame camera - when compared at the same apertures.

However, if you increase the distance to take in the same field of view as the 20mm lens the effect of moving back will increase depth of field, but the change in distance changes the perspective.

If the goal is to have great depth of field, the smaller cameras, even with larger minimum apertures, the smaller sensors will deliver that.