Gee, I didn't get any answers to my
question.

So, I did some investigating, and, yes,
now there is a theme in both still
photography and movie making: Don't use
any film. Instead, detect the photons
with an electronic sensor, i.e., a thin
little rectangle of CCDs (charge coupled
devices). And for what used to be a view
finder, just use the data from the sensor.

So, these are all digital cameras
(camera backs), that is, use an electronic
sensor and use no film.

Now a big example of this theme is the
smart phone, either iPhone from Apple or
an Android phone.

It's possible to make movies with a smart
phone. But now an example of a high end
camera for movie making is from a company
Red (this investigation today was the
first I ever heard of it), and one of
their cameras can cost $30,000.
Apparently compared with a smart phone, a
Red video camera can have more pixels in
the sensor, more dynamic range, and a
higher frame rate.

And, yes, there are digital camera backs
by Nikon, some of the other, old still
image camera makers, and even Sony as I
recall relatively new to cameras.

For my question about my old Nikon lenses:
The old lenses were designed to work with
the famous SLR (single lens reflex) Nikon
F camera of 1959. The SLR meant that for
the view finder, a mirror moved down,
behind the lens, and in front of the film,
and kicked the image up to a prism and
into the view finder. So, this way the
view finder showed essentially exactly
what the film would see when a picture was
shot at which time the mirror pivoted up
and out of the way of the light to the
film and a shutter over the film moved and
exposed the film.

So, the many lenses for the Nikon F camera
were called F series lenses. Well, my
collection of Nikon lenses are all Nikon F
series.

Now Nikon has some digital camera backs
that can still use F series lenses. These
cameras are called FX or full frame
cameras, and, yes, the sensor is about the
same size, width and height in
millimeters, as old 35 mm film.

Some of these are SLR, that is, have a
mirror. The Nikon D650 is an example.

But Nikon also has a new series of digital
camera backs with, right, no mirror,
called their Z series. These are also
full frame and can use F series lenses
but to do so need a tube between the back
of the lens and front of the camera back.

So, to use my old Nikon lenses with a
digital camera, I could buy a D650 digital
SLR camera back or a Z series camera back
with an adapter tube.

The sensors commonly have either ~24
million pixels or ~48 million pixels. And
there is some question about the dynamic
range of the pixels.

It appears that there is an engineering
problem of handling the data rates of 48
million pixels per frame, with a lot of
dynamic range (bits) per pixels, at a high
frame rate, say, 60 or 120 frames per
second for slow motion.

Another theme for these digital still
cameras is to be able to take enough
frames (exposures) per second to become
essentially movie cameras. It appears
that this engineering problem is slowing
progress of these former still image
cameras to being good movie cameras.

It appears that the Nikon Z series camera
backs have little or no traditional
optics, that is, lenses, mirrors, or
prisms, and, instead, are all electronic
or nearly so. E.g., the view finder is
replaced by a small video screen.

Well, IMHO, any such all electronic device
is highly vulnerable to rapidly falling
prices. So, I would guess that the Z
series prices will have to fall.

Soooo, if I get a digital camera back that
will accept my F series lenses, I should
go for a cheap one; for something more
capable I should wait until prices come
way down.