How many "pixels" on 35mm/s35mm film?

[Peter Hodgins]

I know they are not pixels .... but ....
How many "recording locations"/"photo sights" are there on a frame of 35mm movie film?
How many "recording locations"/"photo sights" are there on a frame of S35mm movie film?
What size are these "pixels"? What are they called?

 

[Peter Hodgins]

I got an answer from wikipedia ....


How many pixels are there in a frame of 35mm film? A print?

This is a somewhat controversial question, and there are many possible answers. Film is an analogue medium, so it doesn't have "pixels" per se, though film scanners have pixels and a specific resolution.

Today the one thing most people agree on is that it's a lot more than any current consumer digital camera. The debate is about how much resolution the digitals will have to reach to start matching the film.

The very short answer is that there are around 14 million "quality" pixels in a high-quality 35mm shot. That's a shot with a tripod, with a decent lens and a quality, fine-grained film, in decent light. There may be as few as 4 million "quality" pixels in a handheld shot with a point-and-shoot camera or camera with a poor lens. And of course if focus is poor, or light is poor, or the camera was not held steady, the number will drop down below the 1-2 million pixels of the modern consumer camera. Of course, one can have a bad shot with a digital camera too, not using all its resolving ability.

It's important to note another key difference. Film, as an analogue medium, does not record just 256 greyscales or the corresponding 16 million colours. And film scanners, even doing just 8 bits per colour, get 24 bits of data for every single pixel. Today's digital cameras only get 8 bits of data for each pixel and they guess (interpolate) the other 16. So the colour accuracy for even a scanned film image is much better than the modern digital camera. Good film scanners can also extract more than just levels from 0 to 255. They can often go to 12 bits (0 to 2048) to detect much more detail in shadows, and provide more contrast. As such a film scanner gets as much as 36 bits of information for each pixel, instead of 8.

The film itself tends to be able to hold around 1000 to 1 contrast range. Quality slide film can handle more levels, though over a slightly narrower range. Generally one desires at least 12 bits per colour to represent it. Your eye, by widening and closing the iris, can sample an astounding (eye-popping!) 7 decimal orders of magnitude of range of contrast, which would need at least 24 bits.

So there is a lot of information in film. However, not all of it is usable information, which causes the debate about the equivalence in pixels. Film is made up of chemical grains. The more you blow up film, the more you start seeing noise caused by those grains, and eventually the very clumping of the grains themselves. Of course some are bothered by the grain more than others.

 

[Dan Hudgins]

Film resolution

Film resolution

Film as a dropper MTF curve and grain noise in single frames. When you watch many frames show at sound speed they merge and you see more detail than is in a single frame.

You cannot merge frames together and get the same effect in simple software since your eye tracks details around as you watch images on the screen.

When film is scanned the lack of registration in the movie camera and scanner causes the details at any given point in the camera lens's image to move around on the pixels of the scanner camera, this can average the images when merged in the eye to see details that would fall on two pixels for some frames and single pixels in other frames.

What is a more important issue than how much detail is in the camera negative is how much detail is on the screen in the theatre.

Because the lens in the movie theatre projector is somewhat out of focus much the time, and more so now since there is not a projectionist to adjust the focus every few minutes like they did in the past while adjust the carbon arcs, the image on the screen will only resolve about 1280x720 at 80% MTF to 50% MTF or less.

Although it is good to use a higher resolution scanner to archive film images to be sure that about an area of 3x3 or 9 pixels are used for each 35mm camera lens circle of confusion, that does not mean that when you look at the scanned images on a filmout you are seeing a 1:1 result, you loose resolution in the scanner lens and you loose resolution in the film recorder, and you loose resolution in the printing negative and the print stock, and you loose resolution in the projector and you loose resolution in your eyes looking at the screen in a dark room.

So even if the negative has some small details at 16K on black and white film (color film is lower resolution because of dye bleed) maybe 1 to 5% MTF, you are not going to see that in a film-to-film print because you cannot get a optical printer to resolve that, and contact prints blur the image more than that, so it is almost pointless to ask how much detail a camera negative can hold.

You can see some 3K scans of Super16 negatives at these links,

http://reduser.net/forum/showthread.php?t=28486&page=5

http://reduser.net/forum/showthread.php?p=402805#post402805

The first things you will notice is that the DOF from the lens is the main issue with the image resolution, not the scan or the film. The film grain is high in those scans because that is what film looks like when scanned at high resolution without noise reduction.

Much of what people think "film" looks like is digitaly scanned and "cooked" to the point that is looks nothing like "real" film images. When optical printing was used it acted like a low pass filter to hide many of the defects in film negatives and master positives. Also print stocks like 5302 have/had heavy black bleed in the dense areas that covered up the grain in the shadows of the negatives. Color print stocks tend to also have some bleed in the dense areas that also helps cover up grain in the shadow areas of the negatives.

The resolution of film stocks varies with the exposure, so the can be less resolution in the highlights and shadows of 4th generation prints made from the neg-pos-neg-pos process since the dense areas of both the negatives and positives will be lower than the mid-tones in many cases.

 

[Manuel Wenger]

No matter how it is cut – film material always
possesses the same performance data:
the smallest reproducible detail (20 % modu*
lation) on a camera film negative (up to
200 ASA) is about 0.006 mm. We can
think of this as the size of film’s “pixels”, a
concept that is well known from electronic
image processing. And it does not matter if
it is 16 mm, 35 mm, or 65 mm film: the crys*
talline structure of the emulsion is indepen*
dent of the film format. Also, the transmission
capability of the imaging lens is generally
high enough to transfer this spatial frequency
(0.006 mm = 80 lp/mm) almost equally well
for all film formats.
The film format becomes relevant, however,
when it comes to how many such very small
details are to be stored on its surface – that
is the question of the total available storage
capacity. In the table below the number of
“pixels” are indicated for the image’s width
and height.
Based on the smallest reproducible detail
of 0.006 mm the table gives an overview of
the storage capacity of different film formats.

S16 2058 × 1237 pixels
S35 4153 × 3112 pixels
65 8746 × 3835 pixels

this is taken from a very detailed article about sharpness and resolution from Arri.

Manuel

 

[Marco Graziaplena]

http://www.arri.de/camera/tutorials/4k_systems_theory_basics_for_motion_picture_imaging.html

and download it

 

[Tom Lowe]

I think the short answer is, about 4K. Faster film, maybe less.

 

[Brandon Fraley]

my limited understanding:
negative=about 4K
distributed print=less than 1080

 

[Patrick Tresch]

A must read!

http://www.arri.de/fileadmin/media/arri.com/downloads/Camera/Tutorials/SystemsTechnologyBrochure.pdf

Thanks for the link

Patrick

 

[Dan Hudgins]

Always?

Always?

film material always
possesses the same performance data:
the smallest reproducible detail (20 % modu*
lation) on a camera film negative (up to
200 ASA) is about 0.006 mm.

S16 2058 × 1237 pixels
S35 4153 × 3112 pixels
65 8746 × 3835 pixels

Those points are have some issues:

1) Sound recording film can resolve between 250 and 1000 lp/mm and can give nice continuous tone images when processed in Phenidone A, the results on 35mm are closer to what you get on color film from IMAX in resolution on the negative.

2) Lens resolution is in ratio to some extent to the focal length, so 65mm lenses would not resolve as many pixels are you indicate at many or all stops. In 16/S16mm the color films have less resolution than the better lenses, in 35/S35 the lens and film are closer in resolution, and in 65/70 the film may have a small adavantage over the lens in resolution.

Color films never needed to have high resolution since the movie projectors could not resolve much over 30lp/mm most of the time. Also with newer color film stocks of high speed you want the dye to bleed to hide the grain better, so the goal in color film stocks is not high resolution.

Black and white films stocks like CFT, Sound Recording, and Microfilm can be used for motion picture work when processed for continuous tone images, they were not marketed for use in motion picture cameras since there are no projection systems that can project high resolution images, and black and white film stocks with high resolution were developed after black and white cinematography ended.

It would be possable to shoot three strip and get higher resolution images than you can on color "tri-layer" color film stocks, but since 65/70 is a dead format true high resolution production does not seem to deliver the returns that would interest producers.