Wednesday, 24 August 2016

Cinema Screen sizes, an explanation.

A conversation I often have with people is about screen sizes of movies.  As I used to work as a projectionist, it annoys me greatly when dvds/blu rays are played in the wrong ratio, resulting in a distorted picture.  It also annoys me even more when a show that was originally designed for a certain ration is pushed into another. 

So with that in mind, I made up a chart using the wonderful technology of a ruler, paper and a pencil, Scanner came along later (Changed to something nicer because my hand writing is nasty) so that the explanation will become easier.

First of all, let’s get some clarification on the terms I will use:
  • Ratio is the comparison of the sides of the screen, i.e height and length. A Widescreen cinema picture has a ratio of 1.85:1.  If 1 = 1 metre, then it will be 1 metre high and 1.85 metres long.
  • Masking is fabric on the sides and sometimes top of the cinema screen that is used to sharpen the edges of the projected image.  Often mistakenly called ‘the curtains.’
  • Widescreen [cinema]  (Shortened to “WSC”) is the image on screen with a screen ratio of 1.85:1
  • Cinemascope  (shortened to “CS”) is the image on screen with a ratio of 2.35:1

Cinema screen ratios differ from the size of the screen on TV.  When the screen length widens this is often interpreted by the average viewer as widescreen, but is in fact cinemascope.  This confusion partly stems from the TV sizes, as a TV ‘widescreen’ image is 16:9, which is terribly close to cinemas 1.85:1, but not perfectly so. 

When the cinemascope size is seen on a TV, the image will have black bars at the top and bottom of the screen.  This is usually referred to as ‘anamorphic’ in dvd cases.  Some examples of dvds that show in cinemascope on the TV are the Pirates of Caribbean, Transformers (2007 onwards) and Harry Potter movies. You can test these yourself to see the black bars at the top and bottom of the screen, showing an image that is longer than it is tall.

When watching a broadcast of these movies from most TV channels, I have noticed that they will go and make arrangements to have the image fill the whole screen of the TV, thereby cropping the image quite a bit on the left and right hand sides.  Apparently to avoid missing any important details on the sides of the picture, they will scroll the image across if need be, thereby cropping the opposite side even more so, but since the point of interest is focused, the cropped section is not missed.  If you watch carefully, you will often see a slight distortion on the credit roll as they often just force it into TV widescreen to fill the screen.

To illustrate the cinema sizes, I have made up a little chart.

Cinema Ratios

So as you can see, Cinemascope has the most length, Widescreen has the most height (In regards to picture volume) and the other is so rarely used, I wonder why I put it on the chart.  In case you are wondering, these are all in scale, with a side height of 1.

Here are the screen sizes for TV.

Tv ratios

So now the common TV ‘widescreen’ image is 16:9, which comes down to 1.77:1 (Cinema W/S is 1.85:1).  Which is close, but not quite the same. However a WSC cinema image will look almost exactly the same.  So therefore, to get the CS format on a TV,  black bars need to cover the space at the top and bottom of the screen.

For TV 4:3 is the standard format of the old ‘square’ CRT TVs.  A good example of this format is most early cartoons are in this size.  Watching them on a 16:9 TV will result in back space on the left and right of the screen, but you can force them to the 16:9 ratio, however the image will be badly distorted.  This applies to most old video games as well.

Be aware that a lot of enhanced Blu ray releases force shows into 16:9 when they shouldn’t be.  For example, I have Transformers the Movie from the 1986 cartoon on blu ray and it has been forced to a full screen image on a 16:9 display.  This has cropped a massive amount of the picture, as it should be shown as a 4:3 image.

Extra Bit

I included masking in the terms, but see I didn’t mention it.  In the days of film projectors, masking was often used to keep the edge of the image sharp.  Masking would consist of thick black fabric and depending on the setup of the screen be at both sides of the screen, or at the top and bottom.

In the case of the side masking, CS would allow for the largest picture, whereas in the case of the top/bottom masking, WS would allow for the largest picture.  In modern cinemas (That is ones that use digital projectors) the projected image is sharp enough on the sides to get away without using the masking, but masking does manage to make it look just that touch nicer.

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