Questions Regarding the Widescreen Frame

[Tim Polster]

Hello,

I only own 4:3 cameras, so I have not worked much with widescreen footage.

For an SD frame, does the widescreen format actually have less pixels than the 4:3 frame?

4:3 is 720x480
16x9 is 720 x405?

Also regarding lenses, if my 4:3 lens is 6.4mm to 121mm, and I put that lens on a widescreen camera, does the wide angle coverage stay the same as the 4:3 frame, or does the 6.4mm represent more on a widescreen chip?

Or in other words, do the mm markings on lenses represent the same field of view on 4:3 & 16x9 chips?

Thanks

[David Mullen]

4x3 and 16x9 recordings in SD have the same pixel ratio, just that the pixels are skinnier in 16x9, which is why a 16x9 DVD image looks skinny but full-frame on a 4x3 monitor unless you have the DVD player convert the signal to become 4x3 with a 1.78 letterbox.

But SD cameras may have either 4x3 or 16x9 sensors (most have 4x3 sensors, just as most HD cameras have 16x9 sensors), so some cameras may be cropping a 4x3 sensor to create a 16x9 image, or cropping a 16x9 sensor to create a 4x3 image.

[David Heath]

Originally Posted by Tim Polster

Or in other words, do the mm markings on lenses represent the same field of view on 4:3 & 16x9 chips?

They *SHOULD* represent the same diagonal field of view, which effectively means wider horizontal but lesser vertical fields of view.

A given lens, for a given nominal chip size, will have a circular coverage. The relevant chips should then sit within that with their corners all on the same circle, if that helps you visualise it.

[Andrew Kimery]

SD 16:9 DV is roughly 853x480.


-A

[Greg Boston]

Originally Posted by Andrew Kimery

SD 16:9 DV is roughly 853x480.

True for graphics and other elements with a PAR of 1.0. However, SD video is 720x480 whether it's widescreen or not per the DV spec. For 16:9, the pixel aspect ratio changes via a flag in the video stream that must be interpreted by the equipment displaying it. It's true though that if you are going to display it in a player or medium that doesn't understand that flag, the video must be converted to 853x480 to display properly.

-gb-

[Tim Polster]

Thanks for your replies.

So when the DSR-450 says it is widescreen switchable, is it using 4x3 chips and just turning off pixels on the top and bottom to get a 16x9 image?

If so, the 16x9 image is actually using less chip area than the 4:3 image.

Or much worse, is it using 16x9 chips (the size from above) and turning off the sides to get 4:3.

If the 720x480 pixel count is never violated, either way, the chip size of these cameras seems to be smaller than the good old 4:3 2/3" chip if 16x9 is involved.

Am I off track here?

If I am correct, then it is no surprise that HD cams are limited in low light due to the starting point of a smaller chip than a 4:3 camera.

It is like to get performance equal to a 4:3 chip, lens openings need to be enlarged for 16x9/HD to get equal chip real estate.

Please tell me if I am wrong.

Thanks