Can someone try to answer this

Suppose a scene was shot with identical cams except one is PAL and the other is NTSC

My question is whether the NTSC cam would crop the vertical height of the image since it is 480x 720 versus 576x 720?

Yes, you will lose 20% vertical resolution by shooting in NTSC as opposed to PAL. This does not mean however you should choose your model solely on this information. Other factors will come into play like ease of conversion to your target standard. Any resolution advantage of shooting in PAL is often countered by the disadvantages in converting from PAL to NTSC.

Good answer, James. I agree wholeheartedly.

another thing to note is that this 20% drop is also factored by the pixel count. Usually you will see PAL cameras running ahigher active pixel count

the differences are starting to close up as HDV comes to the fore

Also there is a temporal difference (25 instead of 30 fps) and a
different power standard (230v/50 hz instead of 110v/60hz) for
the adaptor etc. Some people (in the past) reported seeing lights
flicker when they where shooting with a PAL camera in the states
(since the lights where on 60hz instead of 50hz for the camera).

to summarise then,


on the PAL cam you have a tight close up from hair to chin and for the same settings and distance on the NTSC cam you give your subject a shave and haircut, right?

<<<-- Originally posted by John Jay : to summarise then,


on the PAL cam you have a tight close up from hair to chin and for the same settings and distance on the NTSC cam you give your subject a shave and haircut, right? -->>>


Ah, no, John. The recorded picture would be the same as well as the frame aspect ratio (4:3). The difference is in the aspect ratio of the individual pixels. They are not square pixels but rectangular ones. The NTSC pixel aspect ratio is 0.9 (portrait) while the PAL pixel aspect ratio is 1.0666 (landscape).

In the pre-digital era the PAL signal used to be 768x576 square (!) pixels (well, not pixels really). When you divide 768 by 1.0666 you get 720 pixels. I don't remember the pre-digital NTSC pixel count.

hmmm,

this graphic from an Adam Wilt article would suggest some vertical cropping

http://img.cmpnet.com/dv/magazine/2004/1204/DV0412tdFig01.jpg


I can see that PAR will affect horizontal scaling to maintain 4:3 aspect

forgetting about resolution ftm, can I get a definitive answer on whether an NTSC image is vertically cropped?

You could probably do about anything you wanted when converting. I use Ulead MSP, and when you begin an edit session you define the output. (NTSC, PAL, DVD formats, low res for internet, AVI, HDV 720p. Once this is defined you can bring in just about any file type you wish. It will be converted to the output you have defined. There are addition tools to "map" inputs to the output you have defined. I use this a lot converting 16:9 to 4:3 and visa versa. I can letterbox, crop, make it anamorphic - whatever I wish. While PAL exists as an I-O option, I have not used it, but I would think it would work the same way.

In general, it's better not to convert things. Your shooting format should match your distribution format as closely as possible.