I can understand having 4:3 for SD framing, but why the others?

Also, why no other widescreen markers like 2.4:1?

I can understand having 4:3 for SD framing, but why the others?

Also, why no other widescreen markers like 2.4:1?
In some countries the most important marker is the 14:9 one. HD is relatively new in the UK, but most broadcasting here has been 16:9 SD for about a decade now. The standard technique is to shoot and digitally transmit 16:9, but "shoot and protect" 14:9 for the analogue transmission. For this the centre 14:9 section is letterboxed in the 4:3 analogue SD frame, the logic being that this technique loses much less of the image than a 4:3 center cut, whilst being a much less obvious letterbox than a full 16:9 version.

The technique has generally been accepted to work extremely well, and although the techniques been adopted in a lot of countries, AFAIK was originally a BBC initiative - http://www.informotion.co.uk/delivery_widescreen_book.pdf

thanks for the info. I learned something.

How about the lack of 2.4:1? I'd think with support for 24p for film, that 2.4:1 would be nice for filmmakers to have

How about the lack of 2.4:1? I'd think with support for 24p for film, that 2.4:1 would be nice for filmmakers to have
Maybe - but (excuse my ignorance) wouldn't that be more likely to be done with anamorphic lenses, so you'd need to use different viewfinder scans, not simply use markers?

Absolutely right, Brent! I am missing CinemaScope markers (2.35 : 1) as well and I can't think of any plausible reason - except overlooking - why Sony left out that very aspect ratio. It probably is the most common wide screen ratio used today, and even the Canon A1 has it.
Another feature for a coming firmware update.