aspect ratios? What are they and changing them?

gaia1muse · #1 (**permalink**) 04-19-2008, 05:49 PM

I'm using Sony Vegas 4.0

I come from an old school of 4:3 ratios in still and film photography.

But the new width and height numbers 740x480 -- are they still using that to determine aspect ratio? That would be 4:2.66 And if that is NOT used for the aspect ratio -- then what do those numbers respresent?

Secondly - if those numbers are not the aspect ratio -- where is the aspect ratio indicated and how do I set the aspect ratio?

Also -- can I change the those figures in the middle of a project if I need to? I'm submitting to a film festival that wants 4:3 which would be 740:555 if the top numbers represent that. But I don't see that listed anywhere. Or am I dancing on the heads of pins here? Or even asking the wrong question...lol.

Thanks!

Mark W · #2 (**permalink**) 04-20-2008, 12:07 AM

Aspect ratios is a huge subject, and an interesting one.

From about 1930 to 1950 ish everything was shot in the 'academy ratio', this was about 1.35 :1 and is nearly exactly the same as 4:3 - old style tv.

The 60s and 70s saw a kind of 'wide war' with cinemas selling themselves over tv on that basis. There are lots of aspect ratios used in film but video is most often 4:3 or 16:9 reflecting normal and widescreen tv formats. CCDs in cameras are also 4:3 or 16:9 reflecting this.

It's not only the pixel ratio that determines the aspect ration, it is also the pixel aspect ratio - sounds more confusing than it is as all editirs have presets for the 2 aspect ratios in pal / ntsc / hdv.

To change aspect ratios you usually mask the picture.

I nearly always shoot 4:3 as my cam is native 4:3 and I find composition easier in 4:3.

Sithxace · #3 (**permalink**) 04-20-2008, 01:35 AM

as for what the numbers actually mean... the first number is width and the second is height... so 16:9 means that the width is almost twice as wide as its height.

gaia1muse · #4 (**permalink**) 04-20-2008, 03:00 AM

So 720 to 480 IS an aspect ratio -- correct? (or 4:2.66) Are those number -- 720 and 480 -- pixels?

Mark W · #5 (**permalink**) 04-20-2008, 04:35 AM

An aspect ratio is the width and height - that is all. This can be made of various ratios of pixels as pixels in some formats are not square.

TimStannard · #6 (**permalink**) 04-20-2008, 08:28 PM

Quote:

Originally Posted by gaia1muse

So 720 to 480 IS an aspect ratio -- correct? (or 4:2.66) Are those number -- 720 and 480 -- pixels?

No. It's not an aspect ratio. Yes, they are pixels.

The first thing to realise is that the pixels are not square.

There are two sorts of aspect ratio, and 720 x 480 relates to neither!

There's image aspect ratio - which is the aspect ratio of the image you see (normally 4:3 or 16:9) and there's the pixel aspect ratio (PAR) - which is the ratio (wdith x height) of each of the the individual pixels making up the image.

What you may find surprising is that the actual number of pixels making up the image is the same (in the case of NTSC 720 x 480 and PAL/SECAM 720 x 576) irrespective of the image aspect ratio. It's just the shape of the pixels that changes.

There are articles available which explain this in detail and also explain why my simple maths doesn't actually work (which is why I've shied away from a worked example)

But the long and the short of it is:

Let the software worry about PAR - and concentrate on creating images in either 16:9 or 4:3. If you create a photo whose dimensions are in the ration 4:3 and import it into a Vegas project whose dimensions are 4:3, Vegas will look after converting it to a 720x480 image with the correct image aspect ratio.

As for your film festival entry, ensure that the project settings are set to 4:3 (File | Properties | template | NTSC DV) and your render using an NTSC DV template and all will be well.