Aspect ratio

[DannyG]

Ok so lets see if i understand this part correctly. I get what pixel aspect ratio is and I get what frame aspect ratio is, but since math was never my strongpoint, I get a little dizzied over how and what happens when you try and mix different ratios. If you shoot something anamorphically in 16:9 and try to display it on a 4:3 screen, the tv will will reshape each pixel rectangularly so that there are 12 pixels per what is usually 1, right? so that the ratio is 4:3. And basically 3 things can happen:

1) the pixels are reshaped like above and the image is distorted

2) you constrain the proportions, but make one smaller to get the whole image on screen but with the black bars

or 3

3) you constrain the proportions w/ out increasing resolution and the image is zoomed in somehwhat with what doesn't fit on screen being cut off.

Is any of that correct? I was going through the premiere guide and reading up on aspect ratios. I started to feel the same headache i had in high school geometry and algebra and trig. At least now i know what accounts for differences in NTSC and PAL...the rectangular pixels in NTSC are horizontal while PAL is vertical. So if you try to play NTSC video in a PAL system will it a)not play at all, b) distort, or c) flip each pixel 90 degrees and you have a totally undecipherable image

 

[MarkG]

Actually, most PAL VCRs, DVD players and TVs will play NTSC just fine: it's the other way where you have problems.

 

[FilmUnited]

Aspect Ratio

Aspect Ratio

Just as a sidenote: anamorphic generally refers to the 2.40:1 aspect ratio, not 16 x 9. However, in the digital world, 16:9 has become popular, partially because many HD tv's started coming out at 16 x 9, which is part way in between the 1.66:1 ratio of super 16/35 and the traditional 1.85:1 ratio traditionally used in movies. 2.40:1 is the anamorphic standard in the film world, where the widened image is squeezed onto a 4:3 negative and then later corrected with a lens the opposite of the one used to compress. As far as digital, which I am not as familiar with, it seems that a similar process occurs but the "widening" of the "distorted" image is done digitally. The black bars you are referring to depend on if the camera you are using is creating the 16 x 9 effect by matting or by actually squeezing the image. If you play the image back in the camera and the black bars appear, chances are there is no squeezing going on, just a matte of black bars over the image conforming to the aspect ratio.

Helpful ratios:

1.33:1 Standard 16 / 35 mm, Digital, TV
1.66:1 Super 16/35
16x9 (1.77:1) HD TV / Digital Widescreen
1.85:1 Traditional Film Matte Aspect Ratio
2.40:1 Anamorphic Widescreen


At least that is my understanding. Please someone let me know if I am wrong. Good luck,

Corey

 

[MarkG]

If you play the image back in the camera and the black bars appear, chances are there is no squeezing going on, just a matte of black bars over the image conforming to the aspect ratio.

Depends on the camera. The XL1 shows 16:9 footage as anamorphically squashed 4:3, while the TRV900 shows it letterboxed... but both cameras use digital scaling, so neither is really a good choice for 16:9 shooting unless you use an external anamorphic lens.

 

[laurent.a]

There are basicaly three ways for a camera to produce 16/9 :

1) A real 16/9 pickup device produces about the total same resolution as a same size level 4/3 would since the diagonals are the same. Say if you have a 2/3'' pickup device, if its'4/3, it's higher than 16/9 but 16/9 is larger. There is no squeezing at any time in both prod or post-production.

They may be 4/3 switchable. The image in 4/3 would be smaller as this of a real 4/3 2/3'' device.

2) Some 4/3 2/3'' switchable pick up device provide a low resolution 16/9 image (smaller than the one obteined with a 16/9 2/3''

3) But the best way with a 4/3 pickup device, is to put a anomorphic prime lens. The image is resized electronically/digitally during post production

Say you have a 16/9 image on a tape.

If you monitor it with a 4/3 monitor, it will be horizontally compressed and fit the whole screen.

A 16/9 image has to be monitored on a 16/9 screen. When you switch the monitor on 16/9, letterbox is displayed, ie black lines are displayed on top and bottom of the image, and the whole lines are normally displayed, with no anamorphic or squeezing work of any kind.

One thing is you have to make sure when you master (say after editing) a tape or dvd, that you record in 16/9, if not, it will be squeezed by a 16/9 monitor, as if you wanted to display a 4/3 image in a 16/9 monitor.

But you need a 16/9 display to dispaly it properly.

It is possible to master a 4/3 tape of a 16/9 film, as it can be displayed in 16/9 on a 4/3 screen :

edit in 4/3, put black bars on top and bottom, master in 4/3. The vertical resolution will be a little worse than the 16/9 master on a 16/9 display, that's all.

You can also master a 16/9 from a 4/3 material : edit in 4/3, put black bars, that will cover and produce a lost of a part of the image (but if you know it before shooting, you can put gaffer tape and hide the lost part on the production monitor (as you can't do it on the viewfinder), then you have to apply a squeeze ratio and squeeze the image at mastering (remember a 16/9 monitoring would squeeze the 4/3 image), considering 4/3 to 16/9 is applying a 1.5 coefficient.

You can, at last, master a 4/3 tape of a 16/9 product shot in 4/3 that will display 16/9, as you don't have neither 16/9 camera or monitor ! but the resolution is not so good. Say a 16/9 dvcpro 25 or dvcam will match with a 4/3 dvcpro 50 or digital beta camera, both giving material for the same 16/9 dvcpro 25 or dvcam master.