Home Video Systems Visual Resolution Comparison

1997,2001 Henrik 'Leopold' Herranen
This page is still not yet polished. However, I believe it's already useful.
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Index

Introduction

Intent

The intent of this document is to display graphically the difference of luminance resolution of several home video systems.

Disclaimer

This page is meant to be seen only with a browser that supports graphics. The pictures are the point of this document. Therefore there are no alt tags in the pictures.

To get the full result of this document, use a display device that can show at least 16-bit colour. Otherwise the subtler differences will disappear.

What This Document Covers

This document covers luminance resolutions of several video systems because that is the single most interesting aspect in a video system, and because that is the easiest to simulate with a computer program.

What This Document Does Not Cover

This document does not cover chroma resolution, noise, compression artifacts, NTSC cross-luminance and cross-chrominance artifacts, time base errors, contrast, gamma, or any other aspect of video picture than luminance resolution.

So What Have I Done?

To make things clear for people on the Net, I have made a luminance resolution comparison of the following NTSC-based video systems: I have used two test pictures: one that is of the new 16:9 picture aspect ratio, and one that is of the traditional 4:3 aspect ratio. The pictures will first be shown as reduced to 25 % of the real size both vertically and horizontally. Then, the same pictures are shown upscaled back to their original size so that you can make a comparison about how they look on the screen.

Note: Because the concept of pixels do not directly apply to analog devices, the numbers for all but DVD and CD-I are close approximations.

As said earlier, this comparison is made for NTSC. It is, however, valid also for PAL: all resolutions are slightly higher, but the respective quality order of the video systems remains the same (although PAL broadcast is much closer to Laserdisc and DVD than NTSC broadcast).

The 1.78:1 Aspect Ratio Picture

This part of the document shows how a picture of an aspect ratio of 1.78:1 can be displayed on the different video systems. If the aspect ratio of the source material is wider than this (like 2.35:1 for Panavision movies), some letterboxing is required in all systems. However, as the amount of letterboxing needed will be the proportionally same for all systems, it has no effect to the resolution comparison.

1.78:1 Picture Downscaled

To get you disillusioned, this is how big our first test picture would be with the highest HDTV 1920x1080 resolution:

See how ludicrously small the DVD image below looks when compared to HDTV? But, well, it's the best we have at the moment. So let's go on.

DVD has a nice feature: films can be encoded on the discs natively in a 16:9 format, giving you 720x480 pixels. The 16:9 format could actually be used in any media, but because all DVD players can downscale the picture to a normal 4:3 aspect ratio (with some loss of resolution) for use with older TV sets, the feature is widely used.

This is DVD in the 4:3 mode, where the image is stored as letterboxed and the resolution is down to 720x360:

Laserdiscs have a slightly worse resolution than a 4:3 DVD, at 560x360 pixels:

Broadcast is only 460x360 pixels.

VHS at 300x360 pixels. The interesting thing in VHS is that the aspect ratio of the "pixels" is quite weird: about 1:2.

Last, and least, is CD-I with all of its 320x180 pixels. Add to this the horrendous compression artifacts (that are not depicted here), and you can now guess why there aren't any letterboxed films for CD-I.

1.78:1 Picture As You See It On TV

In this part, I have upscaled the pictures back to the same size that was used in the example of HDTV. The program used for scaling was pnmleoscale. While the program creates some interesting-looking ringing effects, I usually find it gives a much more accurate representation if a picture is to be scaled up a lot, like I have to do in this case for most of the pictures.

HDTV:

Even DVD with 16:9 enhancement looks like garbage when compared to the clarity of the HDTV signal. Just look at the smaller details:

DVD without 16:9 enhancement. Look how the fine details are slightly worse than in the previous picture because 25% of the scanlines haven't been used:

Laserdisc. See how the detail is still slightly getting worse. If you compare this to DVD with 16:9 enhancement, you will see a noticable difference.

Broadcast. Again there is a slight degradation of quality.

VHS. As you always knew, the difference to a good broadcast is stunning.

CD-I. Very little is left of the original image. Not quite HDTV, if I may say.

The 1.33:1 Aspect Ratio Picture

Here we compare the picture quality of a standard 1.33:1 aspect ratio image, where DVD can not make use of it's 16:9 enhancement mode.

1.33:1 Picture Downscaled

Here DVD loses one of its assets: all the other systems can now use the whole vertical resolution, too. However, DVD is still the winner of current TV systems at 720x480:

Laserdisc is now quite close to DVD at 560x480:

Broadcast is slightly worse than LD at 460x480:

VHS bites the dust at 300x480:

And again, clearly last, is CD-I at 320x240. However, the difference to VHS is not as great as you would think from the numbers, because CD-I uses almost square pixels, whereas the "pixels" of VHS are very much rectangular-shaped, and the limiting horizontal resolution makes the picture look unsharp.

1.33:1 Picture As You See It On TV

DVD:

Laserdisc. Now that DVD doesn't have it's 33% better vertical resolution edge, the systems look actually quite similar. However, in real life the fact that information is stored on Laserdiscs in the composite domain and on DVD in the component domain, will make the colours of DVD better.

Broadcast:

VHS:

CD-I: