What is 'VHS Quality'?

Jon Ahrens asks: "Whenever you scan reviews on video technology, the articles consistently use a phrase "...VHS quality transmission". How do you measure VHS quality, qualitatively or quantitatively? And if quantitatively, what are the measures used, for example, number of pixels, depth of color, etc.? Are there specific IEEE or NBA standards that explain VHS quality?"

Comments

NTSC info off the top of my head.

[meldroc]

NTSC (the standard signal for American TVs) has 525 lines of resolution, but only 480 lines of visible picture. The remainder is taken up in the vertical blank interval. The signal is interlaced, so the odd scanlines are displayed on one frame, the even scanlines on the next frame. As far as horizontal resolution, there isn't a real pixel value since the signal is analog.

However, I remember some facts from when I used my Atari 400 computer. It had a maximum resolution of 320x192 pixels in graphics mode 8, in a single color. When I placed single pixels or vertical lines on the screen, they would be blue colored if they were on an odd column, and red if they were on an even column. This was commonly used as a hack to make graphics mode 8 display red and blue as well as black and white.

This shows the limits of a typical TV set. The dot pitch is so large that these color artifacts show up in 320x240 resolution. Your typical VHS VCR would be capable of the equivalent of 320 pixels across (the signal may have finer horizontal detail, but the TV won't be able to make use of it,) and 480 lines down, interlaced. Color is analog, so it can't translate to color depth, but NTSC got the nickname "Never Twice the Same Color" for a reason.

In short, VHS/NTSC quality is truly awful, the only reason it's viewable at all is because the picture is constantly moving, so your brain can interpolate more detail into the image from the multiple frames.

VHS Quality is...

[Tower]

an oxymoron.

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