PAL VHS

After having a look at what PAL looked like on images that were broadcast to your television or arrived from a home computer, I wanted to have a look and see if I could simulate how a PAL VHS image would be mangled.

From what I could gather, a PAL VHS picture was 576 lines but it only stored a maximum horizontal resolution of around 333 pixels. On the back of an envelope I worked out that meant that the image stored on a VHS tape had about 46.25% of the horizontal resolution of a broadcast PAL image.

Therefore, suppose the original image was this Telefusion Yorkshire one (click to see it at full size):

Before: the original 720 x 576 pixel image

Then it would be stored as this much red information (click to see at full size):

Red - 100 x 576 pixels

This much green information (click to see at full size):

Green 195 x 576 pixels

and this much (or, rather, little) blue information (click to see at full size):

Blue 38 x 240 pixels

And when combined you'd get an image like this:

After: Simulated PAL VHS image

Incidentally, PAL images have non-square pixels. So in order to see the "before" and "after" images on this page in the correct aspect ratio I have scaled them horizontally from 720 pixels up to 788 pixels.

PAL with telly

After re-reading Alan Pemberton's article on PAL, I realised I'd been a right numpty in my post about recreating the effect of PAL on images.

I re-read the following:

Y = 0.299R + 0.587G + 0.114B

A light bulb went on, and I realised I'd been completely wrong in the way I was scaling my Red, Green and Blue images before combining them. This also meant that the Gaussian Blur step was not needed.

What I needed to do to with the colour channel images I made from my initial 720 x 576 images was to horizontally scale them in The GIMP by following amounts:

• Red to 720 x 0.299 = 215 pixels
• Green to 720 x 0.587 = 423 pixels
• Blue to 720 x 0.114 = 82 pixels

Here's the logo I created for my friend Greg Taylor's company before:

Before image. Can you spot Emily Moore?

And here it is after using this revised method:

Now with PAL - click to enlarge the images

I'm sure I'll come back to this again, but I'm finding it interesting.

Telefusion Yorkshire

A friend of mine, Greg Taylor, went freelance recently and started a new company. When he told me he had registered his company as "Telefusion Yorkshire Ltd", the name was immediately familiar to me.

Telefusion was a sucessful TV rentals business in the 1960s who were based in Blackpool, Lancashire. By the late sixties they decided to copy their TV rentals rivals Granada and Rediffusion and diversify into television broadcasting. They set up a subsidiary called "Telefusion Yorkshire Limited" and successfully bid for the new ITA Yorkshire franchise in 1967. Of course, Telefusion Yorkshire Limited became better known by the name it went on air with: Yorkshire Television.

Several years ago I had asked a friend of mine, Robin Carmody, if he could find a real Telefusion logo for me, and he came up trumps:

A real Telefusion logo

When Greg told me about his new company I forwarded him the example Robin had sent to me as I thought he would be interested to see it. He was and replied "You can draw it for me if you like!". I couldn't resist, so I fired up Inkscape:

My .svg version

Greg then asked if I could create something incorporating the word "Yorkshire". I did this in Inkscape and then distressed it in The GIMP. What I did was add scratches, glow, gaussian blur, lens distortion, rotation, noise, made the lightness of the background uneven and so on.

Add Dorothy Sleightholme to taste

After creating this rather "retro" logo in Inkscape Greg then asked if I could make something a bit more up to date. Eventually, after playing with Inkscape 0.47's filters and an extreme lens distortion in The GIMP I got the TSW-styled image I was after.

Where's Wil Malone?

And this week, I was delighted to see Greg is using it on this website. Best of luck with your new venture Greg - and careful where you go with that pointer!