Video Test Cards Free Download
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Video Test Cards (Free Download)
Alan Roberts (firstname.lastname@example.org) writes:
Someone on Computer Video magazine's DVdoctor-hosted message boards (www.dvforums.com) was asking for video test cards, so I thought I'd knock out a few.
They are all free to use - they belong to no-one. I generated all but one of them in Jasc's PaintShop Pro.
Clearly, there needs to be a description of what they do and how they do it. I started writing an explanation, but this could easily have become a book, so I decided instead to produce a short tutorial, which might eventually get reworked into the first chapter of a book. Or not.
The tutorial is
a PDF file that has been zipped into a file which can be downloaded
In the PDF file you will find a brief introduction to how television works. It's aimed at those who don't already know, but should also be useful to those who do, since we there are precious few books on the subject, and the few that are published are always out of date by the time they hit the press.
It'll help you set up your video editing environment, by explaining how it all works and what compromises you have to make.
There are two sets of test cards, downloadable as zip files.
Don't be tempted to use the wrong set, you'll get silly answers. They are all intended to be used within television systems - you put them onto a video editing program's timeline directly as stills. Don't bother printing them, your printer will almost certainly do something nasty to them, and cause problems if you then put them in front of your camera.
One zip file contains test cards for 625-line systems (with 720x576 image format - and incorrectly known as 'PAL'). This can be downloaded from here:
The other is for 525-line systems (720x480ish format, and correctly known as NTSC). This can be downloaded from here:
There's also a focus chart included as a bonus. You CAN print this and use it for checking lens alignment.
Those of a non-technical persuasion do not need to read any further.
Others may like to know that there's a neat trick you can play with the lens alignment chart:
Focus on it with the camera fairly close up. There will be a grey blob in the middle, where your lens or the TV system has run out of steam.
Now gradually defocus the lens until that grey blob is really big. By now you should be starting to see a pattern in the middle, keep going, it'll go grey again, still keep going and it'll appear again.
Each time a pattern reappears in the middle, it's actually in antiphase with the previous pattern. What you're seeing is the Fourier transform of the disc of confusion, each new pattern is another lobe of the Sin(x)/x function that results from doing the Fourier transform of a pixel aperture, the phase reversals occur because they are alias patterns.
If you want to discuss
this or any other matter concerning the use of these test cards, you
can email me (Alan Roberts) at email@example.com.
Apple users may already have installed on their Macs a suitable program for handling zips - Stuffit Expander. If not, check your OS and program installation CDs. Failing that, a free version of the program can be downloaded from here.
The same link will also allow Windows user to download a version of Expander.
The ability to read PDF files is built into Mac OS X, but if you are not running that OS, then you may need to install Adobe Acrobat Reader. The program often comes on installation CDs of software such as video editing programs, typically if these CDs also contain manuals in PDF format. Acrobat is also often included on magazine cover CDs.
If you don't have a disc with Acrobat reader, you can download versions for various operating systems (not just Mac and Windows) free from here.