Dan Mons

FreeCalRec601 – DVDs for calibrating CRTs

Before I start, I offer my apologies to my US friends for the spelling of the words “grey” and “colour”, as well as a big hello to my fellow Australians and English speakers in the UK and Canada.

Some time ago I released a series of YouTube videos that covered the basics of colour science as it applies to retro gamers, particularly those that use CRTs (although the same theory applies to LCD, Plasma and OLED technology as well).  These videos went on to demonstrate how to use a tristimulus colorimeter – a small device that sits on your screen and measures colours VERY accurately – to colour calibrate your display’s grey levels and gamma, white point colour temperature, colour saturation and colour accuracy (see the image above for an example).  These same devices and methods are used by photographers, home theatre installers, video and film production professionals, VFX artists and countless other industries to accurately calibrate displays to given colour standards.

The full playlist is available here:


One of the greatest challenges in calibrating displays comes in getting good quality test patterns to send to your screen.  These aren’t particularly difficult to come by for HD displays, however their price can be quite eye watering at times.  Here’s a seller of hardware test pattern generators that I have used for my work.  Check out those prices:


Thankfully there are very capable and generous open source options.  Members of the AVS Forums have created a free and open source tool called ColorHCFR which will generate test patterns over HDMI (which can then be converted with a cheap DAC into VGA if you don’t have native VGA) and also read values off tristimulus colorimeters (see the image at the top of this article for an example of what the process looks like).  However getting a signal out to a SD CRT is challenging, as it requires sending 240p/480i modes out of your computer’s HDMI or VGA port, which is tricky.  ColorHCFR itself can be downloaded for free here:


Likewise the AVS Forums have produced an excellent set of videos you can use with ColorHCFR to calibrate a display, titled “AVS HD 709”.  These target the Rec.709 standard (the standard for 720p/1080i/1080p HD [High Definition] displays using SDR [Standard Dynamic Range]).  Strictly speaking, SD [Standard Definition] displays and consumer CRTs should target the Rec.601 standard, however Rec.709 is quite close.  The AVS HD 709 media comes in a few formats, including simple MP4 downloads, and a Blu-ray format ISO that can actually be burned to DVD-R media.  The latter can be played in devices like a PlayStation 3 or 4 that can handle the Blu-ray format, however because the content isn’t actually in DVD format (despite being burned to DVD-R media), it won’t play in a regular DVD player or a console like the PlayStation 2.  You can find AVS HD 709 downloads and instructions here:


To fill the gap for Standard Definition CRT users, I’ve created a set of free and open source DVDs that can be download and used with ColorHCFR.  These target the Rec.601 standard, and are offered in DVD format as both code to generate the images (using free tools like ImageMagick and ffmpeg), and ISO images you can download and burn to DVD-R.  In a complete absence of creativity, I’ve titled these “FreeCalRec601”.

These can be played on any standard definition DVD player, or any console that can play DVDs (a PlayStation 2 works perfectly, and can be used in any output mode supported by the console – Composite, S-Video, Component YPbPr, or RGB/SCART).  The DVDs are region free, and should force any region PlayStation 2 into the matching region of the disc.  Rec.601 slightly differs for “525 line mode” (NTSC – 480 picture lines plus blanking lines), and “625 line mode” (PAL – 576 picture lines plus blanking).  Ensure you use the correct DVD (and player if you’re not using a PlayStation 2 that can change output modes) for the content you intend to use the most, as the line count (“resolution”) and colour standards are specific to the region mode.

The project can be viewed on GitHub, and links to the ISOs are on the main page’s readme:


I’ve also created a very quick and dirty video showing off the DVDs, although I don’t perform a full calibration in this video.  If you want to see a detailed explanation on how to calibrated a display from start to finish, check the playlist linked at the top of this article.

If you use these and have any feedback or questions, you can message me on Twitter: