Harding test

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The term Harding test is generically understood to mean an automatic test for photosensitive epilepsy (PSE) provocative image sequences in television content. This is properly known as a PSE test since the publication of the Digital Production Partnership (DPP) technical requirements[1] and the DPP PSE Devices[2] document (in the UK) in October 2013.

The Harding FPA (flash and pattern analyser) is proprietary software that is used to analyse video content for flashing and stationary patterns which may cause harm to those who suffer from photosensitive epilepsy. It is an implementation of the guidelines set by the regulator Ofcom in the UK. It is available in both tape-based and file-based versions, allowing video streams from SDI, composite, component, HDMI, and files to all be analysed, in resolutions up to 1080i. Versions for both Microsoft Windows and Apple Mac OS X are available. There are other manufacturers of similar and different solutions now available which are also approved on the DPP Devices list.[3]

Photosensitive epilepsy[edit]

Photosensitive epilepsy affects approximately one in 4,000 people and is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights, bold regular patterns, or regular moving patterns. In 1993, an advert for Pot Noodles induced seizures in three people in the United Kingdom, leading to the then regulator the ITC introducing these guidelines. Similarly, in Japan during 1997, an episode of the children's cartoon 'Pokémon', Dennō Senshi Porygon triggered over 650 admissions to hospital leading to the episode being banned from television worldwide. More recently, 18 viewers "reported ill effects" while watching a promotional film for the London 2012 Olympics.[4]

The Broadcast Code of Advertising Practice requires that TV ads are tested and pass the 'flash test'. Clearcast, the company responsible for clearing ads for UK commercial broadcasters, is flash testing all ads before clearance.

Testing procedures[edit]

The algorithms behind the Harding test itself were first developed by Cambridge Research Systems Ltd. and are based on research by Professor Graham Harding.[5] All Harding FPA products implement the same guidelines. Other manufacturers' products broadly do the same.

The software is currently used by many television stations in the UK to check for compliance with these guidelines. If a programme fails, it usually means re-editing the offending scenes. Normally the problem can be rectified by reducing the number of flashes in the scene and/or reducing the intensity of colours (most notably saturated red).[6] After re-editing the problem areas, the entire programme has to be re-tested in order to obtain a Harding FPA certificate.

Cambridge Research Systems, the company responsible for the Harding Test software, operates the Onelineflashtest.com together with Clearcast. This is the first and only authorised fully automatic online flash test service for video.

In 2010, HardingTest.com was launched to provide users with a way of testing video remotely, without the need to have an in-house Harding FPA machine. This provided a much-needed service for freelance editors and smaller production companies who previously had to export their movie to video tape to send to a larger post-production facility for testing, all of which increased time and expense. This service means users can upload a digital video file and have it tested and results returned within minutes rather than hours.


  1. ^ "Technical Standards". DPP. 
  2. ^ "PSE Devices" (PDF). DPP. 
  3. ^ "How To Interpret HardingFPA Results". Cambridge Research Systems Ltd. 2011. Retrieved 23 February 2016. 
  4. ^ "How is TV made safe for people with epilepsy?". BBC News. 2007-06-07. 
  5. ^ "Epilepsy fears over 2012 footage". BBC News. London. 2007-06-05. Retrieved 2008-04-09. 
  6. ^ Harding, G.F.; Harding, P.F. (2010). "Photosensitive epilepsy and image safety". Applied Ergonomics. 41 (4): 504–508. doi:10.1016/j.apergo.2008.08.005. PMID 18930180.