Byte Me Article 232 – Refresh rates dictate image quality

Refresh Rates Dictate Image Quality

In this last article in the current series on all aspects of picture quality we look at the influence of refresh rates.  A screen refresh rate is simply how many times your screen image gets refreshed every second.  Similarly to an annoying blinking fluorescent tube, if your computer screen is not refreshing quick enough then your eyes will detect this as a less convincing or less comfortable image.

So just how fast is fast enough?  Unfortunately there is no exact answer as we are all different in our expectations of image quality and the answer also largely depends on what we are viewing.  For example as I type this document there is nothing changing on my screen except for the current letters that I type.  In this case I am using an LCD screen with a standard refresh rate of 60Hz which is more than sufficient.

So in this case the image that I am looking at is getting refreshed 60 times every second.  For comparative purposes an easily noticeable blinking fluro may be flickering as slowly as around 15 times every second (15Hz) – although some people can attribute headaches to fluorescent lighting refreshing as fast as 100Hz.

2015-08-01 Byte Me Artilce 232 - Screen Refresh Rates

If you have good eyesight and want to play a shoot-em-up game with lots of movement then you probably need to get a screen and video card to supply a refresh rate as quick as 100Hz to even 200Hz.  At less of a rate than this you will mostly likely detect an amount of jitter in the movement of fast paced items on your screen.

This phenomenon of screen flicker was much more of an issue with the old style crt screens (the old school deep boxey monitors) as they needed to totally redraw the image on each refresh – whereas LCD screens more approximately just redraw the changes.  Previously with crt screens even typing a document like this required a screen with a refresh rate of around 120Hz for the user to feel comfortable.

As a helpful hint you can set your screen to as high a refresh rate as it can support without fear of wearing it out or causing premature failure.  Simply right click on your screen and go to ‘screen resolution’ – then to ‘Advanced settings’ – then to the ‘Monitor’ tab and set the drop down ‘screen refresh rate’ to as high a rate as is supported.  When you click ‘apply’ the screen may go blank for a few seconds but then come good again – but with a better more solid image.

This is also why we are seeing (no pun) modern TV screens appearing from manufacturers with refresh rates advertised as high as 200Hz.  Quite simply if you are viewing fast moving content such as sporting events then the faster refresh can make a difference as long as the event is broadcast in these frame rates in the first place.

What is the upshot of all of this?  Technology manufacturers are trying to make whatever screen that you are looking at have the appearance of simply looking through a plate glass window to the real world.  In many respects they are getting so close to this goal that some viewers are now saying that the image looks too good and too real and as a result it can become an unreal image???  I fail to agree!

If you find that you are getting headaches after several hours in front of your screen and your work dictates that you use a computer a lot then investigate how good your existing screen is and at what refresh rate it is currently working.  If it can be increased then less eye strain and fewer headaches may result. 

Future Byte Me topics can be emailed to [email protected] and Bruce is contactable at Kerr Solutions, 205 Musgrave Street or on 49 222 400.

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