Understanding Vision

Aspects of Vision 4: Contrast

Contrast is about how well the thing you’re looking at stands out from its background.

Mostly, we find things easier to see if they have good contrast. The best contrast is black and white, but sometimes that can appear a bit stark, and a softer contrast is used for comfort. Pale colours and shades of grey can feel more refined, pleasant and artistic, but when things become too pale they can become difficult or impossible to make out.

It’s frustrating when we encounter black food labelling on a grey background, or a bank form all done in pale blue on white. Even worse is trying to read an old receipt where the print has faded out almost completely.

Faded receipts are a fairly common problem

Embossed text is also low contrast, as found on some food packaging where the expiry date is stamped into the box, rather than printed on. Also credit cards traditionally use embossed numbers, rather than printed — thankfully, this is now starting to change.

Embossed text on credit card

“my bank expiry date” by Swiss James is licensed under CC BY 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/2.0/?ref=openverse.

Adjusting contrast is easy if we can manipulate the object and the background separately. For instance, if we are trying to thread a needle using white thread, we can make it easier to see the thread by putting a black background behind it.

Low contrast print is a much more difficult problem, because the object is the print and the background is the paper — they are part of the same physical object, so what you do to one, you do to the other as well. You can examine it in better light, which helps, but not because it makes the contrast any better — it’s just simply that we see better when we have better light, so we have more chance of being able to read the text. More on that later.

Archaeologists and historians often come across very faded documents. Sometimes the only thing they can do to decipher them is to photograph the documents and use a computer to brighten the background and darken the text — which is exactly what most electronic video low vision magnifiers do (much more on that later).