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How Many Shades of Grey?sepiana.jpg

All this excitement about 50 shades of grey got me thinking about how many shades really satisfies us fussy graphic arts types and how we can get there.

You might be surprised to find out that a typical one colour black halftone doesn’t give us that many shades. A little bit of maths is needed to explain this:

A typical high quality image setter that creates the halftone dots on the plate has a resolution of 2400 dots per inch (dpi).  Don’t confuse this dpi with the printing line screen (lpi). The dpi is the number of dots or pixels that are used to make up each halftone dot.

In order calculate how many different size halftone dots you can create, divide the dpi (2400) by the linescreen, for example, 200lpi. This gives us 12 in each direction or 144. In other words each halftone dot is made up of 144 pixels which can be turned on or off, so you could theoretically have 144 different sized dots or shades of grey. For example if 108 pixels out of the 144 are “on” it will create a 75% dot.

The reality, of course, when ink is transferred to paper is that this is significantly reduced due to potential dot loss and dot gain.

So it doesn’t give us much to work with if we want to create a beautiful print close to the original detail in a photograph.

This is where printing a second grey colour or duotone comes in. It doesn’t simply double the number of shades, but will visually square the range of shades available : 144 x 144. It’s not quite that good in reality but you get the picture.

Imago is fortunate to be partnering with a factory who can take this several steps further with a patented ink and separation process to print with 4 greys producing images with gorgeous rich blacks and plenty of detail.

So come and get your thousands of shades of grey at Imago.

WRITTEN BY: Howard Musk, Imago NY