PROOFING and checking colour in the right lighting conditions and understanding the correlation between the viewing distance and required resolution for a print can save a lot of time, avoid back-and-forth exchanges with customers and ensure the correct quality results.
I will never forget an argument I had with a customer almost 20 years ago. We had matched and printed a specific grey colour perfectly for an outdoor banner in the correct lighting conditions in our print production environment. However, the customer opened the banner at his office, rejected the colour immediately and sent it back.
We were very confused as to why the customer was so adamant the colour was wrong. After much back and forth, we discovered that he had opened the outdoor banner indoors under office lighting that cast a reddish hue. If he had opened the banner outdoors in natural light, he would have seen the colour was perfect.
Most common office lighting casts either a reddish or blueish hue on prints, making it nearly impossible to judge colour. And more often than not, the colour will look different in natural light.
The ideal light for checking the colour of a printed proof is 2 000 lux illumination and a colour temperature of D50. Most electrical wholesalers sell daylight fluorescent tubes that simulate this daylight viewing condition. To improve colour matching in your print production environment, I recommend installing these daylight light tubes and painting the wall a neutral light grey.
You can also save yourself many headaches by reminding customers to check the colour of a printed product in natural light outdoors, as they often don’t have a daylight light at their offices.
The relationship between viewing distance and resolution
The further you are away from a printed image, the harder it is to make out the detail. On the flip side, the closer you are, the more you start picking up tiny details.
Some observations indicate that an unaided human eye generally can’t differentiate detail beyond 300 pixels per inch (PPI). However, this figure depends largely on both the distance of the view and the viewer’s visual acuity. It is also important to note that the human eye reacts differently to a bright interactive display (PPI) than it does to something printed on paper (dots per linear inch).
In printing, PPI refers to the input resolution of an image or photograph, while DPI refers to the output resolution of a printer or imagesetter; in other words, the physical dot density of an image when it is reproduced as a real physical entity, for example, printed on paper.