It is often said that one should print at 300 pixels per inch (ppi) to all printers for best results, and that higher ppi is a waste and the eye can't tell the difference even if the printer could. Is this true?
The human eye, under best lighting conditions, can resolve objects slightly less than one arc minute (Blackwell, 1946; reference and plots are in my book Visual Astronomy of the Deep Sky, click here to go to my visual astronomy pages ). One arc-minute corresponds to 0.003 inch at a distance of 10 inches. The inverse of 0.003 = 344, but it takes at least two pixels to resolve something, so double this number and we get about 700 ppi as the resolution of the eye at one arc-minute. The eye can do a little better, so perhaps 1000 ppi is the limit.
Laser printers used to be 300 dots per inch (dpi), but evolved to 600 and even 1200 dpi. Why? People could see ragged edges on letters on 300 dpi laser printers. At 600 dpi edges appear smoother. Some can tell the difference between 600 and 1200 dpi printers if the paper quality is high. This attests to the power of the human eye. Of course, this applies to high contrast subjects. But many images have high contrast components too.
Many powerful images with impact often have incredible detail. If that detail translates to sharpness (called "tack sharp" or razor sharp") in a print, it can give an image that "WOW" factor when people look at it. Can modern inkjet printers deliver such detail?
I personally use an HP1220C inkjet printer. I also have Lightjet 5000 laser prints made on photographic paper at about 305 and 405 ppi. The tests here show how the HP1220c printer performs at different dpi. The HP can work in both 1200x1200 dpi and 1200x2400 dpi modes with my Windows XP driver. The tests here are with 1200x2400 dpi, but there is essentially no difference at 1200x1200 dpi.
Below are the images printed on HP premium plus glossy photo paper with the image set at 150 ppi, 300 ppi, and 600 ppi. Tests of resolution charts show the HP printer just resolves 600 lines per inch (lpi), thus 600 ppi prints might show an advantage. The prints were scanned at 1200 ppi and downsampled to 900 ppi for this presentation.
It is often said that one should print at 300 pixels per inch (ppi) to all printers for best results, and that higher ppi is a waste and the eye can't tell the difference even if the printer could. Is this true?The human eye, under best lighting conditions, can resolve objects slightly less than one arc minute (Blackwell, 1946; reference and plots are in my book Visual Astronomy of the Deep Sky, click here to go to my visual astronomy pages ). One arc-minute corresponds to 0.003 inch at a distance of 10 inches. The inverse of 0.003 = 344, but it takes at least two pixels to resolve something, so double this number and we get about 700 ppi as the resolution of the eye at one arc-minute. The eye can do a little better, so perhaps 1000 ppi is the limit.Laser printers used to be 300 dots per inch (dpi), but evolved to 600 and even 1200 dpi. Why? People could see ragged edges on letters on 300 dpi laser printers. At 600 dpi edges appear smoother. Some can tell the difference between 600 and 1200 dpi printers if the paper quality is high. This attests to the power of the human eye. Of course, this applies to high contrast subjects. But many images have high contrast components too.Many powerful images with impact often have incredible detail. If that detail translates to sharpness (called "tack sharp" or razor sharp") in a print, it can give an image that "WOW" factor when people look at it. Can modern inkjet printers deliver such detail?I personally use an HP1220C inkjet printer. I also have Lightjet 5000 laser prints made on photographic paper at about 305 and 405 ppi. The tests here show how the HP1220c printer performs at different dpi. The HP can work in both 1200x1200 dpi and 1200x2400 dpi modes with my Windows XP driver. The tests here are with 1200x2400 dpi, but there is essentially no difference at 1200x1200 dpi.Below are the images printed on HP premium plus glossy photo paper with the image set at 150 ppi, 300 ppi, and 600 ppi. Tests of resolution charts show the HP printer just resolves 600 lines per inch (lpi), thus 600 ppi prints might show an advantage. The prints were scanned at 1200 ppi and downsampled to 900 ppi for this presentation.
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