I once heard that you should set your final image resolution to a whole number fraction of the printer's max DPI. For example if the printer prints at 1140 you have set your image resolution to 360 which is 1/4 of 1440. Sounds like a myth to me, is there any merit to this? Is there any harm in image quality in printing at higher resolutions than necessary?
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#1. "RE: Resolution for printing on ink jets." | In response to Reply # 0mythrenegade Basic MemberTue 02-Jul-02 06:58 PM
No myth. Basically your printer is going to create the dots "between" the pixels so to speak. So if you send it a 360dpi image, it can easily scale that to the 1440 by using four dots for every one in your image. If you send it an image at 300dpi it now becomes an inexact science, and the image quality can degrade. If you have a photo that is 400dpi, reducing the resolution to 360 while you have total control is of value, because you can examine and identify things that you may not like and change them. Once you print, control is out of your hands.
I usually try to have my images at 720dpi when I print them. At the same time I have printed images at higher resolutions and they look fine. One problem is that the Epson printers are general 1440x720 dpi, which usually means you shouldn't give them a 1440dpi image, or they are losing half of your vertical resolution.
If you are looking at a 500dpi image or so, I wouldn't worry about it. It's really of most importance when you are close.
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#2. "RE: Resolution for printing on ink jets." | In response to Reply # 1BJNicholls Charter MemberWed 03-Jul-02 12:43 AM
Myth that comes from a misunderstanding of printer resolution.
Your printer doesn't deal with a bitmap directly, and it's not a continuous tone printer even if it did. Continuous tone means that one printed dot equates to one pixel. To do this, the printer would have to be able to mix colors and fill in a perfect square on the paper to reproduce your bitmap. In reality, the colors aren't mixed, they are laid down in a pattern of pure color in various dot sizes and it takes several printed dots to represent a tone and color.
In an inkjet printer, an interpreter converts the bitmap data you send it into a dithering pattern that is this larger scale assemblage of dots. Whatever resolution output you feed the printer, it has to create a pattern that is randomized (stochiastic), and built using percentage combinations of colors and by controlling the variable droplet size tones from the printhead.
It's a waste of time bothering to convert a non-specific bitmap frequency to a multiple of the printer driver setting. Worse, you compromise image quality for each resampling you do of an image.
An exception that requires resampling is when the image doesn't have enough resolution (160 ppi or less image res at the output dimensions) for the print size. Then it's helpful to upsample to disguies stairstep edges can be seen at too low a resolution.
I sometimes have to downsample images greater than 500 ppi at the print size. My printer can produce dithering errors at very high output resolutions. It may be pushing the limits of the dithering interpreter or it could be an issue with my particular printer. It's image specific for me, but I suggest you watch out for it. It is visible as a band that has a different texture alignment than the tones on either side.
On an inkjet printer, I don't think anyone could tell if the source file had a pixel pitch much higher than 300 pixels per inch. I certainly can't. The stochiastic pattern can't resolve image details much finer than that and certainly not more than twice that res. If you're upsampling your files to get 720 ppi at print size, you're doing more harm to the image from the interpolation rather than getting the imagined benefit from matching the pitch of the printer's stepper motor.
#3. "RE: Resolution for printing on ink jets." | In response to Reply # 2jnscbl Basic MemberWed 03-Jul-02 12:32 PM
Whew! I can finally admit in public that I often print 170-180 ppi 8x10's, and they look pretty good. Thanks for the explanation.
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