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Printing raster text, sharpness


Chiter Chater

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Will grayscale or color printing of raster anti-aliased text at dpi equal to monitor's ppi produce text of sharpness similar to that of the same text displayed on a monitor?

If not, why not?
 

MrToM

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Not sure why you would want to do this but one is not to reason why.

It depends on the resolution you set for the image (which you didn't specify)...if your monitor has a low resolution then printing at the same low resolution will result in an inferior print, but if your monitor has a resolution of 600 ppi, (which I doubt very much), or more then the print will be fine...but only if the image resolution is appropriate.

NOTE: The image is NOT representative of the practices used.

Take a capital 'A' with AA set to 'Sharp'...

ddp_ppi_MT_A.png



The pixel dimensions can be obtained by selecting the pixels and reading the bounding box dimensions in the info panel...

ddp_ppi_MT_B.png



With the image resolution set to 100 ppi, we can calculate the printed size of the image...

ddp_ppi_MT_C.png



Printing that at 100 dpi would result in 'x' amount of ink being used for the size of print...

ddp_ppi_MT_D.png



Increasing the image resolution to say 300 ppi means the printed image will be smaller...

ddp_ppi_MT_E.png



Using the same dpi over a smaller area doesn't affect 'quality', its just using less ink...

ddp_ppi_MT_F.png



Increasing the dpi means using more ink over the same area so in theory you get a much better 'quality' print...

ddp_ppi_MT_G.png


Setting the print dpi to the same value as your monitor ppi is a peculiar practice for sure but if you intend to do it for whatever reason then the results you get will very much depend on what you set the image resolution to be.

I don't do much printing now but If I did then I would keep my print dpi to around 600....for a 'really good' print I would probably use 1200 dpi....but again that would depend on other factors too.

Regards.
MrToM.
 
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Chiter Chater

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But if text looks sharp at say 90 ppi on a computer monitor, why wouldn't it be sharp on paper at 90 dpi?

I know AA makes it look sharp at low ppi, but don't those gray AA pixels get printed on a paper in grayscale or color modes?
 
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MrToM

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...But if text looks sharp at say 90 ppi on a computer monitor, why wouldn't it be sharp on paper at 90 dpi?...
Who said it wouldn't?

If your settings are correct it'll look just as good....but remember the mediums are completely different...one is light the other is ink.

...I know AA makes it look sharp at low ppi, but don't those gray AA pixels get printed on a paper in grayscale or color modes?
Yes.

Regards.
MrTom.
 

Tom Mann

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But if text looks sharp at say 90 ppi on a computer monitor, why wouldn't it be sharp on paper at 90 dpi?...
Because it takes many, many dots of ink on a printer (ie, dpi) to print one pixel (ie, ppi). Figure, at least a factor of 10x more, and usually much more than that.

Tom M
 

Chiter Chater

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Because it takes many, many dots of ink on a printer (ie, dpi) to print one pixel (ie, ppi). Figure, at least a factor of 10x more, and usually much more than that.

Tom M
No, the printing ppi has to do with the number of pixels used when printing on an inch of paper.
It has nothing to do with the actual number of dots used to represent information from pixels.
 

Tom Mann

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I'm sorry, but I just don't understand what you are getting at in your last post.

Of course they are separate numbers. Your comment:
"...the printing ppi has to do with the number of pixels used when printing on an inch of paper. It has nothing to do with the actual number of dots used to represent information from pixels.."
is nothing more than you simply repeating (albeit, in slightly different words) exactly what I said in my earlier post, and precisely is why they are given different names, ie, ppi vs dpi.

As a concrete example, lets suppose that your file was 2000 pixels wide and the paper onto which it is to be printed is 10 inches wide. Then the number of pixels per inch on the paper will be 200. However, to get smooth gradations in color and tone, the printer manufacturer may have to restrict the number of the little microdroplets that make up each pixel from say, a minimum of 600 dpi (at the most coarse, but fastest setting) to 2400 dpi or more at the most fine (and slowest) setting.

So, yes, this is exactly why, in a previous post, I said that for a good print the dpi number typically is many times larger than the ppi number.

Below is a nice graphic that illustrates this difference. Notice that for every pixel in the file (and on the monitor, if the magnification is set to 100%), there are around a half-dozen or more dots on the inkjet print.
xxx-inkjet_dots-vs-monitor_pixels.png

This very nice graphic is from: http://blog.fractureme.com/photography/dpi-vs-ppi-difference/

So, do you now understand why I responded to your question of why does 90 ppi on a monitor appear much sharper than 90 dpi on a piece of paper? To be very clear about it, to get the equivalent sharpness of 90 on-screen pixels per inch, you would need many times that number of on-off microdroplets per inch (ie, printer dpi), say, at the bare minimum, 600 dpi, and depending on the exact design of the printer, as many as 2000 or more dpi.

Basically, the printer is trying to represent the (say) 256 possible levels of each of the RGB colors (ie, almost a continuous tone image), with lots of different on-off patterns of sub-pixel sized droplets. It's very analogous to why the photos in half-tone, bulk printed material (eg, newspapers) look so crude unless the number of halftone dots per inch is much higher than one would think.

HTH,

Tom M

PS - I'm sorry to have to do this, but to remove a possible source of confusion, some of the comments made by MrToM earlier in this thread are just flat-out wrong and should be ignored, e.g., "...Who said it wouldn't? If your settings are correct it'll look just as good....but remember the mediums are completely different...one is light the other is ink...". (a) they won't have equivalent sharpness, as I've just demonstrated; and (b), the difference between an image rendered in emission (ie, "light") and rendered in absorption (ie, "ink") has next to no impact on sharpness / resolution, rather, the major impact is on things like how very bright tones are rendered (emission can be made almost arbitrarily bright, whereas the whites in a print can only be as bright as the illuminating light), maximum degree of saturation possible, color gamut, etc.
 
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jupiterboy

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So, most type is going to be rasterized in the plating. My understanding is that most plating is currently about 3,600 dpi.

If you want clean type and want to rasterize it before plating, you need to reconsider the whole aliasing and look to a 1-bit image at a high resolution—600 to 3,600 dpi—depending on the paper and conditions. Thankfully, 1-bit images are small in size, and have the additional benefit of being able to be assigned a single ink or spot color.
 

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