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Old Jul 20, 2004, 10:21 AM   #1
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I had been told that 360 ppi is the highest level for output to the Epson 2200. This is essentially 2880 dpi / 8 (bits?). Is this correct?



I'm trying to find out at what ppi you reach a redundancy point when printing with this printer. Also, is the dpi resolution/8 a good method for calculating this for other printers?



Also, although this isn't forum of the 8650 Kodak dyesub, I'm curious about the same question. I see that on their spec page it calls it a 300 ppi continuous tone printer. I'm assuming that anything above 300 ppi is a waste of file size, and possibly could be do more harm than good.



Thanks!
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Old Jul 20, 2004, 12:43 PM   #2
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A moderator on another board whose opinions and work I have come to appreciate says he doesn't see much improvement over about 180 PPI on his Epson 2200. That relates well with what I've found on my Canon S9000. They are both 4 picolitre dot size printers with similar resolution, with the Epson having slightly higher resolution.

4 and 5 picolitre printers typically use 32 dots to represent a pixel. Divide the 2880 resolution of the Epson in the vertical by 32 gives 90 PPI, which is obviously too low. The printing trade has always multiplied the calculated LPI by 1.5 for optimum output and some think the multiple should be 2 for highest quality output. The multiple has something to do with the diagonal distance between the dots. Using the 2X multiple you get 180 PPI, which seems to correspond with some people's experience.

Resolution in inkjets has seemed to increase at about the same rate as the amount of dots required because of ever-smaller dots. The Epson R800 is up to 5760 DPI in the vertical, but with 2 picolitre dots is using 64 dots per pixel. The math still works out the same.

Photoshop up through at least version 5 gave a message that it was sending the image to the printer at 300 PPI regardless of how high a resolution image you fed. I don't know how many posts I read from people with 1440 DPI printers who thought Photoshop was grossly cheating their printer of pixels. I imagine Adobe support spent a lot of time explaining that as well, and they dropped the message. I suspect Photoshop is still sending the image at a maximum of 300 PPI and just not including the message. They do that because I don't think there is a printer on the market that can use more than 300 PPI. Wish I could figure out a way to check. Printing to file doesn't give a file you can check – at least I haven't figured out how to do it.

Run your own tests and tell us what you think. I doubt you will see much improvement over 200PPI. I don't resample until my PPI gets below 180.

I don't think it does any harm to send a higher PPI image to any printer. The printer driver probably does as good a job of downsample as you could do yourself.
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Old Jul 20, 2004, 1:05 PM   #3
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Thanks for your reply,



Here are some "general" numbers I was given at a recent class that I took:



B&W Laser Printer =72ppi (600 dpi), 150ppi (1200 dpi)

Dyesubs:

Kodak=300ppi

Oly/Fuji/Can=314ppi

Fuji Pict=400ppi

Sony5x7=430ppi

Color Laser = 272ppi (1200 dpi)

Ink Jet = 272ppi (4 color), 314ppi (5-7 color), 396-486ppi (addressable)



These numbers were probably based on specific printers, and were taken from the notes I wrote down. It's one thing to have a list, but it's another to know the reasoning behind the numbers - if there is one.
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Old Jul 20, 2004, 1:53 PM   #4
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I have never owned a laser or dye-sub color printer. So I haven't spent the time to try to understand what they are doing.

It appears your inkjet numbers were derived by dividing the resolution in the vertical by the number of colors. I don't think the number of colors has anything to do with it. If a 4 color and a 7 color printer both use 32 dots to produce a pixel then the input resolution should be the same. I suppose different printer drivers can compile the file differently and some might be more efficient than others.

Don't take anyone's word for it. You can put four 4 X 5.33 pictures on an 8.5 X 11 sheet. Start with a large image and downsize it to 200, 250, 300 and 350 PPI. Look at the results and determine where you stop seeing any difference.
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Old Jul 26, 2004, 4:36 PM   #5
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slipe wrote:
Quote:
[snip]

It appears your inkjet numbers were derived by dividing the resolution in the vertical by the number of colors. I don't think the number of colors has anything to do with it. If a 4 color and a 7 color printer both use 32 dots to produce a pixel then the input resolution should be the same. I suppose different printer drivers can compile the file differently and some might be more efficient than others.
Quote:
[snip]
It's weirder than that. When you go from 4 to 6 you are addingtwo half intensity colors (Photo Magenta and Photo Cyan). When you put them down on the paper it simulates a dot 1/2 the sizethat is possible by the printhead. That is the theory in practice it is not that good because the color of the paper is bleeding through (which is why you don't have a Photo Yellow) and the dot spacing is not being reduced but you do get better pictures at an apparently higher dpi. The 7th color is on the Epson and is light black (same idea).

The new 9900 uses this and another trick. It has two premixed colors (Red and Green) so when it puts down a dot of Red or Green it is like putting two dots directly on the same spot.

I don't think the formula is correct either but I am also not sure we can classifly pictures in PPI when talking about other than CYMB printing, this is because it will now vary based upon the subject of the print.

You hit it on the head with the driver doing the work. It has a lot of ways of making the same colors and based on the paper selection is doing some pretty impressive interpolation.


slipe wrote:
Quote:
[snip]

Don't take anyone's word for it. You can put four 4 X 5.33 pictures on an 8.5 X 11 sheet. Start with a large image and downsize it to 200, 250, 300 and 350 PPI. Look at the results and determine where you stop seeing any difference.


Great advise but make sure to pick a picture to do this with and not some kind of test pattern. A test pattern will not show the effects of the tricks used.

The picture Steve used in his graffitti wall is great example of a picture to use, lots of colors and including people with non-organic probably gives the best use.

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