In the same vein, we read that the Ultrachrome printers deliver output up to 1440 x 2880 . How does this relate to the limit of 360 ppi ? Am I mixing apples and oranges ?
In the same vein, we read that the Ultrachrome printers deliver output up to 1440 x 2880 . How does this relate to the limit of 360 ppi ? Am I mixing apples and oranges ?
I'm trying to answer a lot of these question also (for an epson 1280).
A few things I do know:
the printer's output resolution (780x2880, or whatever) has little to do with the ideal resolution of the art that you send to it. It doesn't work the same way as screen printing, but it's similar in enough to use as a comparison. An image setter might have a resolution of 2400dpi. Because of the way different densities are created within a line screen, however, this resolution needs to be sixteen times the final screen frequency. Which leads to 150 lpi. At this maximum screen frequency, art resolution beyond 300dpi (possibly less) is completely wasted. This is one third the full resolution of the imagesetter.
Similarly (though not exactly for the same reasons) it's ludicrous to send a 2800dpi (at final resolution) file to your epson printer. Never mind the limits of human vision, which is a whole other can of worms. You will be sending gobs of information that the driver will simply discard, and possibly do so in a way that is not friendly to your final output.
The question of what the ideal resolution is for any given driver still remains, and I'm curious to hear it.
Text is a different story. Same with photos that include text layers. This is line art, and as such can use all the resolution you can give it (within the limits of the printer). 2880dpi might not be overkill for text if the paper is smooth enough.
Ken, the native resolution of all of the current Epson printers is 360 dpi. A 360 dpi file should always be sent to the printer, so that the printer's driver does not need to interpolate. If you send it a file at any other resolution, including a 720 or 1440 dpi file, it will interpolate it to 360, with a degradation in quality.
Then, it takes each pixel in the 360 dpi file and divides that pixel up into a grid of very fine dots. If you are printing at 720x1440, that means the printer prints a 2x4-dot pattern for each pixel. If you print at 1440 x 2880, it supposedly prints a 4x8 dot pattern, but as far as anyone can tell, there is no visible difference in the print.
So, res your files to 360 dpi before printing. It does not matter whether you have to res up or down; the printer needs a 360 dpi file.
~cj
Ken - I don't doubt Chris is correct about the 2200. I am basing the 300 DPI note on what someone else said to me in another Internet forum. With my old 1270, there is no clear increase in print quality with 300 DPI versus 360 DPI, but with the 4000, I noticed the difference right away. Maybe the 1270 is better at interpolating, maybe it has smaller droplets, or maybe it's a function of the 1270 dye inks versus the 4000 UC inks. I was told (on the other forum) that the reason was because on the 13x19 printers, the sweet spot was 300 DPI rather than 360 -- hence my note above. I agree it would make more sense if it were 360 DPI for all of the printers, at least for all of the UC printers.
It would be interesting to pull up that Yahoo! Wide Format Group thread again, because I could swear that there was a note from someone who seemed very knowledgeable stating there was a certain paper type where the Epsons interpolate to a 720 DPI image when you select 2880 in the print driver (I want to say it was with Premium Glossy, but it escapes me), and that otherwise the native resolution is 360 DPI for all papers.
Am I missing something? I see time and again persons dicussing the relationship of file resolution to printer resolution in DPI (dot per inch) for both situations. I thought file resolution is mearsured in PPI (pixels per inch). Can someone set me straight?
Michael, nothing is official. It cuts down on confusion if you use PPI for images, but DPI is well entrenched among users, so you just need to infer what is intended by the context. I guess you can think of either dpi or ppi for images, but only dpi for inkjet printers.
I see that Mike Chaney (author of Qimage) says that the Epson driver operates at 720 ppi:
http://www.ddisoftware.com/qimage/quality/#quality
I've been using 360 ppi as many other people have. But Mike is the smartest guy on earth (TM) when it comes to this stuff, so I'm switching to 720 ppi. If mike is wrong then we're at "the end of time" so there's no risk in switching.
I'm not being sarcastic, if Mike says it's 720 ppi it's 720 ppi. That'll be about a 1 gig print file for 24x30 at 16 bits. (and your wife said that old computer would do...HA)
Don -
Thanks for the wonderful link.
Note that the author provides two images with which you can test the resolution of your Epson or Canon printer... now we're talking !
Concerning Qimage, is it used primarily for printing ? In other words, one uses a Photo Editor to perform corrections, etc., - and then uses this to print ? In my workflow, I always use PSD files, since they use a lossless compression algorithm and are native to Photoshop. I'm puzzled about how this would all work together. Any insights would be most welcome !
Ken, yes most people use Qimage as the printing program after photoshop edits for efficiently placing multiple images on a large sheet or roll. It will print psd files. It doesn't have its own file type doesn't normally change the photoshop file. Look at the Qimage web site for the many more features Mike has added since the program's beginning.
This program may not be worth purchasing for an LF photog who usually prints one at a time. For printing a large number of images it is indispensable. It's $45 and there is a free trail. With this program, it is well worth going through the tutorial first. I didn't and was frustrated.
Note that in his quality comparison he is using photoshop 6.
An interesting statement Mike makes at the top of the linked document is that the 720 ppi number is less important for files that are upsized. With our LF images and newer scanners we don't usually need to upsize. I've been doing a lot of looking at resolution from the Canon 9950f scanner so I'm curious to examine prints from a 720ppi scan.
"An interesting statement Mike makes at the top of the linked document is that the 720 ppi number is less important for files that are upsized."
Yes, since one of the advantages he offers, is his algorithm for downsizing: Throwing out the right pixels, in the right manner, to avoid introducing artifacts, like jagged lines, noise, etc. When I get back to my "digital darkroom", I intend to try printing his test files on my Epson 2200, and I intend to observe the difference between what Qimage delivers, and what Photoshop CS delivers.
Thanks again. It's postings like this, which help keep some of us large format photographers on track, towards making more beautiful images, as beautiful as the lastest technology allows.
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