Effects of Epson printer's native resolution

[Robert Ludlow]

Hi, this is my first post here. In earlier posts, members stated that the Epson Ultrachrome printers upscale lower resolution files to 360 ppi. So the question that occurs to me is how good a job of interpolation does the printer's driver do? Maybe I'm better off doing my own interpolation using Photozoom Pro, which seems to do a very good job. Recently I had an old digital image I wanted to print large, and I upsampled it from 117 ppi to either 180 or 240 (I'm too lazy to look for the file) before printing it on my Epson 7600. Would I have done better to go all the way to 360? Or are they saying that if I had sent it to the printer at 117, the driver would have interpolated it up to 360 and it would have looked just as good as the file I iterpolated up to 180 or 240? Thanks for your help with this; hope it's not too confusing.

[Bill_1856]

Whut? Huh?

[Robert Ludlow]

Sorry, I was afraid I might not have been clear, so I'll try again. Two recent posts on this forum stated that when you send a file to one of the Epson Ultra-chrome printers, unless your file's resolution is 360 ppi, the Epson driver resamples it to 360 ppi. One of the gentlemen referred to this as the Epson driver's native resolution. He went on to say that if the file you send is 360 ppi, then the printer prints it 360 ppi, or pixel for pixel. In the past, when I wanted to make a large print on my Epson 7600, if the file's resolution was lower than 180 ppi, I would always upsample to 180 or 240 ppi. My question is this: If Epson's printer driver is going to upsample every file that's lower than 360 ppi, maybe I should upsample to 360 rather than 180 or 240. I use Photozoom Pro for interpolation, and it seems to do a very good job. So why not use Photozoom, unless Epson's driver does a better job of interpolation (i.e., upsampling). A related question is, why upsample my 120 ppi file at all? If the Epson driver is going to make it 360 ppi, why not just leave it at 120?

[Bruce Watson]

You can leave it and let the driver do the upsizing. That's what it's there for.

But... you can also do some testing. Print the image twice. One letting the driver upsize, and the other you do the upsize in your image editor of choice. See what you think.

[Robert Ludlow]

Thanks, Hogarth, I will do some testing. Earlier this year there were several lengthy discussions on Yahoo's Epson Wide Format forum about this issue, and it's an understatement to say that there was a wide range of opinions about what resolution is best when printing on an Epson wide-format printer. One person swore by 720 ppi; another pointed out that Epson recommends 300 ppi. So your answer--the printer upsizes everything lower than 360--seems blessedly simple. All I knew before was that many knowledgable people recommended an even multiple of 720. So now I'm having a hard time understanding the purpose of interpolating lower-resolution files. Suppose I want to make a 24 x 36 print of a file that comes out to just 100 ppi at that size. What I have done in the past with some success is to use PhotoZoom Pro (formerly S-Spline Pro) to res that file up to 180 or 240 ppi. But if I properly understand your point, when I send it to print, the Epson driver further interpolates it to 360 ppi. So are you saying I should just print at 100 ppi and let the Epson driver take care of upsizing? I'm going to try that, but it seems really counter-intuitive and I suspect the file I upsample will look much better.

[Matthew Parker]

This is my first post here but I think I have something useful to contribute.

I have an Epson 7600 and have found answers to many questions on the epsonwideformat yahoo group. It seems if i remember correctly that there was a long discussion about this very question some time back so if you do a search there you are likely to find an answer.

Matthew Parker

[Bruce Watson]

But if I properly understand your point, when I send it to print, the Epson driver further interpolates it to 360 ppi. So are you saying I should just print at 100 ppi and let the Epson driver take care of upsizing?

That's what I'm saying. People have done the tests - they send the Epson driver files at 359dpi, 360 dpi, and at 361 dpi, and can see the difference (the 359dpi and 361dpi both get resized to 360dpi, while the 360dpi image is printed untouched). I've tried it, and I can see the difference. I put the prints on the wall side-by-side, and my wife picked the 360 dpi one as the better print without knowing what the difference was.

It's not much of a difference really. If the prints aren't side-by-side, you won't know that anything is different. But it's a simple test to make; I advise that you do it yourself and see what you think.

Now, I've got to point out that sending 100 dpi information to the printer is going to result in a low resolution print no matter what does the upsizing. Upsizing creates more data, but it doesn't create more information. You aren't miraculously going to be able to read the sign down the street, or have the tree branches etched sharply against the sky. I'm sure you already know that, but I'm just saying...

Finally, I should point out that this is an Epson driver thing, not an Epson printer thing. If you use a RIP like StudioPrint, the RIP isn't going to resize anything (I've done the same test with StudioPrint, and everyone thinks the three prints are identical). The RIP will just convert what you send it into little dots on the paper to the best capabilities of the print engine. The Epson driver could do this, but it resizes to 360dpi (or 720 dpi, depends on the printer apparently) first. We don't know why.

[Ken Lee]

Every time you up-size or down-size (or even just save the image) to a different resolution, some detail gets tossed out as pixels are interpolated. If we take this argument to its logical conclusion, then wouldn't it be best for the original image to be gathered at a multiple of 360 ? That way, there would be the least amount of loss.



So tell Epson you want to scan at 3240, not 3200 ppi ! I'm only half-serious, but it makes some sense. That's why re-sizing the image to print, followed by sharpening, are the last 2 operations to perform in a careful digital workflow.

[chris jordan]

Robert, there is a difference between the interpolation algorithm in the Epson driver, and the interpolation algorithm in Photoshop. Photoshop's is better for several reasons, so do all of your resizing in Photoshop. If you do side-by-side test of detail-rich images (such as diagonal one-pixel lines on distant telephone lines) you will see stair-steps in the print made using the printer driver's interpolation, that are smooth in the image resized in Photoshop.

It is also beneficial to do your sharpening at the final output resolution, after you have sized the print to 360 dpi; otherwise artifacts such as edge halos will be enlarged by the driver's interpolation, making your prints lower quality than they could be.

So, the workflow is: do your Photoshop layers, tonal adjustments, etc.; then save; then flatten and resize to the print size at 360 dpi; then sharpen; then do a save-as for future prints of that size; then print.

~cj

www.chrisjordan.com

[Bill_1856]

I didn't realize that this was the computer forum. There are already lots of them on line.