720 dpi output

[gary t'to]

If you were outputting at 720 dpi would you use the 360 or 480 output sharpener?


Thanks,
Gary

[Jeff Schewe]

I'm assuming you are uprezing using Qimage? If so, you need to sharpen based upon you REAL PIXELS not Qimage's uprez. If the native size is 360, you would use the 360 output sharpeners. You sharpen based upon the real dimensions and the real pixels, not the uprezed output resolution.

[gary t'to]

Actually, I wasn't using Qimage . I was using Photo Zoom. I was trying to test sending different resolutions to the printer based on some of what I have read at Qimage's site. What do you mean by "You sharpen based upon the real dimensions and the real pixels, not the uprezed output resolution" ? I thought the idea was to resize and uprez before final output sharpening?

Thanks,
Gary

[Jeff Schewe]

PhotoKit Sharpener needs REAL PIXELS in order to properly sharpen. That means you need to have your final dimensions and resolution set BEFORE running the output sharpener. You can't run the output sharpener and THEN uprez.

[adiallo]

Jeff,
So what about images with real pixel data @720ppi? Not too hard to reach even on large print sizes with hi res drum scanners. And some RIPs do take advantage of higher than 360ppi output.

[gary t'to]

Jeff,
Now I am totally confused. In your first post , you say "You sharpen based upon the real dimensions and the real pixels, not the uprezed output resolution." In another "That means you need to have your final dimensions and resolution set BEFORE running the output sharpener. You can't run the output sharpener and THEN uprez." Don't these two statements contradict each other? If not please explain because I am totally confused. If I start with a 10.2x6.8 ,300ppi tiff and I want a final size of 11X14,360 ppi , do I not resize and uprez and then apply a 360 output sharpener? Thanks.


Gary T'to

[Jeff Schewe]

Gary,

Uprezing for printing simply doesn't buy you much of anything. If your image is 10 x 6 at 300ppi, you won't get a substantial benefit to uprez to 11 x 14 at 360ppi. It's "make believe" pixels. If you are doing substantial imaging and retouching, uprezing before doing expensive image will be helpful. But uprezing just to throw more pixels at the printer won't. You can try ans test this yourself.

Digital captures tend to be able to be able to be uprez'ed 2X with little problem. But understand that the final result of the uprezing needs processing. It needs edge sharpening and perhaps additional localized sharpening or softening. Uprezing should be done early in the imaging processing. Not at the very end of the process.

The explaination I was trying to give above is that for images printed using an uprez routine such as Qimage that proports to do uprezing to a "native resolution of the printer" (which is a faulty contention by the way) one can't pretend that the image has real 720 ppi resolution.

There's a lot of confusion regarding "image resolution" and "printer resolution". There's also confusion regarding original image "native resolution" and "interploated resolution". Thes best output will come with "native resolution" from an image. An image whose native resolution is 240ppi won't print better if you simply uprez it to 360ppi before printing. If you uprez to 360ppi AND do image processing including edge sharpening and other processing, then yes you can see an improvement in the fial print. How much improvement? It all depends on the type of image and how well it is processed at the higher resolution. But often, with no additional processing, uprezing does nothing -FOR- an image other than making the file bigger.

[Jeff Schewe]

amadou,

In our testing, Bruce and I determined that the maximum resolution of an image file that produces perceptible improvement is 480ppi. We tested Mike Chaney's contention that uprezing to 720ppi "improves" the output. We did not find that to be the case.

If you have "native resolution" of 720ppi (such as a high rez scan) we don't believe the difference between 480 and 720ppi gets you anything at all. Which is why we dispute the contention that uprezing to 720ppi (as Qimage does) produces "better" results. It can produce better results if you are printing high contrast test charts (the sort of chart Mike Chaney offers for download) because Qimage uses a Lancos Sync algorithm which is particularly good at uprezing high contrast line pairs, but less good at uprezing images with high frequency textural information.

Even if you are printing out on an R800 at 5760dpi, I really don't think you'll be able to "see" any difference between 480ppi (properly sharpened) and sending the printer 720ppi.

We've also talked to a variety of experts-people at Epson, ColorByte (that makes ImagePrint) and Adobe engineers. They've all said that the actual "native resolution" of the Epson print head is 360 dpi. That is the physical limits of the print head's ability to place descrete dots. The actual output of 1,440 or 2,880 (or above) is the function of the error diffusion's ability to create the actual droplet. It IS still useful printing out at higher printer resolutions because the print engine's ability to more accurately create the droplet impoves at higher resolutions. It's just that at the point of actual printing, the "native resolution" of the final ink on paper max's out at 360 dpi.

[gary t'to]

Jeff,
OK, so if the native resolution for a 10x6 is 300ppi and you wanted to print an 11X14, on an inkjet, what would you do for the best results?

Thanks,
gary

[Jeff Schewe]

I would reassign the resolution to 7.5 x 12.5 at 240ppi, sharpen for 240 ppi and print. If at aquire I took the native resolution of a digital capture shot in raw, I would have uprezed the processed file either in Camera Raw or in Photoshop after processing. I would capture sharpen, spot and cleanup, add photo noise and then sharpen for whatever the uprezed ppi was for the print size I needed. The ket is to uprez either in the raw process or shortly thereafter and do whatever image processing is required to optimize the image for the final size I needed.