Too many megapixels? Six is enough for an 8x10.

Started Apr 26, 2009 | Discussions thread
Joseph S Wisniewski Forum Pro • Posts: 34,165
Digital printing at high resolution...

Ralfs wrote:

Joseph S Wisniewski wrote:

(then again, I'm nuts enough to go to a 9 shot stitch in an 8x10,
because it has a look you only normally get from a view camera
contact print).

Even if you have a very high resolution original, are any of the
digital printing techniques capable to come close to the crispness
you get form an 8x10 contact print?

Indeed there are...

The obstacle is our printing technique.

You would be surprised what you can do with a fairly common inkjet. All current inkjets, despite their insane dpi ratings (Epson bills one as a 5760 dpi machine) dither that high resolution into a "basic cell" that's typically either 300 or 360dpi. That won't match a good contact print.

Many of the newer machines drop to a much smaller basic cell at their highest resolutions. The newer Epsons, including the popular 2880, have two 2880 modes, and the fancier sounding one drops to a 720dpi basic cell, as do the machines with the 5760 dpi cell.

720dpi is 14 line pairs per mm, 8x10 only beats that with low speed emulsions, point source lighting, and vacuum contact printing frames.

There's other tricks you have to learn, like to not use the "bidirectional" (aka "high speed") mode, because even if you go through the annoying head calibration procedure, the alignment still isn't good enough for smooth tonality or fine detail.

And the most important thing is to feed the printer at its native basic cell resolution. If you just hit "print" in PotatoeShop, it dumps the image to the printer driver at the images dpi resolution. The printer driver uses a crude "nearest neighbor" scaling, and that does ughy things when either scaling up or scaling down. In other words, starting with an image resolution higher than 720dpi (5750x7200) actually makes things look worse. It's up to you to scale the image exactly to native resolution. Or use a program like Qimage, that performs the scaling automatically, using scaling methods better than PotatoeShop.

If I want something really killer, I normally start with an 80MP 10,000x8,000 image from a 3x3, 4x4 or, 5x5 stitch, because 10kx8k is very close to sqrt(2) * 720dpi * (8x10). (the 3x3 will typically end up a bit smaller than 80mp).

Scaled properly to 41mp 7,200x5,760 with a sharp cutoff low pass filter, you compensate for a DSLR's AA filter limitations, and get full bandwidth 14 lpm to feed the printer driver.

The look really is like nothing else you've ever seen.

-- hide signature --

Rahon Klavanian 1912-2008.

Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.

Ciao! Joseph

http://www.swissarmyfork.com

 Joseph S Wisniewski's gear list:Joseph S Wisniewski's gear list
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