Pages: 1 2 [3]   Go Down

Author Topic: PPI > DPI total confusion  (Read 9165 times)

Mark D Segal

  • Contributor
  • Sr. Member
  • *
  • Offline Offline
  • Posts: 12512
    • http://www.markdsegal.com
Re: PPI > DPI total confusion
« Reply #40 on: August 16, 2017, 07:03:12 am »

It's 360/720 or 300/600 (P20000/10000) for Epson.

My understanding is that in OS X, the OS renders and uses a unique interpolation algorithm similar to bi-cubic or bi-linear (it's done via Quartz Compositor).  In Windows, it's done by the driver and is based on NN.

Also, in the Settings dialogue, don't choose "Processed by Printer" - that's not to do with resolution directly, but it makes a decision about whether to send RGB to the printer for conversion to ESC/P or whether to do it on the computer within the driver.  Sending it to the printer means the RGB is sent as a JPG (i.e. lossy compression).  So don't do that :-)

Phil, which "Settings" dialogue do you have in mind here: is it in the printing application or in the driver? (Unfortunately, there are "settings" all over the place!)
Logged
Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....."

Ferp

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 295
Re: PPI > DPI total confusion
« Reply #41 on: August 16, 2017, 08:54:03 am »

My understanding is that in OS X, the OS renders and uses a unique interpolation algorithm similar to bi-cubic or bi-linear (it's done via Quartz Compositor).  In Windows, it's done by the driver and is based on NN.

That's my broad understanding too, although I can't comment on the specific algorithms used.  QuadToneRIP expects 720ppi as input and its author Roy Harrington has said that on OS X, QuadToneRIP requests that resolution and the printing pipeline delivers it.  This resampling must be done in the printing pipeline, since there's no reason for Photoshop, Lightroom, Print Tool etc to do it.  On Windows the OS doesn't resample and so Roy has said that QuadToneRIP has to do it itself if it receives an image in something other than 720ppi.  Given this I'd expect the Epson or Canon drivers would perform this function if you were printing through the driver.

[Clarification:  The Epson Windows driver resizes to 360ppi, and only to 720ppi under the finest detail setting.  300 / 600 ppi for Canon.  QTR always operates on 720ppi.]
« Last Edit: August 16, 2017, 09:59:33 am by Ferp »
Logged

Farmer

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2848
Re: PPI > DPI total confusion
« Reply #42 on: August 16, 2017, 06:21:53 pm »

Phil, which "Settings" dialogue do you have in mind here: is it in the printing application or in the driver? (Unfortunately, there are "settings" all over the place!)

Yeah, fair question.  Under "Speed and Progress" (which appears in slightly different places depending on the driver and the operating system - but that tab is the one you're after).  By default, it's all good.  It would only be an issue if someone has gone in and changed the settings themselves for some reason (generally with the idea that the driver/computer is released earlier from the print job - not really necessary these days).
Logged
Phil Brown

Mark D Segal

  • Contributor
  • Sr. Member
  • *
  • Offline Offline
  • Posts: 12512
    • http://www.markdsegal.com
Re: PPI > DPI total confusion
« Reply #43 on: August 16, 2017, 07:29:09 pm »

Yeah, fair question.  Under "Speed and Progress" (which appears in slightly different places depending on the driver and the operating system - but that tab is the one you're after).  By default, it's all good.  It would only be an issue if someone has gone in and changed the settings themselves for some reason (generally with the idea that the driver/computer is released earlier from the print job - not really necessary these days).

For OSX 10.11.x whether the SC-P5000 driver or ACPU, which accesses the same driver, there is no such tab.
Logged
Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....."

Farmer

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2848
Re: PPI > DPI total confusion
« Reply #44 on: August 16, 2017, 10:01:17 pm »

For OSX 10.11.x whether the SC-P5000 driver or ACPU, which accesses the same driver, there is no such tab.

Sorry - Windows only!
Logged
Phil Brown

Mark D Segal

  • Contributor
  • Sr. Member
  • *
  • Offline Offline
  • Posts: 12512
    • http://www.markdsegal.com
Re: PPI > DPI total confusion
« Reply #45 on: August 17, 2017, 07:48:16 am »

Ah - fine, so I'm not missing anything. :-)

(I remember that tab from my pre-2010 Windows days. I think most of those functions are distributed around other tabs in the Mac Driver).
Logged
Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....."

Doug Gray

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2197
Re: PPI > DPI total confusion
« Reply #46 on: September 20, 2017, 05:38:09 pm »

First off, it is not clear at all that resampling is best done in a linear space. That's how Lr did it in their earlier releases, and that was the source of some of their (now fixed) printing problems.

Second, if your resampling algorithm is nearest neighbor (NN), which is the algorithm used by Epson in their driver, you get the same answer no matter what nonlinearity you choose. NN is a meataxe resampling algorithm but that doesn't keep Epson from using. it.

Jim

Interesting post by a fellow that photographed a team of young women wearing narrow, vertically striped shirts. When he prints it he says he gets moire. Quite believable.  There's an example of downsizing in Photoshop using gamma=1 as well as standard sRGB. It illustrates production of moire in Photoshop alone without gamma correction or switching to a gamma=1 space.

https://www.dpreview.com/forums/post/60143219
Logged
Pages: 1 2 [3]   Go Up