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#1 2017-11-08 15:15:06

andrzej1_1
Member
Registered: 2017-09-07
Posts: 50

Correct DPI settings.

Hello,
I am trying to get correct display and I have few question:

1) In my case Xorg is calulating DPI as (101,101):

NVIDIA(0): DPI set to (101, 101); computed from "UseEdidDpi" X config

But it is not correct value, because I am using 1920x1080 resolution with 21.5" monitor, so my DPI is 102.46 (https://www.sven.de/dpi/)

EDID:

00 ff ff ff ff ff ff 00 1e 6d a3 57 88 8f 00 00 
32 14 01 03 6c 30 1b 78 ea 95 35 a1 59 57 9f 27 
0e 50 54 a5 4b 00 b3 00 81 80 81 8f 71 4f 01 01 
01 01 01 01 01 01 02 3a 80 18 71 38 2d 40 58 2c 
45 00 dd 0c 11 00 00 1e 00 00 00 fd 00 38 4b 1e 
53 0f 00 0a 20 20 20 20 20 20 00 00 00 fc 00 45 
32 32 34 30 0a 20 20 20 20 20 20 20 00 00 00 ff 
00 30 31 32 55 58 4c 53 31 32 37 34 34 0a 00 86

Why Xorg computed 101 instead of 102?

2) If mine monitor's DPI is about 102.4, will be better set it to 101, 102, 103 or maybe 96 or 120?

3) DPI mean dots per inch, so really it is not related to display, but to printing. I wonder, DPI settings in Xorg are really about DPI or it is mistook for PPI (pixels per  inch)?

Thanks in advance.

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#2 2017-11-08 20:54:14

circleface
Member
Registered: 2012-05-26
Posts: 639

Re: Correct DPI settings.

1) I have no idea, but the difference between 101 and 102 should barely be noticable.
2) I would leave it as is unless things look bad.
3) DPI and PPI are usually used interchangeably.  You are right though, PPI makes more sense, but DPI is just used for historical reasons.

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#3 2017-11-08 22:40:48

seth
Member
Registered: 2012-09-03
Posts: 50,005

Re: Correct DPI settings.

What circleface said. In addition and out of curiosity: output of "xrandr -q", please?

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#4 2017-11-08 22:46:39

progandy
Member
Registered: 2012-05-17
Posts: 5,184

Re: Correct DPI settings.

With your EDID it is possible to calculate two different DPI numbers (according to http://www.edidreader.com/ )

* Basic Display Parameters -> Maximum Horizontal Image Size: 48 (cm), Maximum Vertical Image Size: 27 (cm)
Horz.: 1920/48*2.54 = 101.6 => floor: 101
Vert.: 1080/27*2.54 = 101.6 => floor: 101

* Standard Timing -> Descriptor 1 -> Horizontal Display Size: 477 (mm), Vertical Display Size: 268 (mm)
Horz.: 1920/477*25.4 = ~102.24
Vert.: 1080/268*25.4 = ~102.36

Last edited by progandy (2017-11-08 22:47:51)


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