IT-Consultant: José Roca (PBWIN 10+/PBCC 6+) (Archive only) > Graphics and Multimedia

Changing screen aspect ratio to correct hor/vert pixel distances?


Norbert Doerre:
I'm engaged in writing CAD Software.
One problem occuring more or less visible exists with all LCD/TFT screens: Their aspect ratio cannot be sufficiently corrected.
Normally their distance of pixels is larger in vertical direction than in horizontal direction. I experienced deviations until 6 Percent.
PC-Screen manuafacturers inform only about pixel resolutions, not about size conformity.
Therefore users viewing only images are satisfied with their high resolution and mostly don't even notice these deviations.

In professional CAD systems, where for example measurements are done directly from screen with pixel accuracy, for example in aviation business, screens are manufacured much more precise and much more expensive.

Well, i think that circles looking like vertically oriented ellipses are not the best choice with cheap CAD screens, and so i have been trying to change the aspect ratio of a graphic screen since some years, but w/o real success. Screen management of Windows always tends to fall back to it's incomplete hardware driver handling on the base of those pixel only oriented manufacturer's drivers. They don't regulary aknowledge the difference of pixel distances in vertical and horizontal directions.

Is there anybody in this forum who has the knowlwdge about how to change a common screen's aspect ratio permanently with for example a driver or with a service?

Patrice Terrier:
With LCD display because of the LCD matrix, the best ratio is always get when using the largest screen resolution.

On old cathodic tube it is related to the size of the metalic grid being used by the triplet gun.

I can't see how you could change this on a LCD display.


Petr Schreiber:
Hi Norbert,

I think it might sound as silly advice, but if not for other then for health reasons, I would recommend to the customer to buy good LCD monitor.

For CRTs, I remember there was an option to manage stretch in horizontal and vertical direction via OSD menu. At least it worked on my old Sony Trinitron display, and it kept this setting until you changed it.

I remember that working in ProgeCAD on LCD was much more eye friendly than on the (even very good) CRT.

I just created simple example drawing circle over whole LCD, measured it with ruler, and there was no deviation observable on my display.

I think buying even cheap LCD (but DVI or HDMI connection is a must) will do good, I have Samsung F2380, it even includes pivot, and it renders lines nicely and without any deformations.


Norbert Doerre:
Thank you for your kind answers!
Well, CAD business is not very much privileged in the modern mass world of gamers and always results into much more questions than answers.
With my two NEC 2470 WVX 61 cm TFT screens, i'm at least able to shrink the displayed area vertically so that i get only a small < 2.0 mm black horizontal area on top and below the usable screen area w/o loss of quality and with a good geometric quality.
But common users with common screens tend to say: "I payed for the whole screen area, so why can't i use it w/o vertical distorsion?" :P


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