Trucos de diseño para diseñar como locos
If you have ever opened an image document downloaded from the Internet with PhotoShop and the message below was shown this is your publication:
Pixel aspect ratio correction is for preview purpose only. Turn it off for maximum image quality
To be honest it was the first time I ran into that message, but then, when looking at forums about the problem, I realized that it was quite common. Will not I had enough images downloaded from the Internet.
Closing the warning window it opened the image whose proportions were shown in a distorted way I didn’t like at all, it was oddly strange because the thumbnail looked perfectly, so I proceeded to find a solution to the problem.
Ok, don’t panic. As strange as it may seem at first PhotoShop’ alert indicates that changing the proportions of the image is performed only in preview mode. Yes, it is very difficult to work with an image that is distorted. Also, who says that then go to either display correctly if the final product is printed or upload to the web. Moreover, where shall be modified the display type of the pixels? The alert does not indicate in which menu you must configure the display options.
The PAR (Pixel aspect ratio, PAR) is the mathematical relationship between the width and length of a pixel in the image. Do not confuse this parameter with the relationship between width and length in an image (Display aspect ratio, DAR) or a screen that at first glance may seem the same as these two parameters are deeply related. The mathematical formula to calculate the aspect ratio of the pixels is very simple, for a pixel width (x) and height (y):
If the pixels are square, which is most common in both monitors and image formats, the aspect ratio of the pixels is 1.0. There are other image formats which for various reasons do not use square pixels. The most common are the video formats HDV or D1/DV with varying ratios of between 0.9 NTSC and 2 standard Anamorphic. In the image below you can see the difference between an image formed by square pixels and the same image on rectangular pixels.
But what to do when PhotoShop warns of pixels with different proportions of 1?. Go the menu View/Pixel Aspect Ratio/Square. Now the image look perfectly.