Why pixels are not corresponding to the size I want?

Question

Hello,
Recently I've detected a problem in my Adobe Illustrator CS6.
I open the software, define the art board area in pixels (I checked it at Preferences > Units), but when I export my images they become bigger than they are.
Example:
This is an image 10x10 pixels, exported at Photoshop (everything is ok here):
This is an image 10x10 pixels, exported at Illustrator.... much bigger!
Here it is the options chosen at preferences:
And what appears in work area:
Does anyone knows what is going on? What can I do to solve this?
Please tell me something. This way is hard to work...
Thanks in advance.
Best regards,
Inês Guilherme

Answer 1

Maybe, just guessing here, the resolution set for the photoshop doc was 72 and the one for illustrator 300?
No, no, no. There is no "resolution" setting for a native Illlustrator file like that for a raster image.
When uisng a program like Illustrator, FORGET PROGRAMS LIKE PHOTOSHOP. They are entirely different things and you're just confusing yourself.
Inês,
In a program like Illustrator, the page rulers refer to real-world units of measure when the document is printed. A pixel is NOT a real-world unit of measure. Ask yourself 'How big is a pixel?' or 'How many pixels is it from Earth to its moon?' Those are nonsensical questions. A pixel can be any size, because a pixel is nothing but a color value. Thinking of pixels as distance is like thinking of colors as distance. How many colors is it from where you live to New York City?
When you work in a program like Photoshop, you are basically working within a SINGLE RASTER IMAGE. That single raster image has a fixed number of pixels. That's why Photoshop's rulers can make sense when they are set to pixels; they are not using pixels as a measure of distance; they are using pixels as a COUNT of pixels.
But when you work in a program like Illustrator, you are NOT working in a single raster image. You are working within a model of a region of physical measure (a page) which can contain vector-based paths (which have no pixels), vector-based text (which has no pixels) and any number of MULTIPLE raster images.
Each of those MULTIPLE raster images on the page has its own independent number of pixels, and its own independent scale, AND its own independent position (which doesn't even have to correspond to any whole increment of the rulers; the sides of those raster images on the page may be positioned BETWEEN the "pixels" indicated on the rulers).
So in a program like Illustrator, you can have an image which contains 225 pixels across (or any other number, and another image which contains 25 pixels across (or any other number). Both of those images may be scaled on the page to the same UNIT OF MEASURE dimension. For example, both of those images may be scaled to one inch in width. The rulers, if set to "Pixels" would indicate that they both "measure" 72 "Pixels" across. But they would still contain different numbers of pixels, regardless of how many "Pixels" Illustrator's rulers indicate they "measure".
Now given those very basic differences between what you're actually doing in a program like Photoshop and what you're doing in a program like Illustrator, what can the page rulers in Illustrator possibly mean when they are set to "Pixels"? Illustrator's rulers ALWAYS refer to a real unit of MEASURE, not to a mere COUNT of "Pixels." So when Illustrator's rulers are labeled "Pixels" they still have to ACTUALLY correspond to some unit of real-world measure.
And they do: When you set Illustrator's rulers to "Pixels" you are really setting them to "Points". A point is 1/72 of an inch.
So when you have your rulers in Illustrator set to "Pixels" and you draw your 10 x 10 "pixel" square, you are really drawing a 10 x 10 POINT square. And assuming you drew it as a path, it has no pixels whatsoever. It doesn't become rasterized until you either invoke the Rasterize command, or until you export it to a raster format. When you export it as a raster image, the only way the resulting image will actually contain 10 x 10 pixels is if you export it at a resolution of 72 pixels per inch.
In other words, because Illustrator's rulers ALWAYS assume a scale of 72 pixels per inch when it uses "Pixels" as a bogus unit of measure, then you have to specify 72 PPI at the time of export if you want the number of pixels in the resulting raster image to correspond to the bogus "number of pixels" indicated by Illustrator's rulers.
JET