Inkscape vs Adobe Illustrator vs Xara

Since we're storing and editing scalable vector graphics in an open format it shouldn't matter which editor is used to create the images. Sadly all three have small deviations from the defined standard, when saving in their standard output.

The biggest annoyance is the difference in physical size, even when using their pure svg output. This is well known and stems from the different assumptions they make on pt (72 or 96dpi). At least Inkscape aloows users to change their point definition - One does have to alter a configuration file and thus making older Inkscape files also render to unwnated sizes.

So while this is fixable it is a fix that has to be applied to every workstation.

Example

Let's assume you made a 4x4" cube cube in Adobe Illustrator. Since Illustrator works with 96dpi the cube is actually 384x384pt in size. Now save that file as svg and open it in Inkscape. The cube will then appear to be 5x5", because Inkscape uses 72dpi, but 384 divided by 72 is 5.

Annoying isn't it?

Point?

Point is a unit of measure that has been redefined over the centuries. It's the base unit when talking about fonts and typesetting. Every new advance in printing and typesetting has led to a redefinition, because in essence it defines the resolution of the print. Definitions have ranged from 0,18mm to 0,4mm. Nowadays the DTP point (a.k.a PostScript point) is used. The norm defines it as 72 points to the inch (72dpi) or about 0.3577 mm.

Who's right?

None are. All are. Yes the point is defined at 72dpi, which is the currently valid definiton of point. So Inkscape and Xara are doing it right.

On the other hand that norm stems from a time, when screen resolution also was 72dpi. Nowadays screens are 96dpi and using 96dpi will make the svg render smoother. Adobe as DTP market leader is adopting to a changing landscape and providing better service for their customers. Possibly pushing for a new norm. As market leader they have huge influence on these kind of things. Similar to Microsoft on Office and OS norms and definitions.