Re: AW: Non-square pixels test

Posted by Gabriel Landini on Dec 02, 2005; 2:17pm
URL: http://imagej.273.s1.nabble.com/Non-square-pixels-test-tp3704327p3704332.html

On Friday 02 December 2005 13:16, Gerhard Holst wrote:
> even if any function would exist, allowing for measuring this, what would
> it mean?

I would allow to apply a scaling factor to any pixel measurements one can do.

> In case of Interline CCDs or CMOS image sensors with microlenses
> on the pixels, you might find out with special test setups if the
> acceptance angle varies between horizontal and vertical. Nevertheless it is
> impossible to exactly find out just by the image.

Perhaps I put my question wrong. I was talking about the scaling that people
apply to compensate for non-squared pixels. I agree that pixel aspect ratio
cannot be known from an arbitrary image.

> I am in doubt, if this information can be gained just from an image.

It can if the user has added the pixel width and heigh (and this gets stored
in the tiff tags, I believe. The problem is that I do not know what to test
for it.

On Friday 02 December 2005 14:07, Wayne wrote:
> Pixels are nominally square if cal.pixelWidth = cal.pixelHeight.

Great, that is what I wanted.
Many thanks to both.

Gabriel