LaTeX and big font size

I have a small problem with MatLab. For the labels of my figures I want to use LaTeX (nothing complicated, just Greek letters and subscripts) but the font size also has to be big. Up to a font size of 24 there is no problem, but when I increase it to 30, the Greek letters shrink a lot instead of getting bigger like the other part of the text. Does anyone know a solution to this problem?

[Walter Roberson]

Duplicated by http://uk.mathworks.com/matlabcentral/answers/15658-latex-and-big-font-size