As you know, matlab deals mainly with matrices. So, the size function gives you the dimension of a matrix depending on how you use it. For example:
1. If you say size(A), it will give you a vector of size 2 of which the first entry is the number of rows in A and the second entry is the number of columns in A.
2. If you call size(A, 1), size will return a scalar equal to the number of rows in A.
3. If you call size(A, 2), size will return a scalar equal to the number of columns in A.

A scalar like scale in your example is considered as a vector of size 1 by 1. So, size(scale, 2) will return 1, I believe.

Hope this clarifies.

This often confuses beginners who do not bother to read the documentation. *Explanation* The important thing is that the _last output variable_ is the product of all remaining dimensions, as the documentation clearly states: _"...but |dn| equals the product of the sizes of the remaining dimensions of X, that is, dimensions n through ndims(X)."_ Beginners also forget that an image is (usually) not a 2D matrix, but is a 3D array. So you have a 3D array (RGB image), and are returning only two outputs... the docs clearly explain that the second output will be the product of dims two and three: rows*3 == 500*3 == 1500 (because the third dimension encodes RGB, so has size 3). *Solutions* 1. One solution is to use three outputs (for a 3D array): [rows,cols,pages] = size(...) Where |pages| corresponds to the Red, Green, and Blue "pages" (or layers) of the image. 2. Use just one output: >> size(ones(2,3,4)) ans = 2 3 4 3. Specify the dimension being measured: >> R = size(ones(2,3,4),1) R = 2 >> C = size(ones(2,3,4),2) C = 3 *Further Reading* This topic has been on this forum and in the MATLAB blogs: You can test it too: >> [R,Z] = size(ones(2,3,4)) % Z is product of dims two and three R = 2 Z = 12 >> [R,C,P] = size(ones(2,3,4)) % each dim is returned separately. R = 2 C = 3 P = 4 The moral of the story: read the documentation.