values changing in imread and imwrite

I simply want to read a tiff and then write it back out using the imread and imwrite. I am working with 16 bit images. Whenever I write the tiff and load it into arcmap these tiffs show different max values. Is there something happening in the reading and writing process that would affect this?

Thank you

[Walter Roberson]

What is class() of the data read in by imread() ? And do you use exactly the same array for imwrite() or do you have any operations at all on the data before you imwrite() it?

[Jorge Delariva]

The data is all 16 bit tiffs. I would like to do operations within, but first I want to sort out this business of them changing in between read and write.

[Walter Roberson]

16 bit does not tell us the data type. Is it uint16, int16, double ?

What is max(OriginalImage(:)), min(OriginalImage(:)) ?

If you use MATLAB to imread() the image written out by imwrite() then what are max() and min() of the values returned?