How to adjust the image intensity pixel limit?

I have been using matlab to read off intensity values of fluorescence image, and these are the commands I usually use to find out the mean pixel of an area.

I=imread('image.jpg') J = rgb2gray(I); figure, imshow(J); A=J(400:650,600:850) figure, imshow(A) impixelinfo mean(A(:))

But as the exposure time of the fluorescence image gets smaller, the image pixel values hit a max of 256 only. So, I wonder if there's any way to raise that limit higher to read a higher value intensity, or say changing the bit?

[Image Analyst]

256 is not a normal max for any data class (uint8 or uint16). What is the class of your data, and what are the max values when the exposure time is larger? Usually a larger exposure time means a brighter image and higher values.

Answer 1

[Matt J]

Using CAXIS you can

[Ling Fang Toh]

I'm not sure what is CAXIS

[Matt J]

It's a command that will change the intensity range over which an image is displayed.

 >> doc caxis