Why was gamma applied? In the raw data, microtubules (green) at the centriolar region at the nuclei were in the 28000 to 30000 intensity range. Single MTs at the periphery dropped in instensity to 3000 to 4000 range. (Darkest background was at 128.) To view the 7x to 10x differences, gamma was applied to non-linearly boost the darks withough saturating the brights. Therefore, we better see all structures but we lose the ability to make judgments about relative intensities.

Grayscale so you can see the red channel and green channel at higher contrast.

More technical explanations can be found on the web, but a good functional one for how we usually use gamma is that we increase the apparent brightness and contrast of dim intensities while not saturating the bright intensities.

Slope of the function is the contrast.

In the brights, the contrast is reduced. In the darks, the contrast is increased.

Is this acceptable? Yes, but you need to say so. And in many cases we don't realize that gamma is being applied. Every traditional photograph has a logarithmic distribution of intensities based on chemistry. The electronic detectors we use to collect light may have a linear response, but every type of display we use applies gamma. Cameras typically have software that processes images in non-linear ways, but the cameras we use in the lab preserve linearity over a very wide range.

Yes, you have more fine control with the curves function in Photoshop and, yes, you can write similar custom functions in ImageJ or Python.