When using an image file like png Blender automatically applies a gamma curve. If I want to store a value like e.g. 0.5 in a png file without the value changing, do I need to use the standard view transform or the raw view transform?
I was always told that the standard view transform keeps the image as is and only apllies the gamma curve for the png data format, but when I left click to inspect the png image in the image editor the values seem to have changed.
You're asking about three different things: How Blender stores png and edits png images; how blender converts images to its internal format; and how blender displays its internal format.
See Color management, display transforms for an overview. Blender transforms images into a linear color space for internal processing. How that's done depends on the image color space settings. It transforms the linear color space to a display-dependent color space for display. How that's done depends on the display settings.
If you want to render a non-color image, set the View Transform to "None". This would be done, for example, to render a depth map.
If you want to bake or texture paint a non-color image, this has nothing to do with the view transform. Instead, you specify how Blender should read or write color by setting the color mode in an image texture node referencing that image datablock-- typically, to non-color for non-color data. This would be done, for example, to texture paint a bump map, or to bake a selected-to-active normal map.
If we have a .bmp, that file contains a 2D array of 8 bit triplets. We can interpret those triplets as integers as we want; we can inspect the actual file and look at the places those values are stored. If a particular number is 127, and we ask Blender what color that is, Blender will give us different answers depending on how we reference that image. If we reference it as non-color data, Blender will tell us that color is about 0.5. If we reference it as sRGB data, Blender will tell us something different. The number itself is neither sRGB or non-color; the file itself is neither. sRGB and non-color are ways to interpret what is contained in that file.
