I created a texture with a white background, however when applying it to an object it is darker than it should be. Here viewed in rendered mode in Eevee, however the same happens in cycles:
This is the shader, just directly plugging the texture into the material output, no shading:
Does anyone know why this is happening and how to prevent it?
It's probably due to the View Transform of your Color Management being set to the default Filmic. If you switch that to Standard, and optionally choose your contrast level, you might get something closer to what you expect to see:
You might find it suprising that a color management mode which produces such a dull, flat looking image is the default one. That's a common reaction, especially if you're a relative beginner. But as you get more familiar with the (surprisingly complex and contentious) world of color reproduction, you might get to understand and start to appreciate its underlying logic and advantages. It's a relatively older video but Blender Guru's The Secret Ingredient to Photorealism is a nice introduction to the discussion, if you're interested.
