I found out that for a raster in float32 Identify Features tool reports rounded values. For example on the screenshot it reports that the pixel value is -0.3, although the real value is -0.300000011920929 (and I can see the real value using "Layer properties/Transparency/Add values from display" ). How to disable rounding in Identify Features tool? I'm using QGIS 2.18.12
This is a limitation of how floating point numbers are stored in a fixed-sized binary format (float 32 in your case); it's not unique to QGIS.
This page shows what's happening, if you're curious.
e.g. in python
>> import numpy as np >> print(np.float32(-0.3)) -0.30000001
so it looks as if the problem is the other way around, perhaps the display of the transparency dialog could be changed to be more like the identify tool.