Landsat 5 RGB image looks very dark in QGIS

When I combine B-3,2,1 by "Raster>>Miscellaneous>>Merge" in QGIS 2.14.3 I get very dark looking images but when I use the same bands in Sentinel-2 toolbox it looks much better.

Landsat-8 data works fine with "Raster>>Miscellaneous>>Merge" too.

Any idea/suggestion why is this happening?

Answer

This is normally due to poor colour rendering.

Try adjusting the Contrast enhancement option in layer properties. "Stretch to MinMax" is a good default

Also decrease the max value for each band/ inceasing the min value. This will allow more colour space for the values in your image