What I mean here is that unless you take special measures, by default, taking and viewing an image won't show you anything else other than a bunch of assumptions. The camera you took the photo is assuming how bright and what color tones the scene must have had, the monitor assumes what that picture file should be displayed as and if you print it, then the printer takes it's own assumptions.
To cut it short and get on topic, preoccupied by all these assumptions and having problems with some inconsistent results, I tried to put some order into things and started with the most basic step you can take, the white balance.
The theory is pretty simple. Most respectable camera out there offers the option to set a custom white balance level based on a sample photo taken of a gray card or alike. Since I wasn't so found of the gray card idea, I choose the alternative, a white balance lens cap. Basically it's a lens cap that has an extra transmissive window in it that the camera can picture and consider for the custom white balance.
My fault was to grab whatever came first and trust the retailer, so I stopped on a so called Lambency 77mm White Balance Lens Cap. "so called" because after unwrapping it I couldn't find any reference about Lambency producer on the package, nor any other producer for that matters. Chose the 77mm because it would suit two of my four lenses.
The quality of the product is plain modest, cheep plastic and bad taste golden ring around the window. The fixing mechanism on the lens is the same as that of Nikon lenses. Took same test shots around the house and it did correct my incandescent light fairly well. Must be noted that in order to get the test shot with the cap on you need to set the lens on manual focus.
The worst complain about this product is that it broke the very next day after I got it. While being on the camera in my backpack, the translucent dome came off. It turned out the locking mechanism was poorly designed and it broke with no way to put the dome back other than glue it back with a plastic hot glue gun. It's not a fix that will solve the problem for good since it's prone to failure because of the dome design that sticks out.
Conclusions: attention, attention, attention.. Not to jump head first next time. I'm not sure how much I'll use this product from now on since I lost my trust in it and I already plan on getting a more reliable color checker board.