Hi I have had the GH4 for some time now and use it pretty much every day. I have also conducted a lot of tests, all sorts of tests...however as my main business is 3d and graphics I dont like to just test, my main business is creating.

Now to get to the point, I have read on this forum "User Reviews and Opinions" that the GH4 image is really 3K not 4K.

Now this may or may not be right, I have no wish to get in a flame war about this, my only interest is to establish some real world facts. Here is what I have found...(after quite a few tests) I did the recent one in UHD mode (3840 x 2160) in 4K photo mode...which BTW works the best for me (I use 25p) I use it because of the incredible detail if you get the focus right.

I have a 2560 x 1440 27 inch monitor, and in my tests I have recorded videos of several complex scenes leafy trees and so on, captured a still image of the movie and analyzed that image in an image editing/art program (any art program will do PS or Painter etc...). When zoomed right in at 2400%, you can see the individual pixels with different color shades very clearly, and consistently those screen caps show a different color in each pixel, except in areas where there are large amounts of color with no shading, this color differentiation is clearly seen by eye in full zoom and confirmed by simply sampling the color pixel with the eye dropper tool, if the image is really 3K, then I assume this would not happen. I am happy to be proven wrong, but my tests show that at the very least the GH4 uses a different color for each pixel of either a 4K image or a UHD image.

Now another point is that a group of 4 x 4 pixels (16 pixels) is very small on a 2560 x 1440 27 inch monitor, I can only imagine how small they may look on a 4K monitor that is 27 inches. All in all, my findings are that (especially in 4K photo mode...but also in the UHD/4K modes ) the detail of the GH4 is almost beyond what your eye can see in 99% of circumstances and you would need to be sitting quite close to large 4K monitor to really see any difference. My verdict on the GH4, an amazing camera in just about every respect!!

And yes I use iDynamic in high contrast areas (bright sun, treees and shade) and it works amazingly, but you do need enough light and it will not introduce noise in that circumstance. Cheers