Andy Shipsides takes a look at why people shouldn’t try to match Rec. 709 from different cameras, and why they look different:
At AbelCine, we do a lot of camera matching; customers bring in their cameras, and we do our best to create matching scene files. Recently, two cameras were brought in with a simple request attached, reading, “Please match to Rec. 709.” This may seem like a normal request to some of you, or it may have you scratching your head. The term Rec. 709 implies a lot of things, and leads to a lot of confusion.
…standard Rec. 709 has a limited dynamic range; add a knee point, and you get more. Hyper-gammas and Log modes push it even further. …
In other words, monitors conform to the gamma standards of Rec. 709, but cameras generally do not. This is a big reason why setting two cameras to Rec. 709 mode doesn’t guarantee they will look the same. Different gamma means different contrast and dynamic range. Contrast is just half the equation, of course; the other half is color.
Read the full article and his advice here.