This is a continuation in a series of posts on power consumption in the Sony a7RII. The more recent incarnation of the series starts here.
The manual for the Sony a7RII says that the electronic viewfinder (EVF) consumes more power than the liquid crystal display (LCD). My testing has indicated the reverse. That’s because I neglected to force the EVF to turn on in each case by blocking the eye detector. Without a signal that there’s something blocking light from entering the back of the finder, it won’t turn on.
Previously, I determined that the EVF current draw varied a bit with the brightness of the displayed image. The LCD current draw did not. That makes sense, since the LCD is a subtractive display, with various transistors switching on and off to block light that comes from the backlight. In some smart LCD television screens, the backlight varies with what is displayed, and even varies throughout the scene depending on the average level of brightness. The a7RII is not that smart: the display stays lit at the set intensity no matter what’s on the screen. But it turns out that the current to run the organic light emitting diode (OLED) display is not very sensitive to display brightness either.
There are five manual brightness settings for the LCD. Here are the current draws at each, with the display set to High quality:
- -2 — 317 ma
- -1 — 325 ma
- 0 — 328 ma
- +1 — 344 ma
- +2 — 360 ma
When you’re looking at a fairly dark screen — in this case the setup screen for brightness — there is not much variation in the EVF current draw:
- -2 — 422 ma
- -1 — 422 ma
- 0 — 424 ma
- +1 — 427 ma
- +2 — 460 ma
As the image get brighter, the display drawa a bit more current. But not much more. In fact, without going to a lot more trouble than the project is worth, I was unable to measure the increase..
So, yes, the manual is right. The EVF does draw more current. However, because it drops down to rougly 250ma when your eye isn’t at the finder, you may indeed find your batteries lasting longer with the EVF.
By the way, it looks like the “sipping” of current that we saw in active mode in yesterday’s post when the camera is not creating images is the display refresh. Here’s a look at the current draw with first the EVF and second the LCD enabled. the frequency is the same, but the duty cycle is longer for the LCD.
Here’s a comparison of the current with the EVF on when held against the eye and when not.
Eye to EVF
When the eye is against the EVF, the sipping frequency doubles and the amount of time for which current is drawn at the higher rate increases.
Note that the peak current increases a bit when the EVF is on and active. The low current drops in the case that neither display is active (EVF with eye — or thumb, in this case — away from eyepiece). I wonder what the camera is doing when the EVF is away from the eye. It seems like it’s doing some processing associated with live view even though it’s not writing the data to either screen, and that’s what is taking the intermittent current.