So just looking at the A9 again:
"When the auto or electronic shutter mode is selected the viewfinder frame rate is fixed at 60 fps"
That is 1000/60 = 16.6 Milliseconds refresh, and if we are generous, we will assume that there is no frame padding...
Also:
"When [Shoot. Start Disp.] is set to [On], blackout occurs only when the first image is shot (page 48)."
And:
"Notes on shooting with an external
flash
When shooting with an external flash,
light and dark stripes may appear on
the image if the shutter speed is set
to faster than 1/4000 seconds."
This relates to SONY developing some uncorrected lenses and then using a lens profile to correct the final image. They are not alone but the latest wide angle zoom has more distortion than the competition. Confirms the viewfinder is the uncorrected image so not 100%:
"Notes on shooting with the
viewfinder
• The image may be slightly distorted
near the corners of the viewfinder.
This is not a malfunction. When you
want to see the full composition
with all its details, you can also use
the monitor.
• If you pan the camera while looking
into the viewfinder or move your
eyes around, the image in the
viewfinder may be distorted or the
color of the image may change.
This is a characteristic of the
lens or display device and is not
a malfunction. When you shoot
an image, we recommend that
you look at the center area of the
viewfinder."
More on the EVF:
"When shooting with the viewfinder,
you may experience symptoms
such as eyestrain, fatigue,
travel sickness, or nausea. We
recommend that you take a break
at regular intervals when you are
shooting with the viewfinder.
In case you may feel
uncomfortable, refrain from using
the viewfinder until your condition
recovers, and consult your doctor
as necessary.
Notes on continuous shooting
During continuous shooting, the
monitor or viewfinder may flash
between the shooting screen and a
black screen. If you keep watching
the screen in this situation, you may
experience uncomfortable symptoms
such as feeling of unwellness. If you
experience uncomfortable symptoms,
stop using the camera, and consult
your doctor as necessary."
4K shooting, just out of interest:
"Notes on recording for long
periods of time or recording 4K
movies
• Depending on the camera and
battery temperature, you may be
unable to record movies or the
power may turn off automatically
to protect the camera. A message
will be displayed on the screen
before the power turns off or you
can no longer record movies. In
this case, leave the power off and
wait until the camera and battery
temperature goes down. If you turn
on the power without letting the
camera and battery cool enough,
the power may turn off again
or you may be unable to record
movies.
• Under high ambient temperatures,
the temperature of the camera rises
quickly.
• When the temperature of the
camera rises, the image quality may
deteriorate. It is recommended that
you wait until the temperature of
the camera drops before continuing
to shoot.
• The surface of the camera may get
warm. This is not a malfunction.
• If the same part of your skin
touches the camera for a long
period of time while using the
camera, even if the camera does
not feel hot to you, it may cause
symptoms of a low-temperature
burn such as redness or blistering.
Pay special attention in the following
situations and use a tripod, etc.
– When using the camera in a high-
temperature environment
– When someone with poor
circulation or impaired skin
sensation uses the camera
– When using the camera with
the [Auto Pwr OFF Temp.] set to
[High].
• Especially during 4K movie
shooting, the recording time may
be shorter under low temperature
conditions. Warm up the battery
pack or replace it with a new
battery."