Sony A7R IV A7Riv UNDER EXPOSING in Auto ISO mode in dark scenarios

[Jeandre]



I’ve been pulling my hair out trying to figure out why the A7Riv is behaving badly. Essentially when doing a time-lapse with the built in intervalometer we are getting a massively underexposed series of images. This only happens in very dark environments where the auto iso needs to push up high (in our case around 10,000)

What is interesting is that the first image of each sequence exposes correctly within the limitations we set. i.e. We are shooting in Aperture priority mode, wide open at f2.8, the ISO range is set to 100-10,000 in both the menu settings, and on the iso jog wheel settings. We have the Auto ISO SS set to 15”. A correctly exposed image in our very dark setting is f2.8, 10,000 iso and 15” shutter. This is confirmed by reading the scene by half pressing the shutter, and by the first still of every sequence being shot at this setting. For some bizarre reason from the second frame of every shot it then jumps down to iso 500 (same f stop and shutter) and stays this way until the light significantly starts to change, e.g. dawn breaks.

The interval shooting mode works fine in brighter environments, e.g. a city scape at night, but not in dark scenarios, e.g. star lapses.

I have set the camera to have all processing off including:
-High ISO NR off
-DRO off
-High SS noise reduction off

I have tried increasing the interval between shots to way more than the shutter speed just in case some post processing time was needed for something, but this made no difference.

Shooting jpeg or raw, or both made no difference at all.

We have the latest firmware as the camera is new (v1.2).

A full reset of the camera did not solve the problem.

Pushing the AE dial to +3 EV helped push the ISO up slightly to 1000, but shooting this way would obviously over expose the highlights once dawn broke (to be clear, the camera is not underexposing when there is enough ambient light).

We have tried changing the exposure metering modes (specifically with several tests on “Multi” mode and “entire screen average”) this made no difference at all. The fact that the first frame of each sequence exposes correctly, also throws out the idea that the camera can’t expose properly in dark environments.

I came across a forum detailing a similar problem that appeared on the mark3 when doing a firmware upgrade:

https://www.sonyalphaforum.com/topic/12094-sony-a7iii-night-timelapses-with-built-in-intervalometer/

 I am therefore left to think that this is a software issue from Sony that is inherent in the A7Riv. Does anyone have any suggestions on a way around this (besides external intervalometer, and manually changing exposure through the interval duration), or perhaps some insights from Sony on why this problem exists in a high end camera?

 

[DonaldRB]

Hello Jeandre,

Thanks for replying to my thread, which indeed describes the exact same issue as you elaborated. Meanwhile i've moved on to the Sony A7iii, and sadly I can confirm this camera suffers from the exact same issue as the a6400 and your A7Riv. In this case, in interval shooting mode with ISO auto, the ISO never raises higher than ISO 400, even in pitch black darkness. Like you described, the first frame it takes when starting the interval shooting is the correct ISO value, but from the 2nd frame onwards it stays at ISO 400.....

So to conclude, we can be positive this is a bug in Sony's interval shooting software, something that is apparantly present in most of (if not all) of their mirrorless camera's. Do you reckon there's any chance we could inform Sony about this and get a firmware update? It's a malfunction that should be fixed (at least before next Milky way season ).

Cheers!

 

[Jeandre]

Hi Donald,

Yes it does seem to be a bug present in many of their models. If you check this thread https://www.sonyalphaforum.com/topic/12094-sony-a7iii-night-timelapses-with-built-in-intervalometer/ you will see that several people have tried contacting Sony only to get worthless feedback. The more people that complain though, the better the chances that they fix it though. So please do try through any avenues you have.

Interestingly this problem doesn't seem present on the A7Siii, which is great... but the low pixel count is not great for star lapses.

An additional workaround for you for the time being with your camera you could get a dummy battery so that you can run longer time lapses off an external source, so that your USB port is freed up for an intervalometer.

Let me know if you get any leads please