[Advice needed from fellow A7sii users] Sensor noise at maximum ISO

[Moebius]

Hi all,

 

Forum noob here. I have a pressing concern with my recently-purchased A7sii and am hoping that fellow users will be able to shed some light on it.

 

Essentially, my issue relates to the magenta sensor noise that occurs at ultra high ISOs. This was a known problem with the A7s. In some reviews I've read, however, some notable reviewers such as Philip Bloom have averred that their A7sii units no longer have this problem.

 

Here are some samples from my unit: http://1drv.ms/1MVTfuq and http://1drv.ms/1MVTo0J. Can I trouble someone to confirm that this level of sensor noise is typical of the A7sii at maximum ISO? I've sent my unit in for evaluation, and the Sony service staff have insisted that this is normal across all units, but my tests with some demo units seem to suggest otherwise, I.e. The magenta noise seems much less pronounced.

 

Any insights or help would be much appreciated!

[Guest Peter Kelly]

I suspect that this is an individual camera issue, rather than of a certain model, and it has the same cause (or causes).

 

I understand that a good proportion of it is down to light leakage, which would be understandable because any light at very high ISO will show up and be magnified.

Some A7S users advocated simple black tape around the mount to block it off, which apparently worked in some cases!

 

Of course, the other two possible causes would be first a 'faulty' sensor, in that there may be sensor to sensor variation, but if it's within specification then there would be no solution and, second, heat from another part of the camera.

Heat would certainly increase any noise issues, which is why astrophotography tries its best to keep a sensor cool.

 

Personally I think the light leakage is the most probable cause and if it is really important to you then the best option is to swap the camera, assuming you still have the option.

Otherwise, perhaps Sony will 'repair' it under warranty. This might be nothing other than re-assembling it to try to tighten any tolerances.

 

Good luck!

[Moebius]

Thanks for the helpful reply, Peter. Sadly, after two weeks of evaluation at the local Sony service centre, the verdict (apparently from the HQ in Japan) is that the sensor noise of my unit is within acceptable limits and that there is nothing that can be done.

 

I have written in formally to request for a 1-to-1 swap, but am not hopeful.

[Guest all8]

You could follow up on Peters suggestion, mount a lens, tape around the mount, and see if it makes a difference. This was a problem with the first generation.

 

If that helps you could then ask Sony to consider that the Mount might not be correct, rather than it is a noise problem.

[Moebius]

Will give that a go, thanks :-) Interestingly, the Sony engineer insisted that these weren't light leaks. The only 'repairs' they did were to clean the camera. Quite disappointing, really.

[Softies]

You see two kinds of issues here: "amp glow" and high ISO noise.

 

"amp glow" is caused by heat produced by additional electronics you find on sensors. It is like CPUs/GPUs in computers or smartphones that heat up the more they are strained. This is this light shining into the picture from the left side and especially the lower left corner.

 

The other point is high ISO noise. Due to the way how this whole thing works, the higher the ISOs go, the more noise you get. At some point this noise becomes visible, first in the darker parts of the image, and beyond that even in midtones and then even highlights. The noise in the red and blue channels is a bit stronger than that in the green channel (you have twice as many green pixels), which is why this noise has a purple-ish color.

 

ISO400k is really a stretch on the A7s/II, means stuff like that is to be expected. With video it is probably somewhat easier to handle, still pictures need some heavy handed post processing to lower the impact of that noise floor.

 

Many other cameras show similar behavior, just some cameras don't allow the ISO levels to be set to the point where you get these results.

[Moebius]

Thanks Softies. I tried another demo unit the other day and it had even worse noise, so I'm resigned to the fact that this is indeed 'normal' even though some variation clearly exists between different units. Reviewers must've been given pristine units 'cos most of them have been reporting that they have not been experiencing this problem.

[Moebius]

Just a final update from me and I'll put this matter to bed. Sony has declined to do a 1-to-1 exchange, once again citing the statement from HQ Japan that the noise is within acceptable limits. I guess it's a case of caveat emptor here: the reviews that state that there are no magenta issues whatsoever at ultra-high ISOs should be taken with a pinch of salt.

[RRRoger]

I sent my A7sII back!

 

If I shot hand held, I would have kept it for the IBIS.

For my use everything else is better on my A7s.

 

Most of the reviewers are 24P shooters where some Cinematic grain is acceptable or even desirable.

I shoot P30 and the A7s has less high ISO noise especially compared to the A7sII 1080P120 shot with the 2.2 crop.