p.1 #1 · Sony silently applying gain at certain apertures
Hey everyone,
I recently got a Nokton 50mm F1.0 for Sony E mount, and I'm facing a pretty weird behavior from my Sony camera.
On my a7s II, as soon as I close the aperture down from F1.0 to F1.1, the camera decides to boost gain (I'd say a good +0.3 EV at least). After that first "correction", no further gain changes happen across the rest of the aperture range. When I go back to F1.0 though, the gain disappears / resets.
It's not just a display or preview thing, as pictures and recorded footage reflect it as well. Of course I'm in full manual exposure and manual ISO. Lens compensation settings are all off, and DRO is disabled. The gain isn't showing in the settings, it's kind of a silent ISO override.
I tried it with the lens partly disconnected from the mount (so the lens chip couldn't communicate with the body), and unsurprisingly that gain bump doesn't happen.
My guess is that the a7s reads the (extreme) aperture value and tries to compensate for an expected light loss when the lens is no longer wide open, but it still doesn't make much sense to me.
I was wondering if any of you guys using fast Voigtlander E-mount lenses (or any fast lens with eletronic contacts) would be willing to check whether you see the same behavior on your Alpha series body. A quick test looking at the live view in manual video mode, going back and forth between the max aperture and closing down just one click away to see if you get sudden changes in brightness would be super helpful.
I know this is a bit of an unusual request, but I’d really appreciate any feedback, especially if you can mention your camera model.
p.1 #5 · Sony silently applying gain at certain apertures
RoamingScott -> As written in the post I tried with the lens not fully connected to block the exif data transmission and it doesn't happen. I'm curious to see if any more recent Sony models still behave like this...
p.1 #6 · Sony silently applying gain at certain apertures
ImDaJim wrote:
RoamingScott -> As written in the post I tried with the lens not fully connected to block the exif data transmission and it doesn't happen. I'm curious to see if any more recent Sony models still behave like this...
Duh, I missed that, but it proves my suspicion that Sony likely doesn't know what to do with the rather esoteric f/1.1 aperture
p.1 #8 · Sony silently applying gain at certain apertures
RoamingScott -> Yeah that looks a lot more like a bug than a feature. But since the a7s 2 I own is almost 12 years old, maybe newer models handle this differently I'm eager to see other people's results.
p.1 #9 · Sony silently applying gain at certain apertures
I seem to, vaguely, remember this having been mentioned earlier. It may have been the ISO that was increased but not registered in EXIF. Maybe it was something else. Anyone?
EDIT: Sorry, yes, just as mentioned in the topic title... Duh...
p.1 #12 · Sony silently applying gain at certain apertures
Regarding "The gain isn't showing in the settings, it's kind of a silent ISO override." I don't know how a camera can "silently" change exposure or gain in full manual. This is not supposed to happen (otherwise you are not in full manual). Out of interest, switch to Aperture-priority with auto-ISO, then compare f/1 with f/1.1. What happens then?
Furthermore, "It's not just a display or preview thing, as pictures and recorded footage reflect it as well"
What are the "pictures/footage" that you refer to? Do you mean raw files or out-of-camera jpegs? If the "pictures/footage" is about raw files then the observation indicates that the "silent ISO override" must be recorded in the metadata. If this is correct, you should use exiftool. There is a straightforward way to find all differences in the EXIF of two raw files (e.g. one with f/1 and the other with f/1.1).
p.1 #13 · Sony silently applying gain at certain apertures
ruthenium -> I agree this shouldn't happen in full manual mode, yet it does. I don't have the lens with me right now but a few days ago I recorded a video showing the behavior live while going back and forth between f/1.0 and f/1.1.
I added some info in post so you can see what I'm doing with the aperture in real time. I also overexposed the video to show the noise in the shadows and there's clearly a change in noise pattern, suggesting some sort of processing is happening when I close down the aperture.
p.1 #16 · Sony silently applying gain at certain apertures
asked Ai
Sony cameras, particularly when using specific Aperture Drive in AF settings, can indeed alter how they handle aperture and gain (ISO/exposure amplification) to prioritize focus performance or silence, rather than adhering strictly to the user-selected aperture during live view.
Here are the key details regarding how Sony handles this:
Aperture Drive in AF (Silent Priority vs. Focus Priority): When using "Silent Priority" for aperture drive, the camera minimizes aperture blade movement to keep the camera quiet.
Live View Adjustment: In some modes (specifically, potentially when not using "Focus Priority"), the camera may keep the aperture wider than the setting in the live view to allow more light in for better focusing. The camera then electronically adjusts the live view to look as if it is at the set aperture, which can involve manipulating the gain, leading to a "cleaner" or different image than what is actually being captured.
The "Gain" Aspect: If the camera keeps the aperture open (e.g., at f/2.8) for focusing, but the user has set f/8, the camera may be manipulating the sensor gain (ISO) in the live view to make it appear darker, rather than actually stopping down the lens until the shutter is fired.
Variable Aperture in Low Light: Some users have reported that in Aperture Priority mode, the camera may override the set aperture (opening it up) if it is too dark, essentially prioritizing a usable exposure over the chosen depth of field.
Impact on Exposure: The camera's "Aperture Drive in AF" can influence how the lens moves, and if set to "Silent Priority," it may affect focus speed and accuracy.
Recommendation: To ensure the camera behaves exactly as you intend regarding aperture, setting the Aperture Drive in AF to "Standard" or "Focus Priority" is usually recommended, though this may increase noise.
p.1 #17 · Sony silently applying gain at certain apertures
Thanks macwest but I'm afraid all of these points are irrelevant to the current issue, the AI mostly talked about preview / live view overrides for ease of use, which is common stuff. My case is a way more obscure and peculiar image processing related behavior that's probably not referenced anywhere...
p.1 #18 · Sony silently applying gain at certain apertures
Please, tell what was your shutter speed and ISO with f/1 and then with f/1.1.
Do you see this "gain boost" between the two raw files (without corrections)? I am not interested in what you see in camera.
p.1 #19 · Sony silently applying gain at certain apertures
ruthenium -> I used the same ISO and shutter speed on both aperture settings obviously. And as you can see it happens in real time on video at fixed settings so it's certainly not gonna show up in RAW files since it's applying separate gain somewhere else in the processing pipeline. But you're right I should test it with two separate RAW files. I'll try to do that test ASAP.
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