Mini 3 and dual native iso

[yannick_c]

What Dji says about it in tweets

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[Droning on and on...]

According to DJI in that tweet thread:

"DJI Mini 3 Pro features the dual native ISO values of ISO 100 and ISO 800. Photo mode and video mode (24/25/30fps): The sensor will algorithmically integrate the images gained by the two sets of analog amplifier circuits for a better dynamic range of actual imaging."​

So, question answered. Dual Native ISO is active for both still photos and video. Which makes sense.

 

[2Birds1Stone]

Hi, my first tweet, so be gentle

Thank you everyone, this a very interesting thread. I think I mostly understand, but I have one question: How do I control which native iso is used? i cant find it in the settings

 

[Cymru]

Hi, my first tweet, so be gentle

Thank you everyone, this a very interesting thread. I think I mostly understand, but I have one question: How do I control which native iso is used? i cant find it in the settings

You can't.

Ultimately it kicks in and out depending on the ISO setting and other than that you have no real control.
Worse, due to the whole stop increments you need to go high (800) to get it to appear.
The switch is about 500 but you cant set that - its only on auto. You need to set 800 which is pretty much unusable.

You can go into pro mode, leave ISO on auto and adjust shutter speed to get the ISO just over 500.
Also the dual native conversion still can't be disabled for frame rates 30fps or lower so need above that to not lose quality.

 

[Droning on and on...]

Hi, my first tweet, so be gentle

Thank you everyone, this a very interesting thread. I think I mostly understand, but I have one question: How do I control which native iso is used? i cant find it in the settings

You can control it, but indirectly.

In PRO mode, select AUTO shutter, then manually set the ISO. 800 and above will use the low gain amplifier. Below 800 will use the high gain amplifier.

This works for stills and videos. The shutter doesn't have to be AUTO... the analog gain is switched entirely on the basis of ISO. AUTO shutter just makes it easy to keep correct exposure.

 

[51 Drones]

The fact that the manufacturers don't use it as a selling feature is telling.
Dual gain requires there to be two connections from the sensor, ie additional analogue circuitry is added to accommodate greater amplification, a higher gain applied to the sensor signal. An added cost and complexity, especially in a small consumer camera like the DJI Hasselblad system.
Video is quite different than still, video is not multiple stills. There are lots of computation in video, including DLog capture thats not required in still capture. Even RAW capture in video is not multiple stills. Still capture works in RGB whereas video works in YCC (a detailed luminosity channel and two highly reduced colour channels) to minimize data size. Being technically oriented you will know that video capture takes clever advantage of the fact that our eyes are very sensitive to luminosity (gray scale) and quite insensitive to colour.
Camera manufacturers are very careful not to give away too much detail on how they handle the science but I believe for digital stills there are other ways to minimize digital noise and still maintain highlights and shadows throughout the ISO range.
In many respects a camera that shoots stills & video is like two different technology cameras packaged into one box. They share a lens, sensor, storage and display but thats about it.
You should be aware that "dual iso" is not a panercea, I haven't seen a DJI technical explanation but by pumping up the gain for high ISO you substantially clip highlights in order to get more shadow detail.In your setup you have to decide if highlights are important or shadows because if you move to the higher "native" gain (higher ISO) then you clip the capture and loose several stops of highlights.
I think the "dual native iso" in the M3 is used in their new night mode, the reason being that the higher native ISO gives a lot more bandwidth (space below middle gray) in the shadows
One fact to remember, whether it's day or night, whether you set high ISO or low ISO, absolutely nothing changes from a capture point of view at the sensor. The sensor captures X amount of light regardless of ISO setting. If you work in RAW, the same image captured at night with high or low ISO, roughly speaking can be corrected in post and look similar. You either amplify the analogue signal from the sensor or you amplify the signal digitally in post, pretty much the same thing.

Holy crow, I feel like I just took a Masterclass in ISO! How much do I owe you?

 

[Droning on and on...]

Holy crow, I feel like I just took a Masterclass in ISO! How much do I owe you?

Hang on a minute... much of that was factually wrong.

For example, "Dual gain requires there to be two connections from the sensor, ie additional analogue circuitry is added to accommodate greater amplification, a higher gain applied to the sensor signal" is completely wrong. There is one amplifier, no different than the single ISO sensor, just capable of variable gain (in this case, two gain values which makes the design even easier). Further, the amplifier is on-chip – there are no external connections specifically for the analog amplifier in the signal processing path.

Most of the "magic" comes in interpreting the digital values after the A/D stage, as the linear portion of the sensor has been shifted, giving more stops at the high end in bright scenes, or more at the (brightness) low end for dark scenes.

In the case of the M3P sensor, it has a third mode that it can capture both native 100 and native 800 bias on alternating rows. This does require two amplifiers, but no row is wired to both (as in Ed's explanation), VASTLY simplifying the electronic design. This mode is only used for the HQ video modes, resulting in a higher dynamic range video image. It's not used for stills: Both Amps are biased the same (one level for scenes with ISO over 800, other bias for ISO less than 800.

The dual ISO feature works the same for the non-HQ video modes.

 

[charlesostrand]

I've been a photographer for many years, I use professional Nikon DSLR's. I've followed the development of digital photography since its inception and never heard of anyone implementing dual native ISO (more correctly dual gain) in still photography. Nikon D6 ISO goes to 102,000 and expandable to dizzy 3,280,000 and they've never mention dual native ISO or gain. It’s not mentioned in the Spec. Not sure why, maybe the gain is adjusted progressively, no idea but I've only seen it used for video, notwithstanding multiple social media forums unsubstantiated claims about dual gain in still photography. Video technology is quite different to digital still photography. I've followed Blackmagic's development and I have used dual native ISO in the pocket cinema 4K camera for a few years. I'm not convinced it is quite as beneficial as some state. If all else is done correctly for the environment, then there is a small visible benefit, but usually other factors are determining your settings for video like required FPS, shutter speed and aperture then lastly you tweak ISO to get exposure right on.

Not sure about the D6 but Nikon uses dual native iso on many of their models.
I know the D300 has it(no video capability) and I believe the D800 has it as well. Why this info isn’t more available eludes me