Blackmagic Forum

I don't see anything listing what the base ISO is for either of these cameras. I've been using 800.

After reading up about the 6k ISO setting in this thread (viewtopic.php?f=2&t=208229) I'm wondering...

Is ISO be handled differently with the RGBW Sensor?

We consider "native" to be 800 for both. I would also note that I expect people to find URSA Cine 12K to have less apparent noise at the same ISO/EI compared to URSA Mini Pro 12K.

CaptainHook wrote:We consider "native" to be 800 for both. I would also note that I expect people to find URSA Cine 12K to have less apparent noise at the same ISO/EI compared to URSA Mini Pro 12K.

Thanks for this. I have one more question for anyone who can answer... I found this in the manual:



The AI told me this:
Dynamic range is about a camera's ability to capture a wide range of light intensities in a single exposure. This means it can handle both bright and dark areas simultaneously, without losing details in either.

• Does the above chart represent that range of light?
• Is the range allocation in the chart determined by the sensor, software or both?
• What is the purpose of a "Base" ISO, is it the optimal range allocation based on the sensor?
• Why isn't 1600 the "Base" ISO? I ask because it's the closest to half and half range allocation. To me, this is the "widest range of light intensities".
• Is the gamma artificially increased and decreased from the Base ISO? Or, is the gamma artificially boosted from 125 ISO?

I'll stop here.

Que Thompson wrote:

• Does the above chart represent that range of light?
• Is the range allocation in the chart determined by the sensor, software or both?
• What is the purpose of a "Base" ISO, is it the optimal range allocation based on the sensor?
• Why isn't 1600 the "Base" ISO? I ask because it's the closest to half and half range allocation. To me, this is the "widest range of light intensities".
• Is the gamma artificially increased and decreased from the Base ISO? Or, is the gamma artificially boosted from 125 ISO?

The base ISO of a camera is determined by the sensitivity of the camera sensor to light, and it is set by the manufacturer during the camera’s design. It represents the lowest ISO setting at which the sensor can capture the maximum dynamic range, producing the least amount of noise. When adjusting the ISO from Base, the signal is either amplified or attenuated.

Not quite. The cameras mentioned capture RAW, so the ISO is only metadata.

The 'native' ISO should be the value at which you can expose based on middle gray (18%) and find the same number of stops above and below that exposure. Since underexposure finally will end up in noise, the level of noise you want to tolerate is subjective to some degree. Clipping, OTOH, is hard and indisputable.
So, if you want to stay away further from the noise floor, just 'lie' to your camera and rate it as 400 ISO. You'll expose higher, so you'll get cleaner images, but loose one stop in the highlights before clipping.

Also consider that various camera models may have different noise. For example, I have both URSA Mini Pro 4.6K and URSA 12K and both seem to have similar dynamic range (even though one is listed as 15 stops and the other 14) because the 12K has less noise.

Our 'native' ISO is what we consider a good balance (not necessarily equal) of stops over/under middle grey in combination with our determination of an 'acceptable' noise level. Another way to think of it might be, this is our recommended ISO setting for 'general' use.

CaptainHook wrote:Our 'native' ISO is what we consider a good balance (not necessarily equal) of stops over/under middle grey in combination with our determination of an 'acceptable' noise level. Another way to think of it might be, this is our recommended ISO setting for 'general' use.

Thanks.

*DELETED*

Que Thompson wrote:I don't think this is true. I think noise level whether underexposing or overexposing depends on the current ISO. This is shown in the chart that I attached.

The chart assumes you're exposing for middle grey at each respective ISO setting. Dialing in the ISO setting on the camera alone doesn't do anything unless you meter middle-grey for that ISO setting. If that sounds self-evident, it isn't, based on the confusion that chart causes.

f5.6 will produce exactly the same exposure with the camera at iso 100 as iso 1000. Those settings are only metadata. What's crucial is the ISO setting you expose for.

And of course if you expose for iso 100, you'll get much less noise than you would if you exposed for iso 1000. But @ iso 100 you'll lose a few stops in the highlights, in favor of more detail in the shadows (below middle-grey).

Again, all this may sound self-evident, but it isn't to lots of BMD shooters.... ISO on these cameras does not follow the film analogy.

John Paines wrote:

Que Thompson wrote:I don't think this is true. I think noise level whether underexposing or overexposing depends on the current ISO. This is shown in the chart that I attached.

The chart assumes you're exposing for middle grey at each respective ISO setting. Dialing in the ISO setting on the camera alone doesn't do anything unless you meter middle-grey for that ISO setting. If that sounds self-evident, it isn't, based on the confusion that chart causes.

f5.6 will produce exactly the same exposure with the camera at iso 100 as iso 1000. Those settings are only metadata. What's crucial is the ISO setting you expose for.

And of course if you expose for iso 100, you'll get much less noise than you would if you exposed for iso 1000. But @ iso 100 you'll lose a few stops in the highlights, in favor of more detail in the shadows (below middle-grey).

Again, all this may sound self-evident, but it isn't to lots of BMD shooters.... ISO on these cameras does not follow the film analogy.

Makes sense.

And this applies to all digital cameras if recording RAW.

I've read manuals on color management for digital images. I've read tons of articles on determining middle gray versus shadows and highlights.

I have yet to find a single lucid, cogent explanation of why and how, the data above and below middle gray" are different from each other.

Sent from my SM-S908U using Tapatalk

Data is data; I think it's simpler than you suggest. Your exposure choices for middle-grey, whatever value it's assigned -- typically 38.4 for BMD cameras -- will determine how the sensor's total available stops will be distributed.

Open up the lens and as you'd expect, your shadows get brighter but you're more likely to clip the highlights. Close down the lens and shadows get crushed but you're capturing more highlights. All that's moving is the distribution of stops above and below middle grey. But the total remains the same.

If you ask me, the single most destructive youtube ever produced on BMD cameras was filmmaker IQ's claim that iso 1000 was the best setting for highlights. It's true in a very limited sense, but it led legions to think that the actual 1000 setting on the camera was performing some kind of miracle. It wasn't. Even on Prores, where the ISO curve is burned in (not metadata), it wasn't achieving what that youtube led armies of real estate videographers to believe.

John Paines wrote:If you ask me, the single most destructive youtube ever produced on BMD cameras was filmmaker IQ's claim that iso 1000 was the best setting for highlights. It's true in a very limited sense, but it led legions to think that the actual 1000 setting on the camera was performing some kind of miracle.

That chart makes it look like 1600 is the best because it seems that there are a nearly equal amount of stops above and below it. However, I guess that does not take noise in to account.

Que Thompson wrote:
That chart makes it look like 1600 is the best because it seems that there are a nearly equal amount of stops above and below it. However, I guess that does not take noise in to account.

That actually depends on how you light your scene.