This says native ISO is BS...

The place for questions about shooting with Blackmagic Cameras.
  • Author
  • Message
Offline

roig12

  • Posts: 7
  • Joined: Mon Oct 25, 2021 7:56 pm
  • Real Name: Roy Shenhav

This says native ISO is BS...

PostWed Oct 27, 2021 9:53 pm

pocketluts.com/a-only-slightly-less-confusing-explanation-of-the-pocket-4ks-iso-settings

I always heard that I should shoot one of the native ISO's on my BMPCC 4K to have as much dynamic range but it seems by the chart in the bottom of the above link that the dynamic range is always the same and only the range changes.

So if I'm using 100 ISO I will have more details in the highlights and less in the shadows and vise versa right?

So, why shouldn't I just use the ISO I need in order to preserve the details where I need?

Also, if ISO doesn't matter when shooting raw then why would it even affect the dynamic range?

What about high ISO with an ND filter to go back to the same exposure I will get with the native ISO at 400?

Am confused...
Offline
User avatar

dondidnod

  • Posts: 434
  • Joined: Sun Nov 25, 2018 7:52 am
  • Location: Castro Valley, CA
  • Real Name: Donald Keller

Re: This says native ISO is BS...

PostWed Oct 27, 2021 11:52 pm

Norton 360 tells me that that is a dangerous site, so it's not worth it to go there:
NET::ERR_CERT_DATE_INVALID

You will lose 1.1 stops of DR by going to the higher ISO range on the BMPCC 4K.

BMPCC4K 12.7 dynamic range sn ratio=1

"The result: 11.6 stops of dynamic range for a signal to noise ratio of 2 (12.7 stops for a signal to noise ratio of 1) at ISO 400 (10.5 and 11.8 stops for ISO3200), in ProRes 4K DCI 25p."

Blackmagic Pocket Cinema Camera 4K Hands-On Review

https://www.cined.com/blackmagic-pocket ... on-review/

If you shoot in ProRes, it bakes in the ISO and white balance. If you shoot in BRAW, you can set both of these in post, assuming you select the correct ISO amplification range.
Offline

Frank Engel

  • Posts: 729
  • Joined: Thu May 17, 2018 11:09 pm
  • Real Name: Frank Engel

Re: This says native ISO is BS...

PostThu Oct 28, 2021 10:06 am

roig12 wrote:the dynamic range is always the same and only the range changes.

So if I'm using 100 ISO I will have more details in the highlights and less in the shadows and vise versa right?

So, why shouldn't I just use the ISO I need in order to preserve the details where I need?



This is essentially correct, within one of the two native ISO ranges. The two "native" ISOs are selected to provide a typical balance of highlight and shadow detail. Straying from the "native" ISO but staying within that range will shift the center, biasing the detail levels more toward one or the other; however, bear in mind that noise levels can also be impacted as there is virtually always more noise in the shadow areas than in the highlights, so as you increase the ISO setting within a given range, the noise level is still likely to increase to some extent.



roig12 wrote:Also, if ISO doesn't matter when shooting raw then why would it even affect the dynamic range?


It does shift the dynamic range, but at least as importantly it will impact your exposure on set. If you expose for ISO 800 then you are feeding the sensor with less light than you would if you were exposing for ISO 400 and this is not simply metadata as the ISO level itself is. Less light hitting the sensor means less likely to blow out the highlights but more likely to have noise in the shadows.
Offline
User avatar

MrHotter

  • Posts: 149
  • Joined: Wed Apr 25, 2018 3:10 pm
  • Real Name: christian Hotter

Re: This says native ISO is BS...

PostThu Oct 28, 2021 1:27 pm

Shooting at ISO 100 (or 1250) would be fine if you have the exact exposure you want. Where you run into trouble is when you want to get a couple more stops of light in post. You can't lower your ISO in the RAW tab when at iso 100 because you are already at at the bottom of the range.

I shoot live theater and live events, so being at the native ISO helps me when the lighting conditions change from scene to scene.
Mac mini
Apple M1 chip with 8-core CPU, 8-core GPU, and 16-core Neural Engine
16GB unified memory
512GB internal SSD storage
various external drives
Offline

John Griffin

  • Posts: 1191
  • Joined: Sun Aug 23, 2015 4:18 pm

Re: This says native ISO is BS...

PostThu Oct 28, 2021 4:40 pm

ISO is not an exposure control within each gain stage. It’s just a way of moving tones around.
Offline

roig12

  • Posts: 7
  • Joined: Mon Oct 25, 2021 7:56 pm
  • Real Name: Roy Shenhav

Re: This says native ISO is BS...

PostFri Oct 29, 2021 8:38 pm

John Griffin wrote:ISO is not an exposure control within each gain stage. It’s just a way of moving tones around.


What do you mean by moving tones around?

MrHotter wrote:Shooting at ISO 100 (or 1250) would be fine if you have the exact exposure you want. Where you run into trouble is when you want to get a couple more stops of light in post. You can't lower your ISO in the RAW tab when at iso 100 because you are already at at the bottom of the range.

I shoot live theater and live events, so being at the native ISO helps me when the lighting conditions change from scene to scene.


What about lowering the gain control in da vinci? what will happen then if shot at iso 100?

Frank Engel wrote:
roig12 wrote:the dynamic range is always the same and only the range changes.

So if I'm using 100 ISO I will have more details in the highlights and less in the shadows and vise versa right?

So, why shouldn't I just use the ISO I need in order to preserve the details where I need?



This is essentially correct, within one of the two native ISO ranges. The two "native" ISOs are selected to provide a typical balance of highlight and shadow detail. Straying from the "native" ISO but staying within that range will shift the center, biasing the detail levels more toward one or the other; however, bear in mind that noise levels can also be impacted as there is virtually always more noise in the shadow areas than in the highlights, so as you increase the ISO setting within a given range, the noise level is still likely to increase to some extent.



roig12 wrote:Also, if ISO doesn't matter when shooting raw then why would it even affect the dynamic range?


It does shift the dynamic range, but at least as importantly it will impact your exposure on set. If you expose for ISO 800 then you are feeding the sensor with less light than you would if you were exposing for ISO 400 and this is not simply metadata as the ISO level itself is. Less light hitting the sensor means less likely to blow out the highlights but more likely to have noise in the shadows.


So let's make up a scenario where I have too much light and since I don't like touching the shutter speed (keeping it double the frame rate the whole time) and don't like using the aperture too much as I use that for setting the depth of field that I like then I'm down to ISO and ND filters.
So let's say I put an ND filter and it's a bit too dark while I'm at iso 400, so I push it to 600 to see the exposure I want in the monitor.
Is that approach normal?

and to sum the DR thing, so if I need more or less exposure and am using the iso to get there then I won't lose any quality by straying away from the native iso as long as it gets me the exposure I need in order to show the areas Im after more clearly (more shadows or more highlights) right?
I mean, it's always better to expose correctly than keep the native iso and have the image too dark right? but now comes in the iso is just metadata thing so am again confused :?
Offline

John Griffin

  • Posts: 1191
  • Joined: Sun Aug 23, 2015 4:18 pm

Re: This says native ISO is BS...

PostFri Oct 29, 2021 8:59 pm

ISO within each gain stage changes the response curve more with a lift in mid tones as you go up to 1000 iso and flattest when you drop down to 100. Black and white points stay the same so you can’t control exposure by changing the ISO in each gain stage unless you have a scene with a very small contrast ratio where nothing is nr the shadows or highlights. If you are over exposed in the lower gain stage and don’t want to change shutter angle or aperture then your only option is to add more ND filter strength.
Offline

John Paines

  • Posts: 4488
  • Joined: Tue Jul 28, 2015 4:04 pm

Re: This says native ISO is BS...

PostFri Oct 29, 2021 9:03 pm

roig12 wrote:So let's make up a scenario where I have too much light and since I don't like touching the shutter speed (keeping it double the frame rate the whole time) and don't like using the aperture too much as I use that for setting the depth of field that I like then I'm down to ISO and ND filters.
So let's say I put an ND filter and it's a bit too dark while I'm at iso 400, so I push it to 600 to see the exposure I want in the monitor.
Is that approach normal?

and to sum the DR thing, so if I need more or less exposure and am using the iso to get there then I won't lose any quality by straying away from the native iso as long as it gets me the exposure I need in order to show the areas Im after more clearly (more shadows or more highlights) right?
I mean, it's always better to expose correctly than keep the native iso and have the image too dark right? but now comes in the iso is just metadata thing so am again confused :?


No, on just about all of it. To begin, let's simplify: we're talking only about braw and the lower BMPCC 4K circuit, meaning 100 to 1000.

Under these conditions, you have 4 ways of changing the exposure: the aperture, the shutter speed, adding or reducing light and ND filters. Changing the ISO by itself -- without adjusting one of these other factors -- will accomplish nothing, except making the screen brighter or darker.

Put another way, if the aperture, the shutter speed and the lighting remain constant, you'll capture exactly the same image whether the camera ISO is set to 100 or 1000, or anything in between. If you're passably skilled in Resolve -- which sounds doubtful at the moment? - you can verify this yourself.

If all this is still impenetrable I suggest you set the camera ISO to 400 and leave it there. If you want to change the exposure, you need to alter one of the other variables. Leave the ISO alone. It's not a tool of exposure, under the conditions established above.

Where there *is* an advantage to changing the ISO setting is the upper circuit 1250-6400. Where the light is so low you have lots of noise in the 100-1000 circuit, you're often better off switching to the upper circuit, at the expense of a stop or so of dynamic range. But that's another and different matter....
Offline

roig12

  • Posts: 7
  • Joined: Mon Oct 25, 2021 7:56 pm
  • Real Name: Roy Shenhav

Re: This says native ISO is BS...

PostSat Oct 30, 2021 8:07 am

Got it!
So bottom line, for my personal needs, I should always try to expose to the native ISO if possible (or as close as possible to it) using ND filters and if shooting low light then always aim for iso 1250 and above and try to stay in the lowest possible iso since the native at 3200 comes with quite alot of noise.
Offline

Uli Plank

  • Posts: 11704
  • Joined: Fri Feb 08, 2013 2:48 am
  • Location: Germany and Indonesia

Re: This says native ISO is BS...

PostSat Oct 30, 2021 8:41 am

Unfortunately, it's not that simple, it depends on the intended look and lighting concept too.
Basically, you're right: use 1250 or above for low-light and 400 with enough light.

ND filters are needed to avoid diffraction with small apertures and/or getting shallow DoF.
Don't approach Resolve with your expectations from other NLEs! They are all different.
Resolve Studio 17.4.2 , macOS 12.0.1
MacBook M1 Pro, 32 GB RAM
Speed Editor

Return to Cinematography

Who is online

Users browsing this forum: crtkecnkl659, jfykeaucq871 and 22 guests