ISO - Useless while shooting and in post

[Dermot Shane]

6 - We know that to make a good color correction and grade in post, for example in DaVinci Resolve, we should start with a flat log image (IPP2/RedWideGamma/Log3D10).

We do not know that, not really...
transforming RAW into display refered is really not the only way to work, and really not always the best way...
to make an awesome looking image from a RAW file you can work in ACES /Truelight /RCM2 with output of the sensor in linear light
just say'n...

[Michael Tiemann]

As long as sensors have finite dynamic range and non-zero levels of noise in the darks, then the principles of the Zone System (first articulated by Ansel Adams, but practiced and evidenced by so many great image-makers) apply. At the same time, cinematography is more the just calculating and obsessing over exposure details of every single frame for hours. It is helpful to look at a monitor that shows in real-time the promise of WYSIWYG (what you see is what you get).

The practice of treating ISO as a variable for a given image capture medium goes back to the late 19th century. RED cameras provide a digital negative that allows evaluation in real-time, which is amazing. Treating ISO as irrelevant entirely misses the point of the DSMC concept.

Here on REDUSER people are of course welcome to ask and answer however they like (provided they follow the code of conduct). But do not mistake rhetoric for soundness nor boldness for truth. Misconceptions abound, and it is only experience that teaches us the real what and why.

[Nick Morrison]

I personally think ISO is very helpful, even when shooting RAW.

Filmmaking is teamwork, and ISO is a common standard that can be shared with your gaffer, your colorist, your AC, your DIT, etc.

Even if you are familiar with the intricacies of RED and shooting RAW, they may not (and often don't need to be).

[Aaron Green]

I could be wrong about this, but dont RED sensors record at 800 iso, and every adjustment (lowering/raising ISO) is just like turning an exposure wheel in post?

[Phil Holland]

I could be wrong about this, but dont RED sensors record at 800 iso, and every adjustment (lowering/raising ISO) is just like turning an exposure wheel in post?

RED defaults and suggests a Base ISO of 800 as a starting point when Rating your ISO.

Most of the cameras have a recommended ISO Range of ISO 250-3200 with Extended ISOs available. Gemini being a Dual ISO sensor is a bit different, but overall this is what is recommended.

The sensors themselves have a flatline sensitivity in Linear Light, this is a very low number and is indeed the "Native ISO".

To the topic, this is one of those how hard do I disagree with the general statement? A whole bunch.

Fundamentally, and this is true for all digital cinema cameras, how your Rate your ISO and use that information towards your Exposure Strategy is very important. Whether you expose based around Middle/18% Gray or ETTR/Exposing to the Right or even Bucket/Histogram based exposures, where you rate the ISO has an impact on how much Apparent Visual Noise can be seen. It also has an impact on where your values land, i.e. closer to the Noise Floor or Light Ceiling. If choosing Middle Gray as an Exposure Method, what most cinematographers do, shooting lower ISO gets you cleaner shadows, but less stops allocated towards your highlights range. Going for Higher ISO you weight more stops towards highlight information, but your Middle Gray will be noisier. Depending on all things this has implications of where Crushing and Clipping may occur and that's what the RAW Exposure Goal Posts are useful. And honestly even more useful is the GIOSCOPE tool, which really shows you where values land on the sensor and where potential in frame issues arise.

The key with REDCODE RAW and other RAW formats is you have nondestructive control over adjusting your Exposure via RAW controls. As well as Color Temperature. This is actually not the same as general grading controls to do similar tasks. One of the more interesting things I notice omitted from many YouTube grading tutorials is not fully harnessing the power of RAW cameras because many have built upon similar tutorials and workflows presented. Not saying the ways presented are wrong per say, but it's interesting seeing methods actually used somewhat not talked about.

I see a lot of people rate at 800 and call it a day, they end up never changing that. That's cool. More or less like shooting Kodak V3 500T and never pushing or pulling I guess. But I personally switch it up depending on what I'm looking for. I know many who like ISO 1600 for projects from about Dragon onward and there's plenty of Low ISO shooters out there in the 250-400 range. Certainly times where I've had to go up to ISO 5000 or 6400 for sure when the situation calls for it.

If you look at any of my exposure ramp tests over the years, you can see I'm exposing to 18% gray at each ISO Rating to reveal how much visible noise you have at a given output transform/tone map combination. It's how we look at cameras when we test them and also come up with strategies for best practices.

So yeah, my perspective, not useless at all.

[Scot Yount]

This will sound (and is) pedestrian after Phil's post, but one thing about ISO I find very useful, is giving the colorist a starting place on multi-cam shoots. I have a Helium Weapon, a Scarlet-MX, and a Komodo. When shooting all three for instance in a cooking tutorial, I usually end up with the Helium at 400, the Scarlet at 800 and the Komodo at somewhere in between, depending on the lighting. That way the colorist who is grading those in a multi-cam project has images that are all about the same brightness, and to my eye, the same level of noise as a starting place. Of course, this varies according to the setup and since everything is raw, he or she can change it all later if so desired.

[Rui Guerra]

We do not know that, not really...
transforming RAW into display refered is really not the only way to work, and really not always the best way...
to make an awesome looking image from a RAW file you can work in ACES /Truelight /RCM2 with output of the sensor in linear light
just say'n...

Can you share a bit more about this and how/where the selected in camera ISO value will be respected/relevant?

Thanks!

[Rui Guerra]

cinematography is more the just calculating and obsessing over exposure details of every single frame for hours. It is helpful to look at a monitor that shows in real-time the promise of WYSIWYG (what you see is what you get).

Indeed!

The practice of treating ISO as a variable for a given image capture medium goes back to the late 19th century. RED cameras provide a digital negative that allows evaluation in real-time, which is amazing. Treating ISO as irrelevant entirely misses the point of the DSMC concept.

I understand that. My post is really more about the naked technical relevance of in-camera ISO, not so much about the WYSIWYG, creative or cinematographic side of it, which is valuable, of course.

[Rui Guerra]

I personally think ISO is very helpful, even when shooting RAW.

Filmmaking is teamwork, and ISO is a common standard that can be shared with your gaffer, your colorist, your AC, your DIT, etc.

Even if you are familiar with the intricacies of RED and shooting RAW, they may not (and often don't need to be).

Yes, I agree with that. But this is a workflow related convenience, and not exactly a technical "must" that will make or brake the final image. Just imagine that you are a one man band, shooting a ridiculous short film (just one clip, for the sake or argument). How will the selection of a particular ISO value while shooting impact the final footage in a way that it could not be done latter in post? Remember that in this scenario you will be the DOP, DIT and Colorist.

So, do you really need to change the ISO while shooting, and why?

[Rui Guerra]

Thanks Phil, for your post and detailed explanations. I think that we agree in near everything. The main question is just to understand if there is any difference between changing ISO in camera or just in post.
Not wanting to look arrogant here, or doubt about anything you wrote, just trying to make sense of the intricate technology behind RAW ISO.

You raised some very interesting points, that I would like to mention just the most relevant part of them (hope not to decontextualize it too much) so maybe you could develop a little bit more:

Fundamentally, and this is true for all digital cinema cameras, how your Rate your ISO and use that information towards your Exposure Strategy is very important.

Agree that seeing in the monitor an image darker or lighter due to ISO adjustment, is a powerful reminder of what needed to be done or a closer math of the intended result. But if we assume that we would follow the same Exposure Strategy anyway, if we don't change in-camera ISO, would the end result be different in any way (assuming that we will do that ISO rating only in post)?

If choosing Middle Gray as an Exposure Method, what most cinematographers do, shooting lower ISO gets you cleaner shadows, but less stops allocated towards your highlights range. Going for Higher ISO you weight more stops towards highlight information, but your Middle Gray will be noisier.

But the end image quality will not be exactly the same if that ISO changing was only done in post?

Depending on all things this has implications of where Crushing and Clipping may occur and that's what the RAW Exposure Goal Posts are useful. And honestly even more useful is the GIOSCOPE tool, which really shows you where values land on the sensor and where potential in frame issues arise.

This is a very important aspect of this discussion. Indeed the Goal Posts and GIOSCOPE are both based in RAW data, where ISO have no influence. So when we are using those very important tools to adjust exposure, aren't we in a sense disregarding ISO?

The key with REDCODE RAW and other RAW formats is you have nondestructive control over adjusting your Exposure via RAW controls. As well as Color Temperature. This is actually not the same as general grading controls to do similar tasks. One of the more interesting things I notice omitted from many YouTube grading tutorials is not fully harnessing the power of RAW cameras because many have built upon similar tutorials and workflows presented. Not saying the ways presented are wrong per say, but it's interesting seeing methods actually used somewhat not talked about.

This is a major thing and indeed my initial post was assuming the commonly workflow starting with a flat/log image and using color correcting/grading tools (in my example using DaVinci Resolve), although I have in the Camera RAW tab the RAW adjustments I may need in a clip by clip basis, if needed. This is even what as been suggested as a standard powerful method to work with R3D, for example in this RED TECH | KOMODO | Post Workflow | 4K: https://www.youtube.com/watch?v=a3i3JPU1iLs
But I would be indeed very interested in hear about the "methods actually used somewhat not talked about", can you summarize them (or point to some useful links)? Thank you!

I see a lot of people rate at 800 and call it a day, they end up never changing that. That's cool. More or less like shooting Kodak V3 500T and never pushing or pulling I guess. But I personally switch it up depending on what I'm looking for. I know many who like ISO 1600 for projects from about Dragon onward and there's plenty of Low ISO shooters out there in the 250-400 range. Certainly times where I've had to go up to ISO 5000 or 6400 for sure when the situation calls for it.

I understand those options. Just trying to figure out how they truly impact the quality of the final image, if everything else stays the same.

Cheers,