Sorry, another Dragon optimal ISO thread...

[David Battistella]

FWIW When I talk about an "ISO rating", I am talking about metered light. I am not talking about using ISO as digital gain in the camera to "see more". It's up to everybody to understand what you can and can not do within certain scenes. I am also a big advocate of not messing much with settings for consistency, especially if you are not controlling the post production pipeline. IE: you can rate 800 outdoors and 500 indoors for a production treating it like two film stocks.

What I am talking about is the results you can attain by using ISO as a basis for metered exposure, which is using it as part of a system with known metered values.

David

 

[Ulf Krentz]

I think it definitely depends on your OLPF... for the Dragon+Skintone for example 320ISO should be best. I've had a shoot a while ago where we were able to try out all the settings since we didn't have enough light to cover the whole range of our 60m long set.

On the first day we shot most of it on ISO800. Later that day I played around with the footage in DaVinci and it wasn't as clean as I expected it to be. So the next day we changed our "strategy" and shot everything on Native ISO 320. Even though it looked too dark on the screen we were able to pump up the ISO in post without problems up to 1600 - clean image.

I'm also with Terry on this, never expose your image with ISO.

ISO on RED setting is meta data, simple as that. So if you had a better result on your second shoot it was because of more light was hitting the sensor (which is what you usually tend to do with a low ISO setting, compensating the darker image on the display). You could have changed the ISO to 6400 in between - assuming to record a very bright image - with the same aperture and shutter speed you will end up with exactly the same image.

Cheers
Ulf

 

[David Battistella]

On the first day we shot most of it on ISO800. So the next day we changed our "strategy" and shot everything on Native ISO 320. Even though it looked too dark on the screen we were able to pump up the ISO in post without problems up to 1600 - clean image.

Here is how I read your post.

I rated at 800 ISO and the images were not clean enough. I then rated at 320ISO and the images were what I expected.

The word NATIVE should not and does not need to come into play.

David

 

[Ulf Krentz]

David, very nice examples. But beside being nice images these also show the response of tonal mapping in the upper or lower part of the sensor range, opposite but somehow like we had different characteristics when pulling / pushing reversal film in lab. Know your equipment to get the best out of it, its just a so fantastic tool.

Cheers
Ulf

 

[Terry VerHaar]

The ISO is actually a variable of the exposure in the digital world. It was also in the film world, but you would not change film as easily. I use to have two cameras with different films in, and pick one based on the lighting we had available.

Your exposure is a function of the ISO you select at the beginning of the project/day/scene/take. Whether that was because you had a mechanical camera with film rated at a certain ISO, or a digital camera with changeable OLPF to give you too many options, that stays the same. So ISO is an essential part of calculating exposure as much as scene available lighting. Both are variables you can (or cannot) intervene on depending on the situation. Since digital came in, ISO became a variable we can change easily, but it is not always proper to do so.
Even if ISO is a metadata, the limitation of pushing it still stay, as very well explained by Michael: "one should never simply say "any 10 stops across this 16 stop range is as good as any other 10 stops"

PS I do not recommend changing ISO every scene or take...

As others have already jumped in here, I won't belabor my disagreement but I think this is where experience can actually work against one. I never shot motion film but did shoot my fair share of stills on film and I totally see where you are coming from with your thinking about ASA/ISO. But it really doesn't apply here - I worked hard to make myself "unlearn" the idea that it did. And, unlike other digital cameras, RED doesn't introduce electronic gain (and noise) into the signal chain when ISO is bumped up. THAT model is more like the traditional one - complete with the extra noise in the "higher speed film."

And I definitely agree that is is NOT a good idea to change ISO between scenes or takes.

 

[Terry VerHaar]

...I am not talking about using ISO as digital gain in the camera to "see more".

David - I assume the "digital gain" you are talking about here is in the monitor path, not the recorded signal insofar as RED doesn't introduce gain with a change of ISO.

 

[Ulf Krentz]

David - I assume the "digital gain" you are talking about here is in the monitor path, not the recorded signal insofar as RED doesn't introduce gain with a change of ISO.

The "digital gain" referes to the use of an other part of the overall dynamic range. A bit out of context but I like to quote Michael here: One should never simply say "any 10 stops across this 16 stop range is as good as any other 10 stops".

 

[David Battistella]

David - I assume the "digital gain" you are talking about here is in the monitor path, not the recorded signal insofar as RED doesn't introduce gain with a change of ISO.

Correct. It's all metadata. As an example, one can always wind up the ISO to "see a brighter image in the monitor", which is NOT using ISO as a basis for metered light, if you are lighting with a meter, you don't want to move that ISO around once you have decided on your rating (as phil states corectly) between a range of ISO.

David

 

[David Battistella]

The "digital gain" referes to the use of an other part of the overall dynamic range. A bit out of context but I like to quote Michael here: One should never simply say "any 10 stops across this 16 stop range is as good as any other 10 stops".

or,

not all ten stops are created equally! LOL.

 

[David Battistella]

just to really put all this in perspective.

The correct ISO is whatever gives you the results you like, anything else is just academic. There is a point where you can oversimplify things when explaining how things work.

 

[Terry VerHaar]

Yes:

https://en.wikipedia.org/wiki/Exposing_to_the_right

Now, there are some who like a little texture (aka noise) in their image. They know who they are. More importantly, they know what they are doing. And they can make damn good images, too.

Much has been discussed about ETTR and, I think Jarred himself has cautioned for using it judiciously, if at all. This is from the RED web site (I have add italics to some text for emphasis):

"Some advocate a strategy called “expose to the right” (ETTR), whose central principle is to record as much light as possible without clipping—causing the histogram to appear shifted to the far right. While this approach works well with stills photography, it greatly increases the likelihood of clipped highlights with video footage, since lighting conditions are often more dynamic.

Furthermore, ETTR can be misleading since the live histogram doesn’t represent raw image data. An ETTR strategy that doesn’t also pay attention to the goal posts therefore runs a high risk of overexposure—and increasingly so at lower ISO settings. Instead of recording as much light as possible, we instead encourage only recording as much light as necessary to meet one’s goals for image noise, but not necessarily any more than that—all while paying attention to the goal posts and traffic lights in addition to the histogram."

I think the "art" part about exposure is getting a sense for where your scene should lie in the histogram based on what you are shooting and what you are trying to accomplish. As for how much of the image is likely to drift into noise or to clip, I think this is also informative (from the same discussion):

"The height of each goal post reflects the fraction of overall pixels that have become either clipped (on the right), or near the capabilities of the camera to discern real texture from noise (on the left). The full scale for each goal post represents a quarter of all image pixels. In general, the left goal post can be pushed up to about 50% height and still give acceptable noise, but even a small amount on the right goal post can be unacceptable, depending on where this clipping appears in the image."


I'd encourage folks to read (or re-read) this very good information on the RED site:

http://www.red.com/learn/red-101/red-camera-exposure-tools

 

[Hugh Scully]

Variable OLPFs make a big difference, I think. I had got acquainted with the Standard OLPF on this last project. I use a meter and look for a stop so I'm with David in using ISO as a base from which to expose. My tests were admittedly how to be "safe" on the day regarding noise. I'm all for bending the notes, as long as I don't get "pitchy."

I found that shooting > 800 ISO with the Skintone OLPF could create noise in the shadows and so with it I would rate the project at 400 and light from there. I like the way the skintone looks at 800 and above but it's a more difficult balance so I need more experience. With the Standard OLPF I can shoot at 800-1280 with the same comfort I have at 400 - 800 on the Skintone.

At that point it comes down to lighting because frankly, I find that I can be more expressive lighting at 400 but, as with this last project (tiny crew, daylight interiors, no big boy lights), I was grateful to have that Standard for what worked out for me to be another stop. This kind of goes along with what others say but the flexibility with the OLPFs is something to consider as well.

 

[Michael Tiemann]

Terry, you are right to bring the RED.com info about ETTR back into the discussion. And it doesn't contradict anything I said, it just gives yet another example that for everything there is a countervailing reason to do the opposite. Experience teaches which rules to bend so that no rules are broken. There is no shame in using lights or filters to get a good image...

 

[Dominik Bauch]

You need to look at ISO as a rating or number, FROM WHICH you base exposure decisions.

Two things about what is going on with you findings.

You say the images are cleaner when rating at 320 iso, well, simply put when you rate at 320 you open up and allow MORE LIGHT to hit the sensor, this is always going to give you a cleaner look. Tradeoff=less highlight lattitude and rolloff.

Much of this depens on the DR of your scene and what you want to pull out of it.

Filmic is not one ISO setting. It sorta means replicating DR in a wide range of scenes. That is the work of a cinematographer, matching that filmic DR across various scenes and exposure situations. Thats why in digital there is a working range (like phil describes) and that is the best strategy to have. You need to start looking at scenes and determining the best ISO within the range to get the DR you want out of that scene, so there is no one ISO that is going to do the trick.

But you can use ISO as a "basis" for an exposure decision.

With a 500ISO filmstock, other things like filtration and lighting are needed to accomplish this. You wouldnt just rate the 500ISO film at 1600 iso without special instructions and without understanding the tradeoffs and you would be using a lot of fill in some scenes or ND in others to flatten out the DR to create acceptable images.

With Digital sensors the penalty is no where near as high with ISO rating.

Phil is spot on with describing a working range. It's your job to begin to dive in and understand when and how to shift your rating.

David

Just as an example. This was "rated" at 1000ISO, why? to see into the shadows better. if this was rated at 320 ISO I might not be able to see into the shadows and preseve the bits of blue sky and noise (even in a complex foliage scene) is minimal or non existent.

Now this fits the profile of exterior, Day, low ISO etc, but this shot called for a higher rating (or put another way underexposing) for the desire result.

Thanks David, that's very helpful. Makes a lot of sense.

But with your ISO 1000 example, for a properly exposed image less light is hitting the sensor than at a properly exposed ISO 320 right? You'd have to open up the aperture more to bring the exposure up for the ISO 320.
So I would think that in your example above shooting at ISO 1000 would preserve the sky better but give you less shadow control than at ISO 320. As you said ISO 320 would lose the highlights faster.
But you mentioned that you rated at ISO 1000 to see into the shadows better? Am I missing something?

 

[Michael Tiemann]

Thanks David, that's very helpful. Makes a lot of sense.

But with your ISO 1000 example, for a properly exposed image less light is hitting the sensor than at a properly exposed ISO 320 right? You'd have to open up the aperture more to bring the exposure up for the ISO 320.
So I would think that in your example above shooting at ISO 1000 would preserve the sky better but give you less shadow control than at ISO 320. As you said ISO 320 would lose the highlights faster.
But you mentioned that you rated at ISO 1000 to see into the shadows better? Am I missing something?

What you are missing is that, as with the Zone System, there are two systems in play: the "negative" and the "print". Exposing at ISO 320 (which means metering at ISO 320) gives you a fat negative that comes with a lot of forgiveness. Finishing at ISO 1000 (which means interpreting the RAW data at ISO 1000) opens up the shadows that would appear to have less detail if finished at ISO 320.

 

[Björn Benckert]

Iso is digital gain. More iso more noise, less iso less noise. But the the sensor has most "color fidelity" in lack of a better word some place in the middle right between burnout and noise floor. So if you expose so that you got your whole image very much to the the right (when looking at raw or 800 iso histogram) then you will have a super clean image, but also you will loose some color variations in the highlights. And if you do it the other way and expose to the left (again when looking in raw or 800 iso) then you starve the sensor and introduce noise so when / if iso is lifed in post or camera you gain that noise which result in a noisy image, with again, gives low variations of possible color values but this time in the lowlights.

 

[Jake Wilganowski]

my advice with weapon and the standard Olpf is 800-1250 is the sweet spot, if you live in that range you will be fine exposing by eye, no noise, plenty of highlight retention. Don't overthink it. This is a simple and quick rule that works in the real world. There's lots of different and advanced exposure strategies that you can get into, but would require testing and becoming familiar with the different olpf's in different conditions. My advice to newer shooters is std at 800-1250 and shoot away. You will be fine.

I personally record redlogfilm with some curve tweaks, then on monitors I push a custom 3d film lut I've built on top of the log signal. Beautiful Kodak-like colours, and film like gamma curve, I'm a very happy camper. I think a lot of people are going to download some random film lut and put that into weapon and call it a day, but in my experience this looks like crap and doesn't match up exposure-wise with redgammas. You have to play a bit with the log settings and exposure compensation or use a program like lattice to modify the lut. It took a bit of playing around but I do a bit of both and have arrived at a fantastic place

This cam is so f-ing versatile to really get the most out of it you have to dig in. Otherwise you are just driving in the slow lane with a fast car ha

 

[Ulf Krentz]

What you are missing is that, as with the Zone System, there are two systems in play: the "negative" and the "print". Exposing at ISO 320 (which means metering at ISO 320) gives you a fat negative that comes with a lot of forgiveness. Finishing at ISO 1000 (which means interpreting the RAW data at ISO 1000) opens up the shadows that would appear to have less detail if finished at ISO 320.

Not sure if I understand anything of what you try to explain. I don´t even see something like a negative with digital. The sensor pretty much behaves like a reversal film. Ansel Adams zone system was basically build on exposure and adapted development to create the perfect negative for print. This is what we do today when we tweak a gamma curve.

 

[David Battistella]

This cam is so f-ing versatile to really get the most out of it you have to dig in. Otherwise you are just driving in the slow lane with a fast car ha

This is very, very true, Dragon is a completely different beast with STH if you were familiar with MX and I think that is what shocked people, they got their cameras back and forgot to test it as a brand new imaging device (film stock) which it was.

The standard (to me) is the all rounder and the STH ID when I know I'm going to have the light and I want that creamy, filmic top end.

 

[David Battistella]

Not sure if I understand anything of what you try to explain. I don´t even see something like a negative with digital. The sensor pretty much behaves like a reversal film. Ansel Adams zone system was basically build on exposure and adapted development to create the perfect negative for print. This is what we do today when we tweak a gamma curve.

I still think where and how you map middle grey at the time of exposure has a pretty major influence. It depends if you are looking for flatter histograms or ones that are bunched to the right or left, but Bjorn makes a good point about finding the midpoint for that. The more you experiment the more you find the sweet spots.