Understanding ISO with the RED ONE

[Joel Kaye]

Great thread.

The thing about this discussion I'm a little confused about is what are your histograms showing? Or are you guys literally using a light meter based on an ISO and setting the camera? 'Cause once you've bumped the aperture to change the histogram you've effectively changed the rating of the scene.

For instance, Indoors, lower dynamic range: If you rate the camera at 320 and then use the histograms to set your exposure your net result is about like metering to 160 and exposing there.

If you've got film lighting you're fine. If you're the natural lower light light indie guy... well, crush the blacks. Build 16 may well smooth the transition into underexposure and effectively help speed the camera up in these situations.

[Hans von Sonntag]

Great thread.

The thing about this discussion I'm a little confused about is what are your histograms showing? Or are you guys literally using a light meter based on an ISO and setting the camera? 'Cause once you've bumped the aperture to change the histogram you've effectively changed the rating of the scene.

When I'm talking about sensitivity and ASA I refer to the results I find using a light meter. I evaluate the shot afterwards in REDCine using a histogram.

Hans

[Radoslav Karapetkov]

My God, this is complicated! :waaa:

Thanks for this post.

I feel like attending REDUser film school.

When do I pay? :)

(Hopefully - early '09 ;) )

[Dan Hudgins]

My God, this is complicated! :waaa:

How about just adding one stop of fill or bounce board/relector for every stop that you stop down to save highlights.

If you read at 320 then stop down two stops, you read the shade and add two stops of fill to keep the shade out of the noise, then in post darken the shade and you have everything clean and not clipped...

[Clint Childers]

Does changing the ISO in the camera really matter, since changing the ISO in Red Alert or REDCine is basically doing the exact same thing? You could make a conscious desicion to underexpose the image 2 stops outdoors at 320 ISO, and it would effectively be the same as shooting 800 ISO. Then in REDcine change that ISO to anything you like, back up to 800 if you wanted to. Changing the ISO in camera is only playing with how you view the material on the LCD. How you expose the image results in how the image can be graded later. Is that a fair assumption? 320 ISO 2 stops underexposed is the same as 800 ISO exposed normally. True or False?

[Blair S. Paulsen]

Since this is Mac's thread I have stuck with the concept of changing the camera's ASA setting then setting exposure using the adulterated representation for reference. I find this a bit counterintuitive as an approach but for some film folks this is the preferred method.

The core issue in my mind is whether you are willing to cope with more noise in the toe in order to get a more "filmlike" shoulder by ETTL or accept the clip edge risk (harshness varies depending on material) of ETTR in order to reduce noise levels.

[Paul Leeming]

fastlayne, it works if you expose to the right but don't over-expose. The in-camera ISO setting, while metadata, does change how the live histogram responds so if you expose to the right properly then this technique becomes a valid way to retain highlights etc.

Of course you are really underexposing by one stop, hence extra shadow noise, but if your highlights are more crucial then you've made the right compromise for the shot's requirements.

Hans, I've seen around 11 stops on a test chart at a couple of clients we've had, though real world usage does probably bring it closer to 9 if you want usable picture without excessive noise. It depends on what you consider usable I guess as to where you draw the line. Anyway, my point wasn't so much about the exact dynamic range as the technique so read it as 9 if that helps.

DANCAD, good idea re: adding 1 stop of fill for every stop you effectively underexpose. Simple and balances out the "expose to the right and light for the shadows" equation.

[Hans von Sonntag]

320 ISO 2 stops underexposed is the same as 800 ISO exposed normally. True or False?

False. 320 ASA plus one stop is 640 ASA, plus one more is 1280 ASA.

Hans

[Jon Farhat]

Thanks for taking the time to present your tests so beautifully.
j.

[Miguel "Macgregor" De Olaso]

Does changing the ISO in the camera really matter, since changing the ISO in Red Alert or REDCine is basically doing the exact same thing? You could make a conscious desicion to underexpose the image 2 stops outdoors at 320 ISO, and it would effectively be the same as shooting 800 ISO. Then in REDcine change that ISO to anything you like, back up to 800 if you wanted to. Changing the ISO in camera is only playing with how you view the material on the LCD. How you expose the image results in how the image can be graded later. Is that a fair assumption? 320 ISO 2 stops underexposed is the same as 800 ISO exposed normally. True or False?

Since this is Mac's thread I have stuck with the concept of changing the camera's ASA setting then setting exposure using the adulterated representation for reference. I find this a bit counterintuitive as an approach but for some film folks this is the preferred method.

Well, it would be easier to forget about all this, shot 320ISO and underexpose 1 or 2 stops. But then the image in the LCD would appear too dark. I think that´s the reason for all this. XD