ISO Question

[Nodar Nozadze]

Hello folks
I was asked by my friend who is cinematographer to post this here, since he is not on the forum.
He is shooting a feature on Red one (without MX upgrade), most of his scenes are interiors, action takes place in theater, so he will be using lots of available light plus using some additional tungsten. He is working on ISO 160, and measuring on 160, he is asking if is he doing something wrong, maybe its not preferable ISO value for the sensor or maybe its just better to go with standard 320.
Sorry if its the wrong place to ask this.

 

[Michael Romano]

I would meter for 320. You'd need a lot of available lights to pump up an entire theatre to work at 160 ISO! Its my opinion he can save the production money and time by working at 320. The compromise is possibly 250, which can yield better results in tungsten light settings. Remember to watch your raw meters!

 

[Gunleik Groven]

320 is smart for shooting, one can lower it in post if needed for noisereduction, but hawing lower iso when shooting comes at the risk of unintended overexposure...

 

[Dan Hudgins]

90% white and subject contrast range

90% white and subject contrast range

The lowest ISO a digital camera can be rated at is the one that clips the green pixels of a 90% white card subject, some people might say the red/blue pixels, but you get color shifts if you clip any one of the three, so green clip (or most of the three) for a 90% white subject at ADC max should be the way its defined.

Because video tape using Video cameras had very little dynamic range the cameras were operated at their lowest ISO to reduce noise, so the video tape FM record limit was near the 90% white subject signal level, resulting in the "Video Look".

Panavision Panalog seems to use 90% white subject at about 16% ADC signal level if I read their info right, I guess for the green pixels, with the red and blue pixels at about 8% ADC signal, having more room above 90% white subject gives you more of a "film look" because film has a "soft sholder" when processed and printed correctly, and so "Digital Cinema" should emulate the "film look", or its just a high resolution video camera.

The problem with getting the "film look" is that todays sensors in general use are not low enough in noise to "underexpose" enough to get the full film soft sholder effect. Maybe the HDR-x mode in Epic will do it, but thats maybe a year or two off before you can get one, perhaps.

Short of that, being careful about not having subjects that are more than one stop over 90% white in brightness and shooting for green 90% white about two stops UNDER signal clip and using de-Noise and or temporal noise reduction in post get you close enough to avoid much of the classic "video look".

The point being, there is no single ISO number that can tell you if the exposure is right since you need to know the contrast range of the subject matter, you can use smaller ISO numbers for narrow contrast range subjects, and you need to use larger ISO numbers for wide contrast range subjects.

Its Counterintuitive that in the open shade on an overcast day you might shoot at ISO 160 (using fill lights), but in bright sun with deep shadows you might need to shoot at ISO 1280 (using a pile of ND+IR cut) because the bright sun shot has a wider dynamic range in the subject matter.

 

[Andrew Wilding]

If I were him I would set my meter to 250 (or 160 if he has the light for it) but keep my camera on 320 - or better yet view the raw view and make final exposure decisions based on that. I found that on the old mysterium, the meter matched the camera when you set your meter between a half and a full stop slower.