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ISO value in RED


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#1 Jarkko Virtanen

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Posted 20 August 2009 - 09:20 AM

Hi!

I have a friend who owns a RED and keeps saying that you can get more info to the over exposed part of the curve if you use ISO 500 instead of 320.

Do you have any facts or experience about this?

Thanks!

Jarkko.
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#2 Stephen Williams

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Posted 20 August 2009 - 11:15 AM

Hi!

I have a friend who owns a RED and keeps saying that you can get more info to the over exposed part of the curve if you use ISO 500 instead of 320.

Do you have any facts or experience about this?

Thanks!


Jarkko.


Hi,

Whilst that's true many others would suggest exposing to the right and using 160 ISO to reduce noise. It's a matter of testing & seeing what works for you in different situations. There is not one correct answer.

Best

Stephen
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#3 John Sprung

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Posted 20 August 2009 - 01:30 PM

I'd suggest using both: 500 for the bright areas, 160 in the dark areas. That way you account for it having less dynamic range than film. Even better, get comfortable with the false color and histogram displays. They tell you for sure when you run out of range. The Red is in many ways its own best light meter.






-- J.S.
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#4 Stephen Williams

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Posted 20 August 2009 - 02:45 PM

I'd suggest using both: 500 for the bright areas, 160 in the dark areas. That way you account for it having less dynamic range than film. Even better, get comfortable with the false color and histogram displays. They tell you for sure when you run out of range. The Red is in many ways its own best light meter.

-- J.S.


Hi John,

Very true, however when prepairing a light list I assume it's 160 ISO. That often has negative budget implications, prpbably the reason why I still shoot more 35mm than RED on low budgets commercials.

Best,

Stephen
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#5 Jarkko Virtanen

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Posted 20 August 2009 - 04:40 PM

Ok thanks! I have to consider that.

But you are also saying that using ISO 160 instead of 320 reduces the noise? Well that might be the option for ND filters for me then... i'm just starting a production and there's going to be a lot of bright sunny days outside...


J.
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#6 Satsuki Murashige

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Posted 21 August 2009 - 12:02 AM

But you are also saying that using ISO 160 instead of 320 reduces the noise?

Yes. Basically, the Red's sensor has a fixed sensitivity which Red recommends rating at 320ASA (your own rating may vary depending on your tests). When you select an ASA/ISO value, it is just for monitoring. If you shoot at 500ASA, you are underexposing by 2/3 stop. Naturally then, you are also underexposing highlights by 2/3 stop and thus helping to protect them from clipping.

On the other hand, by rating at 160ASA, you are overexposing by 1 stop. The more exposure you give the sensor, the cleaner the image becomes. In my testing, going beyond 1 stop over made no difference. But since Build 17, I've found 320ASA to be very clean already, definitely good enough for greenscreen even under tungsten.

You have to balance these two variables on a scene to scene basis to get a clean image and also to protect your highlights. I would caution against overrating the camera in day exteriors where there is a lot of contrast unless you can live with a lot of clipped highlights. I also recommend using the in camera meters like the spot meter and histogram to judge exposure rather than going off the monitor.
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#7 Stephen Williams

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Posted 21 August 2009 - 02:21 AM

Ok thanks! I have to consider that.

But you are also saying that using ISO 160 instead of 320 reduces the noise? Well that might be the option for ND filters for me then... i'm just starting a production and there's going to be a lot of bright sunny days outside...


J.


Hi,

For bright sunny days 500 ISO is probably the way to go, however using more fill than you need on film would help conciderably with noise. With RED the sky often goes grey/white due to overload in bright conditions.

Stephen
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#8 chris layhe

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Posted 02 October 2009 - 02:09 PM

Thanks for clearing this up everyone. I've been pondering this myself.
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#9 Dominic Cochran

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Posted 05 October 2009 - 08:26 PM

Hi,

With RED the sky often goes grey/white due to overload in bright conditions.

Stephen


Of course as with any format, this can be avoided with proper fill and filtration. I've also had good results rating at 250 and using MacGregor's look profile found on the other site hand in hand with false color.

Edited by Dominic Cochran, 05 October 2009 - 08:28 PM.

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#10 Stephen Williams

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Posted 06 October 2009 - 06:23 AM

Of course as with any format, this can be avoided with proper fill and filtration. I've also had good results rating at 250 and using MacGregor's look profile found on the other site hand in hand with false color.


Hi,

The crew of 'Knowing' would have done so if it was feasible. Sometimes accepting that the RED one has less DR than other more expensive cameras, would help people get the most out of it.

Shooting on film in such a situation can save the production time & money. Horses for courses.

Stephen
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#11 Charley Weston

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Posted 27 October 2009 - 02:27 PM

Hey, a little off topic but does anyone know what the RED Epic or Scarlet's ISO will be rated at? I'm hoping it'll be higher than 320...
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#12 Adrian Sierkowski

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Posted 27 October 2009 - 02:36 PM

No one will know till the cameras actually exist. But again, I'd bet on a 320 rating, though with more DR and a cleaner image to begin with so you could push/pull the chipset a bit more. A tradeoff comes as you cram in more megapixels you loose sensitivity (so i'm told) Hence the sensors might be "better," on scarlet/epic, but due to more pixel-elements on the chip, you're likely to loose sensitivity.
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#13 Chris Kenny

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Posted 31 October 2009 - 11:14 AM

160 ASA sounds a little conservative to me. I find exposing by eye tends to work pretty well at around 250 for interiors, in Rec. 709 (RedSpace lifts the mids a little more). And I'm very noise-intolerant and not as bothered by some about the way digital highlight clipping works, so I'm sure some people would consider even this too conservative.

Of course with the camera recording a linear raw file, there's no real penalty for putting middle gray in the "wrong" place, so there's no reason not to "expose to the right" as much as you can get away with without undesirable highlight clipping (which the camera provides about five different ways to check).
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#14 Aaron Solomon

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Posted 01 January 2010 - 05:49 PM

I haven't been able to get my hands on RED, but I was wondering if the ISO is adjustable or are we just talking about using these ISO's for calculations?

Thanks,
Aaron
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#15 Stephen Williams

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Posted 01 January 2010 - 06:06 PM

I haven't been able to get my hands on RED, but I was wondering if the ISO is adjustable or are we just talking about using these ISO's for calculations?

Thanks,
Aaron


Hi Aaron,

With RED, ISO changes are metadata only. There is no effect whatsoever on the recorded image.

Stephen
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#16 Chris Keth

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Posted 01 January 2010 - 07:27 PM

For what it's worth, he most common rating I see here in LA is 160 followed closely by 250.
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#17 TJ Williams

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Posted 14 January 2010 - 08:42 PM

Its not quite clear to me that if the sensor has the sensitivity of 320 and one rates it as 160 noise will be reduced? I tried this and couldnt seeany diffeence in the noise????
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#18 Satsuki Murashige

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Posted 15 January 2010 - 02:07 PM

Its not quite clear to me that if the sensor has the sensitivity of 320 and one rates it as 160 noise will be reduced? I tried this and couldnt seeany diffeence in the noise????

By overrating the camera, you're overexposing the sensor. You get a better signal-to-noise ratio, and thus a cleaner image especially in the shadows. This works will all digital cameras, as well as with color negative filmstocks. It's subtle, so you won't see it on the HD-SDI out of the camera. You will definitely see it once in Redcine/Red Alert.

Here's some more technical reading on the subject: http://prolost.com/b...ing-part-1.html.
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#19 John Sprung

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Posted 15 January 2010 - 03:03 PM

Its not quite clear to me that if the sensor has the sensitivity of 320 and one rates it as 160 ....


This is one of those strange subtle places where things start going in the wrong direction. Silicon chips don't *have* ISO sensitivities. ISO is defined in terms of film curves and densities and such. There's no definition of the term for any other imaging system.

So, in order to use our familiar light meters, we have to decide that these electronic things sorta work as if they were some ISO number or other. It's subjective, your opinion is as good as the next guy's. Test, look at it, take your pick.

But trust the camera's own histograms more than anything else.




-- J.S.
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#20 Hunter Mossman

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Posted 21 February 2010 - 03:42 PM

Histogram and false color are the way to go. Expose to the right without clipping the whites and you should get the most out of the sensor. I always have my meters on set for red shoots but rarely bring them out anymore.
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