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Duca Simon Luchini

Metering on set procedure: choosing a correct ISO

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There are two very important problems:

1 - What you suggest can surely be useful but doesn't properly answer the questions I made...

2 - Internet is great but also full of poop infos, above all , about all about specific and technical arguments...

Anyway thanks for your reply!

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There are two very important problems:

1 - What you suggest can surely be useful but doesn't properly answer the questions I made...

2 - Internet is great but also full of poop infos, above all , about all about specific and technical arguments...

Anyway thanks for your reply!

 

 

Ok thanks.. sorry I don't know that camera.. and as a stills camera rather than a "proper" video camera with EI mode.. I believe it may behave differently ..

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I don't know about the Canon cinema cameras though. But it might be the same there, making ISO setting at different strategy than on an Alexa or Red camera. Does anyone who's used the Canon cinema cameras know how they work regarding ISO setting? I'd like to know, thanks!

 

From Canon about C300 is this graph:

 

c300_feature_01c.jpg

 

So from their native 850 ISO and upward the camera maintains same latitude in both directions.

 

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I wonder if that just for the C300 I as its only 8 bit recoding.. and the Canon Log is not very severe .. more like a Sony Hyper gamma curve.. nothing like the Cineon "type" curve of Slog or Arri Log C.. ?.. but the C300II and the C700 are 10 bit and probably have a curve much more like Cineon gamma .. I thought native ISO would also be 0 db too..? i.e. 640 ISO.. I cant work out that graph at all..

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Some cameras are a bit more complicated since they use internal noise reduction to try and extend usable shadow information at different ISO settings so it's a bit less linear.

 

With my Nikon DSLR, my approach is to use the 200 ISO setting when possible, expose for the highlights (i.e. generally underexpose in order to hold bright detail) and then play with the raw file to bring up the shadows or brightness in general. But this is partly because I think the "native" sensitivity of many still cameras is on the low side (below 320 ISO) but internal processing allows them to use high ISO settings with minimal noise. But with those DSLR's often you'll notice that the dynamic range is a bit more limited at the high ISO settings because they are adding contrast in order to mask noise problems or a lack of shadow detail.

 

How ISO is "defined" and used in the D-cinema cameras like Alexa and Red was weird for me when i first encountered it, since ISO for me meant adding gain to the sensor signal. On the above cameras the sensor is simply "fixed" sensitivity-wise and you choose how you fill it with light.

 

The photo cameras as far as i know use analogue signal amplification when ISO is raised,

regardless in JPG's or RAW, then goes through ADC.

 

Yesterday i've red a text, must say was tired, maybe didn't got it all, saying ISO amplification in photo cameras goes to a certain extent and from then on all the higher ISO's are digitally applied - the camera processor adjusts levels like Photoshop. A term was used - entering the ISOless zone.

 

...

 

I think the concept of variable over/under range varying with ISO can't be applied

directly to DSLR video. There might be shift in over/under, needs to be tested, but i doubt it will be as in raise ISO 1stop = 1stop more highlights.

 

Best.

 

I

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- how is the dynamic range of a camera (because many camera don't declare it in spec techs...)? Maybe a rough value, but usable...

- at which ISO value can I establish that I have (almost) equal stop above and below the grey middle value?

Sincerely I don't know how to answer to these questions..., but it crucial to test every used camera to know the specific dynamic range, and then apply the reasoning from Igor above.

The same problem about measuring (on set) the dynamic range of the scene - I mean scene already illuminated -. How to make it?

 

Many thanks for a reply!

 

I've done once a simple test with 5Dmk3.

 

I exposed a white copy paper patch to read middle gray ~128RGB,

and then under and over exposed and came to these values:

 

2+1/3 stops over - came to around studio legal white level "235" white

2+2/3 to 3 stops over - neared the full 255 value.

 

3 stops under - around 30 value

4 stops under - was ~15.

 

From that the useful information for me is that @ +2 1/3 is my diffuse white. Over it let the speculars go.

For the bottom @ -3 i can see "things", @ -4 barely.

 

Maybe total of 6-7 stops.

 

I think that was the Standard picture profile. With the common neutral style settings for video

(sharpness 0, Contrast - lowest and Saturation -2 clicks) there was some gain in over, but can't say how much. I used an ISO convenient at the light levels i tested so i can have enough room to go up and down. As i said, a simple test.

 

 

A remark on the levels - all safe and sound if the full 0-255 range is used in the editing.

Some software might automatically clip the levels above 235, bringing them down to be 235.

Same for the bottom. 0-16 = 16.

 

 

I understand your camera is 60D, but think it's dynamic range in video will fall more or less in the above limits. Test it out.

 

 

 

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