ISO 200 clipping at 75% on Ultrascopes and Resolve

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nicholasmilitello

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ISO 200 clipping at 75% on Ultrascopes and Resolve

PostThu Mar 21, 2013 5:33 pm

800 ASA.png
800 ASA.png (594.88 KiB) Viewed 814 times

400 ASA.png
400 ASA.png (584.62 KiB) Viewed 814 times

200 ASA.png
200 ASA.png (531.64 KiB) Viewed 814 times


It would be great if anyone could help me out with a quick test. I have tried a ton of different lens for this test along with a range of f stops.
My problem is that I noticed that when I was shooting RAW, I noticed that the sky was clipping quite a bit. I have seen quite a few tests online and it seems that many would overexpose the sky a bit and with the latitude and 12 bit raw they were able to get the sky back. I am not able too. So I plugged the camera into Ultrascopes and noticed at ISO 200, I cant get the camera to go to 100%. I shot interior looking out a window on a bright day.
Now if I bump to ISO 400 I can go to 90%, and if I go to ISO 800 then finally I am able to clip at 100%. Obviously all the images are overexposed, but I cant understand why my camera is clipping at 75%. I can hardly get any detail back.
SOOOOOO my question would be if anyone could take their BMCC, plug into Ultrascopes, set the camera to ISO 200, shoot at something really bright and see if your scopes go to 100%. Thanks in advance.
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Frank Glencairn

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Re: ISO 200 clipping at 75% on Ultrascopes and Resolve

PostThu Mar 21, 2013 9:53 pm

You have to understand, that ISO is just metadata in raw.

Once you clipped the sensor, it's still clipping at any metadata you apply to it, since it clipped in the first place. Changing the metadata can only bring back what is there, not what you have blown out.

So turn on your Zebras, set them to 100%, your camera to 800 ISO and make sure the zebra just goes away, by closing the iris or using NDs and you are golden.
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waltervolpatto

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Re: ISO 200 clipping at 75% on Ultrascopes and Resolve

PostThu Mar 21, 2013 10:02 pm

Frank Glencairn wrote:You have to understand, that ISO is just metadata in raw.

Once you clipped the sensor, it's still clipping at any metadata you apply to it, since it clipped in the first place. Changing the metadata can only bring back what is there, not what you have blown out.

So turn on your Zebras, set them to 100%, your camera to 800 ISO and make sure the zebra just goes away, by closing the iris or using NDs and you are golden.


generally speaking this is true for most of the sensors/cameras. the best use of the camera (IMHO) is to set it at the optimal ISO form the manufacturer (800 in this case) and light the scene accordingly ( or set the aperture accordingly)

once the data is capture if it is not there is gone.

Broadly speaking the digital cameras only have one color gamut, one white point and one exposure range (and an optimal exposure index), when you say:

"I set the camera for 3200k and 1600 ISO"

you are actually saying:
"I let the sensor capture whatever and i will do math to try to make the data behave like 3200k ( a color space conversion) and 1600 ISO (a x2 gain) "

It is equivalent to use a daylight 800-ISO stock film and use it inside with amber light and underexpose by one stop... Yes you can try to correct in post...
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John Brawley

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Re: ISO 200 clipping at 75% on Ultrascopes and Resolve

PostFri Mar 22, 2013 12:02 pm

Ultrascope is really like monitoring the HDSDI output, which isn't really the same as the RAW data file, because it's only 10 Bit 4:2:2

I bet you'd find the highlights are there in raw (and in ProRes) if you set the zebra to 100% and back the exposure off to just below when they zebra. (irrespective of ISO)


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