Is this normal?

[Christoffer Glans]

So I've just received my brand new Epic MX and I'm testing it out to see if there's any problems. I did a black calibration at 800 ISO, 180° 25fps 5K in complete darkness, lens hood on, aperture at fully closed and even a black t-shirt around the lens. I waited 10-12 minutes with the camera on before calibrating.

Now, the regular image at 800 ISO looks quite alright, but when I get close to or at 12500 ISO there is this uneven brightness on the image. Can't seem to get rid of it with black calibration.
Is there something wrong or is this normal? :001_unsure:

Attached a screen grab and here's a short R3D.
Link

 

[Christoffer Glans]

I did a second black shading, this time at the same settings but I set the ISO to 12500. It's better now, but is this correct? Shouldn't black shading/calibration be done at the shooting ISO?

Here's a R3D of the second calibration.
R3D link

 

[Dominik Muench]

If you blackshade at ISO 800 and increase ISO you need to recalibrate...if you calibrate at ISO800 and choose lower ISO then you wont....thats my understanding.
Yep blackshading should be done at shooting ISO and ideally at frame rate as well.
In all fairness though, I would never shoot at ISO 12500 with my Epic though.

 

[Jacobo Martinez]

I am pretty sure iso has no effect on black shading, its only metadata, only shutter which does effect exposure on the sensor can effect black shading, also temperature can affect. That is why you see the T/E ; Temperature And exposure.

 

[Dominik Muench]

I am pretty sure iso has no effect on black shading, its only metadata, only shutter which does effect exposure on the sensor can effect black shading, also temperature can affect. That is why you see the T/E ; Temperature And exposure.

youre right, exposure time is the key factor:

With RED, black shading can often be ignored and left at the default factory setting. It’s only necessary when exposure conditions differ substantially, such as with extreme changes in temperature and exposure time, or after a firmware update. Conversely, even large changes in frame rate or resolution do not require black shading on their own. The following are the most important considerations, along with general guidelines:

Temperature: when ambient conditions change by more than roughly 30°F or 15°C.

Exposure Time: when going above or below about 1/2 a second.

Firmware: sometimes after upgrades, if instructed.

http://www.red.com/learn/red-101/black-shading-calibration

where is Gunleik on that topic when you need him ? ^^

 

[Christoffer Glans]

I am pretty sure iso has no effect on black shading, its only metadata, only shutter which does effect exposure on the sensor can effect black shading, also temperature can affect. That is why you see the T/E ; Temperature And exposure.

Not according to what I just did. I did two calibrations at 800 and got the same uneven result. On the second calibration, the only thing I did was changing the ISO to 12500 instead (I also did not do the black calibration for "current fps/exposure" on the second high iso calibration, instead I choose the "default").

The result was quite different as you can see in the R3D file of the second calibration. So there must be some difference when calibration at a different ISO?