Black shading - questions and thoughts

[Rob Castiglione]

I understand that this is an appropriate technical discussion and it would be good to get some detailed technical answers.

However, I have kind of let the whole black shading thing go. I only black shade when there is a pretty extreme change in temperature anticipated. I have not black shaded very much at all and have not noticed any particular problems with my images at all.

[Jaakko Rinne]

How come? As I understand it, ISO on RED cameras does not work like it does on, for example, DSLR cameras. ISO setting on Epic and Scarlet does not alter sensor sensitivity or gain. ISO setting is just metadata, in other words.

Like Patrick said, with a higher ISO you're moving middle grey lower into the signal and essentially boosting or lifting data that is nearer to the noise floor. Boosting the lowlights makes noise become more prominent, thus making the effect of a good or a bad blackshade more prominent as well.

Enrique: Sensor/Core temp is on screen at all times if you have the menus enabled.

[Jaakko Rinne]

As I understand it, the Canon C300 is blackshading continuously, using the look around area. This is why it's so killer in low light.

Is this even possible? Isn't the point of the blackshade to map the noise pattern of the entire sensor so the map can be used to substract the noise pattern from the signal? You can't really do that from the look around area.

[Petri Teittinen]

Like Patrick said, with a higher ISO you're moving middle grey lower into the signal and essentially boosting or lifting data that is nearer to the noise floor. Boosting the lowlights makes noise become more prominent, thus making the effect of a good or a bad blackshade more prominent as well.

Hmm. There's so much conflicting info on this subject here on reduser it's getting kinda hard to know what is what.

[Rob Castiglione]

It is worth while doing your own testing. A really good test is just don't do a new black at all and try shooting for yourself in a number of radically different conditions. I became a lot more relaxed about the necessity for black shading after I did this.

[David Barlow]

I too am pretty relaxed about black shading. I generally do it after a firmware upgrade and at the start of a big project. I do not tend to film in extreme environments so I do have it easy in that respect.

However, maybe you more technical people can explain this:

On a recent 3D project, I noticed that the histograms on my two Epics were showing a stop difference in exposure between the two cameras as were all the exposure aids ( false colour etc). The stops WERE the same as were shutter and anything else that could affect exposure. After puzzling over this I checked with the DIT who said the RAW exposures were correct on both cameras but suggested that I do a black shade. I didn't understand why but did it anyway and problem solved. identical histograms on both cameras. We could not see any difference in the quality of the RAW files before and after the Black shade.

Methinks the Black shading process does rather more than simply provide a measurement of sensor noise levels.

David

[Michael Moreno]

Haven't noticed any issues since Red One
I do not mind black shading before most shoots
It's a professional tool..

[nigelsmith]

So has the problem gone away with later versions of camera firmware?
I ask because not long ago the advice was to do black shading before changing shutter speeds for different frame rates,
and to let the camera warm up first, which adds up to a 40 - 45 minute delay before shooting can commence.
This seemed absurd....

[Björn Benckert]

Are you guys having this much noise trouble?
We black shade when upgrading and when doing long exposures, but that about it. Have no noise issues.