BLACK SHADE

[AlexJones]

I know it's a boring subject but while we're on it, let me ask, "Do you need to black shade for every location change or is this more of a maintenance thing?" For safety, I've been black shading when I feel is appropriate (IE: from day on location to interior shoots). I've also been black shading for different times of the day if we are shooting in different times like the difference between sun set and 12pm. From my logical thinking, black shading sounds like it's adjusting the black level for the given lighting situation. When you adjust the BS, it corrects the black from either a grey black or a super crushed black to a proper 0% IRE. Am I Right? Should I be adjusting this calibration this much or am I taking this the wrong way?

 

[Phil Holland]

I've written about it in the Data Sheets and Red Quick Guide, and I'll save you the boring experiments I've done.

Here's my best advice.

- Black Shade when the camera is up to the desired temperature that your fan mode is set to.
- Black Shade when you upgrade your firmware.
- Black Shade when dealing with extreme exterior temperature change. (i.e. snow versus summer day shooting)
- Black Shade when going outside of your calibration spec when adjusting your shutter speed. (common when over cranking)

That's pretty much it. Most people forget that 4th one and don't pay attention to that temperature/calibration graphic on the display and often ask why their over cranked material has noise in it. That's why.

Black Shading itself is doing several things, but it's not changing the "tonality". Although it could if you Black Shade incorrectly. It's generating a calMap to cancel out signal noise and a few other things.

Typically you don't need to worry about black shading during a standard shooting day from morning, to noon, to sunset if you are shooting when the camera is up to calibrated operating temperature. It is important if it's pretty damn freezing out and your last black shade was in warmer conditions.

Interestingly enough, it would appear Dragon provides a bit more freedom on this front in terms of needed to black shade at various shutter speed distances. It has a slightly broader calibration specification from my observations.

 

[Andrew Gentle]

When you adjust the BS, it corrects the black from either a grey black or a super crushed black to a proper 0% IRE. Am I Right?

As Phil said, it's not exactly about tonality. The photosites on the sensor naturally respond slightly differently to each other. The relationship between these differences changes when your exposure time changes dramatically, or when the sensor changes temperature. From what I understand, what the black shading does is calculate a 'dark frame' calibration map at your given temperature and exposure time which is then subtracted from the pixel values in order to calibrate all the photosites to read consistently across the sensor. If your calibration map is inappropriate for the exposure time or temperature, you'll see the differences in readings in the form of fixed-pattern noise. If you follow Phil's recommendations as to when to black shade (and keep an eye on the warning indicators at the bottom which read Cal: T/E in green under good conditions or change to T or E + or - in yellow when the sensor is outside the ideal range for the chosen calibration map) then you shouldn't have any problems with fixed-pattern noise.

 

[jake blackstone]

The simple truth is Red made a big mistake by naming it Black shading. It's a simple FPN (Fixed Pattern Noise) adjustment and not a traditional video camera Black shading. FPN adjustment is something, that's been used and performed for many years by other manufacturers using sensors, like it was done by Phillips/Kodak with Spirit.

 

[Andrew Gentle]

If you turn it on for a DSLR, usually referred to as 'Long Exposure NR' in Nikon menus, it'll take a second exposure with the mirror down for the same length of time as the first exposure if you're doing longer exposures. I don't think they go longer than 30 seconds, though, so it wouldn't do it for Bulb Mode.
This is the DSMC doing a very similar process but only once (well, in two passes) and in advance instead of immediately after the exposure, I believe.

 

[Andre W.]

Quick test you can also do is with port cap / lens cap in place, bump ISO to max (12800) then activate your video false color. The noise pattern should be even across the screen, if it's not, and the camera is at operating temp, then it would be nice to consider doing a black shade.