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- Create Date 25 January 2020
- Last Updated 14 March 2020
9Dice Flat DCP
This DCP is called 9Dice. It is a Flat image in a Full Container.
The image may seem similar to the proposed images from the SMPTE Luminance Study Group. In that group they decided to recommend that luminance measurements be taken from a constrained target instead of from a full screen of white. In tests, a full screen of white may give up to 10% errors in the measurements compared to taking from a constrained target due to lens glaring and flaring.
In fact, the targets on this slide were drawn such that the total number of pixels that are white are equal to 10% of the Flat size screen. So, Flat being 3996 pixels by 2160 pixels, or 8631360 pixels, dividing that by 10 equals 863136 pixels for 10 percent luminance…if the screen were correctly saturated all the way around perhaps.
Divide that by 9, means that each dot is 95904 pixels.
Since pi*r2 is the correct formula for the area of a circle, we can solve for r. We divide by pi to make the formula Area/pi=r2, and if the area is 95904, dividing by pi gives us 30527.2 for r2. Getting the square root of 30527.2 gives us a radius of 174.7 pixels, and a diameter of just under 350 pixels (349.44).
Finally, a round number that I can remember!
That 350 pixels is going to be a varying distance across the screen depending on the length of the throw from the projector lens to the screen. You can calculate that yourself, but here is a clue: Angular Size Calculator
As always, the pass code is QA_b4_QC