A couple of calibration questions... - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Unread 06-15-2017, 01:02 PM - Thread Starter
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A couple of calibration questions...

Hey all. Getting ready to calibrate my new home theater, and there are a couple of new variables I could use some help on.

The first is that I have switched from a television to a projector. I will be using the i1 Display profiled to an i1 Pro. It's a 150" screen... does anyone know how far away from the screen the meters should be?

The second is in regards to 4k HDR and the Lumagen Pro... on my old 1080p screen, I just calibrated to Rec709. Now that I have sources in both Rec709 and Rec2020, do I need to do a separate calibration for each one, or do I just calibrate to Rec2020 and assume everything in Rec709 fits in that colorspace?

Thanks!
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post #2 of 5 Unread 06-16-2017, 12:22 AM
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Distance from screen should ideally be your viewing position.

Rec709 and Rec2020 are very different colour spaces, so will need to be calibrated separately.
Two separate LUTs.

We've worked very closely with Lumagen on HDR calibration with the Radiance Pro, and with the 'Multiplier' capability will be needed for projection based HDR.
There is a lot of info on this with the website User Guides.

Steve

Steve Shaw
LIGHT ILLUSION

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post #3 of 5 Unread 06-16-2017, 09:45 AM - Thread Starter
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So it won't be an issue that my viewing position is 14 feet from the screen? The meters are still accurate at that distance?
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post #4 of 5 Unread Today, 08:42 AM
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Quote:
Originally Posted by earwicker7 View Post
So it won't be an issue that my viewing position is 14 feet from the screen? The meters are still accurate at that distance?
Here's something that might help.
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While viewing position is ideal that is not possible with the instruments you are using. If you have a Jeti or Minolta spectroradiometer that would work but not for your instruments as they have too large of field of view and you need more light for the lower readings.

For a 1" field of view the instruments need to be approximately this far from the screen.
i1Pro 11/16"
i1 display 9/16"

For a projector screen you have to make the field of view larger because the meter will be a shadow on the screen at these distances. You also want to angle the meter to be in the angle of reflection like in Randal's picture and you are not off axis if using a screen with a gain coating. Ideally, your seating should also be in line with the angular reflective angle near the center of the screen vertically. For profiling to use the same field of view your i1Pro should be ~22% further back than the distance of the i1 display. The easiest way to know when you are in the angle of reflection is to adjust the angle of the probe until you get the reading with most light but if you are too far off axis this will only give you the best reading for that position.
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