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post #1 of 6 Old 08-05-2015, 09:30 AM - Thread Starter
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Backlight increase gamma?

Hi,
I did find a strange behavour from my Samsung LCD LED.

When I did increase the backlight to 35 ftl @ 100 IRE (12 in backlight settings) the gamma did also increase by it self from 2.2 to 2.28-ish is this strange?

When I'm on 37 ftl @ 100 IRE (13 in backlight settings) the gamma is 2.2 flat from 30 IRE to 100 IRE.



The sad thing is that I cant adapte 1886 or 2.4 gamma because then the picture looks like when you did mess up the color settings at a windows 95 machine.
So I need to have 2.2 or 2.3.

My day mode at 46 ftl do have a 2.2 gamma, but my night mode at my livlingroom I'm not sure yet.

Is 35 FTL to recomend in a pitch black room or can I have it in my livingroom I did read that 30-35 FTL is the standard, is that correct?

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post #2 of 6 Old 08-05-2015, 09:35 PM
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Hi mac1guru,

No, it isn't so strange that altering your LED TVs backlight changes the overall gamma - any single control can have an impact on others. This is why calibration requires constant checking and re-checking before the process is complete.

You are correct that 30 - 35fL are the typical recommended figures for viewing a display in subdued or evening lighting. However there is nothing wrong with using one reference mode for all viewing conditions if you are happy with the resulting light output and image for daytime use.

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post #3 of 6 Old 08-07-2015, 01:19 PM
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Quote:
Originally Posted by mac1guru View Post
I did find a strange behavour from my Samsung LCD LED.

When I did increase the backlight to 35 ftl @ 100 IRE (12 in backlight settings) the gamma did also increase by it self from 2.2 to 2.28-ish is this strange?

When I'm on 37 ftl @ 100 IRE (13 in backlight settings) the gamma is 2.2 flat from 30 IRE to 100 IRE.
Gamma is derived from the relationship between 100% video and all other levels. 100% itself has no gamma. All backlighting does is adjust the panels light output. So, though changing the backlight will certainly raise or lower the overall light output I wouldn't expect it to result in any meaningful change in gamma because the change in output should be at all levels of video.

I tested this on a Sony LED here, and this is what I got.



See that although the light output changes dramatically, the gamma is virtually unchanged (+- 0.02 is negligible).

You may have set your contrast near the limit for white clipping. That's just a guess.

Tom Huffman
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post #4 of 6 Old 08-07-2015, 01:26 PM - Thread Starter
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Quote:
Originally Posted by TomHuffman View Post
Gamma is derived from the relationship between 100% video and all other levels. 100% itself has no gamma. All backlighting does is adjust the panels light output. So, though changing the backlight will certainly raise or lower the overall light output I wouldn't expect it to result in any meaningful change in gamma because the change in output should be at all levels of video.

I tested this on a Sony LED here, and this is what I got.



See that although the light output changes dramatically, the gamma is virtually unchanged (+- 0.02 is negligible).

You may have set your contrast near the limit for white clipping. That's just a guess.
I have the contrast at 91 and it does get pinkish at 93 so that is maybe the reason.

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post #5 of 6 Old Today, 02:53 PM - Thread Starter
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Quote:
Originally Posted by TomHuffman View Post
Gamma is derived from the relationship between 100% video and all other levels. 100% itself has no gamma. All backlighting does is adjust the panels light output. So, though changing the backlight will certainly raise or lower the overall light output I wouldn't expect it to result in any meaningful change in gamma because the change in output should be at all levels of video.

I tested this on a Sony LED here, and this is what I got.



See that although the light output changes dramatically, the gamma is virtually unchanged (+- 0.02 is negligible).

You may have set your contrast near the limit for white clipping. That's just a guess.
It's a samsung led 2014 that I got.

Contrast start to shift to pink in 94 of 100.
I did put my contrast at 93 of 100.

So I should try to set it at 90 of 100 insted maybe, is that correct?

I guess that you have some experience regarding the samsung led tv from 2014.

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Quote:
Originally Posted by mac1guru View Post
It's a samsung led 2014 that I got.

Contrast start to shift to pink in 94 of 100.
I did put my contrast at 93 of 100.

So I should try to set it at 90 of 100 insted maybe, is that correct?
Just experiment with lower contrast settings.

Tom Huffman
ChromaPure Software/AccuPel Video Signal Generators
ISF/THX Calibrations
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