Why is my 2017 iMac lcd not lighting up consistently?

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iMac Intel 27" Retina 5K Display (Mid 2017)

Model A1419 / EMC 3070 / Mid 2017 / 3.4, 3.5 or 3.8 GHz Core i5 or 4.2 GHz Core i7 Kaby Lake Processor (ID iMac18,3) / Retina 5K display. Refer to the older iMac Intel 27" Retina 5K Display (Late 2014 & 2015) guides as the system is very similar.

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frederik.juul.eilersen @frederikjuu1039

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发帖于: 2020年2月13日

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Why is my 2017 iMac lcd not lighting up consistently?

Hi!

I just bought a brand new (unused still sealed) imac 27” 2017 off eBay, and once I power it on, and the black boot screen appears I can see that some areas of the screen is brighter/lighter than others, but once I use the screen, like in final cut or word etc, it isn’t clear - is this a serious flaw or?

ive run diagnostics on the Mac, and it all comes back clean with no faults, and I’ve checked the display quality & built in terminal (using “system_profiler SPDisplaysDataType” command) and it’s all ok.

ive attached photos to show how inconsistent the black level is when the machine turns on.

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What does the white level look like? As well as the pure colors Blue Red, Yellow & Green across the full screen?

由 Dan 完成的 2020年2月13日

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Dan @danj

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I'm suspecting you are seeing the basic limitations of LCD panels Black Uniformity Of Monitors

The gap between the two panes of glass supports the liquid crystal material. The thickness of the liquid defines the degree of polarization of the light the thicker the material the darker the black but there is a limit of going to far! As the helix of the liquid can cause the image to lose its crispness as it gets thicker.

This then gets into how parallel the plates are from each other so the liquid is thinner or thicker at different areas. The size of the panel is what makes this harder as the plates are only supported along the edges. You can see this effect just by touching the panel the area around your finger will get a bit darker as you push the liquid out from directly under your finger is now thinner.

Newer displays use zone backlighting to reduce this effect (review TV’s to see more about this) even still thats not changing the liquid or the glass only masking it. And if that display was here, in the boot up this same image would likely be seen.

I wouldn’t put too much worry on this as you also could be just seeing the brightness is set at the extreme. Adjust it down will lower the effect.

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Hi

thank you for your answer!

So I should not worry, or try and get apple to have a look at it?

thanks once again!

regards

由 frederik.juul.eilersen 完成的 2020年2月18日

Apple won't do anything for you, other that try to convince you to buy a new system.

Did you lower the brightness? I would just do that.

由 Dan 完成的 2020年2月18日

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What does the white level look like? As well as the pure colors Blue Red, Yellow & Green across the full screen? — Dan
Hi

thank you for your answer!

So I should not worry, or try and get apple to have a look at it?

thanks once again!

regards — frederik.juul.eilersen
Apple won't do anything for you, other that try to convince you to buy a new system.

Did you lower the brightness? I would just do that. — Dan

iMac Intel 27" Retina 5K Display (Mid 2017)

Why is my 2017 iMac lcd not lighting up consistently?

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