設為首頁收藏本站76Youtube 頻道

Post76影音玩樂

搜索
查看: 920|回復: 0

[4K電視] 好文分享,有關HDR的亮度

[複製鏈接]

698

主題

1萬

帖子

43萬

積分

鑽石玩家

Rank: 12Rank: 12Rank: 12

積分
430195

76 榮譽貢獻勲章76 榮譽影音勲章76 榮譽鑽石勲章76 榮譽VIP勲章76 精選榮譽會員勲章

發表於 2017-7-20 11:25 | 顯示全部樓層 |閱讀模式
本帖最後由 chhanthony 於 2017-7-20 11:28 編輯

http://www.lightillusion.com/uhdtv.htmlHDR - WHAT IT REALLY MEANS FOR PICTURE LEVELS
The following is taken directly from the ST2084 (PQ EOTF) specification.
This EOTF (ST2084) is intended to enable the creation of video images with an increased luminance range; not for creation of video images with overall higher luminance levels. For consistency of presentation across devices with different output brightness, average picture levels in content would likely remain similar to current luminance levels; i.e. mid-range scene exposures would produce currently expected luminance levels appropriate to video or cinema.



The PQ based ST2084 HDR specification defines reference white (normal diffuse white) as being 100 nits, which is exactly the same as for SDR (Standard Dynamic Range) displays, as specified for mastering (grading) grade-1 applications. With PQ HDR above 100 nits is for spectral highlight detail only. This shows that the Average Picture Level (APL) of a PQ HDR display will not be significantly different to a SDR display.
Regardless of the maximum peak brightness the display can generate the diffuse white will always be around 100 nits.
The BBC's HLG HDR standard uses 75% of the signal (input) range as nominal diffuse white, which is obviously a 'variable, as the HLG standard is a 'relative' standard, not 'absolute' as with PQ. This is consistent with have any standard SDR TV and running it at higher peak luma levels for daytime viewing, as is the case in most home lounges.
The nominal nits value for diffuse white will vary with the peak brightness of the display, with a 1000 nit display having diffuse white around 175 nits, and a 4000 nits display around 600 nits, depending system gamma (see later for info on HLG system gamma).
So the reality is that HDR should just ADD to the existing brightness range of SDR displays, meaning that more detail can be seen in the brighter areas of the image, where existing SDR images simply clip, or at least roll-off, the image detail.
The following histogram is a simplified view of the difference between a SDR (Standard Dynamic Range) image, and its PQ HDR equivalent.
Note that the APL (Average Picture Level) remains approximately consistent between the SDR and ST2084 HDR images, with just the contrast range and specular highlight levels increasing.
While this is a PQ based graph, the same is true of HLG based HDR.
If this approach to HDR is understood, and images created based on using the additional brightness range for specular highlights, the true potential of HDR will be realised.



評分

參與人數 4威望 +40 金錢 +40 收起 理由
carreyjim + 10 + 10
alanadc23 + 10 + 10 精彩報告
edlsang + 10 + 10
matt88p + 10 + 10

查看全部評分

AV Blog: www.avnewbie.com
Panasonic UB900, Egreat A5, Anthem AVM60, Krell KAV2250 x 2, Theater Amplifier Standard, M&K S-150 x 5 SS150 x 4, Martin Logan Descent-i, Thiel SS2, SS2.2,  SI 1 Integrato
您需要登錄後才可以回帖 登錄 | 成為會員

本版積分規則

重要聲明:本討論區是以即時上載留言的方式運作,Post76玩樂討論區對所有留言的真實性、完整性及立場等,不負任何法律責任。而一切留言之言論只代表留言者個人意 見,並非本網站之立場,讀者及用戶不應信賴內容,並應自行判斷內容之真實性。於有關情形下,讀者及用戶應尋求專業意見(如涉及醫療、法律或投資等問題)。 由於本討論區受到「即時上載留言」運作方式所規限,故不能完全監察所有留言,若讀者及用戶發現有留言出現問題,請聯絡我們。Post76玩樂討論區有權刪除任何留言及拒絕任何人士上載留言 (刪除前或不會作事先警告及通知 ), 同時亦有不刪除留言的權利,如有任何爭議,管理員擁有最終的詮釋權 。用戶切勿撰寫粗言穢語、誹謗、渲染色情暴力或人身攻擊的言論,敬請自律。本網站保留一切法律權利。權利。
快速回復 返回頂部 返回列表