Film/ HDR/ 32位元浮點合成 in After Effects....Part 07

Video Gamma:
因為log色彩空間根本看起來就不自然, 有人說它是一個糟透的色彩空間去工作大概一點也不奇怪. 但是還有另一種色彩空間我們天天會碰到, 它已經跟隨著整個電腦使用歷史,你根本不會覺得有甚麼問題在這種色彩空間下工作,它就是你的電腦螢幕video色彩空間.

妳可能毫無疑問認為在8位元的128(0~255)數值就是黑與白的中間值. 所以製作一個中灰就是全白的一半亮度,對吧！但當你知道其實上述是錯的你可能會大吃一驚！ 其實真正的128數值是要比你印象中的中灰還要暗的許多,甚至在大部分螢幕上顯示128數值還不到全白的 1/4亮度！

在某種系統中"一半的輸入,且給你一半的輸出"我們稱這種系統為"直線性"系統, 但然而螢幕(就像許多真實世界裡的東西)它並不是直線性的, 當一個系統不是直線性(曲線性)的時候,你可以說它是gamma功能的行為模式





Output=input的gamma次方且0<=input<=1, 在此功能下運作,在最暗與最亮數值.(0.0與1.0)的數值是永遠被鎖定的,並且gamma數值就是定義在最暗(0.0)到最亮(1.0)之間的轉化運算行為. 優良的套裝應用程序的gamma可以被套用不同的gamma數值彼此平衡計算在一起,透過套用gamma與1/gamma一起數學運算是彼此相互平衡抵消, 結果是甚麼也沒作用, 還有gamma 1.0就是直線性色彩概念. 在以往Mac螢幕有gamma 1.8與PC螢幕的gamma 2.2, 但真正的重點是說明你的螢幕對於較低亮度的輸入電壓是反應較遲緩的 , 以致造成陰暗影像結果. 但數位影像在螢幕上沒有變暗的原因就是數位影像被反向gamma功能作用著,在數位相機/數位錄影機拍攝時用gamma 0.4545夾入數位影像, 所以在還沒有顯示在任何螢幕上時就先把數位影像所有pixel弄亮許多.

是的！所有的數位都有這一段pre-gamma動作,因為video gamma新組譯的色彩空間不是給合成用的色彩空間,若直接拿這些顯示在螢幕上的(pre-gamma 0.4545)的數位影像用來做合成會引發許多無法控制的問題, 類似log的組譯, video gamma的組譯在較暗區域有更多的層次, 所以video gamma有它特別著重(暗)的部份, 同理之, video gamma跟log的cineon檔案一樣, 要合成前都要先進行色彩空間轉換.

關於gamma問題,妳可能已經一個頭兩個大, 下列還有一些有關gamma應用的地方也一起提出討論.
1: 妳可能有用過攝影學上的灰度卡, 我們大家都知道是18%中灰卡, 但為甚麼不是50%灰卡呢？如果妳問你的攝影學老師,他(她)可能會"hmmm...!? 那是一個很複雜的問題"

2: 雖然我已提到螢幕使用gamma 2.2會把數位影像弄暗, 但為甚麼在電腦中所做出來的 gray scale ramp(灰度漸層)沒有看起來被弄的很暗呢？ 而且50%灰度在螢幕上看起來就像50%灰啊!?

上述原因就是我們人類眼睛也是以非直線性的色彩方式來看世界(天啊！), 其實人類眼睛的gamma 0.4545正好相互抵消把螢幕變暗的gamma 2.2,換言之人類眼睛會把世界萬物影像看的比實際亮度還要亮很多, 還有人眼的gamma 0.4545是非常敏感對於弱光線,在暗部影像有很好的判斷能力,但對於亮部高光的敏感度判斷力都比較弱.

所以被螢幕弄暗的50%中灰顏色光線進入我們的肉眼 ,肉眼gamma 0.4545又把它拉亮起來(此回答第2問題中50%灰度在螢幕上看起來就像50%灰, 且軟體的特效色彩運作是以直線性數學概念), 所以！如果你刷了一個灰色漆在牆上,其實眼睛看起來它會比真實世界色彩要亮！所以真實世界的萬物其實要比你眼睛看起來還要暗的許多呈現著！ 沒錯！我們都錯了一輩子 , 而且已習慣錯了(此回答第1問題中為甚麼18%的暗灰色是中灰的概念, 因為你所看的18%灰是在螢幕的gamma 2.2作用之下變暗的,若你的螢幕可以切換到gamma 1.0或透過應用軟體LUT去看18%暗灰會變成你所熟悉的中灰).

Oh!回到那18%灰的問題,請試著套用我們的gamma 0.4方程式回到18%暗灰上面, 所以0.18的0.4次方等於0.504 TaDa.......!
沒錯！現在是中灰,所以用18%灰卡進行攝影測光所得建議曝光數值所拍下的照片曝光亮度是較為人眼看世界萬物進行時進入大腦印象相符合的！我想你的攝影學老師應該非常清楚的！ hmmmm.....


這裡有篇關於gamma的迷惑, 希望用另一種不同角度去看gamma的存在, 也許會容易些....XD, I hope...

Digital Lighting and Rendering_great book to read!

These days I have been reading a book call "Digital Lighting & Rendering", now is the second edition, written by Jeremy Birn. My classmate Chris Hung told me that book must read around 10 years ago. I think never be late for so such great resource about CG 3d lighting and rendering, and I am getting so much stuff in this book.
I type a small section content which really inspire me a lot!
something about lighting the night scenes:
..."You may noticed that most night scenes in Hollywood movies feature wet pavement, which looks as if it had just rained. This will be true even in dry cities like Las Vegas. Cinematographers are always looking for ways to capture extra glints of light and reflections in their night scenes. Since they have discovered that spraying water on the streets is a great way to get the city lights to reflect off the street, and make prettier night scenes with more highlights in them, they do this even when it is obviously a cheat."........... .

VFX artist always watch....

Lots good references here and also...

Another shake tree from hell....XD

I really don't mean this happen.....

Rendering Synthetic Objects into Legacy Photographs from Kevin Karsch

Thanks David's info....

Rendering Synthetic Objects into Legacy Photographs from Kevin Karsch on Vimeo.

Beau Lotto: Optical illusions show how we see

ILM - Creating the Impossible

Thanks A-Hom's info....

http://www.youtube.com/watch?v=5ZGkneixgpg&cc=1

SoundWorks Collection: The Sound of Transformers: Dark of the Moon

SoundWorks Collection: The Sound of Transformers: Dark of the Moon from Michael Coleman on Vimeo.

2D to 3D Conversions

2D to 3D conversions

2D to 3D conversion is the process of converted a film from 2D (normal film) to a 3D (or stereo) film for viewing with a stereographic viewing system. (polarized glasses, shuttered glasses, special screen, etc)

Conversion had gained a bad name after Clash of the Titans and a few other films that had been rushed through at the last minute. Just as you can’t do a 2000 shot

The Core Skills of VFX Handbook

Thanks Seadog's friend's info

Creating a real-life particle animation

Creating a real-life particle animation

Green Lantern............

IGN comment about Green Lantern trailer....

Your Friend Who Works in Special Effects Probably Needs a Hug Right Now

the article is from here.

and Green Lantern - Official Wondercon Footage [HD]

We can't remember who said it -- maybe Bruce Campbell? -- but a Hollywood actor defined the difference between studio movies and independent films like this: If you know what your movie's release date is before you even start shooting it, you're in a studio movie. That's become even truer over the years: Nowadays, a movie will have a release date before it even has a script. As you can imagine, that makes life incredibly stressful for all those involved with an upcoming tentpole, and today Variety gave us a little glimpse into one such group of individuals: the people at special effects houses.

The Variety article is behind their paywall, but The Playlist gets the gist of it, which is that Warner Bros. was forced to shell out an additional $9 million to pay for extra FX companies to help complete the effects for "Green Lantern," which comes out June 17. But the people Variety talked to at Warner Bros. insist it's not to fix any effects -- just to get them all done in time:

"There is no problem on 'Green Lantern,'" Chris de Faria, Warner's exec VP of digital production, animation and visual effects told the trade. "We try to add things to make the movie better until the 11th hour. That doesn't mean we're risking the movie up to the 11th hour."

This is something studios always want to emphasize when news gets out that a tentpole is rushing to make it to the finish line: "Everything is fine, nothing is wrong, we all know what we're doing, the shareholders have no reason to panic, would you like more cupcakes?" Besides, Warner Bros. are hardly the only ones rushing to hit a deadline: Variety says that one effects house working on Paramount's "Transformers: Dark of the Moon" "has gone to seven-day weeks, 12 hours a day, and canceled the Easter Sunday holiday for its [special-effects] artists."

The Variety article blames all this on the way studios now set up their big movies, valuing the release date over considerations for whether or not it's all that feasible. "So you are always chasing your tail," said Marvel exec VP of visual effects Victoria Alonso, who has "Captain America" to worry about. "You work backwards from that release date, then you add production not being ready to shoot or location complications and you shave the weeks you push from post."

We have friends who work in post-production, and we know that when they get assigned to a big movie that we won't see them for a few months before its release: Their lives are absolutely hellish as they kill themselves getting the movie done. Of late, no tentpole has missed its release, as long as you don't count the last-minute decision not to put out "Harry Potter and the Deathly Hallows Part 1" in 3D as was initially planned. It shouldn't be surprising, then, that big-budget summer movies often aren't very good: The studios are probably just thrilled they got the damn thing out in time.

Understanding Nuke's unique Layer and Channel system (including the Shuffle Nodes)

First thanks SeaDog's great info!
Understanding Nuke's unique Layer and Channel system (including the Shuffle Nodes)

NOLAN’S CHEDDAR

Nolan's Cheddar

Spaceman ICC

Super Bowl Ad Stories: How a 12-Year-Old Rescued This Coke Ad

and here is the story....

personally feel nice and simple idea, but quick and easy understanding story telling... of course I don't need to talk too much about vfx...

好萊塢傳真－視覺特效工作室驚傳倒風

好萊塢傳真－視覺特效工作室驚傳倒風

http://www.cafefx.com/

Asylum VFX Is Closing and news on fxGuide

逆光 ref...

9th Annual VES Awards Nominees

9th Annual VES Awards Nominees