[閒聊] 我對DSLR Log的看法

[LimYoHwan (gosu mage)]

首先先直接給log workflow 成品, 使用ps開啟,可看調整過程

https://www.dropbox.com/s/qo3izwwvsqs1ffv/3D%20LUT%20CREATION.7z?dl=0

和Canon RAW轉Log的描述檔 ( 這是免費所以不是很精準 )
5D3 6D 7D 70D

https://mega.nz/#!OYMXlCJI!TWYt9H_n4kA0hLBuIqYE6AE5lkTXLpcxSM_E0kan2U8

檔案來自國外喜愛調色的FB社團免費提供

討論將Canon DSLR的RAW轉成Log的意義與高階攝影機如RED在拍攝RAW或是SONY A7的S-log
有甚麼差異.
1. Canon DSLR RAW在ACR轉成 Log-C color space
2. RED拍攝RAW在達芬奇可以設定選項為Redlogfilm  LOG
3. Sony A7拍攝的S-log mov (不是Raw檔而是被壓縮的mov)


先講LOG對於RAW的寬容度(DR)的作用

當所述3者都轉成Log模式下

其寬容度理論上來說是 2 > 1 > 3  (  1因為還是Raw, 3 是壓縮過 mov所以我給他比較
低 )

接著我們要討論對於拍照片來說,轉成log有甚麼意義,或是DR有甚麼差

首先,並不是轉成Log其DR會變大,沒有這種事情, 轉成Log模式只是將Raw的資料依照一套

有邏輯的方法調整成明暗細節都可以看到的狀況.

簡單的講

假設我拍好一張照片,用LR的相機描述是Adobe standard轉出來的jpg就是所謂的Rec.709

or H.264

可能這張照片過曝或是過暗(沒拍好),照片的明or暗看不出細節來.

通常我們會去調整RAW,把明暗給找回來.

但是log workflow在你把RAW檔進到LR時將相機描述選成LOG.

這時候你會發現到你整張照片的明暗都清楚了,等於是他自動幫你把明暗給找回來.(其相

機描述檔是有邏輯的設計過)

所有相機在拍攝時都是依照你的快門光圈ISO去記錄訊息. 5D3一樣 高階的RED也一樣

並不會有甚麼RED就是用不同的演算法然後去疊加, 關於DR, 是RED本身就比5D3強 當然DR

較高

然後再講Sony A7S的S-Log, 前面有講他是壓縮過的mov,雖然號稱有高寬容度但他始終不

是RAW, 跟A7S自己的RAW也是差一大截.

log其實他就是個調控檔, 我們拍攝的RAW都是資料. 他將這些資料整理成明暗細節都看得
到的狀況.

我們拍攝的RAW當使用相機的風景,中性,人像等等模式,也是將RAW的資料整理成其風格
(Looks)

而攝影機如Arri RED,也會有其調控檔,當選成Log模式時他出來的跟A7一樣是壓縮過的
mov,他不是RAW!!!

當然Arri Red本身就可以選擇錄影RAW Video, 但是你要知道他也是紀錄資料, 到了軟體
後一樣可以套風格(Looks)

其風格和DSLR一樣有正常色調等等,重點是他原廠就自帶可以選擇Log模式!!

如果說RAW轉LOG很蠢. 那Arri Red 的 RAW可以選擇LOG是怎麼一回事???

而Canon因為ML和其他第三方軟體,本來不能錄Raw video變成可以, 本來RAW不能在LR選成
Log模式,變成可以

這就是我所說Canon也可以玩到別人的東西的意思!

所以將RAW轉成Log一點也不奇怪, Arri Red都是這樣的!

而A7S, Red, Arri當然可以在拍攝就選擇log模式,但他就是個被壓縮過的mov,只是因為容
量的問題而發展的一個功能
(其mov壓縮方式又是另一個課題,在這裡不討論)


接著說轉成log最大的目的,也是重點.

其實很多人轉成log都是為了要模擬film的顏色, Kodak Fuji等等

這是數位化後的一個趨勢


RAW本身就是個資料,有沒有發現到,你用各種軟體去解,每一家的顏色都不一樣,但是其DR

是差不多的.

所以重點在於顏色

所以重點在於顏色

所以重點在於顏色 , 很重要所以要說三次

有人說原廠軟體顏色好,LR顏色不好,DXO又是另一種顏色, 因為各家對於其RAW資料顏色

的描述不一樣!!

所以我們將RAW轉成LOG後,他是一個明暗都看清楚的狀態,同時顏色都被洗掉了

LOG的檔案因此看起來灰灰的,對比度很低,

變成灰灰的目的就是要讓你好更改他的顏色. 也因此產生出了3D LUT(當然也可以手動調

整)3D LUT生成需要專業調色軟體製作,或是購買他人製作好的LUT

3D LUT很多是將LOG轉成Rec.709 ( 同時有顏色與對比度), 有些也是Log到另一個Log

color space的轉換

所以將素材轉成LOG的目的通常是要作一些重要的Project,需要對顏色全面的控制.

也是一個裸體的資料,等著你去調整他,他就是一個為了調色的起始點.

一般處理時,當LR解出來的高光死白,暗部死黑,顏色無法調整, 但是透過轉LOG, 高光暗部

是可以被調整成其他顏色的

而仿間有很多種Canon RAW轉 Log的相機描述檔, 各有優點,有的是免費,有的是付費

其中Arri 的 Logc最有名,因為他是公認大家認為他的顏色最好.

所以產生了將Canon RAW轉成 LogC的描述檔,  或是免費 visionlog, 或是 bmdfilm log

甚至canon 轉 s-log, Redlogfilm 都是存在的

所有這些log的目的,都在提供使用者一個

good starting point for color grading

所以RAW轉log的意義對我來說, DR不是重點, DR還是看相機的能力,

只要曝光正確 基本上明暗細節不是問題

重要的是我如何對顏色的控制,

這樣作很累,但是我強調這麼作是為了個人風格或是特殊project如MV, 微電影,婚紗照

平常用當然是中性直接出圖了

最後補上流程圖.


http://imgur.com/OVpgfie


一位外國鄉民對於RAW轉LOG是有問題的人的質疑

和版上疑問非常像


Applying a logarithmic curve to an image does NOT, as above implies, convert
RAW to Log. The image is STILL RAW, it is just being 'lifted' / 'Compressed'
into a diff. gamma space.

This is what I mean, all this false word-mangling - to confuse a subject
which at this present moment is about THE most confused topic on the web...
(Next to how to keep a retina display clean)....

A REAL great advantage of a LOG Curve is when debayering is done
In-Camera.... Before 'Converting' RAW to a Codec or 'Baking in' the
linearization curve. When working with RAW files, it is pointless to use any
ONE standard linearization curve (Log). It is VERY limiting, in fact. It
would be like trying to apply ONE color-correction to each and every other
clip. Which any colorist would know would be non-sense.

I LOVE working with RAW, as I don't have to work against any LOG Curve
previously applied to the image. And I ALWAYS start with the linear
representation of the image. Then I'll apply gamma to that. And to imply that
applying an Rec709 workspace-LUT to a RAW-image will make it look like 'This
and That' and adhere to this or that standard, is simply put; Wrong. After
'Putting' something into another 'Space' does NOT imply NOT having to further
apply gamma, gain, offset etc. to that particular image... Gamma IS a
logarithmic curve or function if you will...

When shooting RAW - the Canon Camera does NOT apply ANY Linearization Curve
to the image. Hence RAW.... When shooting H.264 is DOES apply a curve to the
image. And in THIS case of in-cam-debayering, the LOG Curve becomes
important... CineStyle was a GREAT example of that. Technicolor KNOW what
they are doing. But it would be UTTERLY non-sense to shoot RAW and then i.e.
in Lightroom apply the Cinestyle LOG Space to the RAW-image. When shooting
RAW, you HAVE to realize that you have the FULL DNA of the image-data, RIGHT
THERE in the palm of your hands with all its might at your disposal. Simply
loading a LUT with a generic LOG-Curve and apply that to each image, would be
limiting yourself in EVERY regard.

Understanding RAW and how to develop it, is paramount for anyone shooting it.
RAW is wonderful and just as wonderfully misunderstood and therefor, easy to
make money off of.


另一位回應, RAW轉Log理由

重點在於

(exposure, white balance happens BEFORE the Log transform) and
have all the space and timesaving benefits of log encoded media.


RAW->Log 是沒有問題的





Of course, working with the raw digital negative DNG will give you the most
options and the best quality. I even said so clearly in my reply to you  ::)

BUT

How are you archiving your footage? Are you storing all your raw files? Are
you working on features running into hundreds of GB or more of storage for
your DNGs? Have you got a very fast machine to debayer raw in realtime or are
you using proxies? (another step). It may come as some surprise to you but
the majority of people here are not working on the latest Mac Pro with huge
raids and infinite storage. My guess is that if anything you are probably
working with Cineform raw!? Which I even recommended OVER AND ABOVE any other
method including Cinelog but Cineform Raw also comes at a price.

You obviously have no grasp of the intended use of Cinelog or those who will
use it. As I also said in my reply we do have several professional users
(DITs, colorists and DPs) who do know their subject and likely understand a
considerable amount more than you.

Not everyone is comfortable working in Resolve but Resolve Lite (which is
FREE) can be utilized to debayer and render much faster than ACR meaning you
can work with the next best thing to the raw DNGs in an EFFICIENT codec in
whatever NLE you choose and usually in realtime on a lower spec system.

No we can't presently do anything about debayering in Resolve but we have a
fully featured DIT app coming that will ;)

To insinuate that our work is there purely to make money from users who do
not poses certain knowledge or skills is highly ignorant, insulting to our
customers and bordering on slander! Just because you have a system that works
for YOU does not mean it will work for everyone else. The same can be said of
what we offer but oddly enough, as I pointed out in my reply to you, our
customers which includes professionals are satisfied with what we offer.

I suggest you look beyond your own blinkered view and 'post-production'
environment and understand that there is in fact a big demand for what we
offer, just as there is for what VisionLog and others offer. Why do you think
ARRI, Sony, Canon, Blackmagic, Red (I could go on) have Log gamma recording
in their raw capable cameras? WE cannot record to 10bit ProRes HQ with a log
profile in-camera but I can tell you one thing. It's probably the #1 feature
request in DSLRs and just as with most DPs who shoot on the big cameras MOST
WILL SHOOT LOG encoded ProRes or DNxHD (some even record to Cineform ;) ).
While we cant record compressed in-camera we can do it in post in a
controlled way (exposure, white balance happens BEFORE the Log transform) and
have all the space and timesaving benefits of log encoded media. No it's not
14bit raw anymore but it grades very nicely :) plus you can store the files
easily! Oh, did I mention realtime playback, no need for proxies, easy set-up
an rendering and technical support?

--
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※ 文章網址: https://www.ptt.cc/bbs/DSLR/M.1443785017.A.DA1.html
※ 編輯: LimYoHwan (36.231.242.253), 10/02/2015 19:29:44
噓 PureTrue: end
推 flashlight: 先推
推 edcrfv5210: 受教了
推 gwofeng: 看不懂END了 但有認真討論有推
→ IloveBlack2: 大師 我實在搞不懂你這篇講的究竟是視訊還是圖像
→ cywangtw1990: 一下說錄影一下說拍照 一下提H264 解釋一下吧
推 Juhnhood: 您的文章要有錄影的調色基礎知識搭配高階錄影才看得懂
→ Juhnhood: 很認真 但是大師您忘了這世間還是凡人居多的...還是感謝
→ cywangtw1990: 我看論述很大部分在討論錄影 可是今天重點在拍照
→ cywangtw1990:  所以我看不懂
→ PureTrue: 原本要自爽Dual iso結果被打臉崩崩轉戰log
推 luswtin: 其實看之前的討論串大概就知道想法了，的確在某方面來說
→ luswtin: 將原本色彩洗掉再重新後製加入想要的色的確是不錯的做法
→ LimYoHwan: Pureture你要吵架請左轉
→ LimYoHwan: 不想討論就不要看阿 end了又回來推文嘴一堆
→ LimYoHwan: Ad47 shinegg我也道歉了 再開一篇純討論 你很行也發表
→ LimYoHwan: 阿
→ LimYoHwan: Cywang影片是一堆raw 跟處理單張raw同道理
→ LimYoHwan: 然後我被打臉啥？我沒有說錯
推 luswtin: 所以不知道sony的raw是否也能轉log?
→ cywangtw1990: 可是為什麼我高DR排成RAW還要去轉log 本身後製不就
→ cywangtw1990: 好了？
→ luswtin: 某些情形先把色彩洗掉再重新安排比較快，色彩也比較統一
→ LimYoHwan: 內容你沒看完 你把英文部分看一遍 都有解釋
→ cywangtw1990: 可是在靜態圖像裡面 聽起來優勢是處理色彩 本身在優
→ cywangtw1990: 勢上 高DR並沒有因此而被當作弱勢啊
→ LimYoHwan: Sony log就是a-log
→ cywangtw1990: 好 我重讀一下
→ LimYoHwan: S-log
推 luswtin: 所以有軟體可以重新將sony相機拍的raw檔轉成s-log，而非
→ luswtin: 直接用機身轉的mov嗎?
→ LimYoHwan: 有喔 cinelog可
→ LimYoHwan: 然後我一直強調轉log是為了顏色
推 luswtin: OK，我來找找資料，謝謝
→ cywangtw1990: 看完了 能理解你的意思 不過我覺得主要討論點在調
→ cywangtw1990: 色
→ cywangtw1990: 那麼我就不討論其他事情了
→ cywangtw1990: 畢竟要回去討論Dual ISO大概又會戰到其他事情
→ LimYoHwan: Dual iso你可看vimeo別人的成品 真的還不錯阿
→ cywangtw1990: 我是說涉及靜態圖像的部分
→ LimYoHwan: Dual iso也是拍連續的raw喔
→ cywangtw1990: (筆記)
→ canandmap: 閱。
推 flashlight: 奉勸原po這裡存在特定幾位好戰分子，不能好好講話你不
→ flashlight: 要見怪....
推 sheng912: 不是好戰…是逢C家必要酸個一番不罷手,都不能好好講話
推 ferrinatice: 說真的，我覺得你把所有的東西混為一談我覺得好難懂
→ ferrinatice: 你的論述
→ LimYoHwan: 寫LR是因為要讓人好懂 其實我是開AE的ACR
→ LimYoHwan: 所以在流程圖是以ACR為主
→ LimYoHwan: AE的ACR可以設定Rec.709 mov h.264
→ LimYoHwan: 講錯是AE不是ACR可轉
推 rextem: 我有問題..文章裡一下子提錄影 一下子提相片.我有點混亂.
→ rextem: 照片我就懶得玩了 我是以錄影為主 所以C家用魔燈後可以錄l
→ rextem: og動態黨嗎？還是要錄RAW再來轉log?另外.不改機錄出來的mo
→ rextem: v還有可以套log調色的類似做法嗎？還是只能用網路上流傳的
→ rextem: 風格黨cinestyle再進軟體調?
→ LimYoHwan: ML錄Rawvideo可用描述檔轉成log
→ LimYoHwan: MOV直接用套cinstyle 但那是被壓縮的 不是raw
→ LimYoHwan: 我這篇沒寫好 其實要花時間寫 所以被抓小辮子了
→ rextem: 就你的文章跟之前我學到的 各家log錄影實際上也都是錄壓過
→ rextem: 的檔案.如你說的log黨實際類似就是套用風格黨 (這可能是我
→ rextem: 理解錯誤請指正).那以C家機器來說.是不是就不用改機 直接
→ rextem: 用cinestyle錄影 也有一定的效果可用?
→ LimYoHwan: 直接用CINESTYLE效果也是有 好調色DR尚可 但輸RAW
→ LimYoHwan: 優點就是容量小 後期簡單
推 rextem: 多謝教導.看來我可以先偷懶不用這麼認真學了.反正手上機器
→ rextem: 跟預計會買的機器也不會有錄log功能...我就繼續學者用cine
→ rextem: style調就好:P
推 po3d: 另外，rec709是數位電視的
推 ad47: 調照片不選sRGB 選rec.709，你說是不是很神秘 ( ′-`)y-～