Lightroom flat field conversion plug-in for red shift problem

george_chang

Found this article online, seems like many Ching is using Lightroom here. I think is pretty handy to have this plug-in at Lightroom to fix red shift problem without the need of other program.

http://tobinators.com/blog/index.php/2013/12/techniques/a7r-more-lenses-and-lightroom-flat-field-conversion/

edwardyung

其實有了Lr5之後, 利用2-3個 Radial Filter + Graduated Filter, 要修正這種紅閘並非什麼大事.
VM21/4 on M9

cshingyau

如用photoshop 又得吾得呀?

raumplan

a very dumb question, if 35mm is the widest i will use in A7, will I get the color shift….?

toys_madman

edwardyung 發表於 2013-12-31 15:51
其實有了Lr5之後, 利用2-3個 Radial Filter + Graduated Filter, 要修正這種紅閘並非什麼大事.
VM21/4 on M ...

edward hing, 可否解釋下個步驟?? 唔該!!!

raumplan

Yes Edward hing, could you please share your method?  thanks a lot in advance.

Daipat

raumplan 發表於 2013-12-31 16:32
a very dumb question, if 35mm is the widest i will use in A7, will I get the color shift….?

I mount 35lux on A7r with Hawks. No red shift.

Daipat

edwardyung 發表於 2013-12-31 15:51
其實有了Lr5之後, 利用2-3個 Radial Filter + Graduated Filter, 要修正這種紅閘並非什麼大事.
VM21/4 on M ...

Edward hing,
Please share the LR5 prcoedures.
I am considering getting a 21mm but need to get a good grasp how to get rid of the red shift problem.  I use LR5 too, Thanks in advance.

george_chang

Edward Ching, please share how it could be done by applying filter in LR. The plug-in above need to built a set of RAW file in different aperture or a calibration file to correct the red shift. If your process is easier, it would be great help. Thanks!

raumplan

X2.

I read the plug-in workflow but the built-in set of RAW files is making things a bit too complicated….

edwardyung

cshingyau,  PS當然可以做Lr做到的東西
raumplan,  我冇A7, 答唔到你, 見其它人講35mm或以上係OK嘅
toys_madman,  raumplan,  Daipat, george_chang,     等我整理一下

成個慨念是2個重点:
1. 選取是什麼紅色,
2. 選取紅色的範圍和深淺,
3. 改正它

嚴謹的做法是用PS
要求不高, 怕痳煩的, Lr5 是可以應下急. 但其實好賴貓的....

PS的方法:
向白色背景用相同相机+鏡頭+光圈拍一張REF圖. 記得測光要+2EV (or ??) 才会是白背景
利用這張REF圖你可以:
I. 準確選取那隻紅色, 求得這隻紅色的invert color (在Lab color的 L,a,b 值中, 把a和b 乘-1取代原來的a和b) 作為用於 II. 的 filter color.
II. 在有紅閘的圖片中, 做一個photo filter - adjustment layer, color是選用 I. 中找到的invert color, 這樣就能把紅色消去, 但這会是全畫幅的調整, 所以我們需要一個 layer mask 只調整紅閘的地方.
III. 也是利用之前那張REF圖經一些調整(Invert, B&W, curves, Blur...)後, 就是一個很好的 layer mask了, 將它copy&paste到 II. 的 photo filter - adjustment layer 的mask當中.
IV. 若要同時修正暗角, 也可重覆II.和III, 只不過今次用的adjustment layer 是 Exposure, layer mask也要有不同的理解/調整.
V. 調整各layer 的 opacity, adjustment 的 density, 以取得最好的效果.

[filter color + layer mask] 是对應每1個 [相机+鏡頭+光圈] 組合的, 所以理論上只要做1次
但如果2部机x2支鏡x8個光圈..... haha, 你就有32-sets data了.
煩嗎?

edwardyung

借用了上面例子的圖片

edwardyung

layer mask 和 修圖後
mask 應該可以再做得好d... 現在有点求求其
此例子並未有修正暗角

edwardyung

filter color 的 L,a,b 是 48,-7,-3

edwardyung

由於原圖很細和是压縮了的jpg... 所以做得不算理想.

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加多張 Lightroom 5 adjustment ONLY 嘅

Graduated Filter G1,G2,G3
Radial Filter R1,R2,R3,R4

george_chang

Thanks! Edward Ching. Will try your method.

Daipat

edwardyung 發表於 2014-1-2 19:11
由於原圖很細和是压縮了的jpg... 所以做得不算理想.

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Thx. Will try.