關於新的Z6/Z7看來國外的Focal團隊已經著手開始研究了
未來不須太過煩惱Nikon無反銳利度不夠卻又只能呆坐無力了
其中文章中的一段我將它翻譯過來
就如同我當初的體驗與預測一樣
Why AF Fine Tune on the Nikon Z cameras?
As I said above, it’s generally assumed that cameras with the autofocus sensor built into the image sensor (i.e. mirrorless cameras) do not need any AF calibration. There’s no chance of the AF sensor being misaligned or the pre-programmed internal calibration between the AF sensor and image sensor to be incorrect like there is in a DSLR (which has a separate AF sensor in it’s base). However, Nikon has included AF Fine-Tune in their Z6 and Z7 cameras – so why is that, and is it really needed?
為何在Nikon Z系列上要有AF Fine Tune功能?
如我上述所說,這功能普遍在使用CMOS上的AF模組時是不太需要的
因為無反相機的特性使的AF模組不太有偏差或是組裝偏移問題像在DSLR上發生的(因為DSLR的AF感測器是分離式置放於機身底部的)
然而在新一代的Z6/Z7相機上,Nikon卻仍舊將AF Fine Tune功能置入,為何如此並且需求在哪?
If the camera uses purely contrast-detect AF (CDAF), you wouldn’t need any sort of calibration. CDAF works in the same way as a human focusing a lens – you look at how sharp the image is, and if you’re not satisfied with the sharpness you move the focus point a bit in a random direction and see if it gets sharper or not. You repeat this process until you get a sharp image. This is a closed-loop, iterative process – closed loop means you adjust and then check your result, and iterative means you repeat the process until you’re happy with the outcome. The end focus position is probably about as good as you’re going to get (although you can never be quite sure as you have to adjust the lens to check, which might then mess up the focus!). The down sides are that CDAF is quite slow and requires good light.
若相機使用純對比對焦(CDAF),用戶完全不需要此類的調教
CDAF的工作原理類似於人在手動轉對焦,你看著影像中的銳利度夠不夠,若是你不滿意你就再稍微隨機前後轉一下,直到影像銳利才停止
CDAF是一個閉環迴圈(Closed-loop)反覆重複的過程--閉環代表你會調整並確認你的結果,重複做這些步驟直到你終於對結果感到滿意
最終對焦位置會幾乎像你想的一樣好一樣精準(雖然以人工來說通常不一定會好,因為要人眼辨識很容易會搞砸)
缺點就是CDAF相當的慢速並且需要優秀的光源條件
Phase-detect AF (PDAF) looks at two paths of light coming to the sensor and with a single measurement can determine both the magnitude (how much you need to adjust the focus) and the direction (towards the camera or towards infinity). So one quick measurement can give you everything you need to know – then you drive the lens the right amount in the right direction and voila, perfect focus…
相位對焦(PDAF)則是依照兩條進入AF感測器的光路徑計算波程差來計算要多少的調整以及往哪的方向(朝向機身或是往無限遠)
只要一個計算就可以給出所有所需的資訊,並驅動鏡頭達到正確的位置(或是精準對焦)
… not quite. This is an open-loop system. It’s fast, but it relies on your measurement being accurate and the lens doing exactly what you tell it to. When the camera says move x amount in this direction, it assumes that x is the perfect amount, and the lens will correctly move to this point.
然而並非如此簡單
PDAF屬於開環迴圈系統(Open-Loop)
事實上來說此種系統相當依賴計算的精準度與器材執行度
當相機下達移動X量值朝向某方向的指令,系統是假設X是精準計算無誤差,並且鏡頭會完全依照指令移動該量值無耗損到達指定點
So what happens if your lens motor/gearing is a bit worn and doesn’t behave quite the same as it did when it was new? What if the lens mount or lens elements are fractionally misaligned due to manufacturing tolerances or an accidental knock 6 months ago, and the focus isn’t measured quite correctly or the movement of the motor doesn’t quite move the lens element where is should be? These are the sorts of things can result in a fractional offset of the focus position, and an out-of-focus image.
若是此時你的鏡頭馬達/傳動裝置有耗損並且無法表現得像是完美的鏡頭情況?
若是鏡頭接環或是鏡頭內部元件有些微的偏差而卻符合製造偏差容忍度?又或是6個月前的意外碰傷導致?此時對焦或許無法精準測量出正確指令或是馬達無法完美執行要求指令?
這些都是可能導致些微的對焦偏差或是脫焦影像的可能
But as long as the focus error is fairly consistent, then AF Fine Tune is your knight in shining armour to get that perfect focus back!
但只要對焦錯誤是相當穩定的,AF Fine Tune功能就可以成為你的救命稻草讓你再次對焦精準
Other mirrorless cameras offering AF Calibration
There are a few other mirrorless cameras which offer AF tuning. Cameras like the Olympus OM-D E-M1 even have the capability to adjust calibration for each individual focus point!
有其餘無反機型提供AF微調功能?
有一些無反機型確實有提供此功能
像是Olympus EM1(EM1 M2也有)就有對於個別對焦點的AF微調能力
I’ve consistently seen reference to Sony mirrorless support AF Fine-Tune but this isn’t technically correct and I wanted to clarify here. There are a few lens mount adapter available for Sony cameras, and at least 2 of them (LA-EA2 and LA-EA4) use Sony’s “Translucent Mirror” technology and incorporate a PDAF sensor in the base of the adapter. When you use AF Fine Tune on a Sony mirrorless, this adapter PDAF sensor is what you are actually calibrating, so it’s only of use if you’re using one of these specific adapters.
過去曾持續地看見一些資料說明Sony無反支持AF微調功能,但這並不正確我必須在此澄清
Sony的AF微調功能只針對部分接環可使用,例如LA-EA2或是LA-EA4(使用Sony的半透明反光鏡科技)此種接環利用置放於轉接環底部的PDAF感測器一同工作
當你在Sony機身上使用AF Fine Tune時,你其實在調整的是該轉接環上的PDAF系統,所以Sony的AF微調只局限於該種特殊轉接環
以上是部分翻譯節錄
文章中有提到關於鏡頭縮光圈到F22之間時,會有相當大幅度的AF微調值差異圖
但明顯可見確實對於純相位對焦的無反機身來說,AF微調功能是無法捨棄的
否則就會出現像我之前的EM1 M2的慘劇
PS.我已經有收到訊息說Sony A9配上428GM若使用AF-C加上單點對焦採用連拍時,若一張一張比對檢視,對於靜態鳥會出現EM1 M2的漂移情形
對於動態則是像EM1 M2一樣沒問題
看來我對純PDAF的無反相機所描述的問題應該真實存在,只是沒有人去紕漏
起碼現在我不怕說買了Nikon的無反會出現反而鏡頭移焦而導致性能不佳的情形了
不然大砲有移焦真的是花36萬買,結果30萬丟水里XD
(沒有準度等於投資的主力都丟水中了)
不過我是很好奇,國外網友幹嘛一直要宣傳Sony有AF微調功能?
要吐一口氣?還是國外一堆認真的魔人用了Sony配了超長焦或是拍靜態卻發覺常常有不準?
所以才要宣導有AF微調功能來滅火?
可能索粉會想笑,根本瘋子
連用無反都還要調焦,完全的調焦魔人
不過要笑就笑吧
讓索粉不要嘲笑比不上我拍鳥照準焦穩定來的重要
人不要臉天下無敵,So狗不叫世界和平
Focal推出2.9 beta版
支援Z6/Z7 AF對焦微調測焦
我也尚未購入Z系列相機,有興趣的朋友可以自行試看看
在這個索尼不用調焦到處轉接樂的時代,到底是Sony運用硬體優勢讓鏡頭調焦問題模糊化,還是Nikon無謂的堅持還要留存調焦系統呢
沒想浪費錢就為了要測試而買了鏡頭和機身,手動把鏡頭改至大移焦再來測試Sony的缺陷與否
就看未來幾年,Z還會不會維持初衷
或是隨波逐流永遠的拿掉微調選項
人不要臉天下無敵,So狗不叫世界和平
本來用調焦板... 不過總覺得還是有點"不清不楚"..
感覺沒有很清晰~ 雖然有改善.. 腦中還是糾結著, 是否還可以更好
所以敗入, Focal Pro ..
購買到安裝好到啟動好: ~10分鐘
請老婆印好target: 沒花到我時間 XD
下班等到安頓好小孩後快點架設好相機等等的環境: ~25分鐘 (含測試target)
實際測試一個鏡頭: ~7-8分鐘吧~
(選擇測試點數多一點, 要不然 -20, -10, +10, +20 就搞定 ..maybe 5分鐘內)
之後把玩一下結果 又測了另外一個鏡頭~
結果分享:
= = = = = = = = = = = = = = = = = = = =
真的感動! 老婆! 真的我的眼睛沒錯! 不是我強迫症, 也不是我對茫然人生的質疑投射現象~
50 F1.4 --> 本來測試板老眼判-3, -4 ---> Focal Pro 測試結果建議 -10
35 F1.8 --> 本來測試板老眼判-4 ---> Focal Pro 建議 -7
我跑3次來平均
有數字清晰度來判斷 真的輕鬆很多~ 我真的不用自己看到流目油.
2.8版心得分享:
環境設備說明:
- win8.1
- Nikon D7200
- 50/f1.4
- 35/f1.8 DX
- 安裝沒碰到甚麼問題, paypal完, 馬上收到帳號密碼, 下載 安裝 輸入密碼自動取得license
- 介面簡單
- 操作上沒有甚麼太複雜的地方
- 基本操作:
>connect camera
>test target (印出的測試標靶), 會說明距離夠不夠, 清不清楚等等
>跑測試, 手動輸入要求的微調 (全自動支援的就可自動跑完)
>看報告
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