关于测光，对焦点与曝光锁定的问题（问题多多，还请版主和各位大师指点一二，跪谢）

jayyang0128

大家知道相机有平均测光，点测光和中央重点测光。
想问问各位大师，是不是它们都不会跟着对焦点测光的？是不是都是以图像中心为基准的？

这里有个实例，２个问题：
在外景人像拍摄中，假如说我的对焦点不在中心位置在侧面，而我要对穿黑衣服的MM的脸部先测光(发现穿黑衣服的脸部很容易曝光过度)，是用我的对焦点对着她的脸，还是图像的中心对焦对着她的脸？

另外，我还发现个问题，在测光后，用了曝光锁定，　如果我想改换对焦点，为什么曝光锁定就自动取消了，这是为什么呢？（我用的是5d2）

多谢！

[ 本帖最后由 jayyang0128 于 2009-8-26 15:33 编辑 ]

bordesign

原帖由 jayyang0128 于 2009-8-23 21:20 发表
大家知道相机有平均测光，点测光和中央重点测光。
想问问各位大师，是不是它们都不会跟着对焦点测光的？是不是都是以图像中心为基准的？

这里有个实例，２个问题：
在外景人像拍摄中，假如说我的对焦点不在中心 ...

5D MARK II好像是没有联动的，                        佳能除了高端机对焦和测光都没有联动，所以只能用中心点进行测光。

用点测光的步骤：半按快门完成对焦和测光——锁定曝光——保持快门半按状态重新构图——按下快门
用评价测光：因为是对整个画面进行3D矩阵测光，所以应先对构图后的画面进行测光。               
锁定曝光是对你的测光点的曝光值进行锁定，松开快门后重新对焦是对焦点的选择。
如果你的测光点和对焦点是相同的那就没什么区别了。
你用M档会好控制很多。

jayyang0128

哇，谢谢版主，太敬业了，这么快就回我了，万分感谢！

ilsh

帮顶一下，这也是我的疑问

development_nz

也顶版主真的是有问必答。

Eyeport

一般来说我只用2种测光模式。。。点测和矩阵测光。。。

单反相机的矩阵测光或者均匀测光一般是在光线比较均均的情况下有效，如果光线过猛，过暗，或者反差大的情况下曝光都会不准确。。。这是就要用到+ev or -ev来进行曝光补偿，大家自己拿相机实验一下就知道了

在拍人像的时候我一般会用点测光为主。。。不过risk就是背景，天空容易过爆。。。看你个人怎么取舍了

Eyeport

波版，王子。。。中心测光的好处在哪里呢？

siyuan79

我和ipod差不多，一般来说拍人用点测比较多，其他时候用中央重点，极少用到全面测光的。

对于测光点，我的理解是取景框的zhong'd

[ 本帖最后由 siyuan79 于 2009-8-26 02:06 编辑 ]

jayyang0128

我也是听说多数情况下用到中央重点，极少用到全面测光的，而且我也是一直这么认为的，但是当我认认真真看了一下说明书后，傻了，佳能相机的第一设置居然是评价测光（我的理解就是全面测光，不知对不对），而我最少用到的最后一个居然才是中央重点，其实也就是说不懂的人拍出的照片多是以全面测光为主的，如果说“多数情况下用到中央重点，极少用到全面测光的”的理论是对的，那佳能为什么要这样来安排，没道理啊。我的感觉好像尼康机的第一设置是不是都是中央重点，如果是的话，那就有意思了啊，这两家的用法用意何在？

yellowS15

小波肯定5D Mk II 对焦和测光真的没有联动???
之前我有一个朋友问我这个问题.. 我还告诉他当然有
因为我记得Nikon连最早入门机例如D50,D70对焦和测光也有联动... 所以我还说得很大声5DMk2当然有

Eyeport

原帖由 yellowS15 于 2009-8-26 10:50 发表
小波肯定5D Mk II 对焦和测光真的没有联动???
之前我有一个朋友问我这个问题.. 我还告诉他当然有
因为我记得Nikon连最早入门机例如D50,D70对焦和测光也有联动... 所以我还说得很大声5DMk2当然有

什么是联动？
什么情况下用centre metering最好啊

yellowS15

联动 means when you are using spot metering, the spot metering point is linked to your AF point.
okay i prepared this example D300 viewfinder screen for you..



if you are in spot metering mode, and use single point AF. you select the AF point as in the picture above so you are focusing on the boy's eye..      your D300 (or basically any Nikon DSLR camera, but i don't know about Canon or Sony or other brands) will automatically use your AF point to do the spot metering.. this is what you called "spot metering linked to active AF point/area"so you should get a pretty good exposure as well when you take the photo. This allows you to take a picture with accurate focusing and exposure quickly, as most of the time, you want the subject you focus on to be also the object with proper exposure.
Of course you can override it or dial in some exposure compensation in the rare cases where you don't want the focused object to be properly exposed.
but if you are in spot metering mode and you camera's spot metering is NOT linked to your AF point... unless you do a AE lock separately, then when you take that picture, it will use the center point to calculate the correct exposure.. in this case, it's the highlight on the little boy's clothes.. so the picture you got will most likely to be underexposed.

Eyeport

原帖由 yellowS15 于 2009-8-26 16:03 发表
联动 means when you are using spot metering, the spot metering point is linked to your AF point.
okay i prepared this example D300 viewfinder screen for you..

http://www.photobyrichard.com/misc/s ...

thanks for the explanation. i thought its always linked automatically, thats why I couldn't figure out whats the use of locking the exposure. LOL...

yellowS15

原帖由 Eyeport 于 2009-8-26 16:18 发表

thanks for the explanation. i thought its always linked automatically, thats why I couldn't figure out whats the use of locking the exposure. LOL...

i actually also thought any DSLRs and most digital compact would have this feature too..   because i remember even back in 2002 or 2003 my Coolpix 5700 already has the spot metering linked to the AF point automatically...

but anyway "AE lock" is still a useful function because there are times when you don't want the correct exposure to be based on the object you lock the focus on.

Eyeport

原帖由 yellowS15 于 2009-8-26 16:38 发表



i actually also thought any DSLRs and most digital compact would have this feature too..   because i remember even back in 2002 or 2003 my Coolpix 5700 already has the spot metering linked to th ...

you are right...for most people such situation will hardly occur i suppose

siyuan79

有个疑问

当使用点对焦的时候就比较明白了，但是如果是使用自动对焦（3D对焦模式之类的），点测光的话，那么测光点是在那里呢？

yellowS15

原帖由 siyuan79 于 2009-8-26 17:13 发表
有个疑问

当使用点对焦的时候就比较明白了，但是如果是使用自动对焦（3D对焦模式之类的），点测光的话，那么测光点是在那里呢？

There are just too many user adjustable settings which will all affect the results.. but there are some of the more common combination settings..  

Assuming you only use shutter button to take picture (i,e, no AF-on button/AEL button) with CPU lens attached:

AF-C mode,  dynanic area AF mode, 51Pt  3D-Tracking,  spot metering, exposure lock not linked to shutter button :  camera use the active (tracked) focus point for spot metering during AF tracking

AF-C mode,  dynanic area AF mode, 51Pt  3D-Tracking,  spot metering, exposure lock linked to shutter button : camera use the user selected focus point for spot metering when you half click the shutter button. Exposure won't change during the tracking

AF-C mode,  dynanic area AF mode, 9,11,21 or 51 Pt non 3D tracking,  spot metering, exposure lock not linked to shutter button: camera use user defined focus point for spot metering

AF-C mode,  dynanic area AF mode, 9,11,21 or 51 Pt non 3D tracking,  spot metering, exposure lock not linked to shutter button: camera use the user selected focus point for spot metering and locked when you half click the shutter button. Exposure won't change during the tracking

AF-C mode,  Auto area AF mode,  spot metering, exposure lock not linked to shutter button: center point for spot metering disregard active AF point,

AF-C mode,  Auto area AF mode, spot metering, exposure lock linked to shutter button: center point for spot metering disregard active AF point. Exposure won't change until shutter button is released.


i maybe wrong with some of these so please correct me if i'm wrong

kingkongenzo

哈哈，又长知识了

Eyeport

原帖由 yellowS15 于 2009-8-26 22:27 发表


There are just too many user adjustable settings which will all affect the results.. but there are some of the more common combination settings..  

Assuming you only use shutter button to take  ...

Thanks for the thorough reply again...the last 2 situations may never apply to me for any serious shooting...haha