Canon and Nikon light metering questions

[Dave (Isle of Skye)]

Hi all,

Sorry if I have not explained myself very well here, I know what I mean, but not sure if I have described it very well, but this is something I have tried to find information on for some time now and feel sure someone here will know the full and complete answers to this.

I have a 5D MkII, I use in camera spot metering mainly, which I believe works by always metering the centre of the full image view, but when I line up a shot, then manually focus and meter, then go into live view mode and zoom right in on the screen and move down the screen view to tweak the manual focusing at one third into the frame for maximum DoF, it then tells me that my original metering is now wrong and needs resetting. So my first question is this - how does the 5D MkII meter in live view mode when zoomed in full on the screen, but away from the centre of the originally metered and not zoomed in frame? Is it still in spot meter mode but now at the centre of the zoomed in part of the screen view instead and hence tells me I need to readjust the exposure? Also outside of live view, if I do use AF and select a different AF point other than the centre AF point, does it then spot meter to that or still use the centre of the frame?

Last question - I have seen a video where a photographer uses his high end Nikon and he seems able (or appears to describe it as such) to spot meter any where in the frame no matter what his AF or manual focus point is elsewhere in the frame, is this a function of the Nikon where you can select where in the frame of the viewfinder that you wish to meter and not just where your AF point is? And if so, is the 5D MkII doing a similar type of thing when I zoom in fully with live view?

Sorry for the complex and rambling set of questions here, but I have great faith that someone here will know what I am asking and the answers.

Thanks in advance.


Photobloke

[Rob C]

As far as I'm aware my D200 and D700 all do spot metering by the simple act of selecting the spot mode on the little switch and using the tiny central area marked. I don't think that af has anything to do with it, but as all my lenses bar one are manual, maybe I missed something.

However, and it's not your question, with digital I gave up on spot in favour of matrix and never looked back. It (spot) seemed a great way to use a built-in meter in the days of transparency film if you couldn't get an incident light meter into the right place. With digital it's all pretty redundant now; the histo serves as well if not better.

Rob C

[Gary Brown]

Nikon DSLRs do spot metering at the currently selected autofocus point (although there are a couple of exceptions). But as far as I know, there's no way to independently select a spot-metering point and autofocus point.

[stamper]

Last question - I have seen a video where a photographer uses his high end Nikon and he seems able (or appears to describe it as such) to spot meter any where in the frame no matter what his AF or manual focus point is elsewhere in the frame, is this a function of the Nikon where you can select where in the frame of the viewfinder that you wish to meter and not just where your AF point is? And if so, is the 5D MkII doing a similar type of thing when I zoom in fully with live view?

Unquote

It is pretty simple to spot meter an area and lock the metering via the exposure lock, recompose and focus where you want. Any decent DSLR can do this and my newly acquired Canon G12 can even do it. I don't know about live view however.

[stamper]

As far as I'm aware my D200 and D700 all do spot metering by the simple act of selecting the spot mode on the little switch and using the tiny central area marked. I don't think that af has anything to do with it, but as all my lenses bar one are manual, maybe I missed something.

However, and it's not your question, with digital I gave up on spot in favour of matrix and never looked back. It (spot) seemed a great way to use a built-in meter in the days of transparency film if you couldn't get an incident light meter into the right place. With digital it's all pretty redundant now; the histo serves as well if not better.

Rob C

Rob, your last statement about matrix and using it will certainly give you good images but I wouldn't write of spot metering and manual or aperture priority mode. It will - imo - give you a more "accurate" exposure if you know what you are doing especially in conjunction with the digital zone system. If someone has the time and the subject isn't moving much then it is the "best" method. Matrix - imo - is a kludge with regards to metering. I believe there are about 30,000 or more images stored in the camera that the camera references when making a metering choice. The problem is what happens when the scene in front of you exceeds the SBR range or when you want to use EV to meter? Matrix isn't suitable for this scenario. I prefer center weight which is more flexible.

[Rob C]

Rob, your last statement about matrix and using it will certainly give you good images but I wouldn't write of spot metering and manual or aperture priority mode. It will - imo - give you a more "accurate" exposure if you know what you are doing especially in conjunction with the digital zone system. If someone has the time and the subject isn't moving much then it is the "best" method. Matrix - imo - is a kludge with regards to metering. I believe there are about 30,000 or more images stored in the camera that the camera references when making a metering choice. The problem is what happens when the scene in front of you exceeds the SBR range or when you want to use EV to meter? Matrix isn't suitable for this scenario. I prefer center weight which is more flexible.

"what happens when the scene in front of you exceeds the SBR range "

But stamper, the metering system doesn't change the light on the subject - it only measures it as best it can. The ETR system can be used to figure out the best exposure by visually inspecting the histogram which covers the entire image area, not a selected bit of it. Even quicker (if you still want to use the rear screen) is using only the highlight burns indication option on the image you see there, but since that apparently reveals nothing more than the effect of exposure on jpegs and not the RAW, it isn't a complete answer either.

I'm perfectly willing to admit that for those exposures where you might intend making multiples from which to create a final composite, that things are different, but that's not really my photography - I'm definitely into snaps!

Rob C

[mouse]

I have no experience with the Canon cameras.  However I can elaborate on the function of the Nikon d700 (and probably the d200 as well).

With all modern Nikkor autofocus lenses both the autofocus and spot meter follow the focus point selected in the viewfinder.

With Nikkor MF lenses (which I use frequently) spot metering is confined to the central focus point regardless of which point is selected.  I use the method suggested above: spot meter using central point and then lock exposure.  Interestingly enough, the viewfinder "in focus" indicator (green dot) does respond to the selected focus point with MF lenses.

No clue about live view. 

[Mike K]

I have a 5D MkII, I use in camera spot metering mainly, which I believe works by always metering the centre of the full image view, but when I line up a shot, then manually focus and meter, then go into live view mode and zoom right in on the screen and move down the screen view to tweak the manual focusing at one third into the frame for maximum DoF, it then tells me that my original metering is now wrong and needs resetting. So my first question is this - how does the 5D MkII meter in live view mode when zoomed in full on the screen, but away from the centre of the originally metered and not zoomed in frame? Is it still in spot meter mode but now at the centre of the zoomed in part of the screen view instead and hence tells me I need to readjust the exposure?

With the 5Dii in Live View the metering is not done by the exposure sensor (in the pentaprism area) but rather in the magnification area (red rectangle) by the sensor.  In this way Live View Silent Shooting mode 1 or 2, the exposure is intiated purely electronically, as the shutter is open and the mirror up for LV.  The shutter does close at the end of the exposure and the sound that you hear is the shutter recocking and opening.  Thus LV SS has less vibration than MLU and a 2 sec delay is not needed if you are using a remote!  For Nikon Live View, the mirror descends and the exposure meter catches a reading before the shot, so there is no advantage over MLU, which in this case, has less vibration.
Mike K

[Dave (Isle of Skye)]

With the 5Dii in Live View the metering is not done by the exposure sensor (in the pentaprism area) but rather in the magnification area (red rectangle) by the sensor.

Thanks Mike, I knew someone here would know the answer and now you have explained it, I can see why I get two different readings, because metering through the light sensor on the outside of the body is obviously going to be different to the selected (zoomed) part of the image sensor from inside the body.

Cheers.

Photobloke