Metering Question

[david911]

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If I set the ISO dial to A, what do the red meter arrows in the viewfinder indicate? I believe that they would only make sense for a given ISO, correct? So what ISO does the camera (M11D) use - the last one? some default?

Thanks for the help,

David

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[Guest]

It is for a given ISO that the camera has decided is closest to what is requires for a correct exposure given the manual exposure settings (speed and aperture) that you have selected

The red arrows and red circle show how well your chosen exposure & Auto ISO settings reflect the metered ideal value. Normally you want to see the red circle only which shows that the settings match what the camera thinks is required.

If you are using manual mode with Auto ISO the camera chooses the ISO value that most closely matches the required exposure. However, the set of ISO values available are fixed and not variable, e.g 64 or 100, and not 64, 62, 63...100, so the chosen ISO will not exactly match the required exposure. Because of this you often don't just see a red circle, but a red circle with a red triangle also. The user manual tells you exactly what the exposure discrepancy is, but you don't really need to worry about it as it'll be close enough.

However, if the manual exposure that you have set is such that there is no Auto ISO that can give a correct exposure then you will only see a red triangle, and no circle,  which indicates that you are going to seriously under or over expose the shot.

[david911]

thanks!

[DadDadDaddyo]

Owing to about a million and a half years of metering with various types of external meters with all kinds of cameras and formats, when using manual mode on a camera with built-in metering, I've evolved into very much a spot metering guy. 

Mostly with a glance through the viewfinder at my intended framing, I decide which value in the scene I want to place at 18% gray (sometimes said to be equivalent to a putative skin tone, but, well, it depends... but it's the reflective brightness of an 18% gray card (do folks even know what that is anymore?...)). 

Then I spot meter on that spot.

Absent other weighting (such as exposure compensation, for example), ever and always, a meter will expose for 18% gray. In other words, whatever it picks up, whether it's the average of the whole scene, the average of the defined "center" zone, or a small spot, it will expose to place that value at 18% gray. 

If I do this on a scene that's got relatively even lighting but with a few very hot spots, and I unthinkingly pick a person's face within that average lighting and use spot metering on the face, those hot spots will be totally blown out. 

Same scene, but using averaging metering, those several hot spots will influence the average and those people's faces might be underexposed.

Highlight weighting will take those hot spots into consideration and drive the exposure according to the mode's program. How will it behave? One will learn from experience. 

Center weighting will be influenced by those hot spots to the extent they're within, or not within, the weighted metering portion of the frame. 

In all these cases other than with spot metering, the metering mode's predetermined characteristics will influence the treatment of the scene. With spot metering, the spot selected for metering will be exposed for 18% gray and everything else will "fall where it will."

For my purposes that's perfect, because I can quickly decide what in the scene I want to place at 18%, and experience gives me an idea of where the other elements in the scene will fall. That's how I influence overall exposure in manual mode. 

Other folks prefer to use one of the averaging or weighted modes but then dial in some exposure compensation based on their accumulated experience and what's in the scene. They're using exposure compensation to put some "spin" on the outcome governed by the mode's predetermined characteristic behavior. 

Either way, getting what you want starts with having an idea of what you want, and then making conscious use of the exposure system and its known behavior to get what you want. 

It ain't automatic. 

[jaapv]

The triangles indicate over and under exposure: half-lighted half a stop, dot extinguished full stop or more. Furthermore they indicate the direction that the aperture or speed dial must be turned 

I would strongly advise against using auto-iso in manual mode; it defeats the purpose of manual exposure: full control. 

[SrMi]

1 hour ago, jaapv said:

The triangles indicate over and under exposure: half-lighted half a stop, dot extinguished full stop or more. Furthermore they indicate the direction that the aperture or speed dial must be turned 

I would strongly advise against using auto-iso in manual mode; it defeats the purpose of manual exposure: full control. 

I regularly use Misomatic mode (Auto-ISO and M mode), as ISO settings do not matter much, and M mode allows me to change the shutter speed quickly depending on the scene's movement. At higher metered ISOs, I even like to apply some negative EC (affects only ISO) to protect highlights without lowering the exposure.