Help me remember about light metering...

[Rocketman1978]

...what my instructor said in a recent DSLR. He said even shooting in P, AV or TV, that you could flip to manual, meter the light and then flip back to setup your shot. I forget why he said this would be a benefit and exactly what data we were seeking in doing this, so perhaps you can fill me in, also include technique if you wouldn't mind.

 

[JAC526]

How the camera meters is independent of what shooting mode you are in (except maybe if you are shooting full auto in which case you may just have one option). You can use matrix or evaluative metering (which averages the whole scene), center weighted metering (which basically just takes light readings from the center of the frame), or spot metering (which reads a very small portion, usually the center focusing dot of the viewfinder). Any of these metering modes are available for AV, TV, M, or P shooting modes.

I'm not sure if this answers your question...

 

[PlanetStarbucks]

Yeh, seems like odd advice. I don't get why you'd want to meter in one mode then another. When you switch between modes on a Canon it doesn't translate the settings over.

 

[dhris]

Hm. I can't make sense of this except if I reverse the suggestion. First put the camera in an auto mode, note the settings, then use those settings as a starting point as you shift the camera to Manual mode.

...what my instructor said in a recent DSLR. He said even shooting in P, AV or TV, that you could flip to manual, meter the light and then flip back to setup your shot. I forget why he said this would be a benefit and exactly what data we were seeking in doing this, so perhaps you can fill me in, also include technique if you wouldn't mind.

 

[Tuffythepug]

Hm. I can't make sense of this except if I reverse the suggestion. First put the camera in an auto mode, note the settings, then use those settings as a starting point as you shift the camera to Manual mode.

That's what I was thinking. I do this myself (meter in auto and then switch to manual) so I can intentionally use a stop or two over / underexposure yet still get the aperture or shutter speed I want in a particular shot; it's the same thing as just using exposure compensation provided by the camera but I do it this way. I see no practical use for metering in manual in and then switching to an auto mode such as P, AV or TV. OP, are you sure you don't have this backwards ?

 

[panblue]

If the metering for whatever reason was way off in Av, the camera is limited to only 2+- EV comp and you need greater compensation. Can't think of a situation offhand but could be one.

Hm. I can't make sense of this except if I reverse the suggestion. First put the camera in an auto mode, note the settings, then use those settings as a starting point as you shift the camera to Manual mode.

...what my instructor said in a recent DSLR. He said even shooting in P, AV or TV, that you could flip to manual, meter the light and then flip back to setup your shot. I forget why he said this would be a benefit and exactly what data we were seeking in doing this, so perhaps you can fill me in, also include technique if you wouldn't mind.

 

[KmH]

Hm. I can't make sense of this except if I reverse the suggestion. First put the camera in an auto mode, note the settings, then use those settings as a starting point as you shift the camera to Manual mode.

Yep! I'm willing to bet money that's what the instructor said.

 

[Rocketman1978]

Hm. I can't make sense of this except if I reverse the suggestion. First put the camera in an auto mode, note the settings, then use those settings as a starting point as you shift the camera to Manual mode.

Yep! I'm willing to bet money that's what the instructor said.

Yeah could be, I know he mentioned metering and changing modes and I know he didn't say carry them over but just couldn't recall. Sort of wish I had a recording device during the class, lol.

Speaking of metering, I was reading in "Understanding Aperture" about spot metering or metering a specific subject to create an intentional over exposure on another subject. Can anyone allude to opportunities where this would come in handy? I've read many places about staying in evaluative (or matrix) metering, which is what I've done thus far but would like to explore some more artistic shooting and think the other metering modes could come in handy for that.

 

[AgentDrex]

The only time I can think of that would benefit from over-exposure is snowtime. That's coming from a northerner so take it for what it's worth.

 

[KmH]

The in-camera light meter is calibrated based on the fact that the luminosity in most scenes is approximately equal to a neutral tone of light gray.

When a scene is brighter than that, like a snow covered field, or a a scene is dominated by a broad white wedding dress, the camera will not meter accurately.

You can use the histogram to determine when you need to intervene - Understanding Digital Camera Histograms: Tones and Contrast

Also check out - Understanding Camera Metering and Exposure

 

[Rocketman1978]

Awesome, thanks!

 

[Tuffythepug]

KmH's explanation pretty much covers it. Note also that your camera doesn't know what your intentions are when you compose a photo. The light meter takes the light reaching it and makes a calculation which will render an 18% gray image as 18% gray; this is the standard by which light meters in all cameras work. Using a spot meter you can read the light reflected off of only a tiny potion of the scene so that you can use that information to make a judgment about your shutter and aperture setting. Whichever portion of your photo that you want to have perfect exposure can have a reading taken off of it and the rest of the scene then falls wherever it may. You can take a reading off the dark areas and the highlights separately and make a judgement about your exposure based upon that information.

An alternative to all of that is to use a hand-held incident meter which measures the light falling on all subjects rather than the light reflected off of them. These are all just tools that allow a photographer to make informed decisions about how their images are going to look.