meter reading question

[puyjapin]

so basically a d90 would have a better dynamic range while in matrix mode than a d40 etc etc

 

[Flash Harry]

so basically if there are lights and darks in a scene u cant expose both proprly?

If your exposing specifically for the bright or dark part of a scene then the other end will either be blown out or blacked up, as said it all depends on the dynamic range of the camera model but I reckon 5 - 7 stops will be maxed out in either direction. H

 

[fwellers]

so basically a d90 would have a better dynamic range while in matrix mode than a d40 etc etc

I don't think that's what I said at all.

 

[dxqcanada]

Using Ansel Adam's Zone System is helpful when thinking about exposure.

The camera's reflective light meter is not giving you an incorrect reading.

Look at Ansel's Zone Scale ...

Now ... let's say we take the camera's reflective light meter and look at the black bag.
The camera says to set your camera at 1/4s @ f8.0 (the camera's exposure scale is at 0).
The Zone Scale says that the exposure is in Zone V (middle grey).
You know that the black bag should be darker than that. Looking at the Zone Scale you figure it should be in Zone III.
In order to render the bag in Zone III you need to shift the exposure down by 2 stops.

To lower your exposure you can either increase your shutter speed (1/16s) or increase your aperture (f16).

Now, you ask what happens to the other objects in the shot ?
If you have properly placed the black bag in the right Zone then the other objects should also be in a matching Zone.
Sometimes that is not the case ... some scenes include objects at extreme ends.
If you take a meter reading of the dark object and the light object they should be within 8 Zones of each other.
ie black object (Zone I) = 1/4s@f8 and white object (Zone IX) = 1/500s@f8
If it is greater than one of the two will be rendered outside the useful Zones (Ansel was shooting film so he based his Zones on that) ... causing under or over exposure.

 

[dxqcanada]

Most camera's now use a Matrix metering system that analyzes the entire scene. It takes into account exposure of the Lightest and Darkest areas ... then provides you an exposure in Zone V.

When using a spot meter you are metering on a single subject within the scene.

A handheld meter can be used either as a reflective or incident light meter. Reflective light metering reads light reflected by the object (like your in camera meter). An incident light meter reads the light falling on an object. Incident light metering is often better as it is not affected by bright or dark objects to provide a Zone V exposure.