How Digital SLR Camera Metering Works (DSLR)

Every modern digital SLR camera from its factory is equipped with technology called Metering Mode, Exposure Metering, Camera Metering or for more practical we call Metering that has been assembled therein. In this article we will try to understand what is metering? How it works as well as some major weaknesses that we have to face (underexposed & overexposed). In the next article, we further understand about metering mode (matrix / evaluative, center weighted & spot metering).

What is Metering? What is the point?

In principle, it is not unlike the roll meter used by the construction worker or the tape measure used by the tailor to measure the length, only this metering is used by DSLR cameras to measure light, which is relatively more subtle than measuring the length.Metering is used to measure the light seen by the camera (light coming into the lens). When we look at a photo object through the camera viewfinder, the light conditions in the object will be measured by the metering system. The main purpose of the camera metering system is to produce a photo that fits its exposure (read again concept exposure). Metering does this by analyzing the light darkness of a photograph object and then determining the amount of shutter speed, aperture and ISO so that the results of your photo fit, not too dark or not too bright.Hmm his dizziness .... Okay, so like this. Imagine your eyes. When you feel the glare of what you do? Squinting eyes instead! You unconsciously reduce the amount of light coming into your eyes so you do not glare (not too bright). Conversely, when you feel the light is too dim you automatically open your eyes wide. Squint your eyes or open your eyes wide so your eyes feel comfortable when you see (the right exposure), that's the job of camera metering system.

 How Camera Metering System Works & Weaknesses

When the camera sees the wall, the metering system will measure the amount of light (the darkness of the light) reflected by the wall (reflective). This is easy when all photo objects reflect the same amount of light.Fuss, in real world each object has a different level of reflection. When we take pictures of the sky, if the sky is perfectly blue the camera's metering will be easy to calculate exposure because there is only one bright level to calculate (blue). But when we shoot the sky with the addition of white clouds, metering must now discourage bright blue sky and bright white clouds and should strive to produce optimal exposure. Now add mountains and rows of trees into the photo object above, then the level of complexity metering gets complicated.How do the camera metering system designers anticipate this situation? The answer is to try to make the average light dark level of an object of any photo. Technically the average light dark for the camera metering system is 18% gray (18% gray or normal gray) - not too dark and not too bright - see photo below. A photo object with a reflection level of light that has a bright, complex darkness will be "domesticated" in this way.18% -abu-grayThis solution in general can indeed be used to take pictures of normal conditions. But when we are faced with the conditions for example you will photograph the face of friends with a perfect white background, the camera will make your friend's face darker because it should anticipate the white background and bring it towards the 18% gray aka underexposed. Or for example when you take a photo of a flower inside a small glass glass placed on a black tablecloth, the flower photo will be brighter than the original because it must bring the black tablecloth to 18% gray alias overexposed.

Then We Should How?

Just as we can not continuously use auto exposure, to produce great photos we can not use the camera metering system without some tricks (leave it in the default position). To be more clear, please read some metering modes that can help us anticipate the weakness of this metering system.