What's the difference between my camera's light meter and an external one?

I've noticed a bunch of threads on light meters. I don't understand why I would need one. I assume there is some benefit over the light meter in my camera, but I'm not sure what those benefits are.

And if an external light meter is better, it begs the question why isn't that technology IN my camera to begin with?

the camera measures the light that reflects off the subject, the meter measures the light hitting the subject.

Most the time you get a better exposure and it is an absolute must for studios, in my opinion.

Viva-photography wrote in post #10687782
the camera measures the light that reflects off the subject, the meter measures the light hitting the subject.

Most the time you get a better exposure and it is an absolute must for studios, in my opinion.

Wow, your first sentence was concise and amazingly effective. Very helpful, thanks.

I wonder how many people use meters and in what sorts of situations. You mentioned studios, are they very useful for outdoor shooting?

You still need to interpret the readings. I find that if you are protecting from blowing out whites, then go by the incident readings. If there are no whites you can usually expose +1 stop over the readings without issue, often more.

Additionally, if you want to meter flash or lighting ratios you need an incident meter.

2 kinds of hand held meters. 1 measures reflected light; the other measures incident light. Sometimes they're combined in 1 instrument. I have a Luna6 Pro that does this. Used it extensively with a rangefinder camera that did not have a light meter. It had a spot meter attachment too. At that time in-camera meters weren't all that sophisticated. They are now.

The incident light meter you place at the position of the subject, normally, and face the camera. Really useful for studio photography where you may be in front of the camera tidying up the scene anyway. Another use? doing landscape photography, if the light is uniformly distributed (same where you are as the subject), you turn around and take a light meter reading. Very good in my case for skiing photos.

So a reflected light meter, you point at the subject and take a reading, or even series of readings.
An incident light meter you point towards the camera from the subject's position.
I found that I learned a lot about light using a handheld meter. It was a really valuable experience.

Generalizing, a handheld meter is specially good for studio work.