Why would anyone waste money on a light meter? It is a fair assessment that most photographers, including very serious ones, can get by without an external light meter. When I say external, it is to differentiate between a handheld meter and the one in your camera.
I seldom rely on a handheld light meter, especially in my studio. However, I still use a light meter in unfamiliar situations. My LCD does not tell me how much something is over/under exposed. The preview image on my camera’s LCD does not tell me the value of each small area of the scene I am interested in. Also, the LCD is not going to tell me when my edge lights are ¼ stop brighter than I intended. The LCD gets me close, but in loading the RAW file after a shoot, I sometimes end up with scenes I wished I had metered more carefully. A ¼ stop might not make much difference in most cases, where you can just selectively dodge and burn. But what about the unintended consequences of spot-exposure adjustments in post-processing, such as loss of subtle texture? Suffice to say, you need to be rather nit-picky about your results to worry about such things, and feel the need to meter.
Some people put a thermometer in beer before they drink it. I have often wondered what is wrong with them. Can’t they tell if they like the beer without having to take its temperature first? This may be the way some people view those of us who use a light meter. Why don’t we just look at the three-and-a-half-inch LCD for two seconds to determine if we like what we see? After all, the LCD displays almost a full megapixel of information. And, if we are worried about the fact that the screen image looks differently based on the ambient light, there is always the histogram.
Unfortunately, the histogram only tells you about the scene in aggregate, not what each light is doing. The LCD really is too small to see what highlight or shadow texture in hair or skin is going to look like when the final image goes to print. The light meter helps me to know what each light is doing across the entire scene, not just the net affect for a single pose within the model zone. The truth is, I usually rely on my LCD and some experimentation to get the light right.
For most people, a handheld meter is overkill. If your images are only destined for a web page, few people may even notice the difference, much less care. If you have strong ideas that produce passionate images, then the nuanced trade-offs between a metered work flow and a non-metered workflow may cancel each other out.
But, I do not anticipate getting rid of my meter. I use a light meter when I am trying a new light setup. This is especially useful before the model arrives. If I do not have enough power to blast through the diffusion material on a new softbox, I do not want to waste time hauling out more power packs during shooting time. If I get a new light, new modifier, an extension cable, or anything else that will affect power output, I use my meter to learn what the net effect is. Basically, any time I am at a loss for knowledge, I seek the most detailed information I can find. When it comes to light output, only my handheld meter can give me that.
So, just as I do not check my body temperature every day to make sure it is still a healthy 98.6 F (37 C), I do not need a light meter when I already know approximately what is going on with the light.
So, I am still waiting for the total phase-out of the light meter, especially the spot meter. Is the “spot-histogram” around the corner? That would be a feature I would use.
Maybe I am a dinosaur, clinging to the tools I loved when I shot and developed film and used flash powder to illuminate the scene. Heck, I still own oil paints; everyone knows that oil painting is a useless technology now that we have photography, right?
A light meter was useful in getting the effect I wanted