In this age of digital photography with our built-in light meters and histograms, why would anyone want a separate light meter?
The main reason is an incident light meter like a Sekonic L-358 (highly recommended), which reads the light falling on its hemisphere as opposed to your reflected light meter built into your camera which reads the light reflected off your subject, can create more accurate exposures.
Why should I care about more accurate exposures when we can shoot in RAW and manipulate our exposes by four stops of light or so in software?
It’s all got to do with the dynamic range of your digital camera’s sensors.
You’re going to read numbers that differ from mine but the principle is the same. If you miss your exposure when shooting digital your camera will be much less forgiving than film.
The human eye can see about 20 stops of light from absolute black to pure white. A great film camera can record about 10 stops and a digital camera records around 5 or 6 stops.
What that means is your digital camera has to record all the graduations in light to be found in the image in only five or six stops.
So if you miss your exposure by a stop to two and you clip either your highlights or shadows they’re gone and software isn’t going to bring them back. This is why amateur cameras have tons of software fixes like Nikon’s D-Lighting which underexposes your image slightly (to avoid clipping highlights) and then rebuilds them in using software settings. It works, and works well, but doesn’t beat getting the exposure right in the first place.
How about using the histogram that appears in your camera’s replay window?
It’s a great tool but not many photographers use it. The histogram shows whether or not your exposure is clipping but it doesn’t give numbers like f-stops or shutter speeds in the same way a light meter does. That’s where your separate meter comes into play.
Exposure is made up of the speed of the film you’re using (now it’s the speed of the digital sensor) in units called ISO. The aperture or size of the opening of your lens (fast lenses that can open to f/1.8 or more create images with shallow depth of field which is what is often wanted in portrait work) can be pre-set in the light meter which will then take the desired ISO to determine the correct shutter speed. You can do the same thing when setting the ISO and shutter speed to get the correct aperture for a more perfect exposure.
Finally when it comes to dynamic range full-frame sensors are better than DX-format sensors and way better than point-and-shoot sensors which can be as small as the size of your fingernail. Full-size sensor camera cost around $3,000 and up just for the body but yield images which have greater dynamic range, less noise in the image and can use higher ISO settings for shooting in less light than other cameras (ideal for wedding photographers). True full-frame camera sensors also capture more megapixels but this isn’t a major concern as just about any camera that has a sensor of 8 megapixels or greater will produce great images in sizes approaching 16″X20″.
You’ll hear a lot of nonsense out there comparing full-frame to DX sensors.
Here’s what it comes down to: For 99.99% of all photography a decent point and shoot is terrific. A step up to a micro four-thirds (Olympus Pens and others) or a Sony APS-C format will allow for more creative photography and better images under more difficult conditions. All of these are light enough to carry around all day.
A decent DX-format camera (think top-end Canon Rebels or Nikon D-7000 or D-90) will shoot everything perfectly well including sports, landscapes, weddings, kids when matched with faster lenses. Most photographers will never need anything better or even be able to notice the difference between these images and those shot on full-frame cameras.
Finally we come back to full-frame. Remember back in the good ole days of film? Wedding photographers traditionally used 2 1/4 cameras such as Rollies and Hasselblads.
A 2 1/4″ by 2 1/4″ piece of film captured a lot of dynamic range. Images shot on these cameras looked way better than images shot on 35mm film cameras and just blow away anything shot on digital. (And again this is why there are many many producers of plug-in filters, pre-sets and editors for Lightroom and Photoshop. We keep trying to recapture the look of large-format film cameras.)
Funny thing about large format cameras. Most of them didn’t have a built-in light meter. You had to go out and buy a separate light meter! Funny thing what?