Is a dedicated light meter worth it for digital photography? The internet is full of divergent viewpoints on this question: some professionals declare yes with categorical certainty, while others say no way now that digital technology has blessed us photographers with the ability to ‘chimp’ our work on the spot and view histograms. Well, after scouring the internet for answers and still feeling left in the dark about the matter, I’ve decided to put a well-regarded meter on the spot to expose some light on the situation for me and the World Wide Web. So, without further ado, this blog entry attempts to assess whether there’s a difference between my camera’s internal light meter and an external third party light meter.
My working hypothesis: All things being equal, I would imagine a dedicated ambient light meter to be more accurate in establishing the ‘true’ exposure value for a given situation than my camera’s internal reflective light meter. My findings after a few hours of first time testing: Ummm, it really does depend, blink!
For this match we have my Canon 5D Mark II camera sitting comfortably in one corner – a proven heavy weight by any standard – and in the other corner my new and unproven lightweight Sekonic Flash Master L-358 Digital Meter clocking in at 153 grams. To help keep the comparisons fair I’ve set my camera on a stable Manfrotto 0555XPROB tripod, and photographed my subjects outdoors under an overcast sky, which provided a natural source of consistent, steady, and diffused ambient light.
To begin the test I powered up my camera and geared it into “AV” mode to see what my camera would automatically suggest is a balanced exposure and correct shutter speed for a specified aperture and ISO value. Then, immediately after taking my picture in “AV” mode, I geared my camera into “M” mode – the mode I almost always shoot in, and jumped over to my subject to use my Sekonic L-358 to capture an ambient exposure reading at the same place of focus I had used in the AV mode. To my great excitement, my L-358 quickly advised me that I should be using a different shutter speed value than the one suggested to me by my camera. So, after I manually plugged and chugged the new settings into my camera, the following pictures proved to be the comparative result…
As you can see, the Sekonic Flash Master L-358 came out swinging right off the bell by quickly blacking out the eye of my 5D Mark II with a few left hooks. But, as any good Rocky movie will attest, never count out a fighter. After I decided to slap on my polarizer lens – a lens filter I almost always use outdoors – my light fight for the all-time sensor title took a full 180, and the reflective meter in my 5D Mark II bounced back big time to pummel the Sekonic L-358 readings into the ground. It was actually so bad at one point, I had said to myself – “there’s just no way those shutter speed values are going to work out better for me than the suggested values given by my camera under AV mode” which I had known to be near true given my experience. Needing instant feedback, I then ‘chimped’ my historgram to confirm my thoughts. And, as you can see, when a lens is sporting a polarizer filter (and I would imagine any other type of filter such as a neutral-density filter) it could be a losing battle to meter with a third party device when not taking such things into account. I do understand why there was a difference with my polarizer on, but my manually not taking into account the couple of stops of light my camera’s sensor experiences from having that filter on was not intuitive, nor something I’d appreciate needing to calculate every time I run a L-358 reading outdoors with that kind of filter on. As my Calculus teacher use to say: Close is only good for grenades Jeff (and now I might add Lightroom…LOL), but after my viewing the shutter readings I obtained from between two different sensors I can confidently state that they were not always close, so there is something going on – leaving me quietly contemplative about whether to declare a light meter as worth it, or at least needing to specify under what conditions they are worth it. Well, that’s it for now, but tune in soon for the next sensor light fight when I pit my Canon 580 EX IIs against each other in a battle over E-TTL Flash vs Manual Flash metering using my Sekonic L-358.