Sekonic L-758DR DigitalMaster:
‘Finally Something New Under the Sun’
Or why Sekonic’s L-758DR Digitalmaster is a step ahead of every light meter you currently own.
by Allan Weitz

So Who Needs a New Light Meter?

There’s nothing new about hand-held light meters. They’ve been around for quite sometime, and there are more than a few meters on the market capable of taking dead-nuts accurate exposure readings. As for the meter built into your camera? It too is quite accurate – in Spot, Center-weighted, and Matrix no less. So the question is…who needs yet another meter?

The answer to this question is a two-parter. The answer to the first part of the equation is 'yes' – the meters you currently own are terrific. Light is light, and most all light meters do a fine job converting light values into f-stops and shutter speeds.

The second part of the equation is where it starts getting squirrelly, and it has nothing to do with the accuracy of your meter. It has to do with the light gathering characteristics – i.e. the accuracy - of the imaging sensor in your camera.

Truth be told, no two digital cameras respond to light the same way. The sensor in your camera is one of dozens of smaller sections cut from a larger sheet - or wafer – that in spite of carefully monitored manufacturing procedures, varies in sensitivity levels across the length and width of its surface. 

The end result is that the specified sensitivity levels of the sensor in your particular camera may or may not jive with the numbers touted on the manufacturer’s website. According to a knowledgeable product manager of a major camera manufacturer, a variance of plus/minus 1/2 stop is considered acceptable for consumer DSLRs. (Case in point - Three ‘identical’ pro-quality DSLRs tested for this article differed in ISO ratings, dynamic range, and clipping points).

The point is that just as it’s imperative to profile and calibrate your computer monitor, your scanner, and your printer to a common standard, it makes equal sense to profile and identify the true dynamic range parameters of your camera’s sensor. And this is where the Sekonic L-758DR Digitalmaster is a step ahead of every light meter you currently own.

Film and Digital Capture - They’re Different Yet the Same

Every film stock has a look and feel of its own. Some films render color neutrally while other films render the same light in a warmer or cooler palate. And as every seasoned pro can tell you, these tonal characteristics vary emulsion to emulsion. Same goes for ISO ratings. They too vary. The ISO number on the box might say 100, but the film inside the box may be closer to 80, or perhaps 125. In a nutshell, not all film emulsions are created equal, and this is why pros test every new film emulsion before going out on a job. (It’s also why they stock their freezers when they find an emulsion that’s true to spec.)

So here’s the punch line - digital imaging sensors are the same. Just as films possess differing color and tonal characteristics, so do CCD and CMOS sensors. And just as film stocks vary emulsion to emulsion in terms of color rendition and light sensitivity, so do imaging sensors. To sum it up, imaging sensors - like film - vary in dynamic range, as well as at which points they start blowing out highlights and clogging up shadow details.

What the Meter Says vs. What Your Sensor Says

Sekonic’s Exposure Profile Target enables you to determine the precise ISO rating and dynamic range parameters of your particular camera. Once the sensitivity levels of your camera’s sensor are established and stored in the L-758DR light meter, your exposures will be finer tuned.  A pre-exposure warning signal alerts you when you exceed the highlights and shadow detail range. As a bonus you’ll be spending far less time ‘fixing things’ in Photoshop.

A Few Pointers about Profiling Your Camera’s Imaging Sensor 

Note- To profile your camera sensor you will need to purchase the optional Sekonic Exposure Profile Target (cat# 401-759), which is available from your Sekonic dealer.

Before creating a profile it is important to create a Custom White Balance of your camera sensor under the same lighting conditions you plan on profile testing. The Custom White Balance procedure is a function of your camera and should be performed according to the instructions in your camera’s manual. The solid grey side of the Sekonic Exposure Profile Target can be used for this part of the process. Creating a Custom White Balance should be a matter of habit regardless of your shooting preferences as your camera’s pre-sets – including Auto White Balance – are often not as precise as the parameters established in a Custom setting.

Separate profiles should be created for ambient and electronic flash as your camera sensor reacts differently to each of these light sources (The meter can store up to 3 camera profiles). When creating profiles for electronic flash it's important to use the same reflectors, umbrellas, and/or soft boxes you normally shoot with to further minimize the variables.

The actual test procedure is a fairly easy chore. It entails photographing the patch side (‘A’ side) of the Sekonic Exposure Profile Target (make sure you light it evenly!), which contains a series of grey patches in 1/6th-stop increments. The target should be photographed +/- 5-stops in full-stop increments, for a total of eleven exposures (if the lens aperture range permits). If you are calibrating a 35mm-based DSLR under ambient conditions, stop the lens down about 3-stops from the widest aperture and bracket your exposures using the camera’s shutter speeds. If you are profiling electronic flash set the lens to about f/8 (allowing for 5-stops over and under the ‘correct’ exposure) and bracket via f-stops. Make sure your strobes are fully recycled before each exposure to ensure uniform exposure times.

In addition to running a profile test at the camera’s native ISO rating you should also test an additional profile at a different ISO rating (i.e. ISO 100 and 400). By entering exposure profiles of two separate ISO ratings into Sekonic’s Data Transfer Software, the software automatically calculates correct exposure parameters for all ISO sensitivities from 3 to 8000.

The Sekonic L-758DR allows you to perform these tests in a choice of four modes – Flash Incident, Ambient Incident, Flash Reflected, and Ambient Reflected. Ambient exposures are recorded using the meter’s lumisphere, which can be extended for 180-degree readings, or retracted for analyzing narrower, flat-field portions of the image. Reflected readings are recorded using the L-758DR’s 1-degree spot meter, and should be read the off center grey patch on the Exposure Profile Target.

The next step is to open the resulting image files in Photoshop, set the eyedropper tool to an area of 25 (5x5) pixels, and locate the patch closest to 18% (medium) grey in the green channel (118G). A variance of +/- 2 is acceptable. Once you determine the patch closest to medium grey you next determine the dynamic range parameters and clipping points of highlights and shadows by sampling the various test patches.

After launching Sekonic’s Data Transfer Software (Mac or PC, included with meter), select which camera profile and exposure mode you tested the camera for. Then select the test ISO and open the data enter menu. Enter the results of your profile tests using the dropdown-style data boxes.  When you are finished entering all relevant data, click on ‘Calculate’, followed by ‘OK’. You now have a custom profile of your camera’s imaging sensor.

Using the supplied USB cable you can now upload the new profile data from your computer to your L-758DR meter. Up to three separate camera exposure profiles (Camera 1, Camera 2, Camera 3) can be stored in the L-758DR for instant recall. When using these profiles the meter automatically adjusts profile parameters based on your choice of exposure mode  - i.e. Ambient, Flash, Incident, or Reflected, at any ISO rating you set it for.

As previously mentioned separate tests should be performed for flash and ambient, as well as reflected or incident readings, as results of each mode may vary. You should also make sure your camera is operating on the latest firmware as upgrades often include tweaking of color management and/or meter sensitivities.

The good news is that while film shooters must test each and every new emulsion of film they purchase, with digital you only have to run one set of profiling tests for each camera and you’re good to go. At the end of the day your image files should prove to be truer-to-life and require far less post-production diddling. Do imaging sensors change over time? Yes they do, but by the time you’d start noticing serious tonal shifts you will have long retired the camera and moved on to newer technologies, maybe even Florida.

It would be wrong to leave out one additional, yet crucial factor, that figures into the equation when determining a ‘correct’ exposure, and that is our eye. The point is that the ‘correct’ exposure as indicated by your light meter is not necessarily the best exposure for the mood and feel of any given photograph. Some photographs look better slightly over-exposed, others slightly under. The image itself defines the correct light value and it’s your job as the photographer to decide where that point lies. The key is to know the starting point, specifically knowing where your camera’s true native ISO lies along with knowing where you start loosing highlights and shadows. Only when these parameters have been established can you truly begin to accurately interpret the tonal values of an image. Otherwise you're only guessing.

So do you need a new light meter? You tell us.
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