Digital Exposure Exposed
Film and digital photography have just enough things in common to lull you into a false sense of familiarity. Basic exposure rules still apply like they did with film, but just like different film stocks had their own exposure rules, digital chips have their own special requirements. Shooting digital is closer to the way we used to shoot 400 speed Tri-x rated at 200-250 ISO. By doing this you effectively lowered the ISO by one stop to open up the shadows and add a little punch to the negative. If you wanted to you could have shot it rated at 400 and get acceptable results but for an optimal negative you rated it slower.
Digital works pretty much the same way. Just because the chip says it is 100 ISO doesn’t mean that your meter should be set to 100 and off you go. First you have to deal with signal to noise ratio. One of the best written articles about how a digital chip works is Expose to the Right> on Luminous Landscape by Michael Richmann.
At Image Mechanics, the way we do it is to expose so that the important highlight detail is walking the edge of being blown out and then process it back down to the desired look. The histogram is a good tool that gives you a feel for overall exposure but it can only tell you that something is blown or clipped, not whether it is important detail that you want to hold in your image. To visually check what is blown or clipped, we use the shadow/highlight exposure warning in Adobe Camera Raw or Lightroom.
The triangles located in the histogram toggle the Highlight & Shadow warnings
The red on Ken’s face shows what highlight details are blown out
This allows us to capture a great digital file, not just one that looks right on the monitor. Using the monitor to judge an image is a great way to be a photographer if the only place your image will ever be viewed is on a monitor. Just because it looks like your intent on screen doesn’t mean it will make a great print. Exposing for the important highlights and processing down the darks is how to achieve a great image file for a great print.
On set we usually ask the photographer or assistant to set their meters at 50 instead of 100 so that we will be in the ballpark for optimal exposure. Often a photographer will under expose to get a dark and moody look on the screen. When they achieve the look they are after, we ask them to raise all the ratio’s by one stop. Skeptically, they accommodate our exposure request, half expecting to not like the end results. Once we use the powerful processing tools in ACR to take the image back to their intent, with significantly less noise in the file, they are happy with the results.
Recently a photographer used us for the first time and was shocked at how “off” he was from his normal exposure. Once we showed him why we expose that way and the resulting noise reduction he was shocked. He was mostly surprised that his digital tech of several years did not know how to get him the best digital file!
This made us start looking at the metering process as a whole which lead us to an impromptu metering test. See Frank’s article Meter Me This. It also prompted me to create this new exposure category for our blog and get off my ass and publish some articles.
Look for a future article where we test the new Sekonic 758 DR meter. It has been hanging around our studio just waiting for someone to review it. It seemed overly complicated and not necessary when we use the ACR/Lightroom’s highlight/shadow warnings to judge exposure. After the test, we have a new found respect for being able to dial in the meter for each digital chip for optimal exposure readings.
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