April 4, 2011

Measurebators and the Historgram

Filed under: 20-minute,photography,skills — Mark Dalrymple @ 9:07 pm
Tags: , ,

Bork portrait

The Grid Live is a new live videocast from the Kelby empire of photography and photoshop training. It’s a neat show with a nice format, easily my favorite of the Kelby TV shows. It’s a simple format, two or three guys talk for an hour on one or two topics. And that’s it. Kind of like Photoshop User TV crossed with DTown but without the obligatory software tutorials. It’s even more fun because they always have sound syncing issues, so it’s like watching a Kung Fu or a Godzilla movie.

Today’s program talked about “measurebators”, the folks who get off on the technology of photography, generally ignoring the artistic side. I have those genes in my lineage, having witnessed my dad use a transmission densitometer on samples of 4×5 film to determine the proper base fog density marklar involved in N+1 zone system weirdness I totally do not understand. My dad also took kick-ass photographs.

One part of today’s show was spent harping about histograms. A histogram is a chart that shows how much of the image is at a certain brightness. A histogram clustered to the left side is pretty dark, a histogram clustered to the right side is pretty light, and a histogram clustered in the middle is gray.

It’s possible to get too enamored with your histogram. Matt K was saying how someone asked him at a training session “what is the perfect histogram”, which of course is a nonsensical question. Low-key photos will have radically different histograms than high-key photos.

Many photographers never look at the histogram, saying “I just look at the blinkies”, which the highlight warnings that flash at you if you exceed the amount of light your sensor can handler. If you looked at the histogram with a blinky scene you’ll see it butted up against the right side.

The blinkies are great. I use them all the time. I also use the histogram. It is very convenient, being only one click away on my camera’s selector. I mainly use it to make sure I’m notxposing a scene. As I mentioned earlier in Your Camera Lies To You, the LCD screen in a dark environment can make a photo look great, and then you go home to process it and it’s a stop or two underexposed. The blinkies will not help you in this case. You can happily shoot and chimp and come home to a mess to process. Sometimes when I’m shooting in manual mode, I forgot to check in with my exposure meter and use inappropriate settings. Again, chimping might not clue you in to an underexposure situation.

Case in point, when I shoot the local Hometown Christmas production I frequently check the histogram because the theater is dark and the lighting conditions change constantly.

Related to all of this is a school of exposure called “Expose to the Right”, or ETTR for those who like unpronounceable acronyms. Basically you try to overexposure your scene just enough where you don’t exceed the capacity of the sensor, but not going over. The histogram is vital in getting this perfect exposure. In post processing you pull the exposure back to where it should be. This concentrates the image’s pixels in the upper (brighter) end of the histogram, which has more granularity than the darker end due to there being more bits available. I use ETTR if I’m doing slow-shooting photography, arty or landscape stuff. If I’m shooting 800 frames documenting behind the scenes of a fast-paced video production department (like I did last weekend), then for my own post-processing sanity I wouldn’t use ETTR.

The take-away? Learn to use the histogram, but don’t be a slave to it. Check in on it every now and then like an old friend. On many shoots I never look at it. I do check-in on my histogram if I’m shooting indoors or somewhere that it is dark, or if I’m running purely in manual mode and I might have forgotten to check my exposure.

1 Comment »

  1. Well said. I also have a problem with the flippancy of the discussion on the GRID. In landscape photography the Histogram as you say is essential, I don’t trust the screen image. Also in landscape I also watch for the blinkies, as those fluffy white clouds can (and do) reflect a lot of light and can be a bugger (but not impossible) in post. In these situations I try to take a number of exposures (not quite HDR but…)some to lighten up the ground and some to darken the sky then either blend or just clone in the clouds with the correct exposure.

    Comment by Michael Harris — April 5, 2011 @ 3:09 pm | Reply

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