The Curious Case Of The Blown Out Chicken

So after all that work to educate myself on using the live histogram on the LCD panel on the back of my G12, apparently there are exceptions to every rule. If you read my previous post, you will know that the G12 offers three different tools to help you decide whether or not the photograph you are about to take is properly exposed. First would be the LCD panel itself. While using the panel to compose the picture works beautifully, I've discovered that the image that appears on the panel looks way brighter than when I look at it on the computer in GIMP. Panel out.

The second method to judge the correctness of the exposure that I use in Manual mode is the exposure value indicator. This is a scale that runs from -2 stops to +2 stops and has a little marker that moves up and down and you change the exposure options. Until I discovered the power of the histogram, I would routinely adjust the shutter speed until the little marker landed on zero. I assumed this meant I had a properly exposed photo. In good light? Yes. In poor light? Absolutely not.

Through the suggestion of some on-line friends, I discovered the third, and best option, the histogram. Essentially a graph of all light in the photograph from dark to light, I noted that as I lengthened the shutter speed to let in more light, I would systematically drive the graph to the right. I would essentially do this until I had a nice even spread across the entire range. Suddenly, my low light photos started looking really good. I still had to adjust them in post processing, but only a little bit instead of huge swaths of lightening.

So imagine my surprise when I took a picture of my Thai Market Salad at Market Gourmet at Montrose (check out the food blog if you want more info) and when I got around to actually examining the photo on my netbook, I discovered something a little bit disconcerting:


This is generally a good photo. What surprised me was how blown out some of the sides of the chicken cubes looked. Okay, let's check the histogram:


A nice distribution to be sure, but I haven't even pushed the graph all the way to the right. I tried applying a High Pass filter to sharpen up the photo thinking that might bring out some of the detail and while it did improve the photograph overall, the detail still remained hidden. I even tried darkening the photo a bit, but that was a bust, too.

In an effort to understand, I returned the very next day (today, in fact) and decided to not only order the exact same salad again, but fortunately, the exact same table next to the window was available from yesterday's lunch. In fact, after setting the ISO to 100 and the f/stop to 8.0, the shutter speed for the first exposure was set to 1/3 of a second, just like the exposure I took the day before. Of course, the salad looked slightly different, but that's okay. I took four sets of exposures, driven at first by the histogram and then gradually backed down in order to hopefully expose more of the detail with an underexposed photograph.

The first set of exposures, I pushed the histogram. And it showed in the resulting pictures. They were too exposed. The second set were better:


Here was the histogram for this picture:


A nice distribution. Maybe pushing it a bit on the right hand side. The photo reveals definite loss of detail on the cut chicken pieces.

Fine. Dial down the shutter speed slightly. Here was what resulted:


More detail on the chicken, slightly darker exposure. Here's the histogram:


Now we're just barely hitting the right edge of the histogram. But things look better. Note that the exposure value indicator was just above the "0" mark for this one. Of the three, I think this one was the best compromise between driving the exposure using the histogram and what I saw on the screen.

Just for extra options, I shortened the shutter speed one more notch and took another photo:


This one came in right at "0" at the exposure value indicator, which is where I used to shoot at. I would've considered this a "proper exposure" about two months ago, but now I know to push it a bit on the G12. Here is the histogram for this photo:


Looking at the histogram, it looks fairly underexposed (you should know that I'm adjusting the shutter speed 1/3 of a stop at a time, so there isn't a dramatic difference in the resulting photographs). While there is the most amount of detail in the chicken, the rest of the photograph looks too dark.

In the end, I would probably end up going with the second photograph that I took today as the "hero" shot. Even though the histogram indicated that I could've pushed it farther to the right, real world examination of the photograph dictated that it was a good balance between proper exposure and overexposure.

For the purposes of disclosure, the first day I shot simply with a UV filter. The second day, thinking that polarized light might be an issue, I used both my UV filter and my polarized light filter, which did help the images out, in fact. All images, on both days, were shot on a tripod with an ISO of 100, f/stop of 8.0, and varying lengths of shutter speed. Each image was "sharpened" using a high pass filter with a value of 10 ... just to keep it all equal.

I guess the moral to the story is that rules are great, until they need to be broken. A rule that seems to be particularly valuable is to take your exposures at multiple shutter speeds. The brightest one (based on the histogram) might not be the best one.