LX7 - histogram inaccuracy - seeing red

Started Feb 19, 2013 | Discussions thread
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James Pilcher Veteran Member • Posts: 8,742
LX7 - histogram inaccuracy - seeing red

In response to a question in my thread about LX7 manual mode histograms, I wandered out at lunch today to run a few tests. Forum member pannayar suggested that he is seeing instances where the live view histogram does not match the histogram in the final image. He is having to check the captured image to be sure he captured what he wanted. Well, I have a few comments:

I ran a series of tests against average and bright/high-contrast subjects. I put my LX7 in A mode, Natural setting with no adjustments to contrast, color, etc. I was going to also test M, P, and S modes, but I determined it was not necessary, as you will read below. I set my camera on a tripod, metered the scene using the histogram, and snapped a photo. Then I looked at the resulting image in review mode. By repeatedly pressing the review mode button I was able to toggle back and forth between the live histogram and the captured histogram.

In every case, with a well-exposed image, the live histogram and captured histogram were identical. Subject matter did not make any difference. These results reinforce my methodology to use the histogram as my exposure meter.

BUT, I started playing around the edges of maximum aperture and minimum shutter speed. I discovered that when the aperture/shutter numbers on the LCD turn red, which means a proper exposure is not possible at these settings, the histogram reverts to whatever. One might expect the histogram to just move far right in the case of impending overexposure. It does not. I have no idea what it is showing me. Before you snap the image, the only quick indicator that the live view histogram and captured image histogram will not match is that the aperture/shutter numbers on the LCD have turned red.

I believe I will see similar behavior in M and S modes. In P mode, I might be able to duplicate the mis-matched histograms if I apply excessive exposure compensation, but I never use P, so that investigation does not interest me.

I had noticed some odd histograms in Lightroom when processing my LX7 images. When I first looked at them, I immediately knew I would never have exposed an image with a histogram that presented that way. I went back and looked at a few of those files just now. Sure enough, either the maximum aperture for the focal length or minimum shutter speed showed up in the image EXIF. I had made a mistake that the live view histogram did not warn against.

So, if you use your histogram as your exposure meter, be sure to keep an eye on the color of the aperture/shutter numbers. It makes a difference. You just might see red.

Jim Pilcher
Summit County, Colorado, USA

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