Education

Understanding Your Camera’s Histogram

February 25, 20122 Comments

Understanding Your DSLR Histogram

You don’t need to be a camera guru to understand the histogram on your digital camera. It only means that you need to learn more about your camera and its features.  To get an optimum exposure and not lose any data, it is important to interpret your digital camera’s histogram to comprehend what it means and make the appropriate exposure adjustments.

What does the graph mean?

Well, what is a digital camera histogram and what do you do with it?  This would be a great time to pull the manual out for your digital camera and learn how to display the histogram on the camera’s LCD display.  On most digital cameras the histogram can be enabled so it displays every time you take a photo.  To explain it briefly, it is a graph that shows the level of brightness of an image from the very darkest levels on the left (value 0) to the very brightest on the right (value 255), on the horizontal axis.  Camera HistogramThe graph’s height, vertical axis, is the measure of the density of image pixels of a particular tonal value.   The taller the graph for a particular tonal value the more shades of that tone will display in the photo. As you can see from the histogram on the left, there are a lot of pixels between the mid-tones and highlights.   This is a histogram from a photo of Badwater in Death Valley which because of the bright sodium deposits most of the pixels will be somewhere between the mid-tones in the center and the highlights.

Camera RGB HistogramSome histograms also display separate graphs for the level of brightness and pixel density for the three primary colors- Red, Green and Blue (RGB).  The histogram also displays in many photo editing software programs including Adobe Photoshop, Lightroom and Aperture, among others.

 

Now that you have a better understanding of your digital camera’s histogram, we can move on to how you evaluate the exposure of a photograph.  After you’ve taken a photo and you are viewing the graph on your LCD display, ideally you want to see most of the graph’s pixel density between the left and right brackets. Continue Reading »

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Panoramas

July 21, 20090 Comments

Certain places just beg to be reproduced panoramically.    You just can’t do some scenes justice with a normal single frame photograph.  I’ve always been interested in panoramas, something about them mesmerizes me.  I guess it makes me feel like I’m experiencing the scene like I did when I was there.

There are a number of methods for taking the shots and probably just as many more methods of stitching the photos together.

You can take panoramas handheld, with a level tripod or with a special tripod head designed specifically for panorama photography.  Nodal Ninja and Really Right Stuff both make panorama heads and I’m sure there are numerous others.  These can be expensive, as with most camera equipment, but produce superb results.  The advantage is the camera can be set up perfectly level and the nodal point, optical center of the lens, can be set.  The Really Right Stuff site has a good explanation (http://reallyrightstuff.com/pano/05.html).  Currently, I take my panoramas with a tripod and a hot shoe bubble level, it seems to work fairly well, but I will eventually purchase one of the panorama heads.

I’ve used several panorama stitching software applications including PTGui and Photoshop.  My favorite is a free program developed by Microsoft Research named Microsoft ICE (Image Composite Editor).  You can download the program at he Microsoft Research site (http://research.microsoft.com/en-us/um/redmond/groups/ivm/ICE/). I recently used this program to stitch together a handheld panorama of Lake Powell down in Arizona.  The panorama was a total of 6 photos, 2 rows of 3.   I took the pictures fairly quickly as we were about to head back into town.  I didn’t really think it would turn out as well as it did.  As a test of ICE I renamed each photo and opened them out of order just to see if the program could figure out which photo went where.  A couple of minutes of processing later and out came a perfect panorama.

You can see a larger version here.

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Until next time!

Jim

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