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Posts Tagged ‘contrast’

Understanding the basic concepts of histograms is all well and good, but what do histograms tell photographers about their images and how are they used in the field? As noted in part one, this series of posts shares some excellent material from Varina and Jay Patel’s ebook, entitled “What the heck is a HISTOGRAM?”  For a more detailed discussion, I recommend this ebook. It’s excellent!

To answer that question requires understanding what “you can learn from a quick look at the graph. First, overall width of the histogram gives you some information about the contrast and dynamic range of your image…A low-contrast image will have a narrow histogram. That means a narrow dynamic range as well. Conversely, a broader dynamic range will results in a wider histogram – and an image with greater overall contrast.” This same concept applies to the three different areas of a histogram: shadows, highlights and mid-tones.

A quick aside: “Dynamic range” is another term that is used a lot in photography, but is often not defined very well. According to Sean McHugh, who pens the Cambridge in Color blog (another excellent resource), “Dynamic range in photography describes the ratio between the maximum and minimum measurable light intensities (white and black, respectively)…[In other words, in] a real-world scene [dynamic range] is simply the ratio between lightest and darkest regions (contrast ratio).” That’s not to say the concept of dynamic range is a one size fits all.  Printers, scanners and digital cameras have different dynamic ranges, as do different models within those groups. For an in-depth discussion of dynamic range and how it applies to digital photography, see Sean’s post Dynamic Range in Digital Photography

Back to histograms. With respect to exposure, “over exposure shifts the histogram to the right, and under exposure shifts it to the left.” Another indication of over or under exposure is if the bars bunch up or spike against the walls of the histogram. As noted in part one, this means there is a loss of detail in the shadows or blown-out highlights.

Remember that no one histogram is correct. “The idea is to match the shape and width of the histogram to the scene.” This is particularly useful in the field, because “on many cameras, the brightness of the LCD monitor on the back of your camera is affected by ambient light…[so] it may not accurately represent the true exposure of your photograph. The histogram provides much more accurate information.”

Consider the histogram below:

Histograms Image 12 RGB

There is a peak in the area straddling the mid-tonal and shadow areas (left side) and a flatter area from the mid-tonal to the highlights areas (right side). The peaked and flatter areas are fairly wide, which indicates good contrast. You might think, however, that this image may be a bit underexposed, as it’s shifted a bit to the left, or has only one area with a lot of detail and rest may be boring or muted. In fact, you would be correct, except for the boring part, of course (wink, wink).

Histograms Image 12

This image was taken on a cloudy day against a backdrop of the club field and trees, which are a bit monochromatic, but this was done on purpose so the puppy (as the focal point) stands out from the background. In the histogram, the background is shown as a consistent number of pixels stretching from the mid-tonal to highlights area (right side) and also to the shadows area (left side). The bars are not very tall, indicating there is not a lot of detail in these areas. The peak is the puppy. More pixels equate to significantly more detail in that portion of the image. The puppy is not brightly lit, so the peak is just left of center in this histogram.

The image below shows a similar histogram shape, but reversed. In this histogram, the background is shown as a consistent number of pixels stretching from the mid-tonal to shadows area (left side) and a little bit to the highlights area (right side). The bars are not very tall, indicating there is not a great deal of detail in these areas. The peak, which is just to right of center, is the black dog carrying the dumb bell. Again, more pixels equate to significantly more detail in that portion of the image.

Histograms Image 10 RGB

Histograms Image 10

Unlike the previous image, this one was taken on a bright, sunny day and shows a black dog happily retrieving the dumb bell. There is more reflective light, which shifts the histogram to the right just a bit. Contrast is good, as evidence by the width of the peaks and the entire histogram.

So next time you are out shooting, take a look at the histogram in camera, and use it as a guide to adjust your settings to get the image you’re after. Part three of this series will feature some tips on how to adjust your images in post-processing using the histogram as your guide.  Until then, Happy Shooting!

 

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Striking a balance so both the dog and the field are properly exposed is a continuing challenge for Schutzhund photographers. While this topic has been explored in earlier posts, one aspect that has yet to be discussed in any great degree is contrast. What is contrast and is it friend or foe to Schutzhund photography? The Digital Photography School blog has a very good post about contrast and explains the concept very simply:

  • Contrast: The difference between dark and light
  • High Contrast: An extreme difference between dark and light
  • Low Contrast: A gradual or lesser difference between dark and light
  • Colour Contrast: Tonal differences, as well as Saturation levels, of colours
  • High Key: Mostly light including whites
  • Low Key: Mostly darks including blacks
  • No Contrast: Is a Whiteout in the Antarctic and very dangerous. Best advice is return to Base Station.

I really like that definition for “No Contrast”, having just been to Antarctica and photographed floating ice (see images below). These images show how different floating ice can look in different lighting conditions and contexts.

In Antarctica as on the Schutzhund field, it is important to remember that white reflects while black absorbs light. Schutzhund fields often are very bright and reflect light, while dark sable and black dogs absorb light. On cloudy days, when everything seems murky, dark sable and black dogs can turn out very muddy and blobs – again they are absorbing available light, which on these days isn’t very much. There is not enough light to provide contrast. Photographers love light overcast, which tends to neutralize the very bright sunlight and provide more even lighting.

Reflective light may play games with color balance, such as a bright blue sky may add more blue to the picture. This was certainly true in Antarctica, where some photos seemed too cool and needed to be warmed up with respect to white balance, in other words remove some of the blue (see Images 5, 6, 8 and 9, which show before and after adjustments). In other photos, in order to get the rest of the photo properly exposed, I elected to let part of the floating ice be very white and reflective (see Images 1, 2, 4 and 10). While it would be nice to have toned some of this down, it is – in fact – pretty close to what we saw.

It is easy to assume that ice and snow are all white, but in actuality ice has a myriad of colors, especially glacial ice, which has many shades of blue, some of which seem to glow!  Also, ice and snow pick up debris and sometimes have penguins and seals handing out. Images 7, 11, 12 and 13 are good examples.

I really like Image 3 as it offers an excellent balance and a lot of detail. It was taken later when the sun was low, providing a very colorful sky and soft light on the ice berg. The sea was dark, which offered a nice contrast.

Going back to the Digital Photography School blog post, here are a few practical tips for “getting the most contrast in a scene”:

  • Shoot with the narrowest aperture possible for light conditions
  • Shoot with the fastest shutter speed possible for light conditions

Also, use your camera’s exposure compensation, adding dark to dark and light to light to help with getting proper exposure. Some photographers also rely heavily on histograms. The next post will take a more in-depth look at histograms and will be up in early March, following the Greater Atlanta Schutzhund Association annual trial on February 23 and 24.

Until then – Happy Shooting!

Floating Ice 1

Floating Ice 1

Floating Ice 2

Floating Ice 2

Floating Ice 3

Floating Ice 3

Floating Ice 4

Floating Ice 4

Floating Ice 5

Floating Ice 5

Floating ice 6

Floating ice 6

Floating Ice 7

Floating Ice 7

Floating Ice 8

Floating Ice 8

Floating Ice 9

Floating Ice 9

Floating Ice 10

Floating Ice 10

Floating Ice 11

Floating Ice 11

Floating Ice 12

Floating Ice 12

Floating Ice-13

Floating Ice 13

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Taking photos that are tack sharp is one of the most difficult challenges in Schutzhund photography. Consider, however, that there may be times when too much sharpness is not necessarily a good thing. More is not always better. Focus is as much an artistic choice as it is a camera setting. This post will look briefly at autofocus settings that enhance focus and artistic choices that enhance the image.

According to Robert Hirsch in his book, Light and Lens: Photography in the Digital Age:

The majority of DSLRs have two focusing modes: Manual and Autofocus. Most DSLRs either have an active (infrared) autofocus (AF) or passive autofocus systems, which automatically focuses on objects at a certain distance to the lens. Active autofocus sends out a beam of red light that the camera uses to measure and set the distance of the subject. In passive autofocus, light that is naturally reflected by the subject is used to read the contrast of a scene and set the focus.

DSLRs also offer autofocus zones, including single-area focus, area focus and closest-subject focus. Within these zones, your camera may allow you to set priority points or zonal areas. In addition, many cameras offer single-servo or continuous-servo focus settings. Single-servo locks the focus at the time of exposure. Continuous-servo focuses constantly while the shutter button is pressed halfway. This is particularly useful for photographing dogs (or any subject) in motion. Professional photographer Nasim Mansurov offers an excellent detailed explanation of DSLR autofocus modes on this blog. I recommend it to you rather than going into a lot of detail here.

Note: Nasim explains autofocus from the perspective of a Nikon shooter, while my perspective is Canon. There are many strong opinions on either side as to which is better. I have no opinion as I think both are excellent, and which you choose to use is a matter of personal preference. At one time, there may have been significant differences as Nasim mentions, but he also acknowledges that the gap is pretty much closed when it comes to autofocus systems.

With respect to autofocus, my preference is to use all focus points with priority set to the center area. I find this works best for tracking fast moving dogs. If your camera model offers it, suggest setting the tracking to be just a bit slower than mid-point. This setting is on a sliding scale in Canon cameras; slower to the left, faster to the right. I also press the shutter halfway when tracking a dog and then press fully when I’m ready to get the shot.

As the dog runs down or across the Schutzhund field, the light changes, which affects the focus, especially when shooting in burst mode. The result is some images in the sequence may be out of focus. How fast your camera writes images to the card also may effect burst mode shooting. Try waiting until you get closer to the exact moment you are trying to photograph and start the burst mode within a few frames. For example, rather than shooting the dog continuously running down the field for the long bite, track the dog with the shutter pressed halfway for continuous focusing. A few moments before dog engages the helper, start the burst mode. I have had good experience with this method.

Artistically, focus or the lack of it can add drama, texture and guide the viewer to key focal points. For example, by playing with the depth of field, the primary subject is in focus, with the foreground and/or background out of focus. The blurriness is called bokeh. It is derived from the Japanese word, boke, which means blur or haze, or boke-aji, which means blur quality.

Another technique that adds texture is to use a softer focus, which can make the photo look like a painting. This can be achieved with the wider aperture, such as f/2.8 to f/5.6, paired with a slower shutter speed. There is no one magical setting and some dogs seem more akin to this technique than others. The images in the slide show that have this “painterly” look were taken at f/5.6. I really like this technique, and am just learning how to use it effectively myself. So stay tuned…I’ll have more to say about it in a future post.

Of course, you can go the opposite direction for amazing clarity and tack sharp focus. This is achieved with tighter apertures, such as f/8.0 to f/11. Using Photoshop or some other editing software, bokeh can be added to bring out the primary subject by blurring other areas of the image or try increasing the clarity and/or contrast. This will help sharpen the image as well.

One more technique that I am still learning is to slow the shutter speed way down to create motion blur. The trick is to get a key part of the image in focus, such as the dog’s head as it launches towards the helper. Panning is a cool technique that is achieved by tracking the dog while in motion and keeping the camera moving while releasing the shutter. Ideally, the result is the dog is in focus, while the rest of the image is not. Think racecars zipping around a racetrack.

The images in the above slide show were taken at a recent seminar on out of motion exercises, offered by Frans Slaman. They show examples of these techniques and how to use focus to create dramatic images. Enjoy and happy shooting!

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