PHOTOCADEMY Lesson #2! Histogram understanding and regular use is imperative to quality digital photographs.
The importance of histograms cannot be stressed enough. Taking a quick look at the histogram when lighting changes or the scene changes can make the difference between a great photograph and a huge mistake. Watch this video and comment below if you have questions. Keep shooting!
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In your light meter you cannot trust
The view of your screen might be a bust
So don't be a fool
You need to use the right tool
Histogram faith is a must
Welcome to Photocademy - This is lesson #2 The Critical importance of photography histograms. Unfortunately there are many tutorials and websites that tell you not to bother using this critical & necessary tool. On the flip side (also known as the correct side) I've heard it described as the 21st century light meter! This is the way I believe you should view it, too.
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What is a histogram? In basic terms it is a graph of the color tones in an image. When looking at the left to right axis of the graph, on the left side of the histogram are the black tones, middle are the midtones and on the right side are the lighter colors and the highlights. The vertical axis shows the quantity of tones in specific colors or lightness values. In our examples today, we'll be showing some histograms captured from the back of the camera as well as some pulled from Lightroom. When possible, we'll show you both.
Let's set a couple of expectations about histograms. First there is no such thing as a perfect histogram. Every image is going to have a different set of color tones, therefore a different histogram. Second, it is giving you an accurate representation of the exposure accuracy vs just looking at your screen. The screen on the back of your camera is just like your smartphone, when you are outside on a bright sunny day it doesn't seem that bright vs at night in a dark room. That difference in the way we see the screen affects our judgement of how well exposed our image is when not using the histogram.
How many times have you had to work with the exposure slider in Lightroom or Adobe Camera RAW? Is it too often? Being able to evaluate your image's exposure before leaving the scene will give you better color, contrast and less noise. It can also prevent overexposure and blown out highlights.
In my opinion shooting digital images is like shooting slide film. You can only achieve top quality images when your exposure is perfect or within 1/3 of a stop. Underexposure of more than that can introduce too much noise especially if you are off by more than a stop.
A term you may have heard in the past is 'shoot to the right'. What does that mean? In basic terms, you want to push the data in the histogram as far to the right side as possible without overexposing. This ensures you have the most data to work with in post production and distributes image exposure within the camera's dynamic range.
Cambridge in Color defines Dynamic range in photography as the ratio between the maximum and minimum measurable light intensities. In the real world, one never encounters true white or black — only varying degrees of light source intensity and subject reflectivity. Therefore the concept of dynamic range becomes more complicated, and depends on whether you are describing a capture device, a display device, or the subject itself.
In other words dynamic range is the difference, in stops, from the brightest to darkest areas of an image that still contain detail.
DXOMark, an independent camera and lens testing and measurement website, measures each new camera's dynamic range. They state that Higher quality cameras have a dynamic range of 12-14 stops, with the D810 topping the scales at 14.8Evs. If we underexpose an image by a stop or two, we lose dynamic range and image data.
In general, when viewing your histogram, make sure there is no flat spot on the right side like in this one. A 1 or 2 stop underexposure of this image would have looked like this which produces muddier tones and must be fixed in post.
Many times this image, especially with a quick glance, would look fine on the back of your camera. If you would double check your histogram you would see there is no color detail in the brighter tones, which should be present in this image.
Just like anything in photography there are exceptions. In this leaf photo there are no bright tones to fill in that part of the graph, so the correct exposure and histogram should have a flat spot on the right side where white and bright tones are on the histogram.
Another example I use often is sunsets. I will rarely create a sunset photo containing data on the right side. The reason for this is I want to darken, or saturate the sunset and the brighter colors to make it more dramatic.
While these two images are both considered high key, (which pretty much just means there's a bright white background with reduced shadows in the image) their histograms look very different. In this first one with the puppy, there are not many colors or tones to be shown, therefore, the histogram is pushed all of the way to the right with a totally flat section where the darker tones would be. In the second dog image, the Lightroom histogram shows you the color values as well as the combined values shown in grey. As a side note, with many modern cameras you have access to this kind of color histogram right through the camera as well. Note how the colors are reading in the histogram. The little spikes along the bottom represent the colors in the image, with more of the data pushed to the right. There is more data in this histogram as compared to the puppy one because there is more data in the scene.
In this image of a farrier at a local farm. As you can see this is a difficult image for the camera to capture. If you were relying on the camera to capture in program mode it would probably look like this with the shadows underexposed and the camera only metering for the highlights. When we look at the histogram of this underexposed image we can see that we have a lot of dark colors, very few midtones, and blown out highlights. In the normal exposure we still have blown out highlights, but the other tones are evenly distributed across the histogram. We also still have very dark areas of shadow, but in my opinion its ok since this is how I intended to capture the scene. I didn't want a full silhouette, but just some detail in the darker areas.
Using the histogram to help judge your image's exposure is paramount to great color and low noise photography. The key is understanding and studying your images and knowing what the histogram is telling you.
The meter in the camera can be fooled by backlighting, colors, metering mode choice and many other factors. Make it a habit to check your histogram each time the scene or lighting changes.
Review some of the histograms from recent photographs. Did you underexpose it? Overexpose it? Look at the adjustments you had to make in order for the final edited image to be pleasing.
Learn how to quickly turn on your histogram on your camera and practice turning it on without looking at the buttons on your camera. It should become second nature, the more you do it the more it will be muscle memory and you won't have to look it up each time.
Take photos in different situations like sunset, indoors, outdoors and high contrast scenes. After each image look at your histogram and evaluate your exposure. If there is something you want to remember take note of it, and if you need to take a photo of your camera's screen with your smartphone.
Our next lesson is the Master Guide to DSLR Metering Modes, followed by lesson #4 is Don't be DUPED by your DSLR's Meter. These videos are the next step to mastering your dslr.