Histogram - An Important Tool To Analyze Your Photographs

Histogram is a graphic representation of the tonal range in a photograph, and it's analysis of the image's tonal range provides a precise check on the exposure. Does histogram really help photographers to understand their images? Yes, it helps photographers to understand the tonal color structure of the photographs. Histogram can show whether your photograph is composed of the dark tones, light tones or the mixed color tones. Histogram can be represented with 256 color tones in a digital format in which the darkest color tone is represented by the number 0 on the left side of the graph and the lightest color tone is represented by the number 255 on the right side of the histogram graph. On the tonal graph, the horizontal axis displays the color tones from the darkest on the left to the lightest on the right and the vertical axis shows the number of pixels that each color tone has. When you frame and compose the shot, your camera's light meter reads the scene before you take the photo and the histogram analyzes the photo you've just taken. You can choose to have a histogram graph appear on the camera's LCD along with the playback display of your photo by using the Multi-Selector Dial button.

Why histogram is so important in photography?

It is a very important graphic tool because it helps to understand the exposure of the photograph you have taken and tells you if it is necessary to adjust the exposure or not. It's not necessary to check the histogram graph for each and every photo you have taken but it's good practice to check the histogram when the scene's lighting condition is tricky. When there are areas of deep shadow and the bright light in the same scene and you're going to take a series of images in the same setting and want to be sure that the exposure is balanced, histogram graph might come handy.

What can anybody get from the histogram graph?

Histogram will tell you if the photographs or parts of the photographs are overexposed (lack of details in the highlights) or underexposed (loss of details in the shadows). When you look at the histogram graph and there is a heavy concentration on the left side of the graph, that means the image is underexposed and you've lost the details in the shadow areas. Likewise, a heavy concentration on the right side of the graph means the image is overexposed and your highlights may be blown out. When you see any one of these kinds of histogram graph, you can think of a solution to balance your exposure whether it is underexposed or overexposed. If your photograph is overexposed, you can increase the shutter speed, close down the aperture or lower the ISO to balance the exposure. And if your photograph is underexposed, you may want to decrease the shutter speed, wide open the aperture or increase the ISO sensitivity level little bit while considering the possible noise in the photograph.

Let's examine these couple of photographs below and analyze the histogram graph so that we can apply it to the practice.

Underexposed Histogram

You can see fair amount of pixels are shifted on the left side of the graph because the photograph is composed with the dark color tones (shot at night) and it is little bit underexposed. You can see the large amount of pixels are in the middle of the distribution indicating that there are mid-tone colors. That's why it is a good idea to shoot in RAW+JPEG mode because sometimes, it is possible to retrieve those loss tones in RAW images but in JPEG mode, it's permanently lost.

Now let’s see an example of overexposed image and see how the histogram graph indicates the problem.

Overexposed Histogram

Here you can see a lot of spikes of pixels on the very right side of the graph indicating that this photograph is overexposed and the highlights are blown out destroying the details in the picture. It has quite a few pixels on the left side as well which tells us that the part of the image is underexposed as well.

You can also set the highlight overexposure warning (default in Nikon D60 I think but has to setup in D90) in your DSLR camera settings. When you set this option, the areas of overexposure will blink in the playback image and you will know exactly which areas of the image are overexposed. Several Nikon DSLR models feature secondary, color histograms, and if you choose to display them, you'll see three small graphs that show the intensity of the RGB (Red, Green and Blue) color values in the scene. If you need to adjust these values, you can do so by controlling the white balance setting in your camera. Some of the Nikon DSLR cameras also allow you to magnify specific area of the photograph during the playback so that you can check the exposure and detail rendering in very specific parts of the image. In effect, you are directing the histogram's area of analysis.

I encourage you to take some pictures and analyze them using the histogram graph and the more you use the graph, more you will be familiar with what histogram can tell you about the photographs.

Direct Flash Light Vs Bounce Flash Light

Good lighting is a key to create a good photograph. It is very challenging aspects of photography as well. It takes knowledge, many years of practice and experiment with the different settings and lighting environment to get master on proper lighting. Some photographers like natural light and others like to use studio strobe, some photographers love one kind of light effect and others prefer different setting. So, it's very hard to say which one is the best lighting strategy and the only way to find out is to experiment yourself and find out which works best for you. I am still a beginner and not in a position to judge anyone’s technique or favor one technique over the other. In my view, it all depends on the shooting environment and what kind of effect you want to get in your photograph. I have seen many photographers divided over the argument of using Direct flash vs Bounce flash. There are some cases you may want to use the direct flash and sometimes you don't want to use the direct flash at all. It also depends on under what situation you are composing the photograph. Most of the time, photographers do not want to use direct flash light for portrait shots because it may produce glare highlights and shiny foreheads due to the light coming out of the powerful source from the short distance which hits directly to the subject. In that case, there are many ways you can soften the light and give more natural look to the photographs.

Index Card Diffuser

Photographers are practicing different techniques to soften the light which helps to reduce the shadows due to harsh light. Mainly, they use either flash diffuser or bouncing the flash lights using any bouncer (ceiling or any reflector). If you do not have the flash diffuser, you can make your own by using a small indexing card over the flash unit and tape it so that it bounces the light to the ceiling and reduce its intensity and producing soft and natural effect to the photographs. But when using bouncing light, you have to be very careful about the surface from which you are bouncing the light because the bounced light will pickup the color of that bouncing surface which directly affects the photograph.

While preparing for this post, I took two shots very quickly. One with the direct flash lights and the other using the bouncing light. In both cases I used off camera flash Nikon SB-600 and fired it from angle. First, I applied direct flash to the subject and the second time I bounced the flash light using the white ceiling surface over my head.

Effect Of Direct Light Source

Effect Of Bouncing Light Source

In this particular situation, I think bouncing the light worked better than hitting the subject with the direct flash light. When the light was bounced, its intensity was decreased and soften the light on the subject. Also, the bounced lights coming from the various angles helped to remove the shadow of the subject.

In my opinion and generally speaking, photographs look more natural with the soft bouncing light than with the direct harsh light producing unpleasant highlights and shadows. But if you do have any different ideas or thoughts, please feel free to share it with us.

What Feature Do You Assign To The Function Button?

This post is a part of our Q&A section. If you want to submit your question, please use the form in the Contact page.

Deepak (Mumbai, India) asked : What camera feature do you prefer to be assigned to the function button on a DSLR camera?

Deepak, to be honest with you, your question forced me to go back and see what are the other options available in the menu to assign to the function button. I always assigned only two of my favorite options and never looked back into other options. In the first part let me talk briefly about what is the function button and why should we use it? And in the second part I will explain what feature do I assign to the function button and why?

Nikon D90 Function (Fn) Button

Function button allows you to change the particular camera setting without going deep down to the menu options. Once you assign the function button to the specific feature, whenever you press the function button, camera will adjust the setting for that particular shot. This feature comes very handy when you want to quickly alter the camera setting without wasting too much time navigating through the menu tree. Now let’s discuss how to assign one of the camera’s feature to the function button. In this example, I am taking Nikon D90 to refer to the menu items. If you use some other DSLR, your menu navigation might be little different.

Step 1 : Press the MENU button on the back of your camera

Step 2 : Go the Custom Settings Menu (pencil icon) and navigate down to f (controls).

Step 3 : Select f3 (Assign FUNC. button).

You have varieties of options available there such as spot metering, +RAW, matrix metering, center-weighted metering, flash off, framing grid, AF-area mode etc. Personally, my favorites are spot metering and +RAW mode. Why? Because I set the metering mode to the matrix metering by default and sometimes if I want to give the credit to the center of the subject for the metering purpose, I want to use the spot metering. When I am ready to shoot, I would then press the Fn button and the camera will use the spot metering for that particular shot and go back to the regular setting as soon as the picture is taken. And the same is true for choosing the +RAW mode as well. When I was beginning to learn the basics of photography, I always shot in JPEG Fine mode but once in a while I also took the RAW images to edit the picture later on the computer and learn more about the post-processing tools and techniques. So, whenever I wanted to take the RAW image, I pressed the function button and shoot with JPEG Fine+RAW mode for the particular shot so that the camera takes JPEG and RAW versions of the image and stores them into the memory.

You can play around with the options your camera has and decide which one you want to stick with for regular use. Thank you again for your question from which I also got chance to learn about other options my camera has. Happy shooting!