Histograms

The histogram is an invaluable tool. It will tell you if a shot is under or over exposed, if it has low or high contrast, the predominant colors of the scene, shadow and highlight clipping, tonal range and levels.

As we explore the histogram we will also be exploring a bit into Adobe Photoshop, Bridge, and Lightroom.

The histogram represents every tone in the photo. From black on the left to white on the right.

The vertical peaks represent the number of pixels for each tone.

There is no such thing as the perfect histogram, it depends what you are trying to create.

However, for general picture taking:

-If the histogram extends past the extreme left or right sides, you will lose all detail in black and white, respectively.

-If the image is relatively dark, the histogram will be weighted toward the left.

-If the image is relatively bright, the histogram will be weighted toward the right.

Let look at the composition of a histogram.

The histogram is divided into 3 main sections, shadows on the far left, midtones in the middle, and highlights at the far right. The histogram below shows the tonal range of a photo in Lightroom.

A histogram is made up of three layers of color that represent the Red, Green, and Blue color channels. Gray appears when all three channels overlap; yellow, magenta, and cyan appear when two of the RGB channels overlap.

Each of these 1 stop ranges contains within it just over 50 discrete brightness levels.

In highkey photos you will see almost every tone at the right highlight side of the histogram. It is a popular misconception that high key is white on white. It's an image that contains very little if any shadows and very little midtone values. Blown out is not high key. You want your tonal values to appear as below without and values hitting the far right

Low key works the same way just sift to the left.

Shadow and highlight clipping can be determined on the histogram of your image.

Clipped areas are either completely white or completely black, and have no image detail.

A quick look at your histogram in camera will let you know it you need to retake your shot. Much better than getting home and finding out.

A histogram also shows the amount of contrast. Contrast is a measure of the difference in brightness between light and dark areas in a scene. Broad histograms reflect a scene with significant contrast, whereas narrow histograms reflect less contrast and may appear flat or dull. Higher contrast images have deeper shadows and more pronounced highlights, creating texture which "pops" out at the viewer.

So why is it important to know how to read a histogram? Because your meter, LCD, and monitor all have the tendency to lie to you.

So you take a photo and you hit the 0 on the meter perfect but your image is too dark, huh…

This reading may have been made because the camera read a variety of areas of the scene and averaged them out, or because you read the highlights, the shadows and some other areas and decided that a particular setting would yield the best compromise exposure for that scene.

If you know how to read the histogram, you can adjust your settings according to the tonal data and get an exposure with a good tonal distribution.

Enter Eeyore! I'd love to have a better subject for you but I've been sick on and off for 2 weeks and I have a fondness for my blue friend here.

Eeyore here was shot in natural light against a bright background(f4.8 @1/45). The camera averaged the scene and determined that this was a 0 exposure on the meter. As you can see in the histogram, the image is underexposed by 1-2 stops. This really isn't what I want. I could try to balance in post processing but you will always yield the best results from in camera. Also, with an underexposed image, you will end up with noise in the deep shadow areas the more you lighten them.

A 1 stop overexposure from the original reading evens out the tonal range and gives a good exposure. You can see at the right that there is

highlight clipping but not in any significant areas.

Have you ever noticed when adjusting levels and curves there is a histogram display? Being able to read a histogram is important in post processing. Understanding it will give you much better control over your PP.

There is no perfect exposure or histogram, it's what you want.

Interruption

So we're going to go a bit off course here tomorrow. I was going to post part 2 on shutter speed but I think I'm going to interrupt a bit with some lighting info and a few other things I think are important and very useful for these upcoming sections. I shall return tomorrow afternoon with lots of fun stuff to drive you nuts!

Shutter Speed: Part 1

Forgive my slowness this last week. I am busy preparing for the new semester to begin on the 12th and trying to find the best way to put this together for everyone. Plus, after a very long battle with HP my laptop is finally in for repair/replacement. Love my tablet to death...hate HP's service center! Anyways, lets get on to something relevant!

I'm going to dial down the technical aspects a bit from here out as I see some finding it confusing. I really want this to be a simple and easy way for everyone to learn.

Shutter speed controls how long the shutter remains open. Like the aperture, changing this setting will produce an array of effects. For sports and fast moving kiddos, you want a fast shutter speed to freeze the action in the scene. Waterfalls, streams, and other water shots can be enhanced by using a slow shutter speed to capture the flowing of the water. It sounds simple enough but usually requires a little extra step to get the results you're looking for.

First thing, if you don't have one already, get a tripod. This is going to be a big factor in the quality of your shots. We will be covering types of tripods and the need for them soon but for now get one and use it. Money is tight with everyone these days so if all you can get is a cheap one it's better than nothing but I'd suggest start saving for a good tripod.

Lets say we're shooting a waterfall and we want that nice flowing look. You have to use a tripod for this. *If you are using a Nikon lens that has VR it should be turned off when shooting on a tripod. There will be a switch right on the lens.* You can shoot this in either Manual(M) or Shutter Priority(S) mode. Using a slower shutter speed is going to let light in longer so we'll need a small aperture(a large f-stop;f16,F22,F25,F32). I like to use shutter priority for this as it's less fiddling for me. In shutter priority mode, you choose the shutter speed and the camera will set the aperture. The shutter speed you choose will depend on how much light there is and how much blur you want.

The shot below was taken quite awhile ago with a D40 at 1/8s f/22. It was shot in the woods so it was fairly dark back there and did not require any extra compensation.

If you are shooting in bright light you will need some added compensation. If you get a blowout you can either add an exposure compensation or use a ND(neutral density) filter. On Nikon's, there is a button on the body that you hold down and turn the dial to add an EV compensation.




Assignment: Let it flow! Water falls, streams, rivers, or even your kitchen sink. Set up on a tripod and set your ISO to 100/200, as low as it goes. Put your camera into (S)shutter priority mode. Start at 1/60s and keep dialing down your shutter speed till you get the effect you're looking for. It doesn't take much to show the flowing of the water but if you want more blur take the shutter speed down a stop. Post your best/favorite image to the group pool. Please put the settings in the description.