foxfirerodandgun Loc: Stony Creek, VA

Thanks for your input. What I have begun to do in regards to the exposure triangle is to take one part of it, in this case the shutter speed settings, and see what results that I get when using different ones. Actually, the posted image was one of 12 that I took of the same subject area using greatly varied shutter speeds, and it happens to be what I feel was the best exposed one of the group.

I used the scale on the viewfinder metering menu to adjust the shutter speed to where the arrow of the scale was at 0. So it is really an image taken using the view finder meter and shutter speed adjustments to achieve what the camera saw as the best exposure for the shot taken. Then I wanted to see what the histogram was telling me verses what the camera was telling me. I noticed that neither side of the histogram went as far as, or touched, either wall of the histogram, so I thought the histogram is telling me that the image isn't to over or under exposed, however, the spike in the blue gave me pause wondering what was causing this.

Once I have a better understanding, and feel confident in using various shutter speed settings in the "S" mode in different situations, and understanding the resulting histogram information, I'll move to the aperture settings in the "A" mode. Then I feel as if the "M" mode will be a snap to use. Does this plan make sense? Many thanks.

rpavich Loc: West Virginia

I'd agree but they don't tell you if what you took is what you wanted to achieve...sometimes I LIKE lost shadow detail.

The ONLY time I can see a use is to answer the question; is anything blown out?

canon Lee

The explanations from others here are generally correct, but the main thing you must understand is that the histogram is the correct exposure for lightness and darkness, ( the width shows light from 0~100),*not the monitor, or what you perceive to be correct lighting. What is important is that the monitor needs to be "COLOR CORRECTED". Your histogram will show you the correct "lightness and darkness" exposures. You look to your calibrated monitor for correcting color to your taste, not brightness = ( exposure and highlights), mid-tones = (shadows), .blacks = ( here you can adjust for details in the black and dark areas). I strongly recommend that you work in Adobe Light Room. Note also there is no such thing as a perfect historgram SHAPE. Turn on your histogram's highlight clipping and shadow clipping indicators. This will be your correct luminous settings no matter if you monitor is too bright or too dark. Adjust your monitors brightness to what your histogram is telling you.

jaycoffman Loc: San Diego

I second this response--thanks.

al13

Easiest to follow explanation i’ve Heard. Thank you

burkphoto Loc: High Point, NC

First, understand what a histogram represents. It is a graphic representation of a frequency table. In photography, it shows you the RELATIVE number of tones of a given value, from 0 (black or no color) on the left, to 255 (white or fully saturated color) on the right. That assumes an 8-bits per color channel image.

The higher the spike at any particular point along the graph, the more pixels of that value are present in the file. A color histogram will have red, green, and blue channels depicted separately. A monochrome histogram of a color image sums all three color channels together and shows you the sum at each value.

Histograms CAN BE interpreted (roughly) to indicate proper exposure, but they can also be misread blindly! A low key image may have ALL values skewed to the left, with no whites or true highlights. A high key image may have ALL values skewed to the right, with no blacks or true shadows. The one time a histogram of a JPEG is *truly accurate* for exposure evaluation is when you meter a reference target according to instructions.

If your white balance is off, the histogram of a JPEG of a photographically neutral gray card will show three separate spikes. The farther the spikes are separated from each other, the less accurate is your white balance! With perfect custom white balance, you will see one, very narrow spike.

Here's a good test for learning the exposure triangle. Mount your fastest lens on your camera. Put your camera on a tripod. Set it to ISO 200, f/4. Point it at a Delta-1 18% gray card that is lit with a constant, invariable light source. FILL THE FRAME with the gray card. Make exposures, varying the shutter speed until you see a single "spike" in the center of the histogram. That is your reference point.

Now, make a series of exposures at full stop intervals, from f/4 to the smallest aperture on the lens. (for example, f/4, f/5.6, f/8, f/11, f/16, f/22).

Open the lens to f/4 and make another series of exposures from the current shutter speed to the shortest shutter speed, and then the other way, from your reference speed to the longest shutter speed.

Return the shutter speed to the reference point. Now adjust the ISO in full stop increments from 200 to 6400. (200, 400, 800, 1600, 3200, 6400)

Return to your reference exposure. Now, vary TWO settings in opposite directions, each by one stop (ISO up, speed faster, or f/stop down, speed slower, etc.) Note that "stopping down" means using HIGHER denominators in the f/stop, because f/stops are fractions. What do you see?

You'll soon learn that of the three variables, ISO controls the amount of *effective* exposure you need. In actuality, ISO is just sensitivity. The higher the ISO, the less light (fewer photons) you need for a correct exposure.

Exposure is controlled by the shutter and aperture, which together let a certain volume of photons reach the sensor. ISO controls HOW MANY photons you need to record a normal exposure.

LIGHT LEVEL is the other variable. The amount of light available in the scene, or that you put into or onto the scene, controls your starting point for settings. (I'm ignoring contrast and dynamic range here, as those are topics for another post.)

My absolute favorite way to use a histogram is to read an exposure target. I use Delta-1 18% Gray Cards, Photovision One Shot Digital Calibration Targets, the ExpoDisc, and the X-Rite ColorChecker Passport. All of those tools can be used to set a Custom/Manual/Preset white balance, too. Each is more convenient in a different situation. The ColorChecker Passport is the most accurate. The gray card is quick and close.

I calibrated my hand-held incident dome light meter (a flash meter) to the camera using the center spike of a histogram from a Gray Card as the reference point. In some situations, the meter is an easier way to judge exposure.

I hope that helps...

DaveyDitzer Loc: Western PA

Thank you for "histograms 201"

foxfirerodandgun Loc: Stony Creek, VA

Thanks to all for your input. I have learned much from it. burkphoto - Thank your for your in depth explanations using gray cards, etc. As I progress in my efforts to learn, this information will become very valuable. Everyone here on UHH has been so willing and kind in sharing their knowledge and patiently responding to my many questions. I have not found this level of camaraderie, and positive comments & input, on any other forum of which I am a member. Many thanks to all.