Guarding the Beaches of LA, by Stuck in Customs on Flickr

Old solution to this problem

If you were facing such a scene in the old days of film, you had to analyze the scene and determine what the key tones were. Often, you needed to hold the highlights and allow some clipping in dense shadows or other dark areas. Sometimes the key tones were dark and you were forced to allow blown highlights. And in some cases, you would decide that the scene couldn’t be compromised. In other words: you couldn’t capture it the way you wanted, so you didn’t!

Thank the spirits we now live in a digital age! Now you can capture this scene using HDR.

My two cents in the HDR argument

Before I move on, I want to address the fact that HDR is frowned upon by some people. There are several reasons for this. Some claim that bracketing or multi-exposure shooting is counter-skillful (elitists). Others think that using HDR is “cheating”, creating a falsified representation of “reality”.

Ignore those people.

HDR is not cheating. Nor is it the path to enlightenment. It’s just another tool in your photography toolbox, to be pulled out when you feel the situation demands it.

Enough ramble! Let’s get on with the subject!

What is HDR photography?

HDR photography is the principle of using multiple shots to capture a high range scene, and then merge these shots together digitally on a computer during post-processing.

The process involves using specialized software tools. These tools will use the different exposures to create an “optimal” representation of the scene, ensuring that the clipped shadows or highlights are excluded from the resulting image. A little simplified, this enables you to expose detailed information in the shadows from the brightest exposures, and details in the highlights from the darkest exposures.

Old suitcase scene analysis

As you can see in the above image, the scene has a high range between the sun on the wall and the suitcase interior. When the interior is correctly exposed, the wall light is completely blown out. And when the sun on the wall is correctly exposed, the photo is underexposed overall, and almost all detail inside the suitcase is lost. To capture this scene, HDR is necessary.

HDR is in its infancy

HDR is still in its infancy. This means that although we’ve had it a few years in still photography, the tools and techniques are going to grow a lot more mature in the future. Camera manufacturers will definitely make use of HDR in some sort in future models to increase their cameras’ ability to cope with high dynamic range scenes.

And also, the tools for post-processing will grow much more mature. Still, some of the tools we have today are already relatively sophisticated. With proper knowledge we are able to create high quality HDR images.

Building the scene

Our own vision is rather limited for taking in a scene as a whole. But our mind has a wonderful way of compensating for this. Our eyes rapidly move around the scene, registering it bit by bit, and our mind then combines these visual impressions into one experienced scene. The brain is also an expert in completing known things where only a part is visible. If we see a car where half of it is hidden by a corner, our brain completes the car for us.

When moving around like this, our eyes quickly adjust to the light and tones of the different areas. And that is pretty much the same as we do with multiple exposures for HDR, except that the camera captures the whole scene in every shot. But we expose for limited areas with each shot.

So, in a sense, one might argue that HDR is more “natural” than capturing a scene with one shot!

Capturing the scene

First and foremost; if you have the choice: use a tripod! Slight movement from hand-held shooting can be compensated by the software, but you will be so much better off by making sure your image data is of the highest possible quality!

How many exposures you need will depend on the given scene. Often, around five exposures are needed. Today, most SLR cameras have a clipping indicator you can enable on the screen, and most also have the option to show a histogram.

Start out by under-exposing the scene. Under-expose to such a degree that the histogram is jammed up on the left side of the histogram, clipping the shadows. Slow down the shutter 1 full stop, and take a second shot (yes, the shutter; the aperture is fixed during HDR shooting!). Slow down another full stop, and take another shot.

Continue shooting in full-stop steps until the darkest part of the histogram is around the center of the scale. (Yes, that means that I should have shot at least one, maybe two stops more in the example shot!) This ensures you record all details in the darkest shadows.

HDR shooting sequence with histograms

Pitfalls when shooting for HDR

There are some pitfalls when shooting for HDR. Among the most common are ghosting, flare, banding and haloing. Ghosting is caused by movement, flare by light from a bright light source. Haloing and banding usually occurs when there are sharp edges between light or dark in the scene. Common examples are around the edges of a window in interior scenes, and at the edge between a dark building wall or roof and a bright blue sky.

I will return to these pitfalls in a follow-up article on HDR tonemapping.

Merging into a HDR image

There are several tools on the market for generating HDR images. I will focus on Photomatix as this is the oldest (and probably best-known) tool out there.

In this introductory article I will not go into details on how to tonemap. I only adjusted a little, mostly the saturation slider. You can experiment with this a little on your own. In a follow-up article I will delve deeper into the technicalities of producing the best possible result using tonemapping.

In Photomatix, click the Generate HDR image shortcut. In the following dialog, browse and select the sequence of photos.

The next dialog is the Options dialog. I recommend that you always check the “Align source images” choice, even when a tripod was used.

Then click the “Generate HDR” button. Photomatix then merges the photos and generates an HDR image. The resulting temporary image then shown is unprocessed and does not show the full range. Your next step is to click the “Tone Mapping” button. This will produce an image where you see the full details in both shadows and highlights.

As stated previously, this article will not cover the tone mapping process. Feel free to play around with the various sliders and see how they affect the photo.

Old suitcase HDR (non-optimized), by Marius Waldal

As you can see above, the various exposures have merged into one photo where both the highlights and the shadows are held, and all details are shown.

I hope this introduction was helpful and that you are hungry for more! I will revisit this subject in a later post with more detailed info on how to perform successful tone mapping!

If you liked this post, you may also like:

1. How to simulate cross-processing in digital photography
2. How to create a black&white image with selective colors in Photoshop
3. Introduction to digital black & white photography

Smoke on the water, by Marius Waldal

A multitude of light sources

Depending on your environment, your surroundings are lit by different sources of light. If you’re indoor, your light source may be fluorescent light, incandescent light, candlelight, a window, or (often) a combination. Outdoor, apart from the sun, your scene may be lit by street lights, fluorescent light or even moonlight.

These various lighting conditions call for some care when photographing, as they all have their specific characteristics. I will guide you through these common light sources and offer a few tips on the way.

The difference between the eye and the camera

It seems prudent to first say a few words about how the camera sees light compared to the eye. Our eyes have an impressive ability to adjust to the available light, trying to achieve some kind of “normality”. Even light with a strong color cast will appear a lot more normal (white) than is really the case.

Not so with a camera, which will record the light as it is. This is why your camera has a white balance control that will try to simulate what your eyes do; “normalizing” the colors in the scene. For several common lighting situations, this does the trick. But some situations, like when you shoot scenes lit by street lights, call for more thought. Learn why below.

The most common light sources

Natural light

Even though natural light is as simple as being only 1 light source – the sun – it is also the most complex type of light, and by far the one with most varieties. There are so many factors that affect sunlight (clouds, haze, temperature, season, time of day, reflections to name just a few), each with their own distinct effect on color. Actually, this subject is so vast that I will dedicate another article to natural light alone. Here I will limit myself to just a few basics.

Untitled by tbg78 on Flickr
This is a great example on the warm colors of evenings. This silo is actually gray, but when hit by the late evening sun, the sunlight paints it orange.

When sunlight (which is more or less white because it includes all colors) hits the atmosphere, some of this light scatters. The short wavelengths scatter the most, and these are at the bluish end of the scale. In the morning and evening more blue light is hindered, causing the remaining light to have a warm red or orange color cast. During the day, the sunlight passes through less atmosphere causing more blue light to hit the earth, and this creates a cooler color cast (often bluish because of reflections from the blue sky).

Different types, and amounts, of clouds affect sunlight in a multitude of ways. Most surfaces reflect sunlight, in various amounts. Depending on these surfaces, the lighting conditions may vary greatly. The weather can be hot, cold, bright, dark, rainy, misty etc, which affect the light in their distinct ways. Even when the sun is gone at night, sunlight hits the earth via the moon (which does not produce its own light but merely reflects the sun).

If you add to this the various angles to the sun or reflecting sources both you and your subject may have (and often, your camera is the only factor where you have control of positioning), you may appreciate how numerous the lighting conditions of natural light are. So stay tuned for a follow-up article on the subject of natural light!

Glowing light sources

Bulbs based on heat (tungsten lamps) – incandescent light – have for a long time been (and still is) the most common source of light in our homes. We are so accustomed to the warm yellowish light created by these lamps that we perceive it as fairly white. But our camera records the yellow color cast as it is. This is sometimes desirable, as it creates a warm, cosy effect. But more often this effect is not what we want, forcing us to adjust the white balance accordingly. As this kind of light is based on heat, the color temperature in the Kelvin temperature scale is pretty low; between 2500K-2900K (not unlike sunlight at sunrise and sunset).

Even warmer is the light emissions from flames, like candlelight or a fireplace. The white balance setting for tungsten usually works well with candle-lit interiors, but as the temperature of candlelight is just below 2000K, even more adjustment may be warranted.

Fluorescent light sources

Another light source that is not uncommon in private homes and very common in office landscapes, shops, malls and other public indoor areas are fluorescent lamps. To our eyes this light looks all white, without much “automatic adjustment” by our eyes. But to a camera, this light has a green color cast. Most people will react negatively on a greenish photo, as green is often associated with sickness and decay, so a white balance correction is most often warranted.

As always, shooting in RAW will reduce the need for choosing a correct setting, as the white balance can be easily adjusted in post-processing. If you shoot in JPG, however, you will need to take into account the fluorescent lighting in your white balance settings. Be aware, though, that fluorescent light sources may wary greatly according to the effect the manufacturer is trying to simulate. The amount of green varies from almost nothing to a stark cast. A manual correction may be necessary.

Vapor discharge light sources

That night, by Rick Elkins on Flickr

Vapor discharge lamps are on the rise. They are not new, but are gaining momentum over fluorescent lamps in many indoor lighting situations. Outdoor, they are the most common lamps for street lights and for floodlights (buildings, parking lots, stadiums etc). The two main types are sodium-based and mercury-based.

Sodium is most commonly used in street lighting. They have a strong yellow color cast, even to the eye.

Mercury-based lamps are not so easily distinguished, as they appear a lot whiter to the eye. On a photo, however, the color cast is quite green.

In some places where a more balanced spectrum is needed, like in a stadium where television cameras are used, a mixed (multi vapor) type is used.

What is special about this type of lamps, is that they peak strongly in a small part of the spectrum (like yellow or green), and at the same time are completely devoid of other parts (most notably blue). This is very obvious if you convert such a photo to monochrome and use the tonal sliders to adjust the photo. You will often experience that adjusting the blue (or similar) slider has now effect, as no blue light has been captured by the camera.

In some cases, the green color cast is so intense that it is very difficult to adjust it properly (mainly due to the very limited color spectrum available). In such cases, I recommend converting to monochrome; either as a black & white image, or choosing a psychologically more acceptable color than green; typically yellow (which is usually accepted by most people, due to familiarity created by the yellow color casts of evening sun).

Mini case study: Street lights

As you can see, the original (shot with daylight WB setting) has a stark yellow cast. At the far back, you can see a car approaching. These lights are also a bit yellow, but a lot whiter than the street lights.

In the second version, I’ve dragged the white balance setting down to 2500k. The street lights are still not entirely white, but looks reasonably normal. What’s also happened, though, is that the headlights on the car have now turned blue. In addition, the lights in the windows of the building all the way to the right have a green cast.

In this particular photo this setting would work ok, since both the headlights and the window lights are so small and unobtrusive. Had the car been clearly visible, we would be less inclined to accept the unnatural look.

The third version shows how these challenges can be avoided by choosing monochrome treatment. There are no important colors in the image that call for using a color version. On the contrary, as the bright yellow neon sign (which IS a yellow sign!) demands too much attention (as discussed in this article). By choosing monochrome, this bright yellow light becomes just another light.

Multiple sources in one scene

The Fabulous Baker Hotel, by Noel Kerns on Flickr

Life is usually not simple. Often, your scene contains multiple different types of light, and this may create complicated situations for photography. Compromise is often necessary, depending on how much control you have over your scene.

The first thing you should do is shooting a test frame to see the different color effects your lightsources create. I recommend using the daylight white balance setting for this.

If you can control your scene and some sources are especially troublesome, turning them off may be necessary.

If you can’t control your scene

If the main part of your scene is lit by one type and the other types only represent small parts of your scene, adjust for the main source. Small sources of light that look unnatural are usually acceptable.

If your scene includes daylight (i.e. from a window, especially if you can see through this window in the frame), your best option will probably be a white balance setting that will ensure this light looks natural. This is because people viewing your photo will have less tolerance for an unnatural appearance of daylight than any artificial light source in the scene.

Without natural light, you need to analyze the scene and decide on which are your key tones. Depending on what type of light source lights this part, adjust your white balance accordingly. Shoot another test frame and analyze the scene again. If this setting works for the key tones, what about those parts of the photo that are lit by other sources? If these now look even worse, you may need to experiment with your settings and select a white balance that creates the most acceptable blend of color casts in your photo. As already mentioned, yellow is usually preferable to green.

Conclusion

The subject of light and color is great. In this article I hope you have learned a little on how different light sources affect your photos, and how you might handle it. Of course, trial and error is key. Sometimes, like in the photo of the Brooklyn Bridge above, the color cast is desirable, as it contributes to a certain mood in a photo. Whenever you walk around in the evening, with or without your camera, train yourself on seeing the colors on different light sources around you. Happy shooting!

And don’t forget: I would love to read your thoughts or insights on this subject in the comments section!

If you liked this post, you may also like:

1. Color in photography – Color theory