Tips for Photographing Real Estate Interiors (5D)

A Post By: David Robinson

In this article, we’ll address the challenges you may face when photographing real estate interiors and a few ways to combat the issues. Shooting bracketed images is the most common and effective way to handle high contrast interiors. Read on below for tips on how to shoot and process interiors.

The problem

Most real estate photographers have entered a room at some stage in their career and thought, “Ah… a dark room with a bright window. Just what I do NOT need!”

Using straightforward post-production techniques to fix either over or underexposed parts of a photograph is practically impossible. So walking into this kind of scene can make your heart sink. The good news is that it’s not so hard to get around the problem posed by these scenes once you are equipped with the right techniques.

Achieving a well-exposed photograph of a dark room with a bright window initially seems impossible. Expose for the interior and the windows are blown out. Expose for the windows and the darker parts of the room are plunged into shadow.

Photo exposed for the interior (1/4 second at f/8), notice the windows are overly bright.

The difference between the brightest and darkest areas, known as dynamic range, is just too great. This is a High Dynamic Range scene, or HDR for short.

Photo exposed for the windows (1/125th at f/8), now you can see the inside is almost completely black.

Our eyes cope with HDR scenes by adjusting the size of our pupils, letting in more or less light as we encounter darker or brighter areas. The brain balances it all out and everything seems well lit.

Unfortunately, when it comes to a dark interior with a bright view, even the best DSLR cameras can’t capture the entire brightness range with a single exposure.

Photo at normal exposure (1/30th at f/8), here you can see some areas are too dark, and the windows are too bright. The camera cannot hold detail in the entire scene, the contrast is too great.

There are two ways you can resolve this issue

1. You can add light to brighten the room and reduce the dynamic range.
2. You can take multiple exposures and combine them using software to emulate what our eyes and brain do.

Adding light

To brighten the room, you’ll generally need to supply extra lighting. Just turning on all the available lights is unlikely to solve the problem.

One option is to bring along portable lighting. However, this is another skill to master, another thing to carry, and even though the cost of lighting is falling it’s still another expense. You may also need to bring an extension cable, and hope that the property has power.

You could also use professional flash units, mounted off-camera and triggered remotely. The term professional is important here because less powerful flash units rarely deliver enough light to solve this particular problem.

Effective use of flash units also requires skill. You’ll probably need several flashguns, and the knowledge of which units to use and where to put them. Again, it’s more expense and a lot more kit to carry, especially when you include stands for the unitstoo.

Taking multiple exposures

So what about multiple exposure approaches? One method is the Photoshop approach where you take only two photographs, one correctly exposed for the room and one for the windows, and open them in separate layers in Photoshop.

Once you have manually aligned the two layers (using the Difference blending mode to guide you, zooming in may help as well), with the darker image on the bottom, you then select the blown-out windows on the top layer (the image exposed for the inside of the room). Using a layer mask, make the window areas transparent, and the properly exposed windows in the second shot will show through from underneath.

Unfortunately, this approach rarely results in a convincing and realistic looking image, as two exposures are not enough to cover the entire range of brightness that our eyes perceive. Additionally, the photo exposed for the window will underexpose the window frame and any ornaments on the windowsill, making them look darker than they should be.

A more effective approach involves taking multiple exposures to capture different lighting levels (bracketed photographs) and using HDR software to merge them into an image that’s well-exposed throughout. Shadows are corrected without additional lighting, and bright areas are pulled back without appearing artificial.

Bracketing is very popular with real estate photographers because it overcomes the problems associated with the alternative approaches. All without the cost and inconvenience of more equipment on location – except for one good quality tripod!

Bracketing exposures

Correctly capturing the exposures is key to obtaining the best results with this approach. So let’s look more closely at how professionals do this when photographing real estate interiors so that you can master it yourself.

Essentially, you take a series of identical shots at the same aperture – but using different shutter speeds. A constant aperture keeps the depth of field the same while changing the exposure allows you to capture well-exposed images for all the different lighting levels in the scene.

It is called exposure bracketing because the varying exposure settings are “bracketed” between the slowest and fastest shutter speeds needed.

The Automatic Exposure Bracketing (AEB) function, built into most DSLR and mirrorless cameras, greatly simplifies the process, allowing you to take three or more bracketed exposures with just one shutter release.

In many situations, especially outdoors, it will also save you having to use a tripod. Any camera movements during shooting (inevitable in hand-held shots) are small enough that software with robust alignment features can automatically correct them.

Camera settings

You start the AEB setup by selecting Aperture Priority (Av) mode.

The rest varies between camera models, but typically involves three steps: selecting AEB and continuous shooting mode, choosing the number of bracketed frames, and choosing the number of EV steps between each shot.

Your camera’s user manual will cover the steps needed for your model.

Exposure bracketing techniques for interiors

Lighting differences in an interior scene with views through the windows are so great, that taking bracketed exposures may involve more than just setting up AEB and taking the shots, especially when you want the highest quality results.

The main problem comes from the camera’s choice of shutter speed for the baseline or “normal” exposure (0 EV). Bright light through a window can influence a camera’s automatic exposure, resulting in a photo set that is skewed towards underexposure.

Another problem is that capturing the scene could demand more exposures than your camera’s AEB provides. Also, since a low ISO is best to minimize noise in the shadows, you may need quite long exposures. Without a tripod, that will result in blurred images that could ruin the shot.

Quick technique

Even though exposure bracketing is more involved when photographing interiors with window views, you can use a relatively quick technique when the lighting differences aren’t too great and your camera offers a broad AEB exposure range. This is how it works.

After selecting Aperture Priority (Av) mode, point the camera at an area of the room that is neither too dark nor too bright, just ‘average’, and well away from the windows.

Note that the shutter speed when the camera is pointed at the sofa is 1/10th.

Take note of the shutter speed your camera displays for that area. Then switch to Manual mode, make sure the shutter speed is the one you noted, activate the AEB function and take the photos.

While this will certainly be better than a single exposure, you lack control with this technique and you can’t always select the right number of photographs to be taken.

Advanced bracketing technique

When you want to maximize output quality, use this advanced bracketing exposure technique to ensure that you take all the exposures needed to cover the entire lighting range. This gives you far more control, although it takes a little longer and the process is slightly more complex.

This video steps you through the technique, from camera setup to determining what exposures to use, through to taking the photos themselves.

One of the main advantages of this technique is that it establishes precise shutter speeds that match the maximum levels of darkness and brightness in the room. It does this by determining the shutter speeds for both extremes of the lighting range.

This is important because misjudging the correct exposure for the darkest areas can result in an image where the interior isn’t bright enough. While failing to capture the brightest areas results in washed-out looking windows.

How to find the shutter speed for both extremes

You can choose between two methods to find the shutter speeds for the darkest and brightest parts of the scene:

• Spot Metering method.
• Histogram check method.

Spot metering method

This is the quickest way to find your needed shutter speeds. Start by selecting Aperture priority, or Av mode, then choose the Spot Metering option from the camera menu.

Spot Metering mode.

Find the longest shutter speed by focusing on the darkest part of the room. While watching the exposure meter in the camera’s viewfinder, adjust the shutter speed until the camera shows it to be the best exposure for that part of the room. Make a note of the recommended shutter speed.

Find the shortest shutter speed by focusing on the brightest part of the room, and repeat the process to find the best shutter speed. Again, note the recommended speed.

Histogram method

The second method to determine the two shutter speeds is more precise and works like this:

• Set the camera’s LCD screen or image preview to display the brightness histogram.
• Take a test shot of the darkest area of the room, then examine the histogram.
• If the left side of the histogram shows a vertical line at the start of the graph, then there are dark areas you’ve not yet captured.
• Take another shot with a longer shutter speed and repeat the process until the histogram trails off to a flat line on the left. When you see that, you’ve identified the slowest shutter speed needed.

• Now take a test shot of the brightest part of the room, and again examine the histogram.
• This time look for a vertical line on the right of the histogram. If you see one, then you’ve not yet captured the brightest parts of the scene.
• Keep taking shorter exposures, checking the histogram after each one until it shows a flat line to the right of the graph. When you see that, you know the shortest shutter needed.

Many DSLR cameras have a feature that shows overexposed parts of an image. When activated, the highlight warning system makes overexposed areas blink or flash when viewed on the LCD screen. If you see this, increase the shutter speed until the blinking areas stop flashing.

How to bracket your exposures

Once you know these two shutter speeds you can use them in two different ways – one that uses the camera’s built-in Auto Exposure Bracketing (AEB) option, and one that does not.

The full manual method

• Switch the camera to Manual mode
• Set the shutter speed to the shortest of your measured shutter speeds and take a photograph.
• Decrease the shutter speed by one stop (EV) and take the next photograph.
• Keep reducing the shutter speed by one (EV) stop for each photograph until you reach the longest of the two shutter speeds you measured.

The semi-automated method

• Open the HDR Exposures Calculator app from HDRsoft.
• Enter the shortest and longest shutter speeds into the app.
• Select the maximum number of bracketed frame your camera supports.
• Select an EV Spacing of 2 if your camera supports it, otherwise go with the highest EV spacing it offers, then click “Get Exposures”.
• Follow the instructions given by the HDR Exposures Calculator, making sure you have set the camera to AEB mode and selected Continuous Shooting mode before taking a bracketed set.

Additional tips to take the photos

You now know how to measure the longest and shortest exposures you will need, and how to set up your camera to take all exposures between them. Correct technique is important too, so here are some steps to follow to make sure you get good results.

1. Securely mount the camera on a tripod, and ensure the camera is level.
2. If the camera is mounted on a tripod, switch off Auto Image Stabilization.
3. Set the built-in flash to Off if your camera has one.
4. Attach a remote shutter release to reduce the risk of blur.
5. Select Manual mode and set an aperture suitable for the lighting and depth of field required.
6. Set the ISO value, 100 is ideal. Digital noise (the electronic equivalent of grain) increases as the ISO value increases, so keep it as low as possible. Try not to go beyond ISO 400.
7. Determine the shutter speed required to best expose the darkest part of the room and the shutter speed to best expose the brightest part. See the section above on finding the shutter speeds for both extremes.
8. Take the exposure bracketed photos as detailed in the previous section.

Once you’ve returned from the shoot, process the images in HDR software. There are various photo applications that can merge multiple exposures to HDR. Photomatix Pro is the first choice among many real estate photographers because it offers presets optimized for interiors, achieving the natural look they strive for.

Using Photomatix Pro with real estate interiors

Photomatix Pro is designed to be easy to use, so you should get comfortable using it pretty quickly.  Here are a few tips to help you get the best out of it for your interior photographs.

Check the Align Source Images option with On Tripod selected (even when you use a tripod, there can be some small camera movement between shots).

Don’t activate the option to remove ghosts. This is important in real estate images as adjusting for ghosting when there isn’t any reduces image quality. If you absolutely must use de-ghosting, for example, because something moved outside a window, be sure to use the selective de-ghosting option, so it can be applied to just the affected window.

When you adjust the merged HDR image, use the drop-down list above the preset thumbnails to show just those related to the Architecture style (or “Real-estate” depending on your Photomatix version).

Lastly, you can use the Finishing Touch panel’s straightening tool to correct sloping floors or walls that aren’t upright. Finally, use the cropping tool to remove edge areas of the photo affected by wide-angle lens distortion or chromatic aberration.

Conclusion

Although getting good photographs of real estate interiors can seem daunting, particularly when bright windows are involved, the right techniques and software make it is achievable without bulky, expensive equipment.

The main points to remember are:

• Exposure bracketing is the key technique.
• For simple scenarios, you can bracket based on an average exposure.
• For other situations, work out the brightest and darkest exposure along with the shots in between.
• Spot metering or the histogram can help you determine these exposures.
• You can take the exposures manually, or using AEB and the HDR Exposures Calculator app.

Do you have any questions you’d like to ask about the tips in the article and taking bracketed exposures of interiors? If you do, please let us know in the comments below. If you have any tips of your own, you’re welcome to share them too.

Disclaimer: HDRsoft is a paid partner of dPS

Tips for Light Painting and Some Common Pitfalls to Avoid

A Post By: Ian Johnson

In this article, I will focus on light painting objects in night scenes during a single long exposure (rather than multiple exposures combined in Photoshop) and some of the pitfalls I have experienced. I hope you will gain an understanding of how different light sources, intensity, and warmth can illuminate your foreground elements in a balanced way to provide a creative twist to your shot.

A beautiful night sky filled with stars is often laced with compelling foreground elements that can provide context and intrigue to your shots. You have likely seen many examples of these things in other people’s work such as a saguaro cactus under The Milky Way in the middle of the desert, a homestead cabin in the middle of an old pasture, or a boat floating on a still lake.

This single exposure captures The Milky Way over a field of yellow wildflowers in central Minnesota. I used light painting to emphasize the flowers which were an important part of the scene.

I am positive you can think of foreground elements in your personal environment. Although silhouettes of those foreground elements can provide you with stunning imagery, you may consider using light painting techniques to emphasize the foreground elements of your shot.

What is light painting?

Light painting is a night photography technique where you use a light source to illuminate an object (in other words you “paint it”). The digital camera era has made light painting much more common as it is easier to check and compensate for your exposure of the shot. Because light painting provides so many creative options there are many forms it can take.

In order to do light painting, you will need to carry a little bit of extra equipment and have some basic knowledge about your camera’s manual settings. A grasp of these basic camera settings will increase the enjoyment of your night out by helping you make beautiful imagery.

Camera Settings

Manual Mode will be necessary to shoot your long exposures. You should be aware of how to switch to Manual Mode and then adjust your aperture and shutter speed. For night photography, you will want to use a large aperture (e.g., f/2.8) and slow shutter speeds of often 5 seconds or more.

ISO changes will be necessary in order for your camera to pick up the most amount of light possible. I recommend beginning at ISO 800 and then adjusting accordingly as you learn about your particular scene and shooting conditions. It is important to remember that a really high ISO will require you to post-process out digital “noise” and each camera model has a range of ISO values it can shoot at before it will become very grainy.

White Balance adjustment is critical to shooting at night and for light painting.Look in your camera’s manual or play with your camera settings to ensure you can access manual White Balance and you can create lower or higher White Balance values. White Balance is measured in Kelvin and most cameras will represent it with “K” after the White Balance value (e.g. 4500K).

I bounced the light off the snow to light this shot because direct light caused the totem to become too bright and out of balance.

Equipment

An appropriate light source is necessary to do light painting. You should consider bringing multiple light sources that have both wide and narrow beams as well as multiple color temperatures. You may consider things such as a headlamp, cell phone, flashlight, or professional lighting as these have different beam widths and intensities.

To determine the warmth of your light source, check the box as it may tell you the temperature rating. For instance, many lightbulbs from the store will say 4500K on the side of them. Some professional lighting sources will allow you to adjust both the temperature and intensity of the light, so you may consider those as you progress and become more proficient at light painting.

Beyond the camera and a light source, a tripod is the next most important thing you can bring when shooting long exposures. Ensure your tripod can remain stable for long (up to several minutes occasionally) exposures.

A friend is a great addition to a night of light painting! Your friend can help sidelight objects while you take the photos, provide for creative solutions to problems, and keep you safe as you move around in the dark.

I use this LED light panel which allows me to control the light intensity and color.

Basic Light Painting Techniques

Each night has unique conditions that need to be accounted for, but I like to begin each night with a familiar set of steps. Set your camera up on a tripod and take a few test shots. I usually start at f/2.0, ISO 800, 10-15 seconds, and 4500K.

From those base settings, you can experiment with ISO, shutter speed, and set a White Balance that looks good to you. Once you have the settings for the scene right, set up a composition you like and which ties together the necessary foreground elements. Begin your exposure then use a light source to paint the foreground in front of you.

This image of the Aurora Borealis captures the beauty of the boreal forest and the subtle aurora behind it. I used standard settings (ISO 2000, f/2.2, 20 seconds) and a light panel to make this image.

Selecting a light source is important. Its qualities will determine how it can be used. There are three considerations you should think about:

1. What is the intensity of the light?
2. How wide is the beam?
3. What is the color temperature of the light?

Keeping these things in mind will help you immensely when you go out to shoot. A wide beam can help you light close objects while a more focused beam can light a more distant one. I often use a professional light panel because it gives me control over the beam intensity, width, and warmth.

A good light source will help you get over the pitfalls identified below.

Pitfall #1: Not matching the color balance

When I first began doing light painting, I had a really hard time matching the color of my light and the context of my scene. Your camera will key in on bright objects in the shot such as the moon, a street lamp, or the Aurora Borealis which will become the dominant temperature in the shot.

Keep this in mind as you take your test shots because you will need to adjust your White Balance according to those light sources. If the White Balance of your light source is adjustable set it to the same as the camera. If you cannot control the temperature of your light source (e.g., a cell phone) then consider adjusting the White Balance of your camera to match the light source. You will know the light source and camera are calibrated together properly when the color of your foreground elements look natural (neutral) to your eye.

I’ve provided some examples of images below which came out well and some that did not (according to my eye) due to incorrect White Balance calibration. You should be able to spot images demonstrating the matching warmth pitfall that we just reviewed. I’ve left some thoughts in the captions of the images to reflect on each further.

It is not too hard to diagnose what’s wrong with this image – I did not properly calibrate the temperature of my camera and light source. The light source is too cold compared to my camera’s settings.

The calibration of camera and light source were close on this one, but the temperature was a bit too cold on the light source as evidenced by the bluish tinge to the tree on the left.

A good match! I was able to use the white of the American Flag to calibrate the light source and camera to get good colors from both the flag and the aurora.

This is a good match on the color balance. There were a moon and aurora on this night, so I only used a headlamp to softly light this sled dog that appears to be watching the aurora.

Pitfall #2: Not balancing the light in your scene

Choosing the right beam width and intensity will help you balance the lighting of the foreground elements to the rest of the scene. A digital camera set at ISO 800 or above is incredibly sensitive to light and it is very easy to “blow out” a shot by overexposing the foreground elements. Here are a few tips to help balance the light in your scene.

• A broad beam will help evenly light an entire scene and a narrow beam can light specific aspects of the scene. I have provided thoughts and examples below about when my light source width was appropriate and when it was incorrect.
• If you have close foreground elements consider bouncing your light source. I often use reflective surfaces like snow to indirectly light the foreground through bouncing. If you cannot bounce the light, try side lighting or lighting the object from behind.
• You can decrease the exposure by closing down the aperture. I have found increasing the aperture (say from f/2.0 to f/4.0) and increasing the exposure time make it dramatically easier to create a balance of light in the scene.
• It stands to reason that if you paint an object for a long time with the light it will show up brighter. You will find that duration is critical when light painting and often less is more. Try light painting the object in a short burst of one half, to one second of light and see if it adequately lights the object.

Blowout! I was light painting these autumn aspens to capture the fall colors with the Aurora Borealis. However, my beam was too narrow for the work I wanted to do.

A small beam allowed me to light up this “old man’s beard” hanging from spruce trees in Southeast Alaska. A wide beam would not have worked here as it would have lit the entire scene.

Here I wanted to capture the glacier face and the aurora together so I placed my light panel behind a block of ice. This masked it from direct view and allowed me to bounce the light off the snow.

A passing car provided the lighting for this shot, and I liked the warmth of the light a lot! The broad beam was most appropriate here.

Food for Thought and Wrapping Up

I hope this article can help you get over a couple of the steep learning curves of light painting. Remember, any light source at your disposal can be used to light your scene and each may have its own unique benefits. Experiment with headlamps, cell phones, car headlights, and professional lighting sources to see what each can provide to the shot.

I hope you enjoy your night out! As I always like to say, “Pixels are cheap”, so make lots of them as you learn light painting.

Shedding Light on the Histogram – 8 Rumors and the Real Facts About this Graph

A Post By: Herb Paynter

There have been dozens of articles and many videos published about the purpose and interpretation of the histogram in post-production. It serves a purpose in both the camera capture and post-production processes.

Tons of pulp has been generated about this tiny graph clarifying the general purpose of the histogram. But there is still much to be learned about this graph. This article will clarify some issues while focusing mainly on post-production concerns.

The individual RGB values are dominant in this image. Only the cracks in the sidewalk and spots of white in the cement cause the spikes on the outside edges of the graph.

Some articles I’ve read portray the histogram as the Holy Grail of digital photography and even describe an ideal histogram shape. Others describe the histogram as an accurate revelation of image health, sort of like a digital EKG. Still, others downplay the value of the statistical feedback completely and totally miss its primary purpose. Listed below are actual quotes from tutorials and articles about the histogram.

The two histograms reveal more information than you might think. The RGB graph reveals the same solid yellow and blue colors while the Luminosity graph represents the combined RGB luminosity (effectively, the grayscale equivalent values).

I’ve been adjusting images for decades; long before the graph was publicly introduced and I’ve worked with it every day since so I’d like to weigh-in on rumors and clarify some facts. Once you understand the histogram’s primary function and limitations, you’ll find it to be a solid feedback resource.

The Histogram’s Vertical Lines Defined

RUMOR #1: The histogram is a graphic blueprint of a digital image. The horizontal span represents the image’s tonal range and the vertical lines reflect the contrast of the image; the higher the vertical lines, the more contrast the picture contains.

FACT: The horizontal axis does reflect the image’s tonal range (from the darkest tones to the lightest), though the vertical lines reveal little about its contrast. Actually, the horizontal distribution is what reveals the overall contrast. Tones located mostly on the right reveal very light (or high-key) images while tones favoring the left side are darker (low-key) images.

The extreme right side wall represents white and the extreme left wall of the graph represents solid black. The highest (vertical) peak of the graph merely indicates the highest ratio of pixels containing that particular color tone as it relates to the others. The lowest vertical level on the graph indicates the tone color with the least number of pixels in the image.

The left graph represents a high-key or light toned image. The histogram on the right represents a low-key or dark toned image.

Histogram Shape

RUMOR #2: There is a preferred “mountain” shape for a histogram. The ideal shape displays a single peak beginning at the “ground” on one side, reaching upward into a bell shape near the middle, and tapering down to the ground on the other side. An ideal histogram contains information from all channels everywhere, from the left to the right in the graph.

FACT: There are as many histogram shapes as there are images. There is no such thing as a good or bad histogram and there is no such thing as an ideal histogram. Because these graphs reflect each image’s distribution of tones, you’ll be hard-pressed to find any two alike.

Only images containing mostly middle tones will actually display a true bell (mountain) shape on the histogram as in the one top left.

Clipping

RUMOR #3: The extreme left and extreme right sides of the histogram should never hit the “sidewalls” of the graph. If the left or right side hits and travels vertically up the wall, an undesirable effect called “clipping” will occur, indicating that either solid black or solid white “no-detail” areas will be visible in the image. Utilize the warning signs (The Blinkies and triangles) and avoid clipping on either tonal extremes of the graph.

FACT: Depending on whether the image is high-key (medium contrast on a pure white background) or low-key (dramatic lighting with a black background), either side of the mountain may actually resemble a tonal cliff. Real-life lighting dynamics make these wall-climbing graphs quite acceptable. Photos captured against white seamless backdrops are purposely exposed to produce dropout white backgrounds.

The U.S. Air Force Thunderbirds screaming across a very bright mid-summer South Florida sky were captured against totally white clouds. The apparent clipping shown in the histogram accurately reports the totally white clouds.

Tone Distribution

RUMOR #4: Histograms that display significant gaps on either side of the graph should be adjusted to distribute the tones more evenly. A well-shaped histogram is a happy histogram.

FACT: Real life lighting doesn’t demand that every scene contain both deep shadows and bright highlights. Images are sometimes brightened or darkened unnecessarily revealing a typical rookie editing mistake. Many times these bookend extremes establish an emotional mood that would be lost if the images were over-corrected in this manner.

This low-key shaded scene contains very little highlight shades at all.

Adjusting the image destroys the rich colors of the low-key scene.

Histogram Gaps

RUMOR #5: The silhouette of the histogram mountain should remain smooth, displaying no gaps or fissures in the mountain shape. These smooth tone transitions are necessary to maintain the photo’s full visual range. Gaps in the histogram’s silhouette indicate an interruption in the gradual tones and will result in banded or posterized stages. These gaps appear because the JPEG image is only 8-bit.

FACT: There are only 256 vertical bars presented in the Histogram. Each horizontal bar represents less than one-half of one percent (0.4%) of the total tonal range (100% / 256 = 0.390625%). Even if a photo contains a very gradual change in tones across a wide area (like an unclouded sky), your eyes will only perceive “banding” if the JPEG image has been degraded by repeated Save functions.

JPEG images contain a maximum of 256 levels (8-bits) of tone between black (solid color) and white (no color). Once JPEG files have been opened and saved a number of times, the number of tone levels can become significantly reduced and tone-banding may occur.

These two histograms appear quite different though the images are very similar. As you can see, “gappy” pictures rarely interrupt the flowing tones in a photo and often clarify more detail.

Full Range Images

RUMOR #6: 8-bit images (256 levels of tone/color per Grayscale/RGB channel) are required for an image to display the full range of detail contained in a high-resolution digital image.

FACT: The human eye is designed to focus on detail in a scene or image. Detail is a product of contrast, and contrast is only noticeable when adjacent colors display significant differences. For the most part, the fewer colors that are displayed, the more obvious are the differences in those colors. This sounds bad but it is actually quite beneficial. It may fly in the face of popular logic but there is a fundamental truth to be recognized. The picture with the least colors (also known as bit depth) is many times the most detailed picture.

The top image contains 256 levels of color per RGB channel; or up to 16,800,000,000 colors. The bottom image contains only 15 levels of color per RGB channel; only 3375 possible colors. This image uses less than 5% of the tones that are used in the top image. Don’t live or die on the issue of bit depth. It is important, but like other issues in life, more isn’t necessarily better.

There is, of course, a reasonable limit to this reduced color observation. Too few levels of color will lose the smooth transitions between colors and thus will also lose detail.

Try this exercise: open a full-range photo in Photoshop and duplicate the image on another layer. Open the Histogram (Window/Histogram). Now select Image > Adjustments > Posterize, enter the number 15 and view the image as a Preview. Watch the Histogram window as you preview the image. The graph will display only 15 vertical columns instead of 256 but the image will look pretty much the same.

The point I’m making is that “gaps” in a normally smooth histogram doesn’t necessarily indicate a visual disaster. Instead, a few gaps might just inject a little more drama in your images.

Smooth Flowing Tones

RUMOR #7: Digital captures should display the highest number of tones possible in order to preserve the smooth continuous tones.

FACT: While nature provides an extreme level of dynamic range and true continuous tone gradation, there is no such thing as “continuous tone” digital images. The word “digital” affirms this statement. Virtually all digital images are comprised of square pixels displaying individual tone values. The perception of continuous tone is an illusion.

These blue pixels were captured from the sky of the Thunderbirds image above. The patch of sky appears as continuous tone in the original picture although the enlarged individual pixels vary quite a bit in value. The top histogram shows the combined channel luminance while the bottom shows individual RGB channel values. It’s complicated.

Exhaustive Reference

RUMOR #8: A Histogram is an exhaustive systematic and statistical accounting of all the internal colors and tones of an image, from dark to light (100% – 0%).

FACT: Each histogram does reveal the relative placement and distribution of all tones and colors, but due to its size, there is a serious limitation to its accuracy. Since editing software histograms are based on a horizontal graph only 256 pixels wide, each representation is a basic overview at best. If the full range of possible colors were truly represented by a single graph, the chart would occupy the wall of a good size room!

Both the top and bottom tonal adjustments were severe enough to create significant gaps in the histogram and to alter the shift of tones in each range, though there are no visible interruptions in the smoothness of each gradation.

Let me break down the numbers. This 256 pixel-wide graph portrays each image’s potential color range using an 8-bit (256 level) interpolation. This means that all 16.8 million possible colors are represented in a mere 256 horizontal point histogram. Tones change levels in 0.4% increments. The graph significantly exaggerates the difference between minor shifts in tonal value.

Human eyes barely perceive a half-percent (0.5%) difference between tones, which is why 256 levels in a JPEG image provides the illusion of continuous tone. This means the histogram uses less than two vertical columns to represent a single percent of change in value.

The two bottom patches are separated by only 1% in tone, though your eyes may have trouble seeing the difference. The top band shows a gradual change between the two values.

What does all this mean? Quite simply, the histogram delivers a good estimation of overall tone distribution but cannot be relied on for accurate measurement. A few gaps in the graph will rarely be visible to the human eye.