HDR Photography Photo Workshop Sample Chapter

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DYNAMIC RANGE

WRANGLING WITH EXPOSURE

SINGLE-EXPOSURE LIMITATIONS

TRADITIONAL SOLUTIONS

THE HDR ANSWER

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Although digital photography is a compellingand satisfying endeavor, there are significant limi-tations to the technology. You don’t often hear ofthem as such, but they affect you every time youpress the Shutter button. The most serious ofthese limitations, as it relates to High DynamicRange (HDR) photography, is dynamic range.

The simple truth of the matter is that digitalcameras are unable to fully capture what you seewith your eyes much of the time. The world is adeeply complex subject whose own dynamicrange from dark to light far and away exceeds thedigital camera’s ability to record it. To make mat-ters worse, you often limit yourself to an averagedor compromised exposure when you rely on a sin-gle photograph and normal processing techniquesto capture and present everything. This chapterprepares you for the wealth of HDR informationand techniques presented later in the book byillustrating the problems inherent in digital pho-tography today. You learn about dynamic range,exposure, metering, and see examples of howphotographs are typically compromised by limiteddynamic range. You briefly see several traditionalsolutions to these problems so you can comparetheir effectiveness to HDR.

DYNAMIC RANGEWithin the context of photography, dynamicrange is the range of light, from little to much,that can be measured and recorded, normally by asingle exposure. It is not how little light can bemeasured; nor is it how much light can be meas-ured. It is the difference between the two.Dynamic range is often characterized by theterms exposure value (EV) levels, zones, levels, orstops of range.

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Quantifying dynamic range can be a problematicaffair. There is no official standard, per se; nor docamera manufacturers list each model’s dynamicrange as part of their specifications. The specificdynamic range of your camera is something youwill have to experience, positively and negatively(see 1-1), firsthand.

If you understand a few technical factors behindthe scenes, as explained in the following sections,it will help you understand why dynamic rangeoften seems so limited.

Blown-out details, quite often skies,are the result of limited dynamic

range. Too much light overexposes parts of the sceneand the camera literally cannot measure any morelight. The resulting image has no details in the overex-posed areas.

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Throughout the course of this book,the context of the term dynamic

range refers to the range of brightness in a scene. It is,in essence, the contrast ratio of the least illuminatedarea to the most. In a larger sense, dynamic range canrefer to any system where you compare two extremes,such as in audio.

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SENSOR WALKTHROUGHTo understand how a camera’s sensor works, ithelps to use an analogy. Begin by imagining abucket. This bucket holds electrons and repre-sents an effective pixel-sized sensor in your digitalcamera. The sensor absorbs photons that strike itduring the exposure and generates an electroncharge that is held in the bucket until the expo-sure ends. The strength of the charge reflects howmuch light was measured. This value is passed toan analog-to-digital (A/D) converter with datafrom the rest of the sensor and turned into animage file.



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As you might imagine, the size of the bucket(called full-well capacity) dictates how muchlight the sensor can measure. The differencebetween a full bucket and an empty bucket is thetheoretical maximum dynamic range of the sen-sor. The larger the bucket, of course, the greaterthe dynamic range of the system.

There are a number of factors that reduce a sen-sor’s dynamic range. These range from electronnoise (see 1-2), which interferes with a sensor’sability to record extremely low levels of light, topixel size and sensor efficiency. Simply put, nosensor is perfect.

BIT DEPTHThe bit depth of a camera is analogous to the stopscale. Each stop doubles or halves light, which isexactly how bits work. Adding a bit to a binarynumber doubles it. Conversely, removing theleading bit of a binary number halves it. Each bit,

HDR PHOTOGRAPHY PHOTO WORKSHOP / Dynamic Range and DigitalPhotography

ABOUT THIS PHOTOThis photo was taken outsideon a bright, sunny day of a vintage World War II aircraft.The dynamic range of thescene was too much for thecamera to handle. The darkplane looks fine, but the skyand concrete are too light. (ISO 100, f/9, 1/125 second,Sony 18-70mm f/3.5-5.6 at60mm) © Robert Correll

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Another factor indirectly affectingdynamic range, and beyond the

scope of this book, is the linear nature of a digital cam-era’s response to light. They do not work as our eyes do.The linear quality of the sensors makes digital camerasincredibly valuable in astrophotography. The directresult is the ability to combine many short exposures,which are more easily attained, into longer ones.

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ABOUT THIS PHOTOThis high-ISO shot of jellyfish amplifiessensor noise along with valuable light. (ISO 3200, f/4, 1/20 second, Sony18-70mm f/3.5-5.6 at 18mm) © Robert Correll



therefore, provides a stop’s worth of dynamicrange. Thus, a 12-bit camera has 12 stops ofpotential dynamic range, which results in 4096levels of light-to-dark discrimination in eachcolor channel.

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Finally, bit depth can also be used to describe thenumber of colors a camera can capture and storein a file. In this sense, a camera with a greater bitdepth has more color-sensing ability. Each colorchannel of a 12-bit camera can contain up to4096 different shades of that color, resulting in atremendous number of total colors that the threechannels can combine to reproduce. However,dynamic range is the story of brightness, notcolor. As mentioned previously, the shades ofcolor are not evenly distributed across the bit-depth system, which results in a skewed intensityrange for each color. Therefore, having 4096 pos-sible shades of each color is not enough to cap-ture the true dynamic range of a scene withoutcompromise. If it were, you would never needworry about a blue sky turning white.

If you’re wondering where 4096comes from, it is 2 to the 12th

power. The base is 2 because we are dealing with abinary system. Bit depth provides the exponent. If yourcamera takes 14-bit raw photos, 2 to the 14th powerequals 16,384 levels.

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That may seem like a lot, but unfortunately, evena 12-bit camera which can measure 4096 discreteshades of light in each color channel does nothave the dynamic range necessary to capture asimple scene at the zoo without blowing outhighs and losing details in shadow (see 1-3).

1-3 ABOUT THIS PHOTOThis photo, processed from a12-bit raw image. (ISO 100,f/5.6, 1/160 second, Sony18-70mm f/3.5-5.6 at 35mm) © Robert Correll



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WRANGLING WITHEXPOSURELike wrestling a steer to the ground in a rodeo,exposure can be a difficult beast to control, espe-cially if you don’t want to resort to flash photog-raphy, EV adjustments, changing ISO, or othertechniques. This difficulty is a practical effect oflimited dynamic range.

EXPOSURE EXPLAINEDExposure is how much light reaches the camera’ssensor during a single photograph. There aremany ways to manage light and its effect on theprocess, but there are two central ways to controlexposure: shutter speed and aperture.

■ Shutter speed. Measured in minutes, seconds,or fractions of a second, shutter speed setshow fast the shutter opens and closes. Thelonger it remains open, the more light makesit into the camera. Faster shutter speeds let inless light. The typical dilemma for a photogra-pher is finding the right shutter speed forscenes with high contrast and movement, asillustrated in 1-4. It is clear that the interiorof the tunnel would need a longer exposure toallow the details to be seen. However, slowingthe shutter speed to take a longer exposurewould increase the amount of light the cam-era senses and not only lighten the inside ofthe tunnel, but it would cause the action inthe scene outside the tunnel to be reduced toa blur. Additionally, the longer exposurewould cause the sky to be blown out.


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ABOUT THIS PHOTO Standing in a tunnel, the outside is perfectly exposed, but the image lacksdetail inside the tunnel. (ISO 100, f/4, 1/200 second, Sigma 10-20mm f/4-5.6 at 16mm) © Pete Carr



■ Aperture. This describes the size of the open-ing in the lens that focuses light past the openshutter and onto the sensor inside the camera.A larger opening lets more light in and asmaller opening permits less light in.Artistically, larger apertures result in a shal-lower depth of field, blurring deeper area ofthe foreground and background. Along withthe focal length of a lens, the aperture is usedto determine f-stop.

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Manipulating shutter speed and aperture are noless important in HDR than in traditional pho-tography, although you will do so with a differentpurpose in mind. In HDR, you often use a hand-ful of photographs to capture a wider dynamicrange of light than is possible in one exposure.

Depth of field refers to the size ofthe area you perceive as in focus,

extending in front of and behind the plane the lens isfocused on (most often the subject). Shallow depths offield have a narrow area in focus, with blur elsewhere.This often results in a wonderful artistic effect. Deeperdepths of field have more in focus, both in front of andbehind the focal distance. Deeper depths of field areimportant in landscape and architecture photographybecause a much deeper area of the photo remains clearand sharp.

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F-STOPS The f-stop is an important subject in photography. F-stops allow the effects ofaperture on exposure to be expressed between different lenses and focal lengths, which is agreat timesaver when determining exposure values. This is because focal length, which is thedistance between the lens and its focal point (which is on the sensor when in focus), is differ-ent from one lens to another. As a result, you do not dial in a specific aperture size when set-ting the exposure; you set the f-number (hence the term f-stop).

For a given focal length, setting a larger f-number (sometimes called stopping down) causesthe aperture to shrink and lets less light into the camera. It also deepens the depth of field.Setting a smaller f-number (also called stopping up) causes the aperture to grow and lets inmore light. This also results in a shallower depth of field.

Manipulating exposure is very important in HDR photography, but the f-number normallyremains the same across exposures. This keeps the depth of field constant. In addition, HDRexcels at shooting landscapes and larger shots where a deeper depth of field keeps every-thing in focus.

For more information on the gearyou need for HDR, please refer toChapter 2.

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EXPOSURE VALUEAs a photographer, you manipulate shutter speedand aperture size (through choosing an f-stop) tocontrol exposure. If exposure is a reflection ofhow much light enters the camera during a pho-tograph, exposure value (EV) illustrates the rela-tionship between exposure, shutter speed, andf-number. EV is not a precise calculation of the



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quantity of light during the exposure. It is a work-ing number that allows the effects of alteringshutter speed and aperture on exposure to bequickly and easily compared.

For example, 1-5 is a high-contrast scene takenfrom the inside of a log cabin. The calculated EVis between 11 and 12 for this exposure, which hasunderexposed the interior and overexposed theview through the door. Looking out the rightwindow reveals the best exposure for the land-scape beyond. The dynamic range of the camerawasn’t large enough to capture the light and darkextremes in this scene at this EV, and moving theEV (by changing shutter speed or aperture onyour camera) just results in a different compro-mise — not more dynamic range. With HDR,you will often take more than one photo, eachseparated by ideally 1 or 2 EV, to extend yourdynamic range. In situations where you cannottake more than a single exposure, there is a technique that uses one raw photo as the sourceimage for HDR, which is a process detailed inChapter 3.

It is easy to find EV tables on the Internet thatlist combinations of shutter speed and f-numberto give you the EV number. You can also calcu-late the range of EV for every combination of f-stop and shutter speed yourself using the formulafor EV and a spreadsheet.

Study the relationship between EV, f-stop, andshutter speed, and know that this is the playingfield for exposure. The settings you normallychoose are limited by your camera’s dynamicrange and the situation at hand. HDR effectivelyexpands the EV you can capture, allowing you toextend the dynamic range of your camera andproperly expose different elements of a photo-graph without having to sacrifice detail or aes-thetic quality.


1-5ABOUT THIS PHOTOShooting from within this logcabin shows how different EV levels make getting theright exposure difficult. (ISO100, f/8, 1/200 second, Sigma10-20mm f/4-5.6 at 12mm) © Robert Correll

You can change exposure, andhence EV, directly in software such

as Adobe Camera Raw and Photoshop, and indirectly inPhotoshop Elements.

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METERINGDigital cameras have built-in meters that measurelight and help set the right exposure. Prior to thisfeature, photographers had to eyeball it (usingtools such as the Sunny 16 Rule) or carry theirown light meter. Metering is an important skill inHDR photography because it allows you to evalu-ate a scene to arrive at the best overall exposureto bracket around or measure the extent of thehighs and lows of a scene in order to extend yourbrackets. If taking a single photograph for HDR,you will meter to take the best photo to startwith.

Many professional photographers carry lightmeters, and you may find having one convenientfor HDR photography as well, especially if youwork with a tripod. Once you mount your cameraon a tripod and compose the shot, you cannotmove the camera to do any further spot meteringwithout disturbing your setup.

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Virtually every digital camera today, and certainlyevery dSLR, has three metering modes, some-times four. Depending on the camera manufac-turer they may be called by slightly differentnames. They are:

■ Average. This mode evaluates different areasof the scene in order to arrive at an averageexposure. Within the bounds of your camera’sdynamic range, this is often the best compro-mise. The problem, however, is that high-contrast scenes (see 1-6) have a way ofoverpowering the camera. You typically losedetails in shadows and highlights.

■ Center-weighted. This mode gives the centerof the scene more weight in determining EV.It is a better choice if the subject is lit differ-ently than the background, but much of thebackground will be ignored in determiningthe proper exposure and so you risk losing itin shadow or highlights.

ABOUT THIS PHOTOThe subject turned out reason-ably well but was slightlyunderexposed because thebright sky overwhelmed theAverage metering algorithm.Spot mode on his face wouldhave been a better choice.Notice the broad range of dark shadows to bright sky inthis casual photo. (ISO 100, f/5, 1/125 second, Sony18-70mm f/3.5-5.6 at 30mm) © Robert Correll

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SINGLE-EXPOSURELIMITATIONSHaving taken a look at how it is often impossibleto capture the full dynamic range of a scene usingtraditional methods of manipulating exposure viashutter speed and aperture, this section looks atthe limitations of trying to capture and present

that dynamic range in a single exposure withstandard processing techniques, which oftenresults in exposure tradeoffs and compromises.

We aren’t saying it is impossible to take outstand-ing photographs in one exposure. However, youshould realize the limitations that have shapedphotography to see how HDR fits into the evolu-tion of the art.

SKIESSkies are notoriously hard to get right when thesubject of the scene is not the sky. The problem isthat a daylight sky is often too bright comparedto other scenery, especially anything in shadow. Itis so light (don’t confuse bright with blue — youcan have a very bright sky that is a deep blue),the sky dominates the exposure. Any attempt tolighten foreground subjects invariably overex-poses the sky, blowing it out (see 1-7).


Many Canon models combineEvaluative and Partial modes (their

terms for average and center-weighted) into a fourthmode called Center-weighted Average.

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The mere fact that there are several methods tometer light in a scene should tip you off to thefact that a camera’s dynamic range is limited, andtherefore most photographs are the result ofchoosing the best exposure compromise. If thiswere not so, you could simply point the cameraand shoot, regardless of the lighting, and every-thing would look great.

Although often expensive, lightmeters can be far more accurate

than in-camera metering and their spot modes can bemore precisely targeted.

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■ Spot. This mode meters the center of thescene only, which ensures what you meter willbe exposed correctly, but nothing else will betaken into account. Paradoxically, this worksgreat for scenes with a large dynamic rangebecause you choose the one thing that getsexposed correctly. Unfortunately, everythingelse often suffers.

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ABOUT THIS PHOTOThis is an example of a blown-out sky. Theperson is nicely exposed but the background is completely lost, orblown out. (ISO 400, f/8, 1/3200 second, Canon 24-70mm f/8 at 70mm)© Pete Carr



BUILDINGSWorking with buildings as your subjects is far dif-ferent than working with portraits in a studio ornearby subjects outside. There are two reasons forthis: scale and sky. The scale of a building is nor-mally far larger than other subjects (landscapes asa whole being the exception). You can’t use aflash to brighten a building, or use an umbrella to

soften the light around it, or turn it in relation tothe sun. You’re basically at its mercy and mustoften wait for the perfect lighting and sky condi-tions to take the photo. Even then, details in thebuilding are often lost because the sky pushes theEV up, which underexposes the buildings, makingthem darker. Trying to expose the building prop-erly usually blows out the sky, as illustrated in 1-9.

The same photograph processed as HDR (see1-8), however, reveals the details that were previ-ously hidden in shadow or lost in highlights.

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The problem doesn’t go away when clouds arepresent, especially if it’s partly cloudy and the skyhas extreme light-to-dark areas of clouds and sky.Overcast days, paradoxically, can be a joy toshoot in because they even out the dynamicrange of the scene.

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ABOUT THIS PHOTO Here you can see how HDR brings the skyback into the image shown in figure 1-7. It is an HDR image created froma single raw exposure converted to three bracketed exposures thatbring out the full dynamic range saved in the raw file. © Pete Carr



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When you know you can’t expose both the build-ing and the sky correctly, you have a choice:shoot for the building or shoot for the sky. This isoften why photographers choose to shoot duringthe Golden Hour. The light is most forgiving dur-ing this time and produces better photographs.HDR won’t make the light at noon better thanthat of the Golden Hour, but it does enable youto bring out more detail in scenes photographedduring off-hours and extends your dynamic rangethroughout the day.

SILHOUETTES AND SUNSETSSilhouettes and sunsets are at the opposite end ofthe spectrum from shooting portraits and build-ings. Here, you typically want the items in theforeground, such as a person or landscape featuresto be in very dark shadows that are silhouettedagainst a brighter sky or sunset.

In other words, the building or landscape is innear total shadow and the sky is properlyexposed. The fact that foreground details are lostwhen shooting silhouettes and sunsets is expectedand aesthetically pleasing.

In both cases, you meter for the brightest objectin the scene, either the sky or the sunset. Thissets the EV high, which is exactly what you want.It underexposes the foreground and turns it to sil-houette or shadow. Buildings turn to black shapescarved out of a red sky, as seen in 1-10.

Difficulties arise, however, when you want detailin these situations (low foreground light at sunsetand dusk) and cannot achieve it for lack of the

ABOUT THIS PHOTOThis is an example of an overexposed photo with a blown-out sky. (ISO 100, f/5.6, 1/250 second, Sigma 10-20mm f/4-5.6 at 10mm) © Pete Carr

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The light during the Golden Hour,which is the first and last hour of

sunlight each day, is generally softer, more diffused,and the shadows are gentler. Of course, if you are nearthe Arctic Circle or in Antarctica, your mileage ongolden light may vary.

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proper exposure. If you’re on the beach with yourfriends enjoying a summer barbeque, you can’tilluminate the entire beach with a flash. HDRphotography helps in those situations. You don’thave to go overboard, but you can get a beautifulsky, silhouette in the background, and properlyexposed subjects without flash using HDR.

TRADITIONAL SOLUTIONSOver the years, photographers have developedquite a few solutions to getting around the lim-ited dynamic range of their cameras. This section

gives you a taste of some more traditional meth-ods so you can see how they compare to the HDRexamples shown throughout the book.

LIGHTINGAdditional lighting helps you bypass the dynamicrange issue by controlling the light differencesbetween subject and background, and hence lim-iting the contrast. For example, if you are a studiophotographer, you have the luxury, and some-times the burden, of complete control over light-ing and environment to achieve whatever artistic

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ABOUT THIS PHOTOThis is an example of a photo intentionally showing huge areas insilhouette. (ISO 100, f/22, 1/45 second, Canon 28-105mm f/3.5-4.5 at 45mm) © Pete Carr



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effect you desire, such as in 1-11. It’s a perfection-ist’s dream. If you need less light, you can blockout windows. If you want more contrast, you can choose a different background or turn itwhite and remove shadows for a high-key effect(intentionally lowering the overall contrast ratioof a scene). You can put lights above, behind,below, or to the side. You can add reflectors,brollys, softboxes, snoots (if you are in doubt

about what these are, check out a lighting orcamera sales Web site), or bounce the light offthe wall.

It is also easy to get by with less. If you have twolights and a white or black backdrop, you havethe ability to create or remove shadows. You canbe creative and place a light behind the subjectfor a nice glow. Many of these options reduce thecontrast of the scene, thereby reducing thedynamic range in your photo.

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ABOUT THIS PHOTOThe lighting in this standard studio shot has been carefully manipulated toprecisely create this crafted look. (ISO 100, f/13, 1/160 second, Canon 24-70mm f/2.8 at 28mm) © Pete Carr



Lighting on location is far trickier because youlose total control. You may have no say over thebackground lighting, which is often up to nature.You do, however, control how bright the model isand can therefore balance that with the back-ground. If you have a few lamps, strobes, orreflectors, you can illuminate the model nicely.Again, this reduces the contrast between yoursubject and the background, which in turnreduces the dynamic range of the image.

NEUTRAL DENSITY FILTERSLandscape photographers use Neutral Density(ND) filters to darken portions of their photos.ND filters filter out all wavelengths of lightequally, resulting in an evenly reduced exposure.

There are two main types of ND filter: graduated(ND grad) and non-graduated. Both types comein various strengths. Unlike software solutions to

exposure, you can see the effect before you takethe photo, and can therefore adjust your settingsto get the best exposure value.

ND grad filters are particularly well suited toscenes with simple horizons, as shown in 1-12.They sky was very bright and had to be toneddown dramatically compared to the beach andwater. An ND grad filter was a perfect solutionfor this scene. Had it not been used, the skywould have been blown out and devoid of detail.

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ABOUT THIS PHOTOHere you can see an ND filter inaction. This is a straight shotwith minimal processingapplied, and you can see hownicely the sky has turned out.(ISO 250, f/6.3 1/640 second,Sigma 10-20mm f/4-5.6 at10mm) © Pete Carr

A filter is a thin piece of glass (someare made from other materials like

plastic) that goes in front of the lens of your camera andis manufactured to filter out certain wavelengths oflight. They are often clear, although some are polarizedand others colored. Many filters are round and screwonto the front of the lens. Others are rectangular andslide into a mount that attaches to the lens.

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ND filters are not without their problems, how-ever. If the horizon is not perfectly straight (trees,hills, buildings, and mountains get in the way andcomplicate things) and you use a graduated filter,details on the intervening scenery are likely to beunderexposed and mountains or other objectsmay look like they have halos around their tops.

In short, ND filters are a great tool to use if thelandscape is neat and tidy, but not the best solu-tion for chaotic or complex horizons. HDR worksin any of these situations because it is not depen-dant on the horizon line being level.

CONTRAST MASKINGContrast masking is a software technique thatevens the contrast of an image. The idea is to usea new layer to bring out details in the shadows ordarker areas and tone down highlights in the sky(see 1-13).

Without getting into too much depth, contrastmasking involves duplicating the photo layer,desaturating the new layer, and then inverting it(it will look like a gray negative). Desaturatingthe duplicate layer focuses the end result onbrightness rather than color and inverting thelayer pushes the original highs and lows in theopposite direction. The final steps are changingthe blend mode of the duplicate layer to Overlay,which lightens or darkens values from the lowerlayer, and applying a Gaussian Blur to it so that itdoesn’t completely mask the original brightnessof the photo. In the end, selective erasing of theinverted layer helps restrict the effect to thedesired areas.

Despite the fact that contrast masking may workin some situations, it can be an inelegant solu-tion. Rather than spend time duplicating layers,

ABOUT THIS PHOTOThis high-contrast sceneincludes a very dark tunnel andbright white clouds. While con-trast masking has helped bringout more detail in the tunnel,the sky is still blown out. (ISO 200, f/5.6, 1/250 second,Sigma 10-20mm f/4-5.6 at10mm) © Pete Carr

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inverting, blurring, and erasing just to get theright exposure by further compressing thedynamic range of a photo, it’s more fun to shootfor HDR and be creative in the processing.

EXPOSURE BLENDINGYou could call exposure blending an early form ofHDR. In fact, it began (as many software tech-niques have) in the darkroom. The idea was totake more than one photo and blend them whilemaking the print. Today, exposure blending ispredominately a software process, and begins withtaking more than one photograph.

For example, to photograph a landscape with abright sky, take one photo of the land properlyexposed, then take another and set the exposurefor the lighter sky. You can take as many photos asyou want, each differently exposed, as long as youuse a tripod and keep the scene composed identi-cally between exposures. Later, blend them inPhotoshop as different layers, as shown in 1-14.

There are a number of ways to perform exposureblending in software. You can change blendingmodes from soft-light to pin-light, or erase partsof the image you don’t need and work them untilthey blend together. Ultimately, this can be atricky and time-consuming process.

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ABOUT THIS PHOTOTwo exposures are merged together in Photoshop to create abalanced photo. (ISO 100, f/4, 1/50 second, Sigma 10-20mm f/4-5.6 at 10mm) © Pete Carr



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HDR photography is very similar to this on thefront end (taking the photos), but in software isvastly different. HDR software such as Photomatixautomates blending and other aspects of this task.

TWEAKING SHADOWS AND HIGHLIGHTSAnother reasonably simple solution to overcom-ing your camera’s limited dynamic range is totweak the shadows and highlights of your photoin your favorite image-processing application.You can recover some detail from a JPEG usingthis technique in Photoshop Elements. It is easyto ruin the image if you try and push too hard,however. JPEGs have only a stop or so ofenhancement in them before they are ruined bynoise and color banding. Tweaking shadows andhighlights can recover some detail in dark andlight areas, such as in 1-15. The tree trunk hasbeen lightened and the bright area of the sky hasbeen toned down a bit with Shadows/Highlightsin 1-16. If the result was a bit gray, as was the casehere, add a moderate amount of contrast backinto the photo to clean it up.

Although you may still want to use this shadowand highlight technique, properly shot HDRreduces the need for most shadow and highlighttweaking for anything but aesthetic reasons.

DODGING AND BURNINGDodging and burning are two techniques thatalso have their roots in the darkroom. Dodginginvolves lightening specific areas of a photo. Forexample, if someone’s face is a bit too dark, youcan dodge to lighten it and make the personstand out more. Burning darkens areas of thephoto. If, for example, the sky is too light, a smallamount of burning can bring it back in line with

the rest of the photo. In these ways, differentareas can be exposed with different amounts oflight, resulting in customized exposure levelsacross the photo.

In theory, dodging and burning are simple, butthe default exposure strengths in Photoshop andother applications are set so high that it’s almostimpossible to get good results without a good dealof tweaking. The key is to take it easy and set thestrengths correctly. If necessary, apply evenly overmore than one application. Using a pen tablethelps tremendously.

The Dodge and Burn tools are located togetheron the Tools palette of Photoshop. The Dodgetool looks like a small paddle that holds backlight and the Burn tool is a small hand. Here aresome tips to help you dodge and burn:

■ After selecting the Dodge tool, set thePainting Mode range to Shadows to bringdetails out of darker areas.

■ Start with the Exposure between 10% and20% when dodging and then alter as needed.

■ Set the Painting Mode range for the Burntool to Highlights to darken overly brightareas or Shadows to deepen existing darkareas.

■ When burning, set Exposure under 10% tostart and alter as needed.

Doing a poor job with the Dodging and Burningtools can create halos around the areas youmanipulated, so be prepared to experiment andstart over. It is also possible to increase noise lev-els in areas as you dodge. Additional noise maynot be a problem, especially if you are workingwith black-and-white photos (see 1-17). In thosecases, a little extra noise looks like film grain andis aesthetically pleasing.



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ABOUT THESEPHOTOS In figure 1-15, thetree is in shadow and the sky ison the verge of blowing out.This called for aShadows/Highlights adjust-ment in Photoshop Elements torecover detail. The results areshown in figure 1-16. (ISO 100,f/8, 1/125 second, Sigma10-20mm f/4-5.6 at 10mm) © Robert Correll

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On the whole, be prepared to continue dodgingand burning even when you shoot HDR, but yourattention will be much more finely focused onthe subtle details rather than trying to rescue thephotograph.

FILL LIGHT AND RECOVERYIf you use Adobe Lightroom or Adobe CameraRaw (from within many Adobe products, evenPhotoshop Elements), there are two very quickand easy ways to rescue hidden details from stan-dard photos: Fill Light and Recovery.

Details get lost in shadow because the limiteddynamic range of the camera forces the photo tobe underexposed in darker areas to avoid clipping

the highlights. Fill Light selectively brightens thedark and midtones of a photo, moving themtoward the lighter end of the histogram. If youare using HDR, the multiple exposures capturethese details more suitably in the first place, soyou don’t have to resort to using Fill Light tobring them out.

Overexposed highs normally happen with skiesand other bright objects, a problem once morecaused by the limited dynamic range of the cam-era. In this scenario, if the subject is exposed cor-rectly, it leaves the sky white or blown out. To fixthis, Recovery works opposite of Fill Light.Recovery takes the highs of a photo and bringsthem down into a reasonable balance with therest of the photo.

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ABOUT THIS PHOTOThis classic black-and-white photo has been enhanced with dodgingand burning. (ISO 250, f/6.3, 1/800 second, Sigma 10-20mm f/4-5.6 at 10mm) © Pete Carr



A gentle application of both techniques is illus-trated in 1-18. The bright remains of the settingsun are too bright, resulting in some blown outpixels. In addition, the sky and outer areas of thephoto are very dark. Using Fill Light helpslighten those areas up and makes the waterclearer from foreground to background. Generallyspeaking, it is not wise to overdo Fill Light orRecovery or you may lose contrast and tone, orelevate noise.

Both tools attempt to lessen the effects of limiteddynamic range by bringing out details that are inthe raw file but may be lost in the conversion toJPEG (see the next section for more on raw).They do not actually increase dynamic range, butthey can help bring out what is there already.

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ABOUT THIS FIGURE A sunset image has been enhanced with Fill Light and Recovery in Lightroom.(ISO 100, f/4, 1/15 second, Sigma 10-20mm f/4-5.6 at 10mm) © Robert Correll



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POST-PROCESSING WITH RAWProcessing raw images (which includes Fill Lightand Recovery) is a very good technique forincreasing exposure flexibility because, unlike 8-bit JPEGs, raw images contain the full dynamicrange of the original photograph. In other words,when a camera converts sensor data to a JPEGfile, it reduces the dynamic range of the photo.Cameras often let you choose an artistic stylesuch as portrait, landscape, or vibrant for it to useas a guideline when it converts from raw to JPEG,but you will directly control the process if you doit yourself.

The tradeoff to control is an altered workflow,increased time spent post-processing, and space.Photographers who have to process thousands ofphotos often find the convenience of JPEG out-weighs the merits of switching to raw. If this isyou, you will find HDR more time consumingthan pumping out JPEGs, but HDR will pay divi-dends for important photos.

In the end, working directly with raw photos is astep towards HDR, but still stops short of it. Youhave more dynamic range with a raw photo com-pared to a JPEG out of the camera, but are stilllimited by processing options of the raw editor.Current raw editors reveal a traditional, single-exposure mindset. You cannot blend exposures,tone map a 32-bits/channel HDR image, or useother techniques unique to HDR.

THE HDR ANSWERThe traditional single-exposure technique is thestandard way most people take photographs. It isvery powerful and you can take wonderful shots

with it. It should be clear to you now, however,that you often can’t have it all in one exposure.When you meter for bright areas the dark areasare too dark. They are not an accurate reflectionof what you see. When you meter for dark areasthe highlights get blown out. When you use theaverage reading your subject may be exposedproperly, but other areas suffer. In high-contrastsituations, you have to make a choice. What doyou want to see well?

In those situations it is normally best to err onthe side of not blowing out highlights. This isgood practice, of course, but it can skew your per-ception of the dynamic range of a camera. Youthink everything is okay when it’s not.

HDR is both a photographic discipline and soft-ware process that attempts to overcome the expo-sure problems discussed thus far. HDR bypassesthe limitations of dynamic range using two inno-vative exposure bracketing approaches. The twoapproaches differ in how you create the bracketedexposures.

HDR PHOTOGRAPHYOne method of HDR photography is to shootmultiple, bracketed exposures (see 1-19 through1-21). You can take more, but three is the mini-mum for good bracketing. The first photo is anormal exposure with a good balance of highsand lows (depending on the subject). This iswhat you should be shooting already. The secondis deliberately underexposed to bring down high-lights and keep them from being blown out. Thethird photo is overexposed to bring up the shad-ows so you can see what is in them.



The other method uses a single raw photo, whichis used as the source to create three bracketsfrom. You end up with three bracketed files (oneunderexposed, one properly exposed, one overex-posed), just as you would if you took three photo-graphs. This technique is especially useful forphotographs of moving objects and other sceneswhere you do not have time to bracket, such as infigure 1-22.

HDR PROCESSINGThe second aspect of HDR is in software. HDRsoftware such as Photomatix creates high bit-depth images from single (called pseudo-HDR) ormultiple lower-depth exposures. After that, youtone map the HDR file to bring out details andcreate (or avoid) artistic effects. HDR software isspecifically optimized for this purpose and auto-mates much of the process. You don’t have to cre-ate complex masks, use blending modes, or varythe opacity of different image elements toachieve your purpose. After saving the tone-mapped file as a JPEG or TIFF, you can furtherpost-process the photo with your favorite imageeditor prior to distribution.

A completed HDR file is shown in 1-23. It wastaken from three bracketed photos which weremerged into HDR, then tone mapped to createthe look you see here. Notice that the sun is inview. This should cause the camera to underex-pose everything else, resulting in dark shadows orsilhouettes. However, details on the facing side ofthe arch and in fact the rest of the photo areclearly visible. This is the power of HDR. Youcan retain more detail in your photos, are able toshoot in a wider range of lighting conditions, andcraft your final product to suit your artistic tastes.

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ABOUT THESE PHOTOS Shown here are examples of a nor-mally exposed (1-19), underexposed (1-20), and overexposed photo(1-21). They show the range of light in your average photo and why youneed HDR to fully capture all this light. 1-19 shows an average expo-sure, which is probably what you’d get on a normal day. 1-20 has beenunderexposed by 2 stops to bring out the detail in the sky. 1-21 hasbeen overexposed by 2 stops to bring out the detail in the building, butat the expense of the sky, which is now just white. (ISO 100, f/8, 1/80second, Sigma f/4-5.6 10-20mm at 10mm) © Pete Carr

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1-22ABOUT THISPHOTOThis was takenat a street festival a couple of years ago. The flash wouldn’t perform so HDR wasused to bring back someof the detail in thesedancer’s dresses and thesky. (ISO 100, f/4, 1/200second, Sigma 24-70mmf/2.8 at 24mm) © Pete Carr

1-23ABOUT THISPHOTOThe largestChinese Archway inEurope is located inLiverpool, England. WithHDR processing andbracketed exposures,shooting directly into the sunset can be donewithout sacrificing thedetail in the arch. Createdfrom three raw photosbracketed at -2/0/+2 EV(ISO 200, f/6.3, 1/125 sec-ond, Sigma 10-20mmf/4-5.6 at 18mm) © Pete Carr



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Assignment

Remember to visit www.pwassignments.com after you complete this assignmentand share your favorite photo! It’s a community of enthusiastic photographersand a great place to view what other readers have created. You can also post com-ments, read encouraging suggestions, and get feedback.

Photograph a High-Contrast Scene TraditionallyThis chapter has given you a lot of information about dynamic range and digital photography.Now it’s time to become personally involved in the process. Grab your camera and complete thisassignment to investigate the effects of limited dynamic range for yourself.

Find an interesting high-contrast scene. It should have a good range of shadows and highlights.Make it a challenge. It can be indoors, outdoors, or some creative combination of the two.Although you may want to experiment with filters, flash, or other exposure techniques, shoot atleast one photo relying on the camera’s inherent dynamic range to capture the scene to share.Try and take the best photograph you can, and note where you are making compromises.

Robert took this photograph on a bright sunny day from within a gathering pavilion at a localpark. The challenge in this situation was trying to strike the right balance between interior andexterior exposure. This photo represents an average exposure, which compromises bothextremes. Interesting interior details such as the wood grain within the pavilion are lost in shad-ows, and although the exterior doesn’t look too bad, the play equipment, grass, and sky sufferbecause of the glare. Taken at ISO 100, f/11, 1/15 second, Sigma 10-20mm f/4-5.6 at 10mm.

© Robert Correll




Documents

HDR Photography Photo Workshop Sample Chapter