SharpeningCompared

Unsharpened / Hybrid / Strong HDR

HDR software is most typically used to render shadow and highlight detail, but it can also be used to enhance tonal separation and detail in any range of tones, even in images with extremely low contrast. The very same tools that are used to compensate for HDR side effects can be used to sharpen any image.

When multiple bracketed exposures are merged into a single processed file, shadows and highlights that exceed the dynamic range of a camera’s sensor are compressed into the dynamic range of a digital file, taking the mid tones with them. Depending on the HDR software used, a variety of tools are available to restore contrast and separation in mid tones. If used aggressively, these tools produce the telltale signs of contemporary or grunge HDR artifacts – halos and texture accentuation. These are the very same artifacts that digital sharpening routines use more conservatively to make images appear sharper – only they look different.

Unlike the hard halo and line produced by the filter Unsharp Mask and more like the soft line produced by the filter High Pass, HDR sliders can give you still more points of control over line and texture, each with a slightly different flavor.

For creative sharpening, compare two HDR software packages; Adobe Photoshop and NIK’s HDR Efex Pro.

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Photoshop’s HDR Toning

Adobe’s Photoshop’s HDR solution offers three points of control relevant for sharpening. One, Radius controls the thickness of the halo / line. Two, Strength controls the contrast of the effect. These two sliders are similar to the filter Unsharp Mask but the effect is much closer to the filter High Pass. Three, Detail accentuates texture, with minimal affects on contours. Unlike the filter Unsharp Mask’s Threshold slider, instead of suppressing the side effect of texture accentuation, this slider gives you the ability to control it independently of contour accentuation. (Settings lower than 100% blur the image but not its contours.) Photoshop typically offers the smoothest continuous tone effects.

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HDR Efex Pro

While Google’s HDR Efex Pro presets are rich and wonderful for visually exploring tone mapping variations, for detail enhancement you really only need to focus on two features. First, the Method, which set the base effect; Natural, Clean, Crisp, Halo Reduction, Subtle, Sharp, etc. Second, the Structure slider, which functions very similarly to Viveza’s Structure. Structure accentuates texture somewhat, which can enhance noise as well as detail, but not as much as Unsharp Mask. When Structure is applied, luminosity contrast increases, more so in shadows than in highlights where very high values stop just short of compromising shadow detail. Unlike, Viveza’s Structure, the effects on shadows and highlights can be modified with HDR Efex Pro’s Blacks and Whites sliders. Think of Structure as occupying the visual territory that lies between Unsharp Mask and High Pass. HDR Efex Pro’s interface is simple yet more versatile, which means you’ll spend a little more time exploring the many options it offers.

(HDRsoft’s Photomatix is excellent for tone mapping but it is difficult to separate contour and texture from tonal enhancement, making it an overly challenging addition to sharpening solutions.)

If sharpening is your goal, resist the temptation to use the other sliders in each interface; they won’t enhance detail only contrast. That said, much like Photoshop’s simpler TMO Shadows/Highlights they can be used to render shadow and highlight detail more clearly.

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Layer stack for blending multiple renderings

Once images are sharpened with HDR software, the rendered effect can be layered with an unsharpened version of an image, providing more control. Use the blend mode Luminosity to affect only the light and dark values. Use the Opacity slider to reduce the effect. (Knowing you can only reduce the effect, you’ll favor applying the HDR software a little aggressively.) Use the Blend If sliders to remove the effect from either highlights (halos) or shadows (lines) or both. Mask the layer to apply the effect to selected regions. You may even decide to use two (or more) different layers with different HDR treatments to customize effects for specific image regions.

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Before (left) & After (right)

And, of course, sharpening with HDR software can be used in combination with any other sharpening technique, like Unsharp Mask or High Pass filtration.

The options you have for controlling the look and feel of detail in your images are simply unprecedented in the history of the medium. Every digital artist will benefit from exploring these options.

Read more on HDR techniques here.

Learn more in my digital photography and digital printing workshops.

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Different HDR renderings accentuate different artifacts

HDR (high dynamic range) imaging captures extreme contrast ratios and subsequently renders them for LDR (low dynamic range) devices, monitors and / or prints. The very things that make HDR renderings appear natural can make them appear unnatural if taken too far.

Midtone compression

You can’t avoid midtone compression, they get caught in the middle when the relationships between highlights and shadows are compressed. But you can take steps to minimize it by being sensitive to this when choosing compression settings and amounts and by taking subsequent steps to expand it.

Tonal inversions

Some compression routines and settings can be so aggressive that they create inversions or solarizations of specific tonal relationships. Avoid this, there is no subsequent cure. If you like the overall effect of an aggressive setting and the inversion is contained to one area of an image you can render an image twice, once for the overall effect and once for a specific area, and then blend the two together using Photoshop’s layers and masks. 

Saturation Distortions

Saturation changes when lightness shifts but color stays the same. Because HDR produces effects that can be aggressive and localized to specific set of tones, the saturation shifts that accompany tonal compression often appear unnatural. Selectively adjusting the saturation of specific hues, with tools like the HSL panel in Lightroom or Camera Raw, can often convincingly cure a majority of these side effects and hide the rest.

Halos

HDR softwares help restore midtone contrast by accentuating contours. When used aggressively this edge contrast can produce halos.

Over the years, these algorithms have dramatically improved their ability to treat the halo (light line) separately from the line (dark line), suppressing the first more than the second. Sometimes, to avoid distracting halos at the border of skies, you may want to make a second rendering for the sky and blend it with another rendering using Photoshop’s layers.

Exaggerated Texture

The contour accentuation that HDR softwares use to help restore midtone separation can exaggerate texture, for better or worse. For this reason, HDR software routines can be excellent detail enhancers that produce different results than the standard image sharpening tools. Once again, the trick is not to overdo it.

Noise

Noise accentuation in HDR images is a bi-product of tonal compression and the routines designed to exaggerated micro detail. Just like LDR exposures, to avoid unnecessary noise use the lowest practical ISO setting. In addition, use exposures that are bracketed by two or fewer stops. Finally, plan to reduce noise after rendering; recent noise reduction algorithms are capable of producing remarkable results.

Banding

To avoid banding (most visible in smooth gradations) use exposures that are bracketed by two or fewer stops. Process files in a high (16) bit depth. When you see banding appear during rendering, change the settings that produce it; there is no satisfactory cure for banding in post-processing.

The vast majority of objections to HDR imaging come from observations of examples where practitioners were oblivious of or insensitive to these regularly occurring artifacts. When HDR renderings are made with these potential pitfalls in mind, the objections disappear. In many cases, viewers don’t realize HDR software was used in the production of a photograph. Some HDR renditions challenge classic photographic aesthetics and offer new ones. If viewers do recognize that these artifacts exist in images and they are appropriate for the visual statement being made, not unconscious bi-products but conscious choices, then viewers who are open minded may experience a sometimes surprising new window onto the world.

Read more on HDR techniques here.

Learn more in my digital photography and digital printing workshops.

8 HDR Myths Debunked

December 12, 2016 | 2 Comments |

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There are many misconceptions surrounding the practice of high dynamic range (HDR) photography. Here are eight – debunked.

HDR is new

Within the first five years of the invention of photography photographers began bracketing exposure to extend the dynamic range of photography. They used chemistry to process their negatives instead of software to process their files – but they still bracketed exposures to capture contrast ratios that exceeded paper, glass, and film.

HDR is hard

High dynamic range imaging has become so commonplace that cameras and software make it increasingly easy to practice HDR techniques – auto-bracketing, merging and rendering.

HDR requires the use of a tripod

While there are times when the use of a tripod is required, when exposures are long in duration, in a majority of cases current cameras’ auto-bracketing features and softwares’ image alignment algorithms make hand-held exposure bracketing highly practical.

HDR requires exposure bracketing with a fixed aperture

Aperture priority (fixing the f-stop) is recommended during bracketing to avoid changes in depth of field between exposures – and so the appearance of a loss of focus, which in extreme cases can make alignment challenging. However, it’s entirely possible to bracket exposure value by changing aperture, especially when depth of field issues are minimal. Shutter speed (motion), aperture (depth of field), and ISO (noise) can all be used to bracket; each has different consequences.

With HDR, you get better results with more exposures

Using too many exposures (half or quarter stops) can produce almost as many artifacts as using too fiew exposures (more than 2 stops); chiefly banding and excessive midtone compression.

HDR looks unnatural

The appearance of HDR images is flexible. What software you choose to render your image and how you choose to use it is up to you. You can produce a classical or a contemporary appearance with many possible variations in between. Whether the technique becomes invisible or obvious is a choice.

You can only choose the look of one HDR rendering

You can blend different renderings of the same image either globally or locally. (Use Photoshop’s layers and masks.) Again, how you choose to render your images is controled by you, not technology.

HDR is cheating

Really?

Read more on HDR techniques here.

Learn more in my digital photography and digital printing workshops.

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back LCD menu

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top LCD menu

It’s easy to set your camera to auto-bracket. The hardest part of this process is navigating a camera manufacturer’s menu. Once you find it – and do it several times – you won’t forget it.

Here’s how to do it on current Canon cameras – the steps are similar for other cameras but the buttons and menus vary.

First, set the number of frames made in each bracketed sequence. Press the Menu button. Use the main command dial (top) to cycle through the menus on the LCD screen (back) Go to the 4th tab (small camera) > 1st list and then the use the jog wheel (back) to select the 5th item. Press the set button to select it. Use the jog wheel to select the number of shots and press the set button once again. While 3 is the most commonly used, it’s not unusual to use 5 or even 7. Because 3 is the most commonly used number, it’s likely that once you set this, you’ll reset it infrequently.

Second, set the difference in exposure values between shots. Press the Menu button.

Use the main command dial (top) to cycle through the menus. Go to the 1st tab (large camera), 2nd list, 1st item. Use the set button to highlight this function and the command dial (top) to set the difference in exposure values, then press the set button again. Remember! Press the set button at the end of this – if you don’t these new settings won’t be saved.

Remember! Continue shooting in bracketed sequences as long as auto-bracketing is turned on. When you return to shooting single shots, turn auto bracketing off. If you don’t, one out of three exposures will be improperly exposed – because your camera is still bracketing exposure. The quickest way to turn auto bracketing off is to turn your camera off and on, which will turn auto-bracketing off on most cameras.

When auto bracketing is activated, on the display at the top of your camera you’ll see a series of bars indicating how many exposures will be made and at what exposure value.

What about exposure compensation? Use exposure compensation or not. Bracketing is extreme exposure compensation. All that matters is that you create multiple exposures that once combined render both excellent highlight and shadow detail.

For HDR exposures that are hand-held set your drive or burst mode to continuous; the fastest setting you have; One Shot is too slow.

For HDR exposures using a tripod, consider using a cable release and mirror lockup to further reduce camera motion.

Practice turning on and turning off auto-bracketing and it won’t seem nearly as complicated as the first time you do it and in time the habit will become so ingrained that you won’t have to think about it any more. But until turning auto-bracketing on and off becomes second nature, proceed carefully and methodically. The most common mistake is to turn it on and forget to turn it off.

Read more on HDR techniques here.

Learn more in my digital photography and digital printing workshops.

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Today’s cameras have the ability to generate HDR merges on the fly. The problem is that they produce JPEGs with a smaller gamut (lower saturation), lower bit depth (fewer shades of gray), and compression artifacts (noise and jagged edges) and they offer no control over the tone mapping process.

If you want a better HDR file, choose to make multiple bracketed Raw files, then merge and tone map them manually. Remember, aside from exposure settings, in camera settings that affect the look of your image have little or no affect on Raw files, which can be processed any way you want to process them.

In camera HDR JPEGs can offer a fast and convenient preview of potential HDR results. You can get the convenience of one and the quality of the other by setting your camera to produce both JPEG and Raw files simultaneously.

Read more on HDR techniques here.

Learn more in my digital photography and digital printing workshops.


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