Monday, October 24, 2016

Aurora HDR 2017: How it Compares

Aurora HDR 2017 is a recent update that added some new features, altered the interface somewhat, and purportedly improved the tone mapping. You can see their website for a complete list of changes since my intent here is to cut to the chase: how well does it render HDR images compared to the other standard bearers. I took several HDR images and compared the results between Aurora, Photomatix 5.0, Lightroom (Camera Raw) HDR Merge, and HDR Efex Pro 2. My criteria was simple, which one created the best traditional landscape photo with the most natural appearance.

The Contenders

Lightroom (or Camera Raw) HDR Merge
This is a relatively new feature that is essentially the best HDR tone mapping option within the Adobe suite. It is relatively devoid of artifacts, produces natural results, and has access to the complete Develop/Camera Raw toolset. It also runs fast and retains the tone-mapped file in raw format (as a 16-bit floating-point raw file). However, control over the dynamic range is more limited to where extreme highlights or shadows in some cases may not render as well as in the other HDR apps.

Photomatix 5.0
Photomatix is a hodgepodge of different tone mapping engines, but the Contrast Optimizer that was introduced in version 5 is the primary choice for creating natural landscape images (and the only method used in this comparison). Contrast Optimizer lacks all the gee-whiz features found in the other HDR products. The few toning controls that exist are frustrating to use and more limited in controlling the dynamic range. In the end, you will usually not produce an image with the same razzle-dazzle you’ll get from the other programs. That said, getting an eye-popping image out of your HDR software is not important or even necessary. Once you have produced a reasonably toned image, you’re essentially done needing 32-bit editing. After that, you can jazz up the image later in Lightroom or Photoshop just fine with 16-bit editing.

HDR Efex Pro 2
This program was my primary HDR converter. It’s not perfect, which is why I had the other programs handy whenever HDR Efex suddenly decided to choke. HDR Efex does a generally good job rendering most images. The interface is “Photoshop-like,” which makes it much easier to use than Photomatix. The tone-mapped image starts out relatively bland looking, which to the uninitiated may look disappointing. But that’s exactly what you want, a neutral image where you add whatever enhancements you want rather than correcting some “Frankenstein” result. HDR Efex’s biggest negative is its propensity for halo artifacts and noise. It can also have trouble sometimes rendering warm highlights by making them appear "bleached." 

Aurora 2017
When I first reviewed this product (click here), I was in awe of it’s features. This program has  every HDR editing tool you would ever need; actually to the point of excess. For me, the biggest “wow” feature was adjustment layers with a convenient way to add luminosity masks. Unfortunately, the luminosity masking feature is flawed (in my opinion) by limiting you to “slices” of the histogram rather than tapered selections for a more natural transition. You can feather the selection, but that’s not the same thing. 

The irony of this robust tool set is, unlike the other programs, you’ll need them to fix the “Frankenstein” image you get after the initial tone mapping. Aurora has a fundamental tone-mapping problem that unfortunately the 2017 version didn’t resolve. Aurora seems to have an obsession with warm tones and over-saturation in general. Many landscape photos are taken during sunrise and sunset where there are rich, warm tones throughout the image. Aurora takes those warm tones and blasts them to the moon. It was for this reason (and also there was no Windows version) that I couldn’t recommend Aurora and didn’t include it in the 2016 edition of my HDR ebook. I twice contacted Aurora and they admitted to the problem and assured me they would fix it in the next update, which obviously hasn’t been the case. Nevertheless, this time I decided to be more patient and after tediously manipulating their color-editing tools, I was able to tame the beast; though I still think the inconvenience is ridiculous and inexcusable.  

Untouched results after rendering three frames in Aurora.
The reds are garishly saturated and out of gamut.

The Face-off

My evaluation was based on producing the best landscape image using all the available tools within each HDR program without further editing in Photoshop or Develop. Keep in mind that further processing in either Develop or Photoshop will likely improve these images and, to some extent, even the differences. 

Bryce Canyon
A general characteristic of these four programs is that HDR Merge and Contrast Optimizer (Photomatix) tend towards a more traditional appearance or, if you prefer, more "film-like." Aurora and HDR Efex have a little of the exaggerated “HDR look.” HDR software has the ability to extract highlight and shadow detail that emphasizes the contrast to almost like a sharpening effect. Too much contrast creates a pseudo-realistic appearance that looks phony. Too little contrast, and the image is flat and lacks eye appeal. The trick is to find the right amount so that the image pops while remaining reasonably natural in appearance. 

The scene below was shot during mid-afternoon and the light was a little more friendlier for Aurora. All images were acceptable and differences may be judged more by personal preference rather than technically. The HDR Merge and Contrast Optimizer images are nearly equivalent, both being acceptable results if you desire a more conventional look. I would give Contrast Optimizer the edge since its handled the highlights a little better. You can easily observe that Aurora and HDR Efex have noticeably more snap, with a little higher saturation and more dramatic shadow detail (without going over the top). Both images are nearly equal in quality and any minor differences could have been evened-up if I had fiddled a bit more with the controls. Nevertheless, I would give the nod to HDR Efex only because I was spared the color correcting hassle necessary in Aurora. A final observation, note the subtle difference between Aurora and all the others in the deep shadows. In this example, I decided to use Aurora’s adjustment layer and luminosity masking feature to select the deep shadows to reduce the blue bias and extract some of the green color from the foliage. 


HDR Efex Pro

HDR Merge


Cathedral Rocks, Sedona
This is a straightforward  shot with five, one-stop spaced frames. While all the results are usable, HDR Efex takes the bottom spot. It is the noisiest and the weak shadowing of the rocks on the right was less natural than the others. Aurora shared the bottom spot, though its shadowing of the rocks was better and it did a better job rendering deep-shadow details. However, the massive color correction dulled the rocks to where the image lost impact. Between Photomatix and HDR Merge, it was essentially a draw. HDR Merge had a little more snappy contrast to the sunlit rocks, but Photomatix did a better job rendering the deep-shadow detail. 


HDR Efex Pro

HDR Merge


Millpond, Bishop, CA
I feel HDR Merge gets top honors. It has the best overall rendering and does well with deep-shadow detail (as all of them did). Photomatix also takes top honors because it provided a well-rendered starting point for 16-bit editing. Aurora and HDR Efex lagged behind. I didn’t care for the sky in HDR Efex (for that slight bleaching effect I previously mentioned) nor the mountains in Aurora. Nevertheless, both are acceptable results and, in this case, Aurora managed to behave better. 


HDR Efex Pro

HDR Merge


Joshua Tree National Park
The magic light sky in this image proved more difficult to deal with than I expected. Aurora takes the bottom spot for this image. I couldn’t tame the saturated reds sufficiently to produce a more natural sky (though some may actually prefer the exaggerated colors). HDR Efex suffered some slight edge-halos and both it and Aurora where the noisiest. HDR Merge I feel hit the sweet spot while Photomatix wasn’t far behind.  


HDR Efex Pro

HDR Merge


Bishop Creek
Of all the images, this one had the most surprising results. First, this scene was a technical challenge. The dynamic range was very high, requiring five exposures spanning six stops. Then, the deeply-shadowed trees along the river had a heavy blue-cast while the background mountains are in daylight, and that created a color balance dilemma. If I balance for the shadows, the snow peaks turn yellow. Conversely, if I balance for the mountains, the trees along the river bank suffer a heavy blue-cast that mutes their vibrant colors. 

To solve the color cast problem, I separately corrected in Camera Raw the three brightest frames that contained most of the shadow detail from the two darkest frames that had most of the mountain detail. HDR Efex, Aurora, and Photomatix all produced the desired color balance. However, HDR Merge apparently used only one of the white balance settings for all the frames. Generally, it’s rare for me to use multiple white balance settings, thus why I wasn’t aware of this quirk.

But the biggest surprise was that Photomatix clobbered the competition. HDR Merge had the aforementioned color balance problem. HDR Efex had problems rendering the background mountains that resulted in weak detail. Aurora initially looked great until you zoomed in. Sporadic areas of fine detail within the trees lacked tonal separation, causing a watercolor-like blurring (see lower enlargements).


HDR Efex Pro

HDR Merge


Aurora Enlargement
Unnaturally colored leaves that lack tonal
separation and look blurred.

Photomatix Enlargement
Natural looking trees, and note the snappier
contrast in the background mountain.

The Verdict

My HDR workflow for several years was to first use HDR Efex and then resort to another program if HDR Efex had problems. Now, given how well and fast HDR Merge works, I use this first and maybe run Contrast Optimizer to compare the two. I’ll go to HDR Efex only if the other two struggled with the highlights or shadows. Sometimes, when the frame exposures are a little sloppy, HDR Efex seems a little more forgiving.

Speaking of HDR Efex, since Google decided to give it away it begs the question why. HDR Efex (and Photomatix to some extent) are getting a bit long in the tooth. The fear is that Google will orphan HDR Efex along with the rest of the former Nik software suite. Only time will tell, but HDR Efex Pro is still one of the best HDR programs out there. Yeah, it has its problems, but if a version 3 is pending, then  HDR Efex may catapult back as the undisputed  top-dog. As for Photomatix, it needs to consolidate its software into one integrated program and become more "Photoshop-like." 

And what about Aurora? Aurora has the best HDR toolset of all the programs—period. Yet, they seem either unable or unwilling to fix what I consider a gross software problem. Actually, I think the reason can be found in their website examples. They all have exaggerated colors and contrast to point of being garish. I think this rendering style is intentional and that their customer target is the Andy Warhol set, not the Ansel Adams crowd. If your interest extends beyond classic landscape scenes into vividly graphic imagery, then this program is for you. Otherwise, if you don't already have Photomatix, I would recommend buying it instead of Aurora (HDR Efex Pro is already free). Between HDR Merge, Photomatix, and HDR Efex, collectively they should satisfy nearly all of your HDR requirements. 

Monday, April 18, 2016

Aurora HDR - The New Champ?

Aurora HDR was released in 2015 for $99 direct from Aurora or $25 for a standard version on the Apple App Store. It is currently Mac-only, but Aurora alluded to a Windows version later in 2016. It competes directly with my three long-standing favorites: Nik’s HDR Efex Pro 2,  Photomatix Pro 5, and Lightroom's HDR Merge. But is it better? 

Aurora Standard vs. Aurora Pro
Though Aurora’s website says the standard version is $39.99, I paid only $24.99 on the Apple App Store, so go figure. You can later credit the standard's cost to a Pro upgrade. Below are the major items lacking in the standard version and my opinion as to the impact.

No raw support
You can’t import raw files and instead need to convert them to TIFF. In my opinion, this isn’t much of a loss since any previous raw edits are not carried over. I always, as a minimum, adjust white balance, apply noise reduction, and enable lens profile before transitioning to the HDR software. With Aurora, just as in Photomatix, you have to do those edits after the fact if you import raw files. If you want any previous raw edits to carry over, you have to convert to TIFF first. That is what I routinely do for Photomatix anyway (HDR Efex Pro automatically does the TIFF conversion for you), hence this isn’t an issue for me.

What, no raw support is no big deal!? 
Those who have read my ebooks or previous posts know that I’m a rabid raw advocate. It’s not that I wouldn’t like raw support (even if prior raw edits aren't supported), it’s just that in the real-world, it’s unlikely you’ll see any difference. Difficult highlights in improperly bracketed exposures may possibly render better using raw files, but that depends on how Aurora performs the conversion. As long as you exercise proper HDR bracketing techniques, you shouldn’t have a problem with TIFF files. 

[Update: Aurora just introduced a $4.99 app that adds raw file support to the standard version.

No deghosting
Given my general distain for this feature, I’m incline to say good riddance. If you really need deghosting, it’s better to use Photomatix Pro because it allows selective deghosting. You don’t need to tone in Photomatix if you don’t want to, just save the 32-bit file after it deghosts the image. Then, you can tone the file on a different HDR program instead.

No luminosity and gradient masks. 
This pertains to the biggest “wow” feature in Aurora: it supports layers and masks! A luminosity mask allows you to easily select either highlights, mid-tones, or shadows and perform separate HDR editing. That’s a terrific feature because sometimes it tough perfecting all the major tonal areas without compromising. HDR Efex Pro has its Selective Adjustment tool that helps in this regard, but that is trumped by Aurora’s layers feature. In lieu of gradient masks, the standard version provides brush tools to customize a layer mask; so though not anywhere as convenient, you do have a workaround. 

The rest

There are other minor differences that you can view on Aurora’s website, none that I judged important.

Tool Set Overview
To keep this review brief, I only address the task of producing a realistic landscape image. If you’re into the grunge or pseudo-realistic look, you’ll need to explore that on your own; though I’ll say briefly that Aurora won’t disappoint in that regard. I also hit only the highlights of the major tools and how they compare to the other HDR programs.

First impressions
I don’t think Aurora ever heard the old saying: less is more. You are initially overwhelmed with an array of tools, some of them obvious as to function, and others with odd titles like Spectrum and Final Touches. Don’t expect Aurora’s numerous video tutorials to help. They’ll worth viewing just to get the overall flavor, but they do a poor job of explaining exactly what each slider does. You’ll need to download the pdf user manual to get a better description, though it can still be wanting.

Aurora includes several presets that cover the usual spectrum of HDR applications. However, I never use presets because most times I find them useless. Even if one is close, I find fine-tuning a preset is more work than just starting from scratch where I can follow a familiar workflow. You should still play with them just to get a feel for the scope of Aurora's capability.  I was, however, a bit amused by their  landscape "realistic" preset, which I felt deviated considerably from the dictionary's definition of the word.

Tone Mapping (Spectrum, Spot Lighting, and Final Touches)
Only Camera Raw and Lightroom’s HDR Merge make tone mapping a straightforward task. Everyone else seems to think it should be mysterious. Fundamentally, tone mapping is adjusting the dynamic range, which is what Photomatix and HDR Efex Pro do (albeit in their own peculiar style). Aurora’s Spectrum slider instead acts as an exposure adjustment that tapers at the endpoints to prevent completely white or black areas. In other words, it behaves somewhat like Camera Raw and Lightroom’s Exposure adjustment. 

The Spot Lighting slider is a puzzling tool that backlights detail to highlight it. Increasing it can cause halo problems, so you’ll probably want to leave it alone and wonder why it’s even there. Aurora doesn’t give the Final Touches slider a very quantitative description other than right is more realistic and left is more “detailed.”

At the end of the day, you usually don’t need to worry about these sliders. Even Aurora says to leave them at default unless you’re dealing with a unique problem. I suggest you collapse the menu and, as Tony would say, fuhgeddaboudit!

With the exception of an added Midtone slider, this panel is essentially a one-for-one equivalent to Camera Raw and Lightroom's Basic panel (Smart Tone being similar to Exposure). HDR Efex Pro is also similar in this respect, which is why both programs have a superior advantage over Photomatix’s more arcane adjustment process.

Aurora's detail enhancement adjustments are superior to HDR Efex Pro and Photomatix. For one, it doesn’t suffer from the noise emphasis that plagues HDR Efex Pro’s Structure adjustment. You also have more adjustment options, though I think they’re a bit overkill. 

For starters, you have the familiar Clarity adjustment found in Camera Raw and Lightroom. Next is the HDR Look, which the grunge lovers will certainly want to crank up. But for traditional landscape work, you’ll likely reduce the effect by moving the Amount slider to the left. Sometimes when trying to maintain a perfectly natural appearance, you still pickup a tinge of that pseudo-realistic HDR look. This adjustment allows you to back that off a bit. Also, this slider may help eliminate minor haloing. But in most cases, you probably want to leave the HDR Look sliders alone and adjust only Clarity.

The Softness and Boost sliders are active only when the Amount slider is adjusted off its zero setting. Softness performs as the name implies and Boost is essentially a gain control. Also, the polarity of these two sliders reverse depending if the Amount slider is positive or negative. For example, for a positive Amount value, a positive Softness value softens the image. For a negative Amount value, a positive Softness value has the reverse effect.

HDR Detail takes the HDR Look down to a finer detail and, as such, can mimic sharpening and induce noise. It’s best to avoid this adjustment unless you’re desperate to spike up your image.

This panel is similar to the one in HDR Efex Pro except it adds a Vibrance slider, which is similar to the same slider in Camera Raw and Lightroom. There is also a Color Contrast slider that is mostly a play-around-with toy and likely not to see much use. Nik has a similar feature in its HDR Color Efex Pro (which comes with HDR Efex Pro). 

This is a sharpening utility exclusive to Aurora. All the controls are conventional and self-explanatory. Instead of a usual single-radius adjustment, you can choose individually or collectively between small, medium, and large details. However, unless you're trying to accomplish all the image editing within Aurora, I recommend waiting till Photoshop or Lightroom. In my case, I use Nik’s Sharpener Pro, which automatically factors in all output-specific parameters. (Click here to see my review on Sharpener Pro.)

Color Filter
This is another feature exclusive to Aurora that mimics a subset of Camera Raw and Lightroom’s HSL/Grayscale panel, but lacks a hue adjustment. Normally, I would defer these type adjustments to either Photoshop or Lightroom. However, you'll need this tool as well as the Color tool to battle the one major flaw in Aurora (which I'll get to shortly).

Some of the Rest
There are Glow and Image Radiance tools that Aurora delights in demonstrating on nighttime cityscapes. There is also a built-in noise reduction filter, which so far I haven’t needed. The Tone Curve tool is identical to HDR Efex Pro’s except it lacks a luminosity channel. However, adjusting the tone curve in Aurora is easier than in HDR Efex Pro, which is very coarse and hard to make fine adjustments. Finally, there is an ND gradient tool, called Top & Bottom Lighting, that is identical to HDR Efex Pro’s Graduated Neutral Density tool. Aurora’s gradient tool is easier to use since it displays reference lines showing the gradient’s position and blend-width while HDR Efex Pro doesn't. 

Image Comparisons
Extra bells and whistles mean nothing if the resulting image is no better than the competition. I compared several images rendered in Aurora against HDR Efex Pro, Photomatix (using Contrast Optimizer tonning), and Lightroom's HDR Merge. At first, Aurora seemed to take over the dance floor, but then it suddenly tripped and knocked itself out.  Turns out there is a serious problem when Aurora renders sunrise and sunset images.

Aurora's Problem
As a landscape photographer, I'm sure you like to take sunrise and sunset images where you have a background lit by a warm, low-setting sun. If so, Aurora isn't for you. The problem is excessive over-saturation, mostly with the warm colors. In some cases, I couldn't control it using Aurora's Color and Color Filter panels and needed to address the problem in Photoshop or Lightroom (if I could). Below is an example of the problem. The image is Cathedral Rock in Sedona, Arizona near sunset. The top photo is Aurora and the bottom is HDR Efex Pro. In both cases, raw files were unedited in Camera Raw before being converted to TIFF. Both images are as they initially appeared after rendering and with all sliders at null (i.e., no presets applied).  

HDR Efex Pro starts out in typical style, an open and somewhat flat image—which is exactly what you want for maximum editing latitude with the HDR tools. The Aurora image was marred by the  over-saturated and garish red-illuminated rocks, with much of it out of gamut. You eventually can correct the problem either with Aurora's color tools or later in Photoshop or Lightroom, but that's not an acceptable solution in my opinion.

Aurora: Image starts out with over-saturated and out-of-gamut warm colors.
Adjusting Color and Color Filter only reduces the problem, not eliminate it.
HDR Efex Pro: Prior to any adjustments, the images starts out
well-rendered with natural color.

2nd Example
Here I show results from all four HDR applications after editing within the applications. In this case, I could control the saturation problem of the backlit autumn tree in Aurora with the Color and Color Filter sliders. I still preferred HDR Efex Pro's rendering of the backlit tree, but on the other hand, the sky was noisy to the point of being noticeable in an 8x10 print. Photomatix and HDR Merge lacked the higher contrast in shadow detail and were less saturated overall. Basically, Aurora and HDR Efex Pro tilted slightly to an HDR "dramatic" look while HDR Merge and Photomatix tended towards a more traditional photo appearance. Which style is best is obviously subjective, but I'm guessing most HDR enthusiasts prefer the added drama. Keep in mind that any of these examples can be further improved in Photoshop and Lightroom.

Aurora: I was able to control the warm backlit autumn-tree
saturation within Aurora.
HDR Efex Pro: Beter rendering of backlit tree, but sky
has noticeable noise.
Photomatix: Good photorealistic results. 
HDR Merge: Good photorealistic results that I preferred over
Photomatix in this particular example.
3rd Example
This image isn't dominated by any sunlit areas (other than the clouds) and I felt Aurora was the best of the bunch. HDR Efex Pro emphasized the detail a bit too much. HDR Merge was good except it had the most problems with the highlights. Photomatix, at first, appears more "plain vanilla" compared to the others. But as I previously stated, due to its open tones it easily lends itself for further enhancement in Photoshop or Lightroom.

Aurora: Best sky rendering and a bit more realistic than HDR Efex Pro 
due to softer texture.
HDR Efex Pro: Very good overall, but a little to much detail
emphasis compared to Aurora.
Photomatix: A more open image that provides good editing latitude in
Photoshop or Lightroom. 
HDR Merge: Good except it struggles with the highlights in the sky.
As I have cautioned in the past, you can’t make a sweeping judgment based on a few images. This is especially true with HDR software that can have a Jekyll and Hyde personality depending on an image’s content and structure. Except in this case, Aurora's over-saturation, especially of warm colors, is a consistent problem. There are a few other quirks too. The screen update to a slider adjustment is sometimes erratic, making it difficult to settle on a final value. Finally, their terminology is a bit unconventional and their documentation leaves a lot to be desired. 

But there is a lot to like about Aurora. Aurora isn’t anywhere the noise maker that HDR Efex Pro is notorious for. Also, Aurora didn’t seem prone to high-contrast edge halos that is also another HDR Efex Pro nuisance. And their Layers feature is dynamite, and along with a rich set of tools and an otherwise excellent tone-mapping engine, Aurora would clearly be the leader of the pack if it weren't for the maddening saturation problem. As it stands now, I can't recommend Aurora for general landscape photography. I have contacted Aurora's technical support and supplied them with sample images. They acknowledged there was "minor" over-saturation and will fix it in the next update. It concerns me they described it as "minor", but if the next update corrects the problem, then I'm ready to declare Aurora the new champ.

[Update: Aurora released a new update (version 1.2.3) in June, 2016. The saturation problem still persists, but they assured me that they're still working the problem.]

Thursday, March 24, 2016

Nik Collection Now Free

This short blog is to help broadcast the news that the entire Google Nik Collection is now free starting March 24, 2016. If you purchased it in 2016, you will be refunded (automatically, I believe). I have posted many articles on the Nik Collection and you can peruse through the Blog Archive to find them. My favorites are HDR Efex Pro, Sharpener Pro, and Color Efex Pro, all that are now permanent tools in my workflow. Beside those, there is Silver Efex Pro, which is considered by many as one of the best black-and-white conversion programs available. The remaining programs are Dfine (an excellent one-click noise filter); and Viveza and Analog Efex Pro, neither which I use but you may find Analog Efex Pro entertaining.

Click here to download the Nik Collection.

Friday, March 11, 2016

Lightroom's Latest Panorama Feature

In a previous post, I wrote that Lightroom and Camera Raw have replaced Photoshop for stitching panoramas in my workflow. The main reason was the stitched panorama remained a raw file, which is the best format for heavy-duty editing before transitioning to Photoshop. (Click here to view that post.) Lightroom and Camera Raw have now added a new feature that ups the ante even more. 

How Big is Greenland?
One of the rather arcane aspects of stitching panoramas is mapping the multiple frames—which represent the "spherical" view of the photographed vista—into a flat medium. It's the same old problem of creating a map of the earth. When you project the round earth on a flat map, suddenly Greenland, for example, doubles in size. Adobe offers many ways to project panoramas, but for most run-of-the-mill panoramas (two to four horizontally shot frames) Cylindrical is the most relevant. Basically, Cylindrical mathematically projects each frame on to a virtual curved screen that is then unrolled flat into a panorama. That projection process is what creates the curvature along the border of each frame after stitching. The problem is the misshapen image creates some image loss when cropped. 

In the past, to work around the crop loss you either accepted the loss or stitched the frames using Photoshop's Reposition option that didn't distort the borders. The latter option could be painful, however, because Reposition was notorious for creating stitching artifacts (example to follow). When Photoshop introduced the Content Aware Fill feature, you could instead simply lasso around the vacant (transparent) areas and perform a Content Aware Fill. But that only worked when the surrounding area was mostly sky, water, or any nondescript subject matter. In the latest version of Photoshop CC, they added to the Photomerge dialog box a new ‘Content Aware Fill Transparent Areas’ check box. This automatically performs the same border recovery method. The operation can’t be previewed, so it’s a gamble how well it works. Fortunately, all the fill areas are presented as a selection that you simply delete if you don’t like the results.

Boundary Warp
Now there is a better option unique to Lightroom and Camera Raw called  Boundary Warp that is  located in the Panorama Merge Preview screen (see screenshot below). With this tool, the image borders are stretched to fill in the transparency gaps. You control the amount of fill-in from none to 100% as you move the slider to the right. There's a reason you may want to control the amount of fill. Remember, when you stretch a portion of an image, you're scaling up and that sacrifices resolution. But in practice, the stretching shouldn't be enough to where, with today's high-megapixel cameras and the scaling confined to the edges, you'll ever notice any image degradation.
Boundary Warp slider located at bottom of Options box.
Below are three examples of a two-frame panorama stitched in Camera Raw using Cylindrical. The first image shows the rounded edges and the potential crop loss. The second image is after cropping and you can see the amount of loss. The third image is after applying 100% Boundary Warp and the image is completely intact.

Camera Raw Cylindrical Panorama: A good chunk of the top 
and bottom would be lost when cropped as seen the next image.
After cropping: All the trees and their reflections take a haircut.
With Boundary Warp: The image is fully intact. 
Bent out of Shape?
This new feature does pose the question if the panorama’s natural perspective and scale are corrupted. However note that on their own, all projection modes already cause some degree of distortion. Assuming most “occasional” landscape panoramas are two to four horizontal frames with a total field-of-view less than 120-degrees (and exclude any significant architectural features) most distortion isn’t significant enough to be noticeable. Applying Boundary Warp essentially restores the image to nearly the same results you would obtain with Photoshop’s Reposition. Reposition is not really a projection, but is more-or-less equivalent to manually aligning the frames together. It works well if you shot the panorama using the shift function in a tilt-shift lens; otherwise as mentioned before, it is notorious at generating artifacts. The same image below is stitched in Photoshop using Reposition and is essentially identical to the Cylindrical image above after Boundary Warp, except for the artifacts (circled in red).

Photoshop’s Reposition: Essentially the same as Cylindrical
after applying Boundary Warp, but riddled with artifacts.
Example of ‘Content Aware Fill Transparent Areas’ 
I've added to the comparisons an example of the same image stitched in Photoshop using Cylindrical and ‘Content Aware Fill Transparent Areas’ enabled. A couple of noticeable artifacts are the extra palm tree in the upper-right corner and the orphan tree-head reflection in the bottom-left corner.
Content Aware Fill: Without the original frames to compare
against, you may actually get away with this image with most observers.
But astute eyes will catch the artifacts, especially the floating palm tree top.