HDR App Comparison

I would like to share my experience with three different HDR camera apps, and compare their performance against each other and the standard Camera app. I am using an iPhone 4S.

Summary
HDR Fusion costs $2.99, but at the time of this writing is on sale for 99¢. It is by far the fastest and simplest of these three, and in my opinion produces the best results in Manual mode, though often the worst in Automatic. I used version 2.0.

Pro HDR costs $1.99. It is slow and tedious to use, and in my opinion produces mediocre results in both Manual and Automatic mode. I used version 4.01.

True HDR costs $1.99. It is even slower and more tedious than the previous app, though in my opinion it produces the best results in Automatic mode, and quite good in Manual. I used version 2.4.1.

Features
All three apps let you create High Dynamic Range (HDR) pictures, by taking multiple shots at different exposure levels and combining them into a single image. The idea is to make the result have proper exposure in both the shadows and the highlights.

Automatic mode lets you tap the shutter button and the app will select the exposure points on its own. True HDR claims to take three pictures this way, but only two appear to be created. Both Pro HDR and HDR Fusion take two pictures, one dark and one bright, and combine them. In my experience, HDR Fusion selects spots that are too bright and too dark this way.

Manual mode lets you tap to select where the two exposure points will be, then tap the shutter button to take those pictures. All three apps use two exposures here. In True HDR, this is called “SemiAuto” mode, as it has a separate “Manual” mode where you tap to select one exposure point, then tap the shutter to take that picture, then repeat for the second exposure. The SemiAuto mode in True HDR has a problem whereby when you tap to select a point, you are not shown how the exposure will look in the on-screen preview, which makes SemiAuto essentially useless.

Library mode lets you choose two existing pictures in your camera roll, and the app will combine them into and HDR image.

All three apps let you decide whether or not the original exposures are saved, and each has a few more features:

HDR Fusion lets you decide to save only the original exposures and not process them. This makes it extremely fast to capture the bright and dark images, which you can later process in Library mode. That way you don’t have to wait around for the images to be processed when you want to get on with taking more pictures right away.

Pro HDR and True HDR both have image adjustment sliders for brightness, contrast, saturation, warmth, and so forth. You are forced to click through the image adjustment screen after taking an HDR picture, as there is no option to automatically save and bypass that screen.

Pictures
I took these three apps out, along with the stock Camera, and used all of them to take the same exact shots with my iPhone on a tripod, in five different scenes.

The first scene is looking directly toward the sun, at the shadowed side of some trees. The first two pictures show what this looks like with the stock Camera app in normal and HDR modes, respectively. Then come the result in Automatic and Manual modes from HDR Fusion, True HDR, and Pro HDR.


We see that the Camera app’s HDR has negligible improvement over the plain Camera. The HDR Fusion automatic mode is very poor, with the sky too dark and the trees too bright. Pro HDR in automatic mode has unsightly “fringing” around the trees, where the sky looks pale. Meanwhile both of the True HDR shots, and the manual shots from both HDR Fusion and Pro HDR look good.

The second scene is from under a bridge in the shade, looking toward water coming over a dam.


Here the Camera app’s HDR mode shows a slight improvement over it’s normal mode, in terms of adding detail to the rocks and the distant trees. However, that is barely perceptible.

Once again the auto mode of HDR Fusion both over and underexposes, making an unacceptable result. However on manual mode HDR Fusion produced the most accurate picture of the bunch.

Both of the Pro HDR shots exhibit strong ringing at the edges of the sky, and their colors are unrealistically vibrant.

The True HDR auto shot has ringing around the sky, though its manual shot is nearly as good as that of HDR Fusion, just a little bit too dark in the shadows still.

The third scene is from the same location as the previous one, but now with a telephoto lens attached to zoom in on the waterfall.


This is starting to get familiar. HDR Fusion on manual mode and the two True HDR shots look best. Pro HDR is oversaturated, Camera is underexposed, and HDR Fusion on auto is not quite right.

The fourth scene is looking up at some trees, with the sun behind one of them.


These are all about equal. Perhaps Camera on HDR mode is slightly better than the rest.

The fifth scene is looking between some trees out at a lake.


Again these are fairly comparable, though HDR Pro is still oversaturated. It looks like HDR Fusion on manual mode provides the best detail on the shaded sides of the trees, while still showing how dark they are.

Performance
Number of clicks to take a single HDR photo in Automatic mode, starting from the camera screen and ending back at the camera screen:
HDR Fusion: 1 (tap the shutter button)
Pro HDR: 3 (tap the shutter, save, and done buttons)
True HDR: 5 (tap the shutter, merge, save, okay, and back buttons)

Time to take a single HDR photo in Automatic mode, starting from the camera screen and ending back at the camera screen:
HDR Fusion: 8 seconds
Pro HDR: 34 seconds
True HDR: 45 seconds

Number of clicks to take a single HDR photo in Manual (SemiAuto) mode:
HDR Fusion: 3
Pro HDR: 5
True HDR: 7

Time to take a single HDR photo in Manual (SemiAuto) mode:
HDR Fusion: 18s (it takes a few seconds to manually pick the target points)
Pro HDR: 31s (apparently the automatic point selection takes longer than doing it myself in this app)
True HDR: 43s (apparently the automatic point selection takes longer than doing it myself in this app)

Number of clicks to make a single HDR photo from two existing pictures:
HDR Fusion: 5 (Capture Mode, Library, Camera Roll, First Image, Second Image)
Pro HDR: 9 (Actions, HDR from Library, OK, Camera Roll, Dark Image, OK, Light Image, Save, Done)
True HDR: 8 (Choose Pictures, Camera Roll, First Image, Second Image, Merge, Save, OK, Home)

Time to make a single HDR photo from two existing pictures:
HDR Fusion: 12s
Pro HDR: 25s
True HDR: 36s

The upshot here is, only HDR Fusion has a true “automatic” mode—the other apps require many extra clicks. Indeed, even in the Manual and Library modes, HDR Fusion takes far fewer clicks. Furthermore, HDR Fusion is extremely fast at processing.

Conclusion
HDR Fusion is the simplest and fastest to use. On manual mode it consistently produces the best results. It takes the fewest clicks to use, and the option to save original images for later processing can make things even faster. Its automatic mode has serious drawbacks, often overexposing the shadows and underexposing the highlights, producing a flat image with poor color accuracy. Luckily, manual mode is simpler and faster to use than even the automatic mode on the other apps.

Pro HDR takes a long time and numerous clicks to work, and its results are almost always oversaturated and exhibit ringing in the bright areas. I do not recommend this app.

True HDR takes an extremely long time, and requires excessive clicking, but its results are good on both automatic and manual mode. If you really don’t want to select exposure points manually, and prefer to spend even more time waiting for the app, and making even more clicks than it would’ve taken to pick the exposure points, then True HDR is acceptable.

Bottom Line
Manual mode in HDR Fusion is faster and needs fewer clicks than even the automatic modes of other apps, and produces better-looking results. If a future update fixes the Automatic mode, so much the better, but even if it doesn’t Manual mode alone is still better than the competitors. For fast HDR photography with good results, I recommend HDR Fusion in Manual mode.

TJ61 said:

I've been curious about the mechanics of HDR photography (at least the type employed in iOS), with regard to the need for a steady camera position (e.g. use of a tripod). Does the method actually combine pixels from different images, and if so, is it a straight 1:1 pixel overlay (tripod required), or is there some stitching going on (maybe no tripod, if you can hold steady enough).

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Good questions!

All three apps, HDR Fusion, Pro HDR, and True HDR, attempt to align the light and dark images. They also do indeed blend pixels from each image.

Their algorithms are different, but when the camera is held freehand in a reasonably steady manner, they all have decent alignment results. Witness:


The above pictures were taken on “Manual” mode for HDR Fusion and Pro HDR, and on “Auto” mode for True HDR (recall that “SemiAuto” in True HDR, the analogue of “Manual” in the others, is currently bugged so it doesn’t show exposures as you set them—True HDR did well enough on Auto in the previous test that I trust it now.)

As you can see, none of them show any visible misalignment. When you hold the camera steady in your hand, all three apps will successfully align the two exposures for most pictures.

However, I took the test a step further. I used a separate app, ProCamera, and took dark and light exposures a few seconds apart while holding the camera freehand. That meant the images were no longer so close to aligning.

Here are the dark and light shots I used:


And here are the results of processing those images in each app:


Now there is some visible “ghosting” at the bridge-sky interface in all three pictures. The discrepancy is largest in the Pro HDR image (which also has unrealistically oversaturated colors). Moreover, the Pro HDR image has similar “double image” problems throughout. Look at the “danger” signs on the fence, the ladder atop the concrete building, the concrete ramp from that building down to the water, and the edge of that building next to the top of the dam where a region of whitewater appears within the concrete. In all of those places, Pro HDR improperly blended the misaligned pictures so things appear twice.

The HDR Fusion and True HDR pictures have essentially perfect alignment except for the edge of the bridge. The True HDR image, as mentioned, has slightly better alignment along that juncture. However, True HDR also cropped out a noticeable area from the right side and top of the picture, leaving a smaller visible area. (I scaled all three pictures to height 800px, but look at what things are visible at the right and top edges.)

Overall, HDR Fusion is nearly as accurate in aligning as True HDR, it retains more area of original images, and it operates much faster. Once again I give the nod to HDR Fusion. Thus, HDR Fusion is now ahead in my book for both Library and Manual modes. True HDR is still ahead on Automatic, but even there it is still behind HDR Fusion on Manual. Meanwhile Pro HDR is inadequate on all fronts.

General Advice
I’ll go ahead and share what’s worked for me with these apps. First, a tripod is very nice, but not necessary. Second, when selecting exposure points on manual mode, try to make sure your main subject appears reasonably well (even if a bit dark or light) in each exposure. That is, you don’t want your main subject completely washed out to white, or totally black, you want it at least discernible in both pictures.

Also, try to make sure the bright areas don’t “bleed” out into the areas you are trying to exposure for. In other words, when taking the “bright” shot to expose for the shadows, try to make sure that the medium-bright areas stay visible—especially the ones right next to the bright areas, because that’s where the contrast is most important. It’s okay to have some fine detail washed out, but you don’t want the washed-out area to extend beyond the highlights that the dark image can properly fill in.

Also, other apps with special features can be used to capture the different exposures, which can then be blended in HDR Fusion or True HDR (recall that Pro HDR is unacceptably poor). For example, here is a picture I took today:


With my iPhone on a tripod, I used SlowShutterCam in Auto mode to take 4-second pseudo-long exposures, one dark and one light by setting the target points appropriately. Then I used HDR Fusion to merge them, Colour Mill to up the saturation, and then back on my computer I used the Gimp to sharpen it.

Honestly it didn’t come out quite as well as I’d hoped (certainly the majesty of the waterfall is diminished without any people for sense of scale—that is a tall cliff!) You’ll note from the lens-flare that the sun is located only slightly above the top of the picture, the upper part of the waterfall is in full sun, and the lower part is in shade, so it was a difficult scene.

That segues to my next point which is, not every picture needs HDR treatment. Only when there are very dark and very bright parts of a single scene, and you want objects in both sections to be properly exposed, is HDR appropriate. Without HDR, the sky over my waterfall would be totally washed out white (I took just such a shot, and it did.) So that scene is HDR-friendly.

Other pictures, where everything is well-lit, are better suited to a normal camera app like ProCamera. And when everything is dark, nothing beats NightCap. For moderately dark pictures with enough bright parts that HDR is needed, you can use a tripod to take a NightCap picture for the shadows, and a ProCamera picture for the highlights (or another NightCap picture—it’s quite good at non-dark stuff too), then combine them with HDR Fusion or True HDR. I’ll give that a shot next time the opportunity arises, maybe a sunset.

migdaddy said:

Personally I find camera +'s HDR to be really amazing

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That aircraft carrier picture looks nice, and I would enjoy seeing it on, for example, an embossed metal lunchbox. However, the effect in those pictures is not HDR.

If you like the effect, by all means use it and be happy with it. HDR, however, means something specific, and that is to capture both the highlights and shadows in proper exposure. This can be used for a variety of purposes, but the first and foremost reason is realism.

With actual HDR, you can make pictures that look the way the scene appeared in real life. Conversely, the squirrel and duck pictures you posted are clearly unrealistic. In fact, the bark on the tree in your first “HDR” picture is difficult for me to look at, with its glaring sharp contrast.

The colors in your “HDR” shots are also obviously artificial. Again, if that’s what works for you, great. But it does not provide actual HDR.

TJ61 said:

And a brilliant write-up! That was very helpful.

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I’m glad I could help. I wrote it mostly because I wished there had been something like that for me to look at before deciding which HDR apps to buy. There wasn’t, so over several months I ended up buying all three. With the benefit of hindsight I now know that HDR Fusion is the best of the lot, at least for my purposes, and I certainly would not have purchased Pro HDR if I had seen side-by-side comparison shots of how it really performs relative to True HDR and HDR Fusion.

TJ61 said:

Your advice to not overdo the HDR was well-stated, too, in that you don't want to sacrifice decent exposure of the subject to get everything else in the picture correctly exposed.

Your waterfall looks great, despite any shortcomings you mention. I've taken pictures in similar lighting situations, prior to knowing anything about HDR, and would have killed for such a result. (To say nothing of the water-smoothing effect, etc. etc.)

I hope you're able to share your write-ups to a wider audience. These deserve way more views than they could possibly get here!

Regards,
Tom

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Thanks, I’m not sure where else I’d post this though. I don’t blog or anything. In any case, one last piece of HDR advice, which you probably already figured out. But for other who might be new to HDR, here’s a suggestion:

In the final resulting image, for realism you want the shadows to remain darker than the highlights. That means, when choosing your exposure points, you want to make the “bright” image not be as bright as possible. In particular, you want the shadows—the parts that you’re exposing the bright image for—to be on the darker side of properly exposed.

Similarly, you want the “dark” image not to be as dark as possible. You want the highlights to be on the lighter side of properly exposed. That way when you combine the two images, the highlights will still be brighter than the shadows, and it will look much closer to how it did in real life.

This lines up nicely with my previous tip, that you want the main subject to be reasonably discernable in both shots. Together, these techniques mean the whole scene will appear sharp and with good contrast, rather than flat.

Well, now I’ve found a shot that comes out better-aligned in Pro HDR than in either HDR Fusion or True HDR. A few days ago I hiked to the top of a mountain and was waiting for the transit of Venus. While I was up there, I took a few lanscape photos in HDR Fusion.

On the left are the results of processing the original exposures with each app. On the right, I first used Photoshop Express to increase the saturation of the dark “sky” exposure, then combined the HDR.


If you look very closely, you’ll notice that the distant mountains on the far left are misaligned in the HDR Fusion and True HDR versions, but they are properly aligned in the Pro HDR picture. On the other hand, at the far right side of the horizon, the Pro HDR picture has severe “bleeding” of brightness, where the bottom part of the sky is way too faded.

As you can see, pre-processing the individual exposures sometimes makes a striking improvement. Similarly, post-processing the result can do so as well. For example, something as basic as opening the HDR image in Preview on a Mac and pressing the “Auto Levels” button in the Color Adjust panel, can make a world of difference. I haven’t done that on any of these, but you can try it yourself and see.

The take-away here is, Pro HDR does a terrible job when there is a sudden switch from dark to light. Both HDR Fusion and True HDR do much better (much better) but they sometimes need a bit of help with saturation. That can be done at the end, or for greater control it can be done on the original images separately.