HDR Software Review Series Pt X – Picturenaut

This is the last instalment in the series of HDR software reviews. If a new application comes along in the future, I may add it to the set and I’m in the process of looking at some new beta versions of a couple previous applications so will likely update those reviews in the future with new information; but for all intents and purposes this is it. What started out as a list of about 5 applications has grown to a 10 part series. From a purely personal standpoint, if I never see the images that have been used in all these reviews again it’ll be too soon. 😀 I hope the thoughts I’ve laid out have been useful for some people and perhaps given some insight from the standpoint of a casual user.

This last instalment will look at Picturenaut. I was initially reluctant to include it because unlike all the other applications in the series, Picturenaut isn’t a commercial product. My feeling is that if someone’s offering a piece of software for sale, it’s open to be reviewed and critiqued but if someone’s offering up a piece of software for free it’s a different matter.

Picturenaut can be downloaded from the HDRLabs website which, as many of you probably know, is owned and maintained by Christian Bloch. Christian is well known in HDR circles and is the author of The HDRI Handbook which is highly recommended as one of the two seminal reads for users of HDR both new and advanced along with Practical HDRI.

In a comment to another one of the reviews in the series, it was mentioned that I should include Picturenaut. I contacted Christian to see if he’d mind (essentially get his permission). He had no problem with it with one caveat. He asked that I relate the story behind Picturenaut. So here goes.

Picturenaut ‘fell out of’ The HDRI Handbook. The book is essentially Christian’s diploma thesis. In the early stages of trying to find a publisher, he was turned down so put the thesis onto the web for anyone to download (it was downloaded over 20,000 times). This is back in 2003 when HDRI wasn’t being used anywhere in photography really but only in the motion picture industry (it’s been used there for several years in CGI). A programmer named Marc Mehl contacted Christian with an interest in trying to develop a program for HDRI. Working together, with Christian helping Marc find and refine the process and the ‘under the hood’ algorithms, Picturenaut was produced. Marc continues to update Picturenaut today. Donations for maintenance and development of the program can be made through the HDRLabs website and all donations go to Marc for continued development. Download it, give it a try and if you like it (you probably will), make a donation (and yes, I have). The other thing that’s important to note about Picturenaut is that it’s got an Open SDK which means that anyone with a knowledge of C++ can develop plugins for it. If you know C++ and you want to help improve the software, have at it.  An Open SDK is what allows users to create their own actions and scripts in Photoshop.

Now, with the story behind the software known to all who read, let’s take a look at the application itself. I have to say I’m more than a little nervous about this one because I know Christian’s going to be reading it at some point and no doubt my mistakes will be pointed out when he comments (go easy on my Christian, I’m just a dumb photographer).

The GUI for Picturenaut is about as clean as they come.  A menu bar at the top with both dropdowns and icons to launch actions.

Picturenaut GUI (click for larger version)

There are no preferences that can be set up so you can pretty much start using the program straight away.  It will open RAW files, it also supports Radiance, TIFF and OpenEXR 32 bit files.  You load TIFF or JPEG images as your source images as well.  There is no batch functionality; which would be a nice future development to see.

To load a bracketed set of images, either click on the icon of the images with the + sign or go to File>Generate HDRI.  A dialogue box opens to select the images.


Image Loading Dialogue (click for larger version)

You’ve got a few options here to consider.  There are the usual Align and Deghost.  Exposure correction is an option that will allow the software to adjust the exposure of the image from the camera as may be necessary to properly compute a gamma curve before averaging the pixel values together.  For example, sometimes you’ll look at the EXIF of your images and your -3 shot might show as -2.97.  Picturenaut will make the necessary correction to properly average the pixel values together if the Exposure Correction option is checked.  The result should be more accurate blending of the source images.  Color Balancing is another option to consider.  Based on the information from the EXIF data, slight differences in colour can occur due to an inexactness in the exposure information as noted above.  Color Balancing will try to correct those errors and match colours in the 32 bit image to the colours in the source files (i.e., prevent false colour or dramatic colour shifts).  If Exposure Compensation is left checked, Color Balancing shouldn’t be necessary.  Next you have a dropdown for Weighting.  This determines how the pixel values in the source images will be used.  Standard uses all the pixel values in each image.  If particular areas of a source image are noisy (i.e., underexposed shadows), noise in the final image could be enhanced.  Mid Emphasis uses primarily the middle-toned values in each image.  This can work well if you’ve fully exposed a bracketed series and have your darkest shadows brought up to a middle tone and your brightest highlights brought down to a middle tone.  If your shadows are darker or highlights brighter, using Mid Emphasis may sacrifice some shadow or highlight detail in the merged image.  The last choice is for Curve.  This is the gamma curve of the source images.  If you’re using RAW files, selecting Linear from the dropdown should be the way to go.  If you’re using TIFF or JPEG images as your source, selecting Computed would be best which will allow the software to reverse engineer the gamma curve and properly correct for it to linearize the data for merging.  Selecting Standard Curve or User Defined should only be used if you know exactly what gamma encoding is used in the source images.

Once you load the source images, you don’t have to wait long to get your merged image on screen.  This is the fastest application of all those tested thus far without question.  To get into the tonemapping, either click the icon at the top with the little sliders on it or go to Image>Tonemapping.  The tonemapping screen is fairly simply laid out as well.

Picturenaut Tonemap GUI (click for larger version)

You can make the preview image full screen and drag the tonemap operators to a second display if you have one.  Moving to a second display is not ‘sticky’ so has to be done each time.  More fulsome dual monitor support would be nice.  In the preview window, scrolling with the mouse wheel will zoom in and out within the image.

There are 4 tonemap operators to choose from.  The one that will likely get used the most is Adaptive Logarithmic.  The other that may get used some is Photoreceptor.  The other two won’t be of use to most folks.  Adaptive Logarithmic preserves colour well and applies a soft shoulder and foot to the contrast curve (film photographers will understand the concept).  For more digitally based photographers, think of the PS Curves adjustment with a short, soft curve at the top and bottom with a long straight section in the middle, or with a very shallow S-shape in the middle.  That top and bottom curve are the shoulder and foot.  Photoreceptor applies a more dramatic straight cut off at the top and bottom which will give more contrast and ‘punch’ to shadows and highlights but doesn’t do anything for the midtones which will tend to be flatter.  Colour preservation isn’t as good and I found I’d get a fairly pronounced green/cyan colour cast to images using Photoreceptor.

Sliders for the various adjustments are live (big thumbs up).  In addition to the adjustment sliders, there are options for adjusting the histogram via a Levels type adjustment and the gamma.  Unchecking Automatic Luminance gives you control of the highlight and shadow points on the histogram.  You can adjust overall Luminance or each channel individually.  I’d recomment leaving Automatic Contrast unchecked.  In the Gamma tab, you can adjust the gamma curve of the tonemap function to better suit your needs, your desired look or your source images.  To do this, you can adjust the sliders, select from the dropdown menu or, if you have gamma curves loaded on your system, use one of those (not many users are going to have gamma curve files of their own).  Generally you’ll start with the default 2.2 and adjust from there or stick with the Computed option in the dropdown.  You don’t really want to use Linear here because your output image is no longer longer comprised of linear luminance values like your RAW input files would be.  You want to apply a gamma correction to your output LDR file.  The Rec 709 checkbox is a setting you won’t find in other HDR software.  This one was a mystery to me so I did a little digging.  As far as I can find, it’s a gamma correction function for HDTV that is different from the still image gamma curves we’re used to using.  In general, checking it darkens the image overall, increases colour saturatoin and boots local contrast.  Check it and uncheck it, see if you like what it gives you.  You can choose the bit depth of your output image as 8, 16 or 32.  You can save tonemapping settings as presets so they can be recalled in the future (nice!).  If you switch between tonemap operators, the last settings you used are retained when you return to a previous operator.  The big thing I’d like to see added is the ability to tag the output files with a colour space.  If you use JPEG or TIFF images with a colour space embedded, Picturenaut will honour that colour space through the merging, tonemapping and saving stages.  If you use RAW files; however, your output LDR image will be untagged.  This can result in fairly dramatic differences in colour from what you see in the tonemap preview when the image is opened in an image editor for further post-tonemap tweaking.

How’s it all work?  Let’s take a look.  The first thing to note is that you’re not going to get the really whacked out, hyper-real results with Picturenaut that you can get with other HDR software.  Picturenaut is intended for real world use where realistic results are expected and desired.  Given that, there won’t be any of the surreal looks shown with previous parts in the series.

The image below is the result of tonemapping the default existing 32 bit file.  Overall contrast is good.  Highlights are very well controlled and there’s good shadow contrast.  Picturenaut crunches dynamic range as well as or better than the other applications reviewed previously.  What should be noted is the blue in the water.  This wasn’t present in the tonemapping preview in Picturenaut and is a result of not being able to tag the output LDR with a colour space.  The blue can certainly be removed with further editing and if TIFF files are used as the inputs, the water retains the white colour it had in the tonemapping preview.  It would take very little additional work to get this to where I wanted it.

Picturenaut Existing (click for larger version)

Let’s take a look at the merge within Picturenaut.

Picturenaut Merge (click for larger version)

It’s a tad dark but I could have produced a bit lighter version during tonemapping if I’d wanted.  The blue in the windows on the right isn’t as strong as with some other software but that can be enhanced with further editing.  The colour in the floor and walls is good.  The brightness in the windows on the left is well controlled.  Again, the software has crunched the dynamic range very well.  With a little more work in PS and/or LR, a very useable result could be achieved.

Picturenaut also has a deghosting function.  Turning it on doesn’t slow down processing very much at all.  As can be seen from the image below, it works fairly well.  Not as well as CS5 HDR Pro; which at this point has the best deghosting of anything out there, but probably pretty close to Photomatix.

Picturenaut Deghosting (click for larger version)

Overall, Picturenaut is a terrific program.  That much better considering the cost.  It’s fast, it compresses dynamic range well, it can generate extremely good, realistic output.  On a commercial interior gig I had earlier this summer, Picturenaut saved my bacon.  I wasn’t getting results I liked with any of the other software at my disposal so decided to try Picturenaut.  Bingo!  Images I could make use of and the client was happy.

Picturenaut definitely goes into the recommended column.  There are a few things that could make it that much better but it’s pretty damn good as it is right now.  As I noted above, if you download it, use it and like it then make a donation which will help keep development going.  We all know there are plenty of photo-related software programs out there that are being sold commercially that are buggy, crash prone and difficult to use that should still be in Alpha development, never mind even Beta.  Picturenaut is the opposite.  It’s a well thought out, well developed piece of software that’s free and should be offered commercially.

As with the others, if you see any glaring or non-glaring errors, let me know and I’ll make the necessary corrections.



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