Using Exposure Fusion For Bracketted Images


Lets set things straight from the start, Exposure Fusion is not a kind of HDR.

Exposure Fusion is a concept promoting the process of creating a low dynamic range (LDR) image from a series of bracketed exposures. In short, EF takes the best bits from each image in the sequence and seamlessly combines them to create a final ‘Fused’ image. Or more technically, the fusing process assigns weights to the pixels of each image in the sequence according to luminosity, saturation and contrast, then depending on these weights includes or excludes them from the final image. And because Exposure Fusion relies on these qualities, no exif data is required, and indeed, if you wanted to, you could include an image with flash to bring darker areas to life.

But in reality does it work. For testing I will be using a bracket of 5 images with a 1 EV spacing (-2, -1, 0, +1, +2); same as I would for HDR. Throughout all of the processing I used the default settings for both the HDR and Exposure Fusion processess, with no extra processing in Photoshop. At the time of testing I can only think of two software packages that have dedicated Exposure Fusion routine, PhotoMatix from HDRSoft and Dynamic Photo HDR from Mediachance. For this test I will be using Dynamic Photo HDR.

My test image is a scene from Prestatyn Beach, shot just as the sun was setting. First image is the 0EV from the bracket of 5. On its own it’s usable but there are some dark areas, especially to the left hand side and the immediate foreground. Probably because I exposed for the brightest object which is the sky.

0EV

Now the idea behind HDR is to allow you to avoid the problem of the dark areas mentioned above, so here’s the HDR image processed with Dynamic Photo HDR 

tonemap
It’s slightly better but it’s still not right and that’s because I used the default settings throughout. Normally I would have adjusted this image to bring out the shadows more. One other thing, I used the Eye-Catching tone-mapping setting, probably the most popular for DPHDR, but as we all know, different tone-mapping settings will affect the final output, without any input from me.  

Next, let’s have a look at the Exposure Fusion method. Like the HDR process I used 5 images. 

fused

Personally I prefer the HDR version, but one thing HDR can do is increase noise whereas Exposure Fusion does not.

When Mediachance brought out their new version of Dynamic Photo HDR they included a new HDR workflow which combined the HDR Fusion and Tone-Mapping processes. Called Complex HDR Fusion it first creates an Exposure Fusion image which is then passed to the Tone-Mapping process for final adjustments.

both

It would only be fair that I include an image processed with the method. It does seem to make the darker areas lighter and I have to say images I have created using this method I have been happy with. As a side note I realise this one has a slight halo, my fault, as I was rushing to get this article finished.

complex

For me the jury is still out on Exposure Fusion and Complex HDR Fusion. During my trials I have had some very good images where HDR has been too noisy and Fusion Exposure or Complex HDR Fusion has done a better job. It’s something I will need to experiment more with, however if I continue to get good results I may well adopt this method for processing my HDR images.

Do you want a tutorial on how to do Exposure Fusion using PhotoMatix. Then visit Kevin McNeals Blog for a neat tutorial

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