Exposure Fusion – Best Way To Blend Images

Exposure Fusion

This week I am going to talk about a topic that confuses a lot of people. The subject of blending images together from separate images is a tough one. There are a few ways but the main ones are manual blending images together in Photoshop through and the second option is using a third party plug-in to blend images automatically. The latest concept is called Exposure Fusion which can be found within the program Photomatix Pro.

Exposure Fusion is not HDR but is a new concept of processing a series of bracketed images, which result in a low dynamic range image. To summarize it takes the best tonalities from each image in the sequence and combines them to create a single image. To be more specific what is actually happening is that the fusing process assigns weights to the pixels of image in the sequence according to luminosity, saturation, and contrast, and then carefully balances the three to make a single image. In layman’s terms what is happening that the best part of each image gets recorded and fused together to combine all of the best elements in final image.

How is Exposure Fusion Different Then HDR?

Exposure Fusion is quite different in many ways then HDR. The only resemblance the two have are that they combine a sequence of bracketed images together. That is where the similarities end. First of all Exposure Fusion is a low dynamic range result rather then a high dynamic range. This means that the final product looks more realistic to how the scene really would like. This means that the shadows maintain a certain amount of shadows and the highlights remain brighter in higher tonalities then a high contrast scene. HDR takes the sequence of images and blends the images seamlessly but does its best to even the tonalities in the extreme tonalities of shadows and highlights. This is what gives HDR the appearance of artificiality and unnaturalness. Exposure Fusion after fusing the images together keeps the tonalities how they would appear if one was to be looking at the actual scene being photographed. When one views a HDR image a keen photography eye can spot the uneven transition between the luminance and can therefore lose the appeal of realism. Now I am not saying that one is better then the other in terms of an artistic point of view but that Exposure Fusion produces results that are truer to the scene that the photographer is trying to capture.

Exposure Fusion Advantages Over HDR

Exposure Fusion processing times takes much less due to a absence of a intermediate HDR image that must be created before one can tone map a HDR image. Thus, processing times are twice as fast when transferring back into Photoshop. The most important advantage in Exposure Fusion is the lack of halos that appear around objects that occur with HDR. Often when combining images HDR produces a very three-dimensional image that looks very impactful but when viewed closer the halos become more evident. As a side note eliminating those halos in HDR can be quite difficult and time consuming. To get around the problem of halos in HDR layer masks and careful brushing is essential.

One very important advantage of Exposure Fusion is that it can combine a series of bracketed images with different depths of field that extend the Depth Of Field in an image and give the perception of more three-dimensional qualities in the image. This presents an advantage to many obstacles when it comes to nature photography. For example, shooting a wide perspective of a scene with wildflowers and a mountain in the distance would normally require a f/16 at least to get everything in focus. The problem arises if there is strong wind or low light and a faster shutter speed is needed to freeze the detail in the foreground wildflowers. It is then necessary to shoot at f/8 for the foreground and combine it with the rest of the images which can be shoot at f/16 to capture the background mountains. Before Exposure Fusion combining a series of images with different Depths Of Fields was limited to only those with the best of Photoshop skills.

Where Can I Find Exposure Fusion?

Exposure Fusion is still fairly new and shows so much promise already that I cannot wait to see what comes next. Presently, Exposure Fusion comes in a few third party programs but not as a plug-in for Photoshop. It presently can be found with PTgui and the preferred Photomatix Pro. If you own a copy of Photomatix Pro, Exposure Fusion comes free with the update to the software. To see more information on Photomatix Pro see above notes to website.

How Do I Get Started With Exposure Fusion
Often the hardest part to any new software is where to begin and how to work it into one’s already present workflow. The good news is that Exposure Fusion is much more straightforward then most third party plug-ins for Photoshop. There are a variety of ways to get started but the easiest way is to choose the series of images in your Photo Media browser and drag onto the Photomatix icon in the dock. I use Adobe Bridge that comes with Photoshop so the two work seamlessly for me. I choose the first image of the series and Shift-Click on the last to include the complete series of bracketed images.





From there, you can right click to open a series of options that ask you how you would like to open these images (then choosing Photomatix Pro) or dragging the set of images on top of the Photomatix Pro icon. Both ways work well and lead you to a very simple dialog box that asks you to choose either: Generate an HDR image, Fuse exposures, or open files only.

For Exposure Fusion choose : Fuse exposures and this leads you to an option box that asks you to confirm that these are the images you would like to use. Within that confirmation box you are also asked if you would like the sources images aligned whether you want them to match features or horizontal and vertical shifts. This is very important to leave on the default of matching features and not the latter.

Exposure Fusion does what it does best and merges the series of images into one single image and Press OK
You are brought to one final dialog box that gives you a variety of options in terms of luminance, saturation, and contrast. I encourage you to leave it on the default and leave Photoshop to make these adjustments, as this is what Photoshop does best. One last option at the top of the page is how you would like things to merge and again leave on the default of Highlight & Shadows – Adjust. And click Process.

Once this occurs the final adjustments are made and you are asked if you would like to save and where would you like it saved. I automatically bring into Photoshop from here and doing my major adjustments in Photoshop.





All of the above seems quite daunting but let to its defaults the whole time from start to finish is less then a minute. Not bad compared to processing times of an HDR image. I am often asked why not make adjustments in Exposure Fusion and the reason is that the adjustments are permanent lacking the flexibility of layer masks and opacity with Photoshop. Always when processing include within a workflow a way to always avoid permanent adjustments and allow a way to go back and make changes without harming the pixels of an image.

Future Of Exposure Fusion
As mentioned earlier the concept of Exposure Fusion is in its early stages and there is great strides made from the days of HDR. I look forward to the advancements of this software and predict that cameras will one day strive to do what Exposure Fusion does but in the camera.

~ by kevinmcneal on February 7, 2010.