In a previous post, we talked about using exposure bracketing— taking multiple photos of the same scene, each at different exposure values—to help improve your chances of getting the exposure right when shooting in tricky lighting situations.
You can also use exposure bracketing to expand the tonal range of your sensor. You see, there’s a limit to the range of contrast that your camera’s sensor can record. So if you are shooting a scene that has both extreme brightness as well as very dark shadows, your camera may not be able to record detail in both extremes. The sensor’s dynamic range isn’t wide enough to record the details in the bright areas and the details in the dark areas in one image.
So in these situations, you often have to make a choice. You can choose to use an exposure that works for the bright areas, knowing that the dark parts of your image will be underexposed and too dark, lacking any detail. On the other hand, you can decide to expose for the dark shadows knowing that the bright areas of your image will be overexposed and overblown.
But by using multiple exposures of the same scene and then blending those separate images together, you can extend this dynamic range to get the best of both worlds and create an image that shows proper exposure for all areas in the scene. This process is referred to as high-dynamic-range imaging or just HDR.
The process of blending two or more exposures can be done manually by using layer masks in either Photoshop or Photoshop Elements or the like.
Or you can use automation to make the process quick and easy. That’s where Photoshop Elements’ Photomerge comes in. With the Photomerge Exposure feature in Elements 12, you can blend two or more photos of the same scene, each with different exposure settings and let the program bring them together to give you a better, blended image.
To use this method, first take multiple shots of your scene, bracketing the exposure and being sure to get shots at exposures for the extremes in the scene. The Photomerge program allows you to use anywhere from 2 to 10 images, so have at it! And be sure to have your camera mounted on a sturdy tripod for these shots. While the Photomerge program will try to align the images if the compositions are a bit off, the blending process works better with shots that are aligned.
Here are two images I snapped in my yard on a recent too-sunny (and a bit too-windy!) fall afternoon.
As you can see, one of the photos exposes the red leaves correctly but underexposes the shadows underneath. The other image shows detail in the shadowed areas but overexposes the foliage.
Let’s see how to work with these two photos in Photomerge in Elements 12.
First, open both images (or as many images as you are using—remember that you can use anywhere from 2 to 10 images with Photomerge) in the Elements 12 Editor so that the photos are visible in the photo bin along the bottom of the interface:
If the photo bin isn’t visible with the open images, just click on the icon at the bottom of the workspace:
Now select all of the images in the photo bin by shift-clicking on each. You’ll see a selection box around each image that you have selected:
To open the Photomerge interface, choose (in any of the editing modes):
When the Photomerge window opens, be sure that the Automatic mode tab is selected and then choose a blend mode:
Simple Blending blends the two exposures together without any input from you.
Smart Blending blends the two exposures together, but gives you the option to do some tweaking with sliders to allow you to adjust the Highlights, Shadows and Saturation:
Now just sit back and watch the magic happen.
I find that the Smart Blending mode does a good job.
But if you’re not happy with the results or if the photos aren’t aligned or if you just want more control over the process, choose Manual mode.
There you will see a workspace showing two windows—one named Source and the other named Final. The idea here is that you are going to tell the software what part of each shot to use in the final merged image.
To do this, drag one of your images from the Photo Bin into the Final window. I usually find it best to use the shot with the best exposure for the background area of the image as the Final.
If you second image isn’t already showing in the Source window, click on it’s thumbnail in the Photo Bin.
You should now see both of the images in the workspace.
Now using the pencil tool, draw over the areas of the Source image with good exposure. These are the areas that you want to use in the Final:
If you make a mistake, use the Eraser tool to remove the pencil marks from the Source image.
Finally, if you need to align the photos, select the Alignment Tool under the Advanced Options:
When you select the Alignment Tool, three markers will appear over each of the images. The markers for each will only be visible when you hover your mouse over that image.
Move each of these markers until they are positioned over the same key locations on each photo. When the markers are properly positioned, click Align Photos.
Click Done when you are happy with your results.
A new, layered file will open. Layer 1 will be the blended image and the Background layer will contain one of your starting files. Since you only want Layer 1, you can delete the Background layer (double click it first to convert it to a regular layer) and save the final file in whatever format you want.
Here’s my final, blended photo:
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We've seen how managing the ISO setting allows you to control the amount of grain that shows in your photos. But it does more than that. Understanding and working with the ISO setting gives us added flexibility in terms of setting the other two exposure settings–aperture and shutter speed.
The bottom line is that ISO is an important and useful tool, and one that you will want to be comfortable with if you are looking to take creative control of your exposure.