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How To: Multi-Shot Panoramic HDR Photos

Every time I am in Pittsburgh, I love going up to Mount Washington and taking photos of my hometown. This time, though, I wanted to do a multi-shot panorama in HDR. I had a pretty good idea of what I wanted to do but had never done it before. Here, I’ll walk you through the steps for turning your multi-shot panoramas into awesome high dynamic range panoramas!

This tutorial assumes you have the following:
- A camera with Automatic Exposure Bracketing capability
- A tripod
- Adobe Photoshop
- Photomatix Pro
- Basic knowledge on creating HDR photos… For a great, basic HDR tutorial see Stuck in Customs.

First, I’ll show you the finished product. The full-size original image is comprised of twelve photographs and is about 750MB and 23 megapixels in size:

Click the photo below for a larger version…

Taking the Shots

First and foremost, you’ll need to actually shoot the images you want. This is, of course, the most important step.

Set your tripod and point your camera at the most important part of your panorama. For this example, I used the large group of buildings on the right hand side. I chose these because they are a natural subject for a city panorama and also because they are the most detailed and complex parts of the finished product.

After the camera is pointing at your subject, begin setting up your camera:

ISO

Use the lowest ISO setting possible. For most cameras, this is ISO100. My 5D does go down to ISO50, but 100 is what I used for this shot. HDR photos, depending on your final settings can have a fair amount of grain or noise in them. Increasing the ISO also will introduce noise into the final images. Multiply that by three and add on the potential grain from an HDR and you’ll see what I mean.

Manual Mode

This is extremely important. If the camera’s aperture, light metering, or shutter speed differ from shot to shot, you’re going to end up with a panorama where each section is different in tone, exposure, and focus. I’m only a Photoshop newbie, but I can imagine how difficult this would be to fix. For a landscape shot, particularly a panoramic landscape shot, I use a smaller aperture to increase my depth of field. In this particular case, it may not matter much since the city is so far away from me, but it’s a good thing to keep in mind. Once you set your aperture (I used f/7.1 in these photos), adjust your shutter speed so that the main part of your panorama is properly exposed. I used the default average metering for this shot, which will likely work fine unless your dealing with drastic differences in lighting. Based on an aperture of f/7.1, the camera’s light meter told me that 10 seconds would give me proper exposure.

Manual Focus

Turn off your lens’ AutoFocus feature. If you use AutoFocus, the lens is going to refocus every time you move the camera to take a new set of shots. For a small aperture and distant subject, you may not notice the difference in the final shot, but, then again, you might. Using Manual Focus is the only way to go. So, again, adjust your focus so that the main part of your panorama is sharp.

Automatic Exposure Bracketing

After setting up the camera’s ISO, aperture, and shutter speed, you’ll want to enable Automatic Exposure Bracketing, or AEB. Most, if not all, SLR cameras have this feature. This will allow you to take three shots at configurable exposure compensation settings. For most of my HDRs, I set AEB to +/-2. This means that the next three shots will be at 0ev (proper exposure), -2ev (2 steps underexposed), and +2ev (2 steps overexposed).

Swinging Through

Now that your camera is all set up to take the photo, look through your viewfinder and slowly swing through the entire range of the panorama and make sure your zoom is set so that you can get the entire landscape in without having to adjust. Without doing this, you may find that your subject is lined up right but when you go to move to the next segment of your shot, something is running outside the frame.

Zoom

If you have a “wide-angle” lens, don’t use it. It may seem like a good idea but it isn’t. Wide-angle zoom lenses sometimes introduce distortion at the edges of the photo. This happened a lot when I had the Canon EF-S 10-22mm lens. I loved that lens but, at 10mm, the objects at the edges of the photos would lean inward. This will totally screw up your efforts to merge your panoramas later. For this example, I zoomed in to 43mm.

Taking the First Shot

For HDR images, it is vital that your camera move as little as possible for the multiple shots you’re taking. This is especially true at night and even more so for night panoramic images. If you have one, use a remote shutter release. Or, if you don’t have a remote shutter release, use your camera’s timer. This will allow you to take the long exposure shots without risking your hand moving the camera when you press the button. As an extra bonus for those of you that use the timer, your camera may take all three shots in a row when AEB is set. My 5D does this and, even though I have a remote shutter release, I still tend to use the timer. All I need to do is enable AEB, use the timer, and hit the button once. After the timer expires (10 seconds), the camera fires off all three shots.

You can shoot in any direction (left-to-right or right-to-left), but I prefer to shoot from left-to-right. It simply seems more natural to me. So, after I set up my camera while looking at the city, I swung it around and began taking photos on the left side of the image.

Taking the Next Shot

When you’re doing panoramas, you’ll want to make sure that each segment overlaps the previous one significantly. I believe I’ve heard they should overlap as much as 30%. That’s fine. The more the better, in my opinion. That will give your photomerging software more to work with when it has to merge them later. So, after you take your first set of photos, make a mental note of some landmark on the edge toward where you’ll be swinging the camera next. When you slowly swing the camera to the next position, make sure that landmark is easily visible and not too close to the edge. Now you’re ready to take the next few shots.

Another word on framing… Photoshop, in my limited experience, does a pretty good job of stitching images together. That being said, try not to have major overlaps right in the middle of your subject or right in the middle of a particular complex area. You want as much of your subject in one frame as possible. That way, if Photoshop doesn’t stitch them together perfectly, it won’t be in a critical part of the photo and may be easier to fix.

The Shots

Here you can see the shots I ended up with after taking after setting up my camera as described above. At each spot, I had the camera take three photos via AEB:

Each segment’s photos are as follows: 0ev, -2ev, +2ev

Segment 1:

   

Segment 2:

   

Segment 3:

   

Segment 4:

   

Export The Shots

Now, we will export the photos to a folder on our hard drive. Make sure to export all the photos at the same exposure level into the same folder. We’ll be merging the photos into three big panoramas before we do any HDR work. I export the photos into folders with descriptive names such as “Pan-OverExposure”, “Pan-UnderExposure”, and “Pan-ProperExposure”.

For example, the following four photos will be in the folder “Pan-ProperExposure”:

     

Repeat for the under-exposed and over-exposed versions.

Merging The Shots in Photoshop

Open up Photoshop and select File -> Automate -> Photomerge:

Next, you will see the following dialog, where I’ve already added the first set of four photos from “Pan-ProperExposure”. You’ll also notice I selected ‘Cylindrical’ for the Layout, though you’re free to experiment with the others for different effects:

Click for larger version…

Click OK.

Now, Photoshop will churn away a bit, depending on the speed and memory in your computer and what you’ll end up with (hopefully) will look like a complete panorama that’s a little rough around the edges.

Repeat this for the other two exposure sets and you should end up with a desktop that looks something like this:

Click for larger version…

On the right-hand side, you should notice that all three layers of each panorama are selected. If the panoramas look acceptable to you, merge those layers into a single image. If the panoramas look “off” you may need to retouch them with Photoshop or reshoot while following the directions at the beginning of this article. Merge them by right-clicking (Ctrl-Click) on the selected layers and select “Merge Layers…” as shown to the right. (Click on image for larger version…)

Repeat this for all three panoramas. After you’ve merged them all, consider naming the single layer something descriptive. Double-Click on the Layer Name and replace it with something like “Pan-Over”. This tells me that this is the overexposed panorama. This will come in handy later. See below:

And, when you’re done, consider saving them as Photoshop documents in case you need to go back.

Uniformly Resizing and Cropping

Now that we have three panoramas at different exposures, we need to crop them to make sure that they’re all the same size. Photomatix won’t be able to merge them if they’re not. To do this, make sure all three panoramas are open and select the Move Tool as shown to the left.

Next, we’re going to pick one of the images where we’ll drag the other two. The other two images will be added as layers on top of the image you pick. In my case, I dragged the low and proper exposure images to the over-exposed image. Once you have done this, you’ll see one image with a few edges sticking out around the side and three layers corresponding to each of the images. See why we named them?

Click image for larger version…

Now, with your mouse, make sure all three layers are highlighted, then go to “Edit -> Auto-Align Layers…” and select “Auto” Projection as shown in the images below…

Click OK.

Once your computer stops churning, all three layers should be perfectly aligned with each other. Now, we need to apply a crop that will resize all three layers (soon to be separate images again). Select the Rectangular Marquee Tool as shown on the right. With this, select the biggest region of the photo that you can without getting too close to the edges. See my example below:

Click image for larger version…

Next, select “Image -> Crop”:

Your result should now be a three-layer image that’s nice and trim.

Separating the Layers

Photomatix requires multiple photos at different exposure levels. So now that we have three layers that are all identical sizes, we need to use that to create three individual files. Select all three layers in the layers box on the lower right-hand side of the screen and then select “File -> Scripts -> Export Layers to Files…”:

Click on the image for a larger version…

Now you have three identical images at different exposures that you can easily turn into an awesome HDR photo! For help on creating an HDR with these three photos, see this awesome tutorial from Stuck in Customs.

Again, here we have our finished product:

Click on each image for a larger version…

And, one more, with a little more color and different post-processing:

Have any panorama or HDR tips? Leave them in the comments below!

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