Taking and Stitching Panoramas

Introduction

The key to good panorama images is getting it right at the taking stage. Composition is different from conventional images but the concepts, for landscapes, of having a good foreground, middle ground and background with leading lines and linking elements still apply. The only rule is - if looks right it is right! It is all too easy to get large areas which are empty of detail so pan/tilt around to understand what is going to show in the images. Avoid moving objects if at all possible.

At the Taking Stage

The following is recommended:

Use a tripod and set it up so that the top is level (some makes have a spirit level to assist with this). It is important when you pan for the shots that the camera pans perfectly horizontally.

Invest in a spirit level that fits in the hot shoe of the camera so that you can also get the camera perfectly horizontal.

Pan your shots allowing a 20-30% overlap between images – you may use the camera either in portrait or landscape to suit your subject. Images with aspect ratios 3 to 5 times longer than wide work well. Beyond that, in my opinion, doesn’t work so well for prints

Vertical “panoramas” also work well – tilt the camera perfectly vertically with overlaps as above.

It may sound obvious but the following are essential for stitching:

• Images must be taken with the same camera
• Images must have the same resolution
• Images must have the same orientation (landscape or portrait)
• Images must be taken with the same focal length (do not zoom between shots)

Strongly recommended:

• Don’t use auto focus
• Avoid extreme wide-angle focal lengths

Exposure advice:

• For best results use manual exposure – use your camera as a meter by checking exposure values across the scene and select a suitable average EV.
• If you must use auto-exposure work in Av (aperture priority) mode so that the aperture of the lens doesn’t change as you shoot the images)
• Use your digital preview to check exposure and avoid overexposed highlights.
• Try to select a scene with even lighting - avoid backlighting for example.
• Use an f-stop which gives good depth of field.

You may shoot in RAW or Jpeg (max quality) as you prefer but see below. Work methodically, take notes if necessary so that you can easily identify the “sets” you want to stitch after you download.

Having said all that I have been able to get very good results with a compact camera set on auto and handheld! However you need to take great care to keep the camera horizontal and to pan horizontally as you take the shots. It can be done!

After taking

Download the images in the usual way. Use a browser such as CS3 Bridge to review and identify the ones you want to use. I set my file order to date taken and this usually puts the sets in the correct order.

If you shot in raw you will need to process the images into PSD or JPG. Do this using Ctrl and click to select all the images of a set you want to stitch. Open them in raw and make any adjustments (as little as possible please!). Use the raw processor to make the same adjustments to each image – this is very important. Save the images in a convenient folder where you can find them. Do not save them as 16 bit – 16 bit images won’t stitch properly. So convert them to 8 bit.

If you don’t need to make any changes then having selected the images use Bridge to convert them. In CS3 Bridge - from the menu bar go to Tools, Photoshop, Image Processor and click. This will open a dialogue box and allow you to convert to PSD or JPG and save the results in a folder of your choice in one go!

If you shot in JPG then you are ready to go immediately!

While not essential it is strongly recommended that no image adjustments or Photoshop work is done on images to be stitched – you can do all that after stitching.

The Stitching Process

This is actually the easy bit!

Two ways to do it – either from Bridge or from Photoshop.

In CS3 Bridge find the images to be stitched and using Crtl Click select the ones to be stitched in your panorama. Then from the menu bar go to Tools, Photoshop, Photomerge. This will open CS3 Photoshop and a dialogue box. The images you selected should be listed in middle. By default on left hand side the Auto radio button is selected. Auto works brilliantly! I have also used Cylinder and got good results – try the different modes if you are curious!

Click Ok and let Photoshop do its stuff. It will take a bit of time as there is a lot going on. Photoshop stitches the images and blends tones automatically.

It will create a large file – if you merge 4 shots of 16 Mb you will get a merged file of at least 64 Mb.

The file has a layer for each image that was merged and you may use these layers to work on to remove “ghosts” of objects that were moving at the taking stage. Not easy!

Before saving I suggest you flatten the image.

In CS3 Photoshop open the images you wish to merge and then from the menu bar go File, Automate, Photomerge. The same dialogue box as described above then opens and you can add “Open Images”. Alternatively open the dialogue box first and use browse to add your images.

Further Processing

You can use all the usual Photoshop tools and tricks to tweak your panorama. It is a big file so some things may take longer than you are used to.

You will of course need to crop but I tend to do all my tweaking first then make any perspective/transform adjustments and lastly crop. I will then resize the image for printing to 240 dpi and a size suitable for my media. This will be a much more manageable file but you will have thrown away a lot of data hence the reason for tweaking before this stage.

Stitching in CS2

CS2 Photoshop also has a Photomerge facility which, although not quite as sophisticated as CS3 seems to work quite well. After the first dialogue box where you add images you will get a second preview dialogue and you may have to manually drag some of your images onto the panorama. At this stage the blend will look awful but once you have Oked and the merge is complete things should look a lot better.

Other Software

There are a number of software products on the market – the more expensive ones designed for professional use to create 360 degree videos etc. I have tried a couple of these – I used to use RealViz’s Stitcher Express which is very good ( and will create 360 movies in Quicktime) but I am so impressed with CS3 Photomerge I will be using it exclusively from now on.

Otherwise

If you can’t be doing with all that – buy an extreme wide angle lens eg Canon 10-22 and crop for a great the panorama. You may get a bit of leaning in your buildings but you can usually tweak that with Edit, Transform, Perspective!

David Robinson ARPS