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Stitcher - making large panoramic prints
Review of Stitcher Pro for high quality panoramic images
Keith has often taken a series of photographs to cover a panoramic view.
Stitching them together (well) is a lot of trouble.
Keith has recently been looking at a specialist program called Stitcher, from Realviz. [Now part of AutoDesk]
Although it offers a great deal in creating VR movies and a host of other smart functions, this article covers one specific area - producing very high quality, high resolution images for panoramic prints.
In this review, it's the Apple Mac version of the software (not yet Intel Mac) we're looking at, but the windows version is pretty similar.
Update Note 2012 -- Realviz was taken over by AutoDesk, and despite an update in 2009, it seems to have been put onto the backburner by AutoDesk - current version still available. See also Keith's review of Autopano Giga for software he uses in 2012
When I'm out and about travelling I often see some pretty spectacular views, like the one below, taken when I was driving to the top of the Grand Mesa in Colorado last Spring.
I've got a range of lenses that I use with my Canon 1Ds and at 16mm my 16-35 2.8L would capture the full width of the view above.
However, one of the things that stuck me about the view was the amount of detail I could see in the distant landscape.
Cropping a single frame to give this view would give the equivalent of 2-3 megapixels at best.
The view below is a composite of 14 overlapping images using a my 70-200 2.8L IS lens at 70mm (portrait orientation) and is probably equivalent to well over 100 megapixels.
The print of this image is over 9 feet wide! (~280cm x 56cm)
The sample to the right shows a very small part of the image at 100% (equivalent to a couple of pixels in the image above)
Detail from panoramic image (this has been resampled from the original 1Ds source resolution for the particular print size)
I printed the image at 110 inches by 22 inches (~280cm x 56cm) on 24" wide paper on my Epson 9600.
At nine feet long, it is a very impressive print, I just have to figure out its framing and mounting now... :-)
I'd stitched images together using Photoshop's Photomerge feature, but that only works with 8 bit images and while I'd produced stitched images from multiple shots taken with a shift lens, I was not always happy with working with 8 bit colour images.
From my experiences making QTVR movies a few years ago I'd looked at image stitching applications and in particular an early version of Stitcher.
The current version (5.5 pro) supports 16 bit images, so I was interested to see what would happen when stitching a dozen 75 megabyte tiff files (apart from a long wait :-)
From my previous experiences with some VR projects, I know that stitching images is not just a matter of overlaying Photoshop layers and flattening them to get a result. Lenses introduce all kinds of distortions, both geometric and as a result from their imperfect designs. I've used DxO to correct for lens problems, but there is still the problem of representing a curved world on a flat bit of paper.
Rather than go into all the details I'd refer anyone wanting a good, understandable overview of the issues to an article on the excellent 'Cambridge in Colour' site. Suffice to say, that with any lens over 24mm and stitching a single line of images, then a cylindrical projection is probably what you want. The help files and tutorial included in the Stitcher application are quite useful as well, these come with the demo version of the program that you can download for free.
The black and white example at the start is based on stitching together 14 16 bit tiff images. You might well choose to use a tripod, but since I generally dislike using the things for landscape work, and didn't have one with me, the 14 images don't quite match up. I took the attitude that at 1/640th of a second with the excellent image stabilised lens I was using, any slight offset or rotation would be a matter for software to clear up ;-)
You should ideally use manual exposure and keep it (and the aperture) constant for all shots in a sequence. That effectively means metering for the brightest shot. You can get the software to adapt to (equalise) brightness variations (it does it well) but it's a lot more effective if you help it as much as possible in the first place.
I used Adobe camera raw (ACR) for the conversion of my raw files to 16 bit tiffs.
I've locked all the settings together for all the images and turned off any auto settings. I've also set the same white balance settings for all images.
At 70mm, the lens I've used does not vignette much, but if it did, I'd have been inclined to make some adjustments to the ACR settings.
This is also one time where I might choose to use DxO (review) for the conversion since it will correct lens problems very accurately (and produce nice images as well).
Notice that I've picked Adobe98 as my output space, since I'm possibly going to print the results (I do sometimes use ProPhoto as well) I only tend to use sRGB when I know that the results are only destined for web use.
Unfortunately Stitcher has no colour management abilities whatsoever. That means it just treats the files as collections of numbers and ignores profiles. It also means that relying on Stitcher preview windows for deciding if your colour is right, is a non starter.
Now, if you've ever read our review policy, you may have seen this bit.
Well this is a first, and what Stitcher does -is- really useful :-)
You just have to remember what profile you were using, and when you open the resulting panorama file in Photoshop, you need to assign the correct profile back to the data. As long as you just rely on Stitcher to get the numbers right, all will be well again when you are back in Photoshop.
The Stitcher interface is fairly intuitive in that the process of choosing images, matching them up, and producing a stitched result. It is presented in a simple manner with a set of icons in the main work area.
I'm only looking at a fairly specific use of the software here, so I'll skip over a lot of what it can do. If you are curious about the other stuff, then do download the demo and have a play...
The images to work on are shown at the bottom of the work area.
The little colour marks on each image tell you whether it has been aligned with others and other relevant info.
You can manually align images if need be.
or, as in this example from another panorama I'll show later, you can just get the program to do it for you. Most of the time it manages fairly well, although I found that the lack of sharp detail in cloud images could cause some difficulty.
Looking towards Great Sand Dunes NP, Colorado - 12 images
Notice the preview pane in the top RH side. This shows a quick view of what your end result will look like. This is the time to make sure that the horizon is level and to notice how your set of images are not entirely level... This particular shot covers over 180 degrees, so the track behind me, that I'd driven up on, is visible in both end images (and yes, they were not loaded in the right order, the software sorted it out)
The program will work out the focal length of your lens and any distortions, although I found that picking two images that overlapped well and running the calibrate option in the Tools menu, helped the software cope with wider angle lenses, such as the example below which has 5 images taken at a focal length of 18mm
Looking towards Colorado Springs, Pikes Peak - 5 images taken with 18mm lens
For stitching images from a shift lens (example later), you cannot set a focal length, and select a 'flat stitch' in the focal length dialogue in the properties settings.
Note that you can only select 'Flat' before you try and align the images.
The relationships between the images is also shown in the image strip window.
Image Strip window
Now that you have the images loaded and aligned, it's time to get the software to do the real hard work.
Once your project is set up (and saved) you go to the render menu to create your output file.
Most of the options are not relevant to my particular use of the software, but I need to set the output file type and name, the portion of the image to render, and the type of rendering I want.
I've selected a tiff file, rendered in cylindrical format.
The user defined viewport is the part of the resultant image I'm going to have rendered.
It's selected in the render area dialogue, by selecting which parts of the image shown I want rendered. You can see where my slight unevenness in taking the shots has led to a curved view that will benefit from a bit of Photoshop work with the cloning tool later... I was standing on a pedestal at the time :-)
Selecting (B)lending method, sharpening and interpolation
Under the rendering options you get to decide just how long you want to wait. Good quality will take an hour or two, while the very best will be ready tomorrow morning - for the size of images I was using.
Smart blending tries to make any stitching errors as invisible as possible - it makes things much easier to tidy up in Photoshop later.
I've turned off sharpening, since I want to do this myself, possibly -after- I've resampled the resulting image to a larger print size. I like the option to be able to selectively sharpen (particularly for print use) and don't particularly want it applied without any direct control. I used a combination of Focus Magic and Nik Sharpener Pro
You can either render the file there and then, or save the project and render several together via the batch processing option.
Rendering underway - note two files in the batch queue window (and yes, my desktop is -that- disorganised)
This is where the serious calculations start. The software is pretty fast with small JPEG images for web use, but start stitching a dozen 75MB files and any current machine will give you plenty of time to get on with the housework.
Unfortunately the software does not currently take advantage of multiprocessing and one of the 2.7G G5 processors in my Mac sat idle for much of the time. With more and more multiprocessor machines coming out I'd expect this to be rectified before long.
The progress bar is also a little optimistic in its estimate of remaining time when handling big images - I suspect it might have been more accurate if I'd had several more GB of memory and some very fast disks.
Big images also eat up memory and disk scratch space. 3GB was OK for the images, but I could see that a lot of page swapping was going on (a sure sign of lack of physical memory) - I'll try again when I have a machine with much more memory.
Here's a shot showing the temporary files created during one rendering run (after about an hour and a half).
Big temp files
You can specify where the temporary files will live, but make sure there is enough space - running out of scratch space caused the image to only partially render.
Given the size of the images, it's very difficult to give an idea of the sheer amount of detail in the prints. I was only able to find any evidence of the stitching process in the image below, and that came from a combination of parallax error (not taking the photo from exactly the same place) and standing on top of a pedestal to get the view, which is well over 180 degrees.
View from near Zapata Falls, Colorado - There are mountains 80 miles away clearly visible in the full size image
A small stitching error, typical of what you might get when taking the pictures hand held. There are tools in Stitcher (stencils) that allow you to select which parts of which image are not blended. You can select regions in layers in Photoshop, and blend the Photoshop (.psd) file images.
This particular error is almost unnoticeable on a large print, but I cleaned it up with a bit of cloning and blending.
There are some excellent tutorials in the Stitcher package, which are well worth going through if you are new to the idea of creating such composite images.
The view from the road to Pikes Peak in Colorado.
One version using 5 images at 18mm focal length and another of a dozen images at 70mm. In the more detailed image, you can clearly see Colorado Springs in the distance.
View from Pikes Peak road toward Colorado Springs - a 30" x 12" print (76cm x 30cm)
View from Pikes Peak road toward Colorado Springs - a 72" x 16" print (182cm x 42cm)
I often use a 24mm shift lens for interiors and architectural work. The image below is from two images taken with the lens shifted up and down. Notice how the verticals are all correct in this view.
The Ballroom at the City Rooms in Leicester
This is where I definitely do use a tripod. I might also take several exposures at either shift, so as to be able to get two 32 bit HDR images, which I then reduce to two 16 bit images to stitch.
In the original image you can see shadow detail on the nearest chair and see detail in the leaves of the trees outside. While standard image formats utilizes 8 or 16 bits with applied Gamma and colour space, the HDR image format extends the bit depth up to 96 bit in a linear colour space.
If you are new to shift lenses, I've written an article about using the Canon tilt/shift lenses, showing what they are and how they can change some of your ideas about photography.
The software is capable of producing stunning composite images, making the best of high resolution original raw files from modern DSLRs.
The lack of any colour management features is in my opinion, a serious omission, but not a problem as long as you just use the program for the job of compositing images.
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It took a bit of experimenting to get the hang of choosing the correct rendering options and viewport, but I suspect that if I'd read the comprehensive user manual a bit more thoroughly first, it might have helped. The on-line help did seem to have a few problems with Safari, the web browser on my Mac, and some of the tips that show when you hold your mouse pointer over options could be a bit more comprehensive (or present at all) ... I did wonder whether it was a case of most QC testing being done on windows PCs rather than the Mac version?
There are cheaper solutions to stitching images, but I was after quality and ease of learning and use. When I produce one of my large prints for exhibition, I want the very best, and I feel that Stitcher has given me the quality I'm looking for, without having to spend a lot of time on the lens calibration and stitching process.
The full version of the software covers much more than I was looking at and is a serious option if you want to do panoramic VR work.
I'll not make images like this very often and the software is simple enough to use that I'll not have to go back to the manual to re-learn it.
The software used was Stitcher Pro Version 5.5 from Realviz which was listed at $349
Note 2012 -- Realviz was taken over by AutoDesk, and despite an update in 2009, it seems to have been put onto the backburner by AutoDesk - current version still available
VR photography for interiors and exterior use
Keith provides Virtual Reality photography training in this specialist area - please see our training pages.
The views in this article represent those of Keith Cooper.
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