Large scale digital process

The following is a summary of my current large scale digital process based on the Lake Mokoan trip and West Gate Bridge series. I expect this process to continue to evolve as I shoot in new locations, gain experience and refine my technique. The next iteration of this process is likely to occur when I visit New Zealand in December.

Capture

The essence of my current process is to capture up to 22 images in a two row panorama (with 50% overlap) that yields a large scale digital image of 20” x 60” @300dpi or 14 images for a 20” x 40” image. Although some of my images are considered full panorama’s at a ratio of 3:1, I am more interested in capturing images at 2:1 ratio (similar to widescreen cinema) which I consider as large scale digital photography rather then panoramic digital photography. I will have no hesitation in cropping a full 22 image capture to the 2:1 ratio if the composition is improved.

This is all captured with my sharpest prime lens, the inexpensive Nikkor 50mm 1.8 AFD. I liken the process to digital scanning of the subject with post-processing providing the final composition. What I do ensure during capture is the thirds rule for either the foreground or background by overlapping the image 50%. For example if the sky is the feature then the bottom of the vertical frame is on the horizon for the first row, I then overlap this by 50% for the foreground. I capture in RAW and save a basic JPEG which I use like a contact sheet for selecting images for full processing. As print is the final output medium, I always shoot Adobe RGB.

Refinements of this technique including HDR capture, which I am currently experimenting with and maximising the DoF by using Helicon focus for which I have not experimented with. I could also introduce a RSS nodal slider but as yet have had few problems with parallax due to the efficiency of the Autopano Pro algorithms.

Pre-Processing – Camera Raw, Autopano Pro

I liken the Pre-Processing stage to the development phase of a film negative. After being frustrated by CS3’s ability to manage multi-layer stitching I discovered Autopano Pro. One of the key features of Autpano is the ability to automatically detect images that are part of a Panorama and stitch those images into a large scale digital image. The software has an automatic color correction feature, which can be tuned manually. Autopano can also use bracketed pictures for a HDR (high dynamic range) workflow. The program supports many file formats, including raw files from Nikon’s and Canon’s. One of the main features of a View Camera is the ability of the tilt-shift to maintain perspective. After experimenting with taking multiple shots on a grain silo, I found that the Autopano Pro software was able to correct the verticals with minimal loss of detail. As you can see from the image below Autopano is not limited to horizontal stitching tasks.

grain silo, tallygaroopna, originally uploaded by Andrew McDougall.

When I first download the images I do I quick sort by separating out the jpegs and getting Autopano do an automatic sort of the images. I always separate each image with my hand over the lens. Once Autopano has detected the panos I am able to select suitable images for post-processing and discard the rest. I then separate out the NEF’s for post processing based on this sort. In Adobe Camera Raw, I will apply global color balance corrections if required and any exposure tweaks before saving the images as Tif files. As the rendering can take some time (30-60minutes), I will often set the rendering to batch process over night. Each rendered file is saved as a PSD file at up to 500MB ready for post processing in Photoshop.

Post-Processing – PhotoShop CS3

Following along with the film analogy, the post-processing stage is like the printing phase in the darkroom. Once the photos have been rendered in Autopano as 16 bit PSD files, I open them in Photoshop. At this stage my workflow is relatively simple, I select from the following techniques to post process the image:

Global corrections:

• Fine tune the White Balance with Match Color – often unnecessary if corrected in Camera Raw, but always worth checking.
• Set the White Point using levels – not required if image includes a bright background like a sky that requires local modification.
• Adjust the contrast using Curves – as for setting the White Point.
• Use Selective Coloring to bring out the color - the RAW capture will be flat when compared to the JPEG.
• Use Hue/Saturation to increase the saturation – as for Selective Coloring
• Experiment with Filters – worth a go

Local Corrections

As mentioned above, the contrast and white-point may need to be set locally when there is a sky involved especially at sunrise and sunset when the area around the sun is clipped (as it should be). I use a number of techniques to alter the contrast including:

• Blending to images (either two shots exposed for the sky and foreground at time of capture or two shots processed at different exposures in Camera Raw – similar to pushing or pulling the negative in film development).
• Using the Magic Wand to mask out the sky or foreground (this is quick but can also be laborious with fine detail and needs to be feathered)
• The current technique I favour for complex horizons is duplicating the channel with the most contrast, choosing Image/Adjustments/Threshold and then applying the masks to either the Levels or Curves layer. The same mask can be inverted for the contrasting portion of the image. It is important to feather the selection (5px) for a smooth transition.

After working through the above techniques I save the file as a layered image so that I can always come back to it – funny how 24 hours later things look different!

Output – Print & Web

With the flattened PSD I choose Image/Shadow Highlight and check to see if this improves the image – I usually find that 10% for both the Shadows and Highlights is a great finish – though there are no hard and fast rules. I then duplicate the channel with the most contrast and follow the smart sharpening workflow to sharpen the image – I may also compare with Filter/Smart Sharpen at 100% 0.5px.

Finally I use Photoshop’s File/Script/Image Processor to create JPEG's at Quality 11 SRGB and RGB as well as SRGB quality 5 for the Web (sometimes this image may need to be tweaked further for the web). I will also create TIF file for printing if required.