Previously I posted an article about the advantages of tilt-shift lens techniques commonly found in large format photography. In this post I will expand on the benefits of combining the in-camera and the post processing of a typical macro photographic image image that contains High Dynamic Range (HDR) content.
A common problem in macro photography is that there is usually a very narrow Depth Of Field (DOF) that places most of the composition out of focus. Traditionally this placed severe artistic compositional limitations that would require very small apertures as well as tilt lenses in order to precisely control the elements of the composition that would be in focus.
Another common technique is to only photograph very flat images and to carefully limit the composition so that the lens nodal plane is parallel to the plane of the flat subject. This is how, for instance, flatbed scanners, reproduction tables, and microscopes operate.
Enter the digital age where we can now stack several images together so that we can selectively use only the best elements of each image and combine them for a final image not possible with analog techniques. For instance the technique of focus stacking has become popular in macro photography. Exposure stacking is also the basic technique used in HDR photography.
Exposure stacking is also commonly used in astro photography to combine several images in order to create low noise star trail photos as well as for combining several monochromatic filtered images to produce a final composite image combining several wavelengths of light and radiation emissions.
Here is an example of a typical macro photo with a very shallow depth of field, Nikon D3s, 50mm f2.8, 41.5mm extension tubes for a reproduction ratio of approximately 1:1. Note that the camera is angled about 30 degrees off axis to the penny surface normal.
Note that both the top and bottom of the penny are out of focus. There are also reflections from the light sources as well as information losses in the shadow areas that exceed the dynamic range of the camera sensor.
By precisely adjusting the camera position distance with a micro adjustment plate between the camera and tripod and taking several frames with different focus points several images can be captured with each having portions of the penny in focus. The image below shows the results of stacking twenty-one separate images to form a composite image with the entire penny in focus.
Note that there is a significant amount of distortion near the edges of the frame and there are still areas outside of the dynamic range capabilities of the very high end professional quality digital sensor.
Now by combining a tilt-shift lens a stack of only three images are necessary. The angle of the camera exceeds that of this particular DSLR lens tilt capabilities, most large format view cameras would generally have much greater tilt capabilities and thus would not require multiple exposures. In the following image seven exposures separated by one full stop were used to create a composite HDR image used for each of the three focus stacked images.
Image shot with a Nikon D3s, 85mm PC tilt-shift lens, f2.8, 41.5mm extension tubes for a reproduction ratio of about 1:1. Note that there are details that can be found in the reflections as well as in the deepest shadows, the signature of realistic HDR images. Also note the lack of severe distortions located near the edges of the frame. Also look back and forth between the images and note that the perspective is also vastly superior with the tilted lens. The tilted lens provides a superior near distortion free perspective that more clearly showcases the angled perspective thus giving the last photo much more realistic depth and clarity.