Whilst digitising the Conway Library, I often come across confusing visual anomalies like the one at the bottom left of item CON_B00756_F007_025. Understanding what has caused the image fault requires a bit of a technical explanation. In this case, what we are seeing is an example of vignetting, which happens when using large format cameras capable of perspective adjustments.
Anyone interested in mastering these issues should study the fantastic Ansel Adams‘ The Camera, in which he states the vignetting “occurs when part of the negative area falls outside the image-circle of the lens and thus receives no exposure” (see chapter 10 “View-Camera Adjustments”).
In this image we can see that the photographer has adjusted the camera movements to control perspective in order to construct an accurate representation of the building that is aesthetically pleasing and free from distortion. However, in making such adjustments, they have inadvertently moved the lens out of the negative area, cutting off part of their image (either by tilting or shifting the front standard too far).
These kind of errors are fascinating as they exhibit the high levels of control required to practice the medium of photography successfully. This type of image control is still carried out by architectural photographers today when they choose to utilise tilt/shift lenses on modern digital cameras. Here, minimising lens distortion and configuring perspective to meet highly rigorous visual requirements.
Adams, A (2003) The Ansel Adams Photography Series 1 The Camera. Little, Brown and Company.
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