One of the single most mentioned 'critiques' of my ku and related pictures is about the corners of the pictures - what's with the vignette / blur/ darkness? ... you should use a smaller aperture for more edge sharpness ... or, the ever popular, I like everything but the corners. These observations come almost exclusively from the ranks of photographers, virtually never from the 'public' who view my work.
As I have explained a number of times, the corner blurring / darkening, aka vignette, is created in Photoshop by a series of actions that produce what I have labeled my Holga effect. The reason that I started to do this is both simple and complex;
1. simple - I like the results that the Holga camera produces (but not the extreme limitations of the camera itself).
2. complex - human vision is 'centrist' in nature. When the eye is motionless and fixed on whatever is in the center of the field of vision, all that is in our peripheral vision is very indistinct. We can see / sense changes in light, objects in motion, etc. in our peripheral vision but only with a very low degree of acuity.
The camera's gaze tends to render everything within its plane / field of focus equally distinct and sharply rendered no matter where it resides in the frame. This is especially true with digital cameras that use smaller than full frame sensors which effectively create extended DOF. Coming from a life of film and a variety of camera formats where DOF is narrow and selective focus is a technique that helps lend emphasis to the object of the camera's gaze, I wanted to use a technique that mimics some of the traditional film camera capabilities of selective focus / narrow DOF.
After a bit of screwing around (and thinking about item #1), my Holga filter was fait accompli. Since then, I have applied the filter in exactly the same manner and amount to all of my ku pictures.
You can imagine my surprise, when a few years later, I discovered that I had reinvented a very old wheel. While reading / researching the history of the medium, I came across a fellow named Peter Henry Emerson (I have mentioned him before), who, in 1889, in his Naturalistic Photography for Students of the Art, championed an approach to photography that was remarkably like my present day Holga filter.
He wrote, "... as has already been shown, the eye is very imperfect, and its images are not therefore perfect, and it could not form theoretically perfect images, even if the atmosphere were pure ether and nothing else, for there are other facts in nature which prevent this ... (a) central spot is a most important factor in the Fovea study of sight and art. For though the field of vision of the two eyes is more than 180 laterally, and 120 vertically, yet the field of distinct vision is but a fraction of this field, as we can all prove for ourselves ... the field of distinct vision depends on the central spots for the reason that the central spot differs anatomically from the rest of the retina by the absence of certain layers which we need not specify here. The absence of these layers exposes the retinal bacillary layer to the direct action of light. Helmholtz says "all other parts of the retinal image beyond that which falls on the central spot are imperfectly seen/' so that the image which we receive by the eye is like a picture minutely and elaborately finished in the centre, but only roughly sketched in at the borders".
For Emerson, the net result was that he made a lot of pictures with unsharp edges and corners.
Apparently, like Emerson, I want my pictures to mimic the human act of seeing and looking at that moment when the eye is fixed upon the thing it wants to see. For me, this is so because I want to draw attention, not only to what is the object of the camera's gaze, but also to the very act of seeing and looking itself.
That is, 'seeing and looking' as a human act, not as a photographic one.