Out chasing a few subjects last night while it was warm and extremely misty, I got caught by the strongest defocus effect that I’ve ever encountered, and it’ll take a little explaining.
First off, there’s a term, ‘bokeh,’ that refers to the out-of-focus portions of a photo, the areas well outside of the focal point, which usually means well behind or in front of said focal point, and many photographers fret about how pleasing their bokeh is rendered for portraits and so on, occasionally spending a lot of money to chase this dream (this is what Leica lenses are known for, and if you’ve ever priced anything with the Leica branding, you know what I mean by ‘lots of money.’) Different lenses surely produce different bokeh effects, but so do minor adjustments in aperture, the difference in distances between subject and foreground/background, contrast and saturation settings of the camera (or the type of film used,) and of course the conditions.
More specific to this post, however, is the ability to blur out foreground elements so far that they almost disappear, producing a faint colored haze in the image, and this is because the lens is capturing more of the light that comes to it past the foreground element, around it, and the larger the front element of the lens, the more this can be exploited. I have a post illustrating how this works here.
I say this because last night I fell prey to the strongest example of this effect that I’ve yet encountered, while out trying to semi-duplicate a previous image of a treefrog. Behold.

I know this looks like I wasn’t paying attention or holding still enough or something of that nature, but the gist of it is, I couldn’t see these intervening leaves at all through the viewfinder. This was with the Sigma 180mm macro, focusing at its maximum aperture of f3.5 but taken at f11, while I was focusing by the headlamp, which is more than adequately bright enough for the job. The wide aperture and focal length of the Sigma was enough to render the blocking leaves completely invisible through the viewfinder, only appearing under the flash and increased depth-of-field when the camera stopped down to f11.
You could say that I simply wasn’t paying close enough attention, and I’d agree with you – if I hadn’t done it twice, trying again after realizing that I’d just gotten caught. The flash was at an angle that illuminated the leaves, but the headlamp was aiming over them or perhaps even blocked by the lens and lenshood. Still, they were right there in my line of vision through the viewfinder and yet I had no inkling they were in the way.
This is an approximate reproduction of the position I was in, except that it was night and the lens was actually attached to the camera and not on a tripod, and the frog was present, and…

[I did actually get the shot that I was after, on the third try, kinda – I was forced to change my angle and thus didn’t quite have the composition that I wanted. Life is hard.]























































































