shooting through a chain-link fence

[chris jordan]

Hey guys, happy holidays; I hope everyone is well these days. I have a question about an interesting phenomenon that I observed shooting in an industrial yard last week. Unfortunately I couldn't get permission to enter the place so I had to shoot through the 15-foot high chain-link fence. I got my camera up as close as possible (the lens was directly against the fence) and tried to line the "sweet spot" of the lens up with the hole in the fence as best as possible. But no matter how I aligned it, there was always a piece of fence (i.e., very thick metal wire) that passed directly across the lens. With no other option, I composed and shot several negatives at f/22, thinking there would be some defect in my originals that I would have to deal with.

But as far as I can tell there is no effect from having had the wire fence directly in front of my lens! I can't find a soft spot in the negatives, nor is there any area that seems darker or otherwise lacking in quality. My every intuition tells me there should be some effect from shooting through the fence but I can't find any. If I put my eye up to a fence like that, it would see a dark fuzzy line, and some part of the image would be blocked by the wire, but that doesn't seem to happen with a camera. Does anyone know the optics of this strange phenomenon, or have other comments or thoughts?

~cj

[Jim Galli]

Hah! And you didn't believe those Ebay truth tellers claiming some tiny portion of a fly spec wouldn't matter. Actually you may have had fence in a non-image forming (for your application) area of the lens. ie. on 4X5 it was way out in the peripherals that did not make it into your image area. Just out of curiosity what lens / format did you use. A 305 G-Claron for instance could cover almost 9 4X5's and the fence would be somewhere in the surrounding 8 you didn't use.

[Ernest Purdum]

Keep in mind that every part of the lens sees every part of the subject, unless blocked by the lens mount itself, or some thing else. In this case, the something else was wire of the fence. The wires were blocking some of the light, but every part of the lens that was not blocked was recording the image. By getting as close as possible, you were following the recommendations long given to people trying to shoot the lions at the zoo.

[John Cook]

Similarly, I once attempted 8x10 photography of a chess set arranged on a chess board. Like just about every table-top subject you can think of, it amounted to an extreme macro shot with 8x10.

As with your experience, most of the pieces were so far out of focus, they totally disappeared and did not record. The few pieces on which we could hold decent focus appeared to be alone on the board.

[Gene M]

This has no bearing on your question but it's interesting. I knew a guy that had such bad buck teeth that he could eat an apple through a chain link fence.

[Sal Santamaura]

Whichever of your lenses you used, I'll bet it was considerably longer than the 25 mm focal length of your eye!

[N Dhananjay]

An object that is exactly one focal length in front of the lens will be imaged at infinity behind the lens (and anything closer than that will not be imaged at all). In other words, an object closer than one focal length in front of the lens will act the way an intrusive lens shade might act i.e., it might vignette the image circle, it might reduce the light transmission etc. If it is a small amount of the glass that is actually blocked by the intrusive object, the rest of the glass still sees the distant scene and images it as it usually will but with a reduction in the light gathering power of the lens. Cheers, DJ

[Andrew O'Neill]

ha ha ha....(sorry!) Reminded me of when I used to live in Japan and I was showing some students of mine that whenever I photographed the big clock on the wall of our classroom, the minute hand vanished on the print....I did a 2 second exposure on polaroid sheet film to prove it to them. They were amazed! How could that be?? They thought I had a magic camera! Oh well, it was a good hook to introduce to them the wonders of loooong exposure photography.