Switching to NightShot swings the IR-blocking filter away from in front of the CCD imaging sensor and also turns on infrared emitters, enabling the camera to see in the dark much like military night-vision scopes.
The emitters are weak so it's not very useful unless the subject is close, and the resulting image contains shades of green instead of a more useful greyscale so it's obvious Sony didn't add any appropriate in-camera processing.
Furthermore, the exposure system is neutered.
Early Sony cams with NightShot could see through clothes using certain exposure settings and this caused a huge ruckus in the media, so Sony acted fast and a little rashly in my opinion. NightShot was made to work in Auto and Program modes exclusively, and the only exposure settings available are wide-open aperture and (on my F717 at least) shutter speeds between 1/60 and 1/8.
Too long for effective handheld work, and that's the least of the problems.
All other settings are also inneffective such as exposure lock, white balance, spot or center-weighted metering--even flash.
Ouch.
(By the way, the other Sonys with NightShot are V1, V3, F707, F828, and the semi-new H9, plus videocams).
All this adds up to the reason I never really messed with NightShot very much.
At some later point I read online that the answer was to add neutral density filters and tape over the IR emitters to prevent horrible reflections on the filters from the F717's end-of-lens emitters.
I tried this and it worked, but my photos were very fuzzy--almost as if the focus could not resolve on anything correctly, so I shelved IR again.
A few months later I finally stumbled on the reason--IR wavelengths and visible light wavelengths don't focus on the same plane at the same time.
In fact, red and blue are far enough apart on the scale to have a small amount of focus conflict.
It was explained that visible light needs to be eliminated for sharp IR photos to happen, and all you need is a screw-on filter.
DingDingDing!
I lamented online somewhere or other that I needed an IR filter but couldn't possibly afford one for a long time, and my plea was heard.
That wonderful gentleman up Fort Worth Way, Mr. Bruce Burton, played Santa Claus last December and sent me an early Christmas present--a 760nm filter he got from an ebay shop.
Apparently he preferred one with a different cut-off frequency so the one he sent me wasn't being used.
To give you an idea of how kind Bruce is, he also offered to let me borrow his F707 while my F717 was in Laredo getting it's failed CCD sensor replaced.
My hero!
Testing Time!
Our Texas Mountain Laurel was an early test subject.
Some wet leaves in the yard became the first IR photo I was proud of after years of messing around and not having any success. Problem was, most IR photos from other photographers that I was seeing at the time were landscapes, and I was never much interested in landscapes. The search for appropriate subject matter begins.
No comments:
Post a Comment