Re-Imagining an Iconic View: Night on Hakodate-dake

[OlDoinyo]

One of the things tourists do in the city of Hakodate is to take the tramway to the top of a high rocky hill at night and take in the view of the city lights from above. At the beginning of the past month, yours truly did just this. Yours truly also had a UV-capable camera, so that after taking a number of conventional images, it was possible to attempt a UV version of a portion of this view. A portion of one of the conventional photographs is appended for comparison. The camera was a Sony A900. For the UV exposure it was fitted with the Steinheil Cassar-S set at f/16; exposure was 607 seconds @ ISO 640; filtration was Baader U2. Display intent is BGR. For the conventional image, a Tamron 24-70 zoom was set at f/11 and fitted with a KolariVision deconverting filter; exposure was 20 seconds @ ISO 100.

 

 

 

Unsurprisingly, there are differences in the view. Some signs are very bright in both photos, whereas others show up only in the visible spectrum. It is evident from the large number of cyan light sources in the UV frame that Hakodate still has a lot of mercury-vapor streetlamps and only a few of the sodium type. The red color on the Goryokaku tower in the middle distance in both photos is interesting; the way it is produced surely is not the same in both images, but I have no theory as yet. There are fewer sources in UV, and numerous areas appearing bright in the visible image are UV-dark.

 

If there is infrared contamination, one would expect it to manifest itself somewhere on the continuum from white to bright blue, as the "red" channel is more sensitive to the 700-760nm range than the other channels. There is no bright blue, but there are a few whitish light sources which invite speculation. Also not much in evidence is the deep red one would expect from a blue light source that emits no UV.

[Andy Perrin]

Was the UV one at ISO 640 or ISO 6400? I ask because my camera doesn't do 640 and it is also a Sony (although I suppose the different models may make a difference there).

[OlDoinyo]

EXIF says 640. I have two Sony cameras and their increments are not the same.