Giant Springs near Great Falls MT

[enricosavazzi]

So I made it to the US. On the first day I managed enough time for a few locations around Great Falls. All following pictures are with "full spectrum" Olympus E-PL6 and Pentax-110 18 mm f/2.8 (stopped down to roughly f/4 with an added diaphragm at the rear of the lens - the lens has no diaphragm). The pictures below are JPGs pretty much out of the camera with electronic flash WB, to show the effects of different filters (no post-processing but minor luminance adjustments, no color changes except as noted in the captions). I cropped slightly to remove a moderate vignetting caused by some filter mounts and the light shade. I added to this set a picture from an unmodified Olympus E-M1 Mark II with 7-14 mm f/2.8 Pro for color comparison. The framing differs, these are not meant to be a multispectral recording of the same subject. Some pictures, however, do show approximately the same subject area.

 

These are said to be the largest freshwater springs in the world. We can see up to perhaps 1-2 m deep in the very clear water, among the water plants.

 

Astronomik L3. This is a UV-cut and IR-cut filter with very sharp transmission shoulders. The L3 cuts some of the violet at one end of the spectrum and some red at the opposite end. The L2 and L1 are also available, and cut less of the VIS spectrum. Since it does not cut red gradually like typical built-in filters, the picture has a reddish/brownish cast with respect to unmodified cameras.

 

Unmodified E-M1 Mark II with 7-14 mm at 7 mm.

 

Baader U. Very little is visible below the water surface, but the details of the surface ripples are emphasized..

 

Zomei 680 nm low pass. This filter is visually a very dark red. We see fairly well to the deepest parts of the water (not in terms of detail because of the surface ripples, only in terms of water transmission)

 

Zomei 860 nm low pass. A very typical filter for NIR photography. We see more through the water surface than in UV, albeit NIR is substantially attenuated by the water thickness.

 

Baader 570 nm low pass. This filter is visually orange. It obviously transmits also NIR. Slightly reduced the red level in post-processing to emphasize the orange/yellow parts.

 

Same as above, showing the deep penetration through the water of the red/orange VIS components, less so of the NIR components. Same post-processing as preceding image.

[Cadmium]

Enrico, Interesting and nice shots!

[Andrea B.]

Enrico, I'm happy you made it to the US with all your gear.

 

I'm enjoying the photographs. I especially like the last one with its abstract play of pink and yellow light. Very nice.

 

The reversal of the light/dark tones in the BaaderU and Zomei 680 photos is really cool!! Those two photos would make an interesting diptych when printed and framed.

 

Looking forward to more.