Somes Sound Near Southwest Harbor

[Andrea B.]

This is one view from the deck of the Maine house where we are staying. Lots of seaweed is visible at low tide. Greening Island is on the left horizon. Great Cranberry Island is off in the middle distance. Southwest Harbor's harbor is behind the trees on the right.

 

There are homes and one old hotel along the shore in this area of Somes Sound. Several boats are moored off the shared docks. Sailing school is held daily a bit further out. Occasionally a regatta breezes by. The lobstermen work this area every morning, hauling traps, culling the catch and rebaiting.

 

Equipment [Nikon D600-broadband + Soligor Wide 35mm f/3.5]

 

Visible Light [f/11 for 1/400" @ ISO 100 in Sunlight with Baader UVIR-Block Filter]

Click for a 1000 pixel wide view in an expanded browser. Looks a bit better.

 

Ultraviolet Light [f/11 for 1/8" @ ISO 400 in Sunlight with Baader UV-Pass Filter]

Click for a 1000 pixel wide view in an expanded browser.

 

Ultraviolet Light [Full size extract from preceding photo. 939 x 428 px.]

Amazing near detail can be captured in long UV wavelengths.

But some distant detail is lost in UV haze.

Click for a larger view in an expanded browser, but lean back from the screen a bit as this is not meant to be viewed with your nose on the monitor. "-) There is a bit of faux detail from minor noise which I did not remove.

[rfcurry]

Gotta love that Titanium dioxide! It makes the paint a pleasing purple.

 

I envy your getaway. :) Enjoy!

[Andrea B.]

So that's what causes it -- TiO₂.

 

We seem to be having a working vacation as the husband-like person is finishing his textbook writing, and I'm UV-photographing flowers every day for what seems like hours at a time. :) But we're enjoying it all - especially the lovely Somes Sound view.

[ahrneely]

Quick question, Andrea. Your exposure difference between the visible light and the UV is approximately 7 stops (6 2/3, if I calculated correctly). Can you recall what time of day and year these images were created? Based on shadows, I would estimate the sun was almost exactly overhead (so, my guess would be noon-ish somewhere near late June).

 

The reason I ask is that I am seeing a 12-stop variance between my visible light and UV response.

 

Of course, there could certainly be equipment variances and not just weather issues. I am using a Canon 20D broad-spectrum (converted by LifePixel) and an El-Nikkor 50mm f/2.8 lens, so who knows.

 

I'm looking for any way to decrease my exposure time without affecting image quality. I've thought of underexposing the UV and compensating in post (I'm using Capture One for white balance), but I'm too afraid of noise.

 

Thoughts?

[Andrea B.]

These photos were made on 09 July 2014 between 3:20 - 3:22PM Eastern Daylight Time (-4 UTC).

 

The UV setting [f/11 for 1/8' @ ISO 400] is equivalent to [f/11 for 1/2' @ ISO 100].

Now that we are the same ISO basis, counting from UV speed of 1/2' to visible speed of 1/400',

I get 23/3 = 7.66 stops difference.

 

Alternately, the UV setting [f/11 for 1/8' @ ISO 400] has an EV of 8, I think.

And the Visible setting [f/11 for 1/400" @ ISO 100] has an EV between 15-16,

which generally corresponds to a sunny, bright day.

There were some clouds but not directly over where I was shooting.

 

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I'm using a converted Nikon D600 which has a very good sensor which can tolerate higher ISOs and longer exposures without noise. It also has a very good dynamic range so shadows are kept a little more open and highlights are less prone to blow in a photo with wide dynamic range such as this scene.

 

How much any of that might account for the EV difference I get between Visible and UV exposures, I don't really know. Lots of variables are at play. And I probably had a day with high UV as well.

 

The Soligor lens is reasonably UV-capable. I would expect a slightly shorter exposure time in UV if using a dedicated-UV lens of the same 35mm focal length. (If there is one!)

 

A UV flash helps a LOT if you are shooting closer and not shooting an infinity-focused landscape scene such as mine.

 

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I have heard it said but cannot confirm from my own experience that the Canon sensors are slightly less sensitive to UV or IR. Nor have I seen any actual measurements of Canon sensor sensitivity to UV or IR.

Update: This appears not to be true about Canons.

 

I think if you simply upgrade your camera to one of the newer sensors (brand irrelevant) and have the camera converted, you might see a better UV response. (You would certainly get some better high ISO capability and dynamic range, less noise and a better photograph.) Whether gaining one or two stops for UV work is worth that expense, well, only you can answer that question.