Technical: Snow sparkles under a full moon

Started Jan 26, 2016 | Discussions thread
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GeorgianBay1939
GeorgianBay1939 Veteran Member • Posts: 4,044
Technical: Snow sparkles under a full moon

We had a good opportunity a couple nights ago so I made a trial run at it.

This is my simplistic thinking:

First, definitions:

Light Value (LV) = Exposure Value at ISO 100 or EV (ISO 100) is a measure of scene brightness , not to be confused with EV which is the pair (f/, ss) camera adjustments for Exposure.

The LV of looking at the sun directly is about 34.

See the above handy link for the following:
LV of sunlit snow or white beach sand is about 16
LV of (looking at) full moon is about 15

Using my spot meter:
LV of moonlit horizontal snow is about + 3

So the DR of sparkles on snow during the day is (34-16) or 18 stops (between the snow and the specular reflections of direct sunlight). Impossible to do anything with that range.

And the DR of sparkles on snow during a moonlit night is about (15-3) or 12 stops (between the snow and the specular reflections of direct moonlight). Although difficult to capture in a single exposure I should be able to blend some brackets to get an acceptable HDR shot using Enfuse or Photomatix.

The experiment:
To speed things up I went to a few places close by and shot hand held, well braced. To do it properly I would use longer exposures and use the tripod. : )

At ISO 125 my camera has a DR of about 10 EV or stops. As with all cameras, increasing ISO drops DR. Increasing ISO to 800 on the FZ1000 probably drops DR by ~ 2 stops. Although I lost 2 stops of DR, I decided to use ISO 800 to maximize my analog gain (to minimize my read noise.) So I traded off DR for less noise.  right?

And I got 2 2/3 stops of shutter speed while shooting wide open (ranging from f/3 to f/4 depending on the Focal Length I used) My shutter speeds ranged from 1 sec to about 4 seconds (2 stops).

BUT then I cranked in -2 EV of Exposure Compensation to keep my shutter interval reasonably short, a second or so. (A 1 second shutter exposure is about my hand holding limit when I am well propped, engine off, dogs quiet in the vehicle.) …. and picked up the read noise again.  right?

The -2EV of EC also helped to prevent blown specular reflections.

Best compromise, I think. What do you think?

I shot about a dozen scenes with the above in mind.  I didn't shoot a range of exposures because it was very chilly with the window open (-20ºC).

Here are three of the better ones.   Yes, I know that I could do a lot better with a tripod and longer exposures at base ISO!  Go full size to see the sparkles better.

orange cast  is from my clearance light.

Advice appreciated, especially from those who have tried this sort of thing, day or night.

Many thanks!

PS  You'll notice some moon flare in the above.  Very difficult to see at night.  I also shot the full moon.  400mm EFL, f/4, 1/1250 sec, IS0 125, EC=-2/3.  Spot metered.  LV ~ 14/15.

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Tom
The best part of growing old is having the opportunity to do so.
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