Sierra Nevada from Mt. Hamilton, California, U.S.A. - Nikkor 500mm f/5.6 E

[Bill De Jager]

Once again I tried to get decent near infrared photos of the Sierra Nevada (a mountain range) covered in winter snow as seen from the Coast Ranges of California.  I've made two previous efforts, both partially stymied one way or another by either mental errors or atmospheric conditions. These efforts have all been made from the east side of Mt. Hamilton (1,333 m or 4,372 feet at the very highest point) east of San Jose, California, located about an hour and a half from my house.  The distance from the point where I have been taking these photos to the peak in the center of the photo below (Merced Peak at 3,576 m or 11,731 feet) is about 198 km or 123 miles. 

 

For these trips I leave before dawn, on a day where I expect relatively clear atmospheric conditions, so I can get the peaks backlit by low sun.  This works best right after heavy snowfall in winter, when the conifers that largely make up the forests below the peaks are still covered with snow.  This provides better contrast and avoids the very flat appearance that is rather typical from a great distance.  Unfortunately, outside of a brief period in December such snowfalls have been non-existent this winter. 

 

This time I tried after a light snowfall on the Sierra Nevada after a lone weak storm passed through the state a day and a half earlier.  (The previous morning there had still been clouds and snow showers on the mountains.)  There were also a few cm of snow on Mt. Hamilton itself.  Atmospheric visibility was worse than expected and photographs of distant subjects in visible light would have been of poor quality.

 

The equipment consisted of:

 

Nikon D610 modified by Lifepixel with a 850nm NIR filter

Nikon D7200, same modification

Nikon Nikkor 500mm f/5.6 E lens with hood attached and RRS plate

Manfrotto fluid head with RRS clamp

Sachtler Flowtech 75 tripod

 

I tried both live view autofocus and enlarged LV manual focus.  Unfortunately, I had forgotten my remote control and loupe.  I compensated for the absence of the former by using the settings for mirror up, self timer, live view so the mirror stayed up prior to the exposure.  I used electronic first curtain shutter with the D610.  The absence of the loupe (something I have not yet got into the habit of using) was keenly felt as the LCD was very reflective.  I missed being able to use the EVF of a mirrorless camera with an enlarged live view free of glare for fine focusing.  It was very hard to see what I was photographing and I was unable to recognize any landmarks in the Sierra Nevada at the time.

 

Shutter speeds were in the vicinity of 1/1000, lens at f/5.6, ISO 1600. VR was turned off.

 

After some trial and error I succeeded in focusing well with the D610.  None of the D7200 photos turned out acceptably sharp; I don't know if this was due to user error (vibration control discipline), lack of EFCS (not available on this model), increased diffraction from the smaller pixel size, or a combination of these.

 

The selected photo below was enhanced by increasing contrast, making other adjustments to levels, and auto haze removal in Photoshop Elements.  I tried to remove one spot caused by sensor dust but others may remain.  Some flare is visible.  While the sun was not shining on the front element directly, I believe that light was reflected off the interior of the hood.  PF-type lenses are well known for not doing well when shooting into the sun so sensitivity to reflected sunlight is not surprising.  The image has been cropped at the top and bottom but only minimally on one side.

 

The high peaks and middle elevations visible in the photo are largely in the southern portion of Yosemite National Park south of Yosemite Valley.  They are located west of the crest of the range; the curvature of the earth and the lower vantage point of the photographer obscured the highest peaks in this part of the range.  None of the park's famous landmarks are visible in this photo.  The one photo that shows the famous Half Dome is of poor quality and is not shown here.  The peaks in the foreground are part of a subrange of the Coast Ranges called the Diablo Range.  The low area between the near and far mountains is the great Central Valley of California.

 

Overall I am very pleased with the NIR performance of this lens despite the flare issue.  With sufficient care in aiming the lens and shading both the front element and the inside of the hood, I expect that very good results can be obtained.  However, the relatively slow maximum aperture may be an issue with sensors having very fine pixel pitches.

 

 

 

[colinbm]

Beautiful IR Bill.
I am surprised at the haze in the middle ground, I thought IR cut through the haze very well, so what situations cause the haze in IR ?

 

[Bill De Jager]

Thank you, Colin.

 

The strongest haze in the photo is below about 1000 m elevation.  That corresponds to a distance (front to rear) of about 130 km, much farther than typical long-distance IR views.  So that's one factor.

 

Normally I'd think such haze in this particular view was due to inorganic dust from soil being suspended in the air.  That's given that the entire area is in the throes of an unprecedented midwinter dry spell, about eight weeks with close to no rain during what is normally the wettest part of the year in this Mediterranean climate.  On the other hand, I'd have thought that the cold front that moved through shortly beforehand would have cleared out the old air and brought in fresh, clean new air. 

 

Nevertheless, it's possible that farmers did agricultural burning the day before the photo.  "Burn days" for farmers in this valley are designated by a government agency responsible for air quality, because of the severe problems with temperature inversions in the valley that make such restrictions necessary.  The air may look bad but that's an exceptional distance being viewed at once.  You can see at least two inversion layers in the photo, the obvious one lower in the valley and a less-obvious one about 60% of the way up the right-hand side of the image.  The fluted ridge at that location is called the Chowchilla Mountains.

[colinbm]

Sounds good, thanks Bill.
It is this clarity in IR that got me into this in the first place, then UV....

[Doug A]

What a dramatic composition and image. It was worth all the work. Glad you stuck with it. Do the Nikon's have a way to boost screen brightness for outdoor use? Two button taps on the Pentax K-1 gives about 2 stops brighter viewing image. I'd be lost without it, especially for UV. I still need to try a loupe.

 

Thanks for Sharing,

Doug A

[Nate]

Great shot Bill. I did a couple shots in NIR the other day, and realised how much I missed it.

[Bill De Jager]

Thank you, Doug and Nate.  In particular, thanks for the reminder about screen brightness.  I've never gotten in the habit of adjusting it so I tend to forget that it's adjustable.  I had it set on a moderate setting (0) to save on battery power.  Given that I nearly always use this camera outdoors and I'm likely to use the LCD for focusing I should and will change that.

 

[Andrea B.]

Wow! I don't think I have ever photographed that far - 123 miles. Very cool!

 

None of the D7200 photos turned out acceptably sharp;

Shutter slap?

 

The haze looks like what we see here with suspended dust on windy days. It seems too low and spread out for any kind of controlled burn? However, our controlled burns are at a much higher altitude in the mountain forests. I don't think I've seen any agricultural burns in this area.

[Nate]

1 hour ago, Bill De Jager said:

I had it set on a moderate setting (0) to save on battery power

You're not alone  My cameras were used only for astrophotography and I had the screens dim for night, and when I started NIR daytime, I couldn't figure out why everything was so dim in live view. Took me about 3 outings before it clicked. Another thing too that I just started using is an  LCD Viewfinder 3X Magnifier. Don't know how I ever lived without it tbh

[Bill De Jager]

28 minutes ago, Andrea B. said:

Wow! I don't think I have ever photographed that far - 123 miles. Very cool!

 

None of the D7200 photos turned out acceptably sharp;

Shutter slap?

 

The haze looks like what we see here with suspended dust on windy days. It seems too low and spread out for any kind of controlled burn? However, our controlled burns are at a much higher altitude in the mountain forests. I don't think I've seen any agricultural burns in this area.

 

Thanks, Andrea!

 

D7200

 

I've been considering getting rid of my D7200 IR (and also my D7200 broad-spectrum conversion) for multiple reasons.  While this camera has better ergonomics than the clunky D610 and the sensor is still a good performer, the smaller sensor, greater vulnerability to diffraction, and lack of EFCS are drawbacks.  I always end up grabbing the D610IR instead, except when I use a mirrorless camera for IR.

 

HAZE

 

The haze could possibly have been very dilute smoke from the day before if there had been adequate mixing overnight.  The burning I'm talking about is from farmers burning prunings from orchards and vineyards, or the woody remains of uprooted orchards (common under the current drought), and that would tend to be coming from hundreds of discrete sources over a very broad area.  Controlled burns in wildlands would be mostly above the main inversion layer in the photo.

 

Looking at particle size, wildfire smoke (the closest analogue to agricultural burning of woody material) mostly creates particle sizes under 2.5 microns.  This paper states a peak for wood smoke in the 0.1-0.2 micron range from one investigation (https://pubs.acs.org/doi/pdf/10.1021/es981277q) and another provides the range of sizes for wood smoke obtained from multiple sources (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2777846/).

 

Silt-sized mineral particles in soil, the soil fraction most vulnerable to being suspended in air by wind, range from 2 to 50 microns under the U.S. Department of Agriculture system (https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1044818.pdf). (Clay-sized particles, which can be far smaller, tend to strongly clump together so are not mobilized anywhere near as easily by water or air.)

 

I would think these differences in particle sizes would favor mineral dust as being a more likely candidate for scattering of NIR wavelengths.  Thoughts?

[Andrea B.]

Interesting references! I don't think I've ever thought about the actual size of smoke or dust as pollutants. 

 

I was going to suggest a small smoke-making experiment to be photographed in IR, but these days this is probably not a wise thing to do in the Western US. 

 

Remember those 4th of July fireworks we used to get as kids which were small black, cylindrical pellets? When you lit them, there was no flame, just smoke. The pellet uncurled into a really long, black, ashy "snake" which held together for a while before disintegrating. 

[Bill De Jager]

 

 

 

12 minutes ago, Andrea B. said:

Interesting references! I don't think I've ever thought about the actual size of smoke or dust as pollutants. 

....

Remember those 4th of July fireworks we used to get as kids which were small black, cylindrical pellets? When you lit them, there was no flame, just smoke. The pellet uncurled into a really long, black, ashy "snake" which held together for a while before disintegrating. 

Welcome to the western U.S.!  Of course air pollution is a concern in many places, but particle size is something that's received increasing attention here in recent years.  First, from a regulatory standpoint, as the previous category of PM10 (particular matter under 10 microns in size) has mostly been replaced with the more restrictive category of PM2.5, particulate matter under 2.5 microns which is particularly damaging to health when breathed in. 

 

Wildfire smoke is mostly under that limit in size, though larger particles and even visible one are created during combustion.  I've had ash on my vehicle from fires hundreds of km away in recent years.  Distance is no guarantee of escape as my wife and I experienced western smoke in Maine (U.S. east coast) last July.

 

On another site a multi-spectral enthusiast posted NIR photos taken last year during one of our smoke episodes that showed much improved visibility, though still hardly unimpaired.  I might give this a try in this coming wildfire season, which again promises to be very bad thanks to the drought continuing to expand across the western U.S.  I have not purchased a set of narrowband filters yet though I've been tempted over the years.  Using them to check NIR penetration of smoke would be an interesting experiment.

 

And yes, I remember those ash 'snakes'!