Eloquent Images by Gary Hart
Insight, information, and inspiration for the inquisitive nature photographer
The Why, How, and When of Fall Color
Autumn Cascade, Bridalveil Creek, Yosemite (2005)
Canon EOS-1Ds Mark II
Canon 70 – 200 f/4 L
1 second
F/10
ISO 160
Autumn is right around the corner. To get things started, I’ve updated a previous post that demystifies why, how, and when of fall color.
Few things get a photographer’s heart racing more than the vivid yellows, oranges, and reds of autumn. And the excitement isn’t limited to photographers—to appreciate that reality, just try navigating New England backroads on a Sunday afternoon in the fall.
Innkeeper logic
Despite all the attention, the annual autumn extravaganza is fraught with mystery and misconception. Showing up at at the spot that guy in your camera club told you was peaking at this time last year, you might find the very same trees displaying lime green mixed with just hints of yellow and orange, and hear the old guy behind the counter at the inn shake his head and tell you, “It hasn’t gotten cold enough yet—the color’s late this year.” Then, the next year, when you check into the same inn on the same weekend, you find just a handful of leaves clinging to exposed branches—this time as the old guy hands you the key to your room he utters, “That freeze a couple of weeks ago got the color started early this year—you should have been here last week.”
While these explanations may sound reasonable, they’re not quite accurate. Because the why and when of fall color is complicated, observers resort to memory, anecdote, and lore to fill knowledge voids with partial truth and downright myth. And while we still can’t predict fall color the way we do the whether, science has provided a pretty good understanding of the fall color process.
A tree’s color
The leaves of deciduous trees contain a mix of green, yellow, and orange pigments. During the spring and summer growing season, the volume and intensity of the green chlorophyl pigment overpowers the orange and yellow pigments and the tree stays green. Even though chlorophyl is quickly broken down by sunlight, the process of photosynthesis that turns sunlight into nutrients during the long days of summer continuously replaces the spent chlorophyl.
As the days shrink toward autumn, things begin to change. Cells at the abscission layer at the base of the leaves’ stem (the knot where the leaf connects to the branch) begin the process that will eventually lead to the leaf dropping from the tree: Thickening of cells in the abscission layer blocks the transfer of carbohydrates from the leaves to the branches, and the movement of minerals to the leaves. Without these minerals, the leaves’ production of chlorophyl dwindles and finally stops, leaving just the yellow and orange pigments. Voilà—fall color!
The role of sunlight and weather
Contrary to popular belief, the timing of the onset of this fall color chain reaction depends much more on daylight than it does on temperature and weather. Triggered by a genetically programmed day/night-duration threshold (and contrary to innkeeper-logic), the trees in any given region will commence their transition from green to color at about the same time each year, when the day length drops to a certain point.
Nevertheless, though it doesn’t trigger the process, weather does play a significant part in the intensity, duration, and demise of the color season. Because sunlight breaks down the green chlorophyl, cloudy days after the suspension of chlorophyl creation will slow the chlorophyl’s demise and the coloring process that follows. And while the yellow and orange pigments are present and pretty much just hanging out while they wait all summer for the chlorophyl to relinquish control of the tree’s color, a tree’s red and purple pigments are manufactured from sugar stored in the leaves—the more sugar, the more vivid a tree’s red. Ample moisture, warm days, and cool (but not freezing) nights after the chlorophyl replacement has stopped are most conducive to the creation and retention of the sugars that form the red and purple pigments.
On the other hand, freezing temperatures destroy the color pigments, bringing a premature end to the color display. Drought can stress trees so much that they drop their leaves before the color has a chance to manifest. And wind and rain can wreak havoc with the fall display—go to bed one night beneath a canopy of red and gold, wake the next morning to find the trees bare and the ground blanketed with color.
Since the fall color factors come in a virtually infinite number of possible variations and combinations, the color timing and intensity can vary a lot from year to year. Despite expert advice that seems promise precise timing for the fall color, when planning a fall color trip, your best bet is to try to get there as close as possible to the middle of the color window, then cross your fingers.
About this image
Looking for something to do in this COVID-constrained world, I dialed my way-back machine all the way back to 2005 and landed on this image. I wish I could tell you I have a memory of its capture, but I don’t. I do, however, have lots of general memories of photographing fall color at Bridalveil Creek in Yosemite, just below Bridalveil Fall. Since I’ve never visited Yosemite in autumn without shooting here, when I set out find a fall color image in my archives, I specifically targeted my Bridalveil Creek shoots.
I started by digging up another image from this trip that I’ve always liked, but felt was too soft to share. Given that I virtually never take a single frame of a nice scene, I was pretty confident that I’d find something similar, and crossed my fingers that the sharpness problem was a one-off that I quickly corrected. This is actually the very next image I clicked, and I was very pleased to confirm that it is indeed sharp.
This image is a perfect example of my approach to intimate fall color scenes: Look for color to juxtapose with another feature in the scene. Often that’s a single leaf (no, I do not place leaves, ever), but in this case I accented a nice little cascade with a group of fallen leaves that were plastered against water-soaked granite. And when there’s water motion in the scene, I usually shoot it at a variety of shutter speeds to give myself multiple motion effects to choose between. Looking through my captures from this shoot, I can tell that’s exactly what I did. This image is a 1-second exposure, long enough to blur the cascade, but not so long that I obliterated all detail. And though I have no memory of it, I know I used a polarizer because I always use a polarizer when photographing fall color, and I can tell that the sheen has been removed from the rocks, leaves, and water.
Autumn Intimates
Click an image for a closer look, and to view a slide show.
Eloquent Images by Gary Hart 
Gary hope you are safe
With all the wildfires near
Thinking of you and don
Clinta williams
Work shop attendee
blubonet@swbell.net
Dallas tx
Thanks, Clinta. Fortunately, I live in an area that doesn’t need to worry about wildfires, but the smoke is terrible. Good to hear from you—hope you’re well.
Thank you for sharing your thoughts on fall color, Gary. I look forward to shooting some color in Ouray, Colorado at the end of the month. Let’s hope that the science behind the color change is in my favor! I also look forward to our workshop in Death Valley 1/2021. Let’s hope that it is a “GO”! Best wishes from me and Colin and hope that you and your family are well, despite all this is going on this year.
You’re very welcome, Linda—hope the fall color gods smiled on you. All systems are go for Death Valley in January. (Fingers crossed.)
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