Flowers

Digital Photography For What It's Worth

Cala lily, Orinda, California. Click to see 800x600. [C-2020Z]

Flowers—irresistible but hard to get

On this page—

The Challenge
Flower Power
Ultraviolet Flower Photography
What About IR and UV Contamination?
References and Links

Last updated July 27, 2004

The Challenge

Before diving into the challenges of flower photography, let's size up our quarry by examining a few flower photographs—some good, some not so good. I took all the samples below with one or another digital camera, some with more understanding and care than others. Click on any thumbnail to see an 800x600 or 600x800 version.

Sample Flower Photographs
Thumbnail	Annotation
	Bottlebrush in full bloom, April. My Oly C-2000Z's penchant for oversaturating flower reds in direct sunlight is evident, but I seem to have gotten away with it this time.
	White cala lily, May, in ultraviolet light using 18A and hot mirror filters. The strong UV reflection from pollen on the pistil draws insects. Camera shake blurs the image despite monopod support.
	Blue agapanthus, August, in infrared light using a Hoya R72 filter. The dead-center composition is embarrassing, but I like the crisp flower head against the blurred dappled background.
	Spreading fleabane, July, Carson Pass, Sierra Nevada, California. This photograph is as much about the arrangement as it is about the flowers themselves. The strong diagonal array reminded me of the Pleiades, the conspicuous young open cluster (M45) in the constellation Taurus also known as "The Seven Sisters".
	Kahili ginger, June, Kilauea Iki crater, Hawaii Volcanoes National Park, wet from a passing shower. Enticed no doubt by its exotic beauty, visitors planted 6 of these invasive foreigners in front of the park's Volcano House hotel a few decades ago. Now they're rapidly displacing native species as they race to take over the ohia and tree fern rain forests atop Kilauea.
	Lepua blossom, June, Sulfur Bank, Hawaii Volcanoes National Park. This leggy ohia tree manages to survive the acidic sulfur fumes emanating from nearby fumaroles marked by the yellow sulfur deposits in the background.
	Young ohia tree with lepua blossoms, January, Napau Crater Trail, Hawaii Volcanoes National Park. Ohias are often the first large plants to colonize fresh lava flows, this one ca. 1974.
	Unidentified yellow flower, perhaps a mamale, January, Kipuka Nene, Hawaii Volcanoes National Park. Pretty flower, very dull composition.
	Hibiscus, June, Kona, Hawaii. The stigma isn't quite in focus, but the flower and nearest leaves are. The blurred background steers attention to the elements in focus. This red came out OK.
	Plumeria, June, Kona, Hawaii. Once again, the flower arrangement carries most of the visual interest. Single flowers are much tougher to compose.
	Flannel bush in full bloom, May, Vollmer Peak, Orinda, California. Busy flower shots can also be yawnogenic, but the jumbled profusion of yellow sepals seems to give this one a sense of motion.
	Chickory, September, Sibley Volcanic Preserve, Orinda, California. Viewfinder parallax exacerbated by macro focus required careful framing with the LCD.
	Ironweed, September, Sibley Volcanic Preserve, Orinda, California. The cluster of flowers in different stages of opening adds a sense of time and space. The very limited depth of field available with macro focus enhances the sense of depth. All represented flower parts are in focus, but not on any one flower.
	Giant thistle, July, Sibley Volcanic Preserve, Orinda, California.
	Echium sp., April, Carmel River State Beach, California. These large blue to violet blooms grace the northern and central California coast each spring. Lacking a conspicuous size reference, their imposing presence is hard to appreciate here.
	Echium in close-up. As the blue flowers open to expose red central parts, these large compound blooms grade from blue to purple when viewed from a distance. Note again the very limited depth of field with macro focus.

As you've just seen, flowers can be tough subjects.

Their beautiful colors are often very difficult to reproduce photographically.
They move erratically in the slightest breeze.
They're small but highly detailed.
Their complex shapes can disappear in flat lighting or set up unwanted shadows in side lighting.
They're often set against distracting backgrounds.
They often require careful composition to remain interesting as solitary subjects.

They're also irresistible, so let's see what can be done to overcome the challenges. But before tackling that in the next section, let's visit the thorny issue of color accuracy.

Color Accuracy

Color accuracy is a constant frustration in flower photography, and digital and film cameras struggle equally in this regard. The narrow-band off-primary colors flowers have evolved to attract pollinators and discourage predators and freeloaders please the eye but tend to resist depiction as linear combinations of primary colors other than those used by the human eye.

Eyes, color films and digital cameras all sample the spectral content of incoming light using different primary colors, and all make different inferences regarding off-primary inputs. Spiky flower reflection spectra have a way of unmasking the substantial variations in peak and shape found in the tri-stimulus spectral response curves characteristic of

human color receptors
light-sensitive color film dyes
Bayer pattern color filters and other components in a typical digital camera's single-CCD color inference system

When discrepancies appear, we naturally regard the eye's color rendition as the correct one. But short of duplicating the eye's spectral responses in detail, cameras are doomed to render narrow-band off-primary flower colors differently.

Anomalous Reflectance

According to the informative Kodak Technical Data bulletin Why a Color May Not Reproduce Accurately, blue morning glories, gentians, and ageratum flowers are cases in point. Along with some common fabric dyes, these flowers exhibit high reflectances at far red wavelengths. Common light sources like the sun and incandescent lamps provide a lot of far red to reflect, but human eyes are much less sensitive to it than color film and digital cameras. Photographs overly reddened by this effect are said to show anomalous reflectance. In a related phenomenon, chlorophylls reradiating in the far red due to UV fluorescence can over-redden or neutralize plant stems and leaves, but chlorophyll turns out to be rare in true flower petals.

Automatic brain-eye system color adjustments far beyond the sophistication of camera firmwares also contribute to the color " inaccuracies" found in camera images. Other color space issues no doubt enter the fray as well.

How Accurate Do Flower Colors Need to Be?

If you're producing a mail-order rose or sweater catalog, color accuracy between subject and final output is a must. For most other purposes, you have some wiggle room. In fact, your viewers probably won't know or care if your flower colors are off a bit—as long as they remain credible and pleasing to the eye.

Color fidelity between your monitor and printer is always important to guarantee predictable output from post-processing, but that's a different issue.

Flower Power

The guidelines below are based on experience and carefully cross-checked reading, but I strongly recommend heavy experimentation with your own gear early in the flower game:

Flower Tips for Visible Light Photography
Issue	Approach
Lighting	Avoid direct sunlight. Pick an overcast or partly cloudy day for best color accuracy. The sidelighting of early morning and late afternoon emphasizes flower forms, but watch out for over-reddening of flower colors. (Your camera will see it well before you do.) Alternatively, shade your subject with an open-weave cloth, translucent plastic sheeting or anything else that diffuses rather than blocks the light. The Blacklocks swear by their diffuser tent.
Exposure	Make appropriate tonal adjustments based on careful spot-metering, then underexpose by 1/3 stop or so to improve color accuracy. Note that flower reds seem particularly prone to oversaturate, at least with my Oly C-2020Z. Like snow, white flowers often need 1-2 stops of overexposure to appear white, as illustrated in the cala lily series below. Dark flowers may need similar degrees of underexposure to match what the eye sees. Manual exposure may be necessary now and then, but aperture priority with exposure correction will generally give you adequate control over depth of field and exposure. When in doubt, bracket.
Composition	Keep it simple. Shoot tight with a clear subject in mind. Collections of flowers may be breath-taking in person, but they tend to lose a lot of their punch in photographs. Good composition makes up for many sins.
Motion	Use steady camera support and fast shutter speeds and seek out still air—you many need relatively long exposures, particularly in wooded areas. A monopod can be very solid if you sit down with it. In hilly areas, mornings are usually calmest. If you're stuck shooting with a breeze, patience, a fast lens, a ready camera prepared with a half-press of the shutter release and multiple exposures often pay off.
Color Accuracy	Consider documenting the flower colors you see in the field using a color standard like the 5x7" Kodak Q-60R1 Color Input Target. (Click here for Kodak's Q-60 PDF file). You'll quickly learn where your eye and camera disagree about flower colors, and your field notes will guide your color corrections at post-processing. In my limited experience, it's not always possible to correct all the inaccurate colors at once with flowers, even with tone curves or equalizations applied to each color channel separately. Good composition and getting colors right the first time are always your best bets.
Magnification	Get close with macro mode but be ever mindful of its dangers. The limited focusing range (20-80 cm on the C-2020Z), the very shallow depth of field and the inevitable viewfinder parallax are traps for the unwary. Always frame close-ups with the LCD. Consider close-up lenses or macro converters if you need to get even closer, but check out this handy C-20x0Z and C-30x0Z macro trick first.
Background	If you can't selectively blur the background to emphasize your subject, consider carrying a black posterboard to block out the background.
Shadows	Subdue harsh shadows with fill flash or an ambient light reflector. For best results, set up an external flash unit 45° from your camera and disable your internal flash to avoid flattening the flower's form. Otherwise, cover your internal flash with a diffuser. (Half a ping-pong ball loosely taped over the tube works well.)
Highlights	Suppress bright reflections off shiny leaves and petals with a polarizer. Blown-out highlights are fatal flaws with no cure in post-processing. There's no real need for TTL control here—simply orient the polarizer's blocking direction parallel to the offending reflecting surface as seen from the camera.

The importance of the first 4 items in this table—lighting, exposure, composition and motion—can't be overemphasized. Beyond working hard to avoid obviously phony colors, I no longer sweat the color accuracy.

More on Exposure

Overexposure is a good way to lose the subtle details that so enrich the visual experience of flowers. The right balance between detail and exposure is often best found through spot metering and bracketing. This is especially true for light-colored flowers, which usually require some positive exposure correction (EC) but can easily end up blown out if too much EC is applied. Medium-toned flowers are generally less challenging with regard to exposure, but my C-2020Z's eagerness to oversaturate reds of any tone in bright sunlight keeps me on my toes.

The series of white cala lily exposures in the table below illustrates the exposure-detail trade-off and the value of bracketing. All shots were spot-metered on the white petals at ISO 100.

Exposure vs. Detail
EC	Exposure	Image	Comments
0.0	f/5.6 @ 1/250		Maximum detail but too gray (the medium gray rendition follows naturally from use of the metered exposure without correction)
+0.7	f/5.6 @ 1/160		Good detail, whiter
+1.0	f/5.6 @ 1/125		Whiter still
+1.3	f/5.6 @ 1/100		To my eye, the best trade-off between detail and whiteness
+2.0	f/5.6 @ 1/80		Overexposed, too much detail lost

Bottom line: When in doubt, bracket. Include overexposed settings for light-colored flowers and underexposed settings for dark ones.

Ultraviolet Flower Photography

Under construction...

Many flowers, particularly yellow varieties like dandelions and the day lilies shown below, display prominent markings visible only in the near ultraviolet (UV-A) band. They target these air traffic control signals at specific pollinating birds and insects equipped with the UV vision needed to see and follow them. UV markings and unique narrow-band visible colors are but two of the many tricks flowers have evolved to attract effective pollinators selectively, without advertising to predators and free-loaders.

Day Lilies with a Monopod
Filter	Light	Thumbnail	EV	Exposure ISO 100	Notes
None	Visible		15.3	f/10 @ 1/400	Note the subtle darkening centrally
18A	UV + IR		6.9	f/2.8 @ 1/15	Pleasing false color scheme
18A+hot mirror	UV only		3.0	f/2.8 @ 1.0 sec	Very dark central markings in UV

A suitably equipped digital camera can provide a window into this fascinating unseen UV world, and flowers make for ready and rewarding UV subjects. For an introduction to the practical aspects of digital UV reflection photography, see the dpFWIW UV imaging section.

Calendulas with a Monopod
Filter	Light	Thumbnail	EV	Exposure ISO 100	Notes
None	Visible		14.0	f/6.3 @ 1/400	Little contrast in yellow petals
18A	UV + IR		6.0	f/2.8 @ 1/8	Handsome false color scheme
18A+hot mirror	UV only		1.0	f/2.8 @ 4.0 sec	Dark central surround in UV

The long exposures typical of digital UV work make bright sunlight, still air and good camera support critical ingredients in UV flower shots. (Note that this bright sunlight recommendation does not extend to visible light flower photography, as explained above.) The monopod used in all the 18A + hot mirror samples above was clearly not steady enough.

Cala Lilies with a Monopod
Filter	Light	Thumbnail	EV	Exposure ISO 100	Notes
None	Visible		12.6	f/2.8 @ 1/800	Note white pollen on pistil
18A	UV + IR		6.2	f/2.2 @ 1/15	Pollen now glows purple
18A+hot mirror	UV only		0.3	f/2.0 @ 4.0 sec	Pollen very bright in UV

I had to zoom out to get a larger aperture on the 18A + hot mirror cala lily above—hence the change in framing.

For a much more detailed look at UV flower photography, see Bjørn Rørslett's fascinating site, Enter the Unreal World of Ultraviolet Colour Photography.

What About IR and UV Contamination?

Luckily, verifiable IR and UV contaminations aren't easily detected in digital flower photographs taken in visible light, even with a relatively IR- and UV-sensitive camera like my Oly C-2020Z. Why that's so isn't entirely clear, but ultimately, the dominant visible light signal must overwhelm the IR and UV signals coming out of the CCD.

The human eye is blind to near IR (NIR, 700-1100 nm) and near UV (UV-A, 320-400 nm) light and has only limited sensitivity to the far reds and violets near the boundaries of the visible band nominally at 400-700 nm. These invisible wavelengths are all abundant in sunlight, and NIR is abundant in incandescent sources as well. Ordinary films tend to have limited UV sensitivity and negligible IR sensitivity, while digital cameras tend to be just the opposite. In theory, at least, UV contamination should be more problematic in visible light images on the film side, while NIR should be more problematic on the digital side.

Since flowers are commonly highly reflective in the UV-A, the NIR or both, you might well expect big trouble in digital flower photographs due to direct IR contamination or to a lesser extent, UV contamination. Indirect contamination might come via fluorescence of flower pigments across the visible-NIR boundary. In this scenario, absorbed visible or UV-A photons excite the emission of NIR and far red photons that in turn stimulate the camera more than the eye. Chlorophyll a and b fluoresce strongly in just this manner, absorbing UV-A through blue-green photons (375-430 nm at full width half maximum) and emitting deep red photons (640-680 nm at full width half maximum), as illustrated in Figure 1 of SCUFA's informative online PDF. Since film and digital cameras are both more sensitive to far red than the eye, chlorophyll mediates a UV contamination of sorts—one resembling the artifact of anomalous reflectance. True flower petals don't usually contain much chlorophyll, but other fluorescent flower pigments might contribute. Sepals masquerading as petals (as in the yellow flannel bush blooms above) might contain enough chlorophyll to participate in such UV contamination.

Here's a crude demonstration of UV fluorescence in catnip.

Don't Worry, Be Happy

So much for theory. In practice, I've been hard pressed to find compelling evidence of either IR or UV contamination in my digital flower photographs. I certainly haven't detected any visible benefit from my Heliopan 8125 IR/UV cut filter, but the 8125 turns out to be only a partial defense against near IR and UV-A contamination. Its complete transmission spectrum clearly shows that the 8125 passes some very, very near IR and some very near UV-A as well. A high quality hot mirror filter might be helpful on the IR side, but I doubt that it would be worth the effort on most higher-end consumer-grade digital cameras.

References and Links

(See also the home page links.)

Blacklock, Craig and Nadine, Photographing Wildflowers, Voyageur Press, 1987.

Enter the Unreal World of Ultraviolet Colour Photography—Bjørn Rørslett's fascinating, copiously illustrated and comprehensive film-oriented UV photography site, with many UV flower shots.

Kodak Q-60 Color Input Targets—a PDF document detailing the use of this compact but pricey color reference. (Right-click on this link and select "Save Target As..." to save the a copy of the PDF file on your computer.)

Spellenberg, Richard, National Audubon Society Field Guide to North American Wildflowers, Western Region, Chanticleer Press, 1998.

Why a Color May Not Reproduce Accurately—a Kodak Technical Data bulletin.

Comments and corrections to Jeremy McCreary at dpFWIW@cliffshade.com, but please see here first.

Last updated July 27, 2004

The Challenge

Sample Flower Photographs

Color Accuracy

Anomalous Reflectance

How Accurate Do Flower Colors Need to Be?

Flower Power

Flower Tips for Visible Light Photography

More on Exposure

Exposure vs. Detail

Ultraviolet Flower Photography

Day Lilies with a Monopod

Calendulas with a Monopod

Cala Lilies with a Monopod

What About IR and UV Contamination?

Don't Worry, Be Happy

References and Links