Welcome to McCann Imaging

Mary and John McCann

We work on imaging research in microscopy and color vision.

Vision Research

Scientific Meetings and Papers:

2009 Google, Jan 22, Mountain View, CA

http://www.mefeedia.com/entry/hdr-and-color-constancy-new-psychophysical-results/14002228

2008 Google, Jan 25, Mountain View, CA

<http://youtube.com/watch?v=ALfiTDYLtAQ&feature=user>

2010

2010 Electronic Imaging, San Jose

Session Chair

Wednesday, January 20, 2010

Art and Science Render

the High-Dynamic-Range World

John Sexton, Photographer, Keynote,
Photographing the range of light:Works by Adams & Sexton

John McCann, McCann Imaging,

The Ansel Adams Zone System: Chemical HDR Capture and Range Compression

Jodi Throckmorton, San Jose Museum of Art,

Tour of "Ansel Adams:Early Works" exhibition

at the San Jose Museum of Art

Carinna Parramen, University West of England, Invited
The drama of illumination: Artists' approaches to the creation of HDR in painting and prints

Christopher Tyler, Smith Kettlewell

Darkness and depth in early Renaissance painting

Rafal Mantiuk & S. Daly,
Luminance of pure black: exploring the effect of surround

Alessandro Rizzi, U. Milano
Object size, spatial frequency content, and retinal contrast

Brian Funt & Lilong Shi, SFU,
The effect of exposure on MaxRGB color constancy

Jonathan Philips & J. Fewerda, Kodak,RIT
Eye tracking apparent gloss: a case study on the impact of dynamic range on rendered surface appearance

Dawid Tajak, Max Plank,
Visual maladaptation in the contrast domain

John McCann,

“The Ansel Adams Zone System: Chemical HDR Capture and Range Compression”

We tend to think of digital imaging and the tools of Photoshop as a new phenomenon in imaging. We are familiar with multiple-exposure HDR techniques intended to capture a wider range of scene information, and tone-scale adjustments to make better pictures. We tend to think of everyday, consumer, silver-halide photography as a fixed window of scene capture with a limited, standard range of response. This idea of silver-halide photography is certainly true of the instant films, and the negative films processed at the drug store, that were most popular between 1950 and 2000. These systems had fixed dynamic range and fixed tone-scale response to light. That response was constant for all pixels in the film image.

The Zone System was formulated in 1941 by Ansel Adams along with Fred Archer. It was earlier than the billions of consumer photos in the second half of the 20th century, yet it was much more sophisticated than today's digital techniques. This talk will describe the chemical mechanisms of the zone system in the parlance of digital image processing. It will describe the Zone System's chemical techniques for image synthesis. Although current HDR imaging shares some of the Zone System's achievements, it usually does not achieve all of them.

Carinna Parraman

Centre for Fine Print Research, University of the West of England, Bristol, BS3 2JT

“The drama of illumination:

artist’s approaches to the creation of HDR in paintings and prints”

For many centuries artists have considered and depicted illumination in art – from the effect of sunlight on objects at different times of the day, of shadows and highlights as cast by the moon, through indirect light as that through an open window or the artificial light of the candle or firelight.

The presentation will consider artists who were fascinated by the phenomena of natural and artificial illumination and how they were able to render the natural world as a form of high dynamic range through pigment. Artists have been long aware of the psychological aspects of the juxtaposition of colour in exploiting the optical qualities and arranging visual effects in painting and prints. Artists in the 16th century were attempting to develop an extended dynamic range through multi-colour, wood-block printing. Artists working at the height of naturalist realism in the 17th and 18th century were fascinated by the illusory nature of light on objects. The presentation will also consider the interpretation of dynamic range through the medium of mezzotint, possibly the most subtle of printing methods, it was used by printers to copy paintings, and to create highly original works of art containing a wide dynamic range of tones.

[EI104-34]

A.Rizzi

“Object size, spatial frequency content, and retinal contrast“

Recent interest in HDR scene capture and display has stimulated measurements of the usable range of contrast information for human vision. These experiments have led to a model that calculates the retinal contrast image. A fraction of the light from each scene pixel is scattered to all retinal pixels. The amount of scattered light decreases with distance from the pixel. By summing the light falling on each retinal pixel from all the scene pixels we can calculate the retinal image contrast. As objects, such as text letters, get smaller, their retinal contrast gets lower, even though the scene contrast is constant. This paper studies the Landolt C, a commonly used test targets for measuring vision, from three perspectives. First, it reviews the visual acuity measurements of detection thresholds with size. Second, it uses models that predict appearance of Landolt C displays based on Contrast Sensitivity Function (CSF). Third, the paper models the retinal stimulus after intraocular scatter. These three different psychophysical techniques are important in understanding detection threshold of the Landolt C. Each approach gives only one piece of the puzzle. Retinal contrast, CSF, and detection threshold measurements all influence our understanding of this commonly used eye test.

[7528-1]

Carinna E. Parraman, John J. McCann, Alessandro Rizzi,

“Artist's colour rendering of HDR scenes in 3D Mondrian colour-constancy experiments”,

The presentation provides an update on ongoing research using three-dimensional Colour Mondrians. Two still life arrangements comprising hand painted coloured blocks of 11 different colours were subjected to two different lighting conditions of a nearly uniform light and a directed spotlights. The three-dimensional nature of these test targets adds shadows and multiple reflections, not found in flat Mondrian targets. Working from exactly the same scene, the second experiment involved the use of watercolour inks and paints to recreate both LDR and HDR Mondrians on paper. A second set of appearance measurements of both scenes were made. Here we measured appearances by measuring reflectances of the artist’s rendering. Land’s Colour Mondrian extended colour constancy from a pixel to a complex scene. Since it used a planar array in uniform illumination, it did not measure the appearances of real life 3-D scenes in non-uniform illumination. The experiments in this paper, by simultaneously studying Low Dynamic Range (LDR) and High Dynamic Range (HDR) renditions of the same array of reflectances, extend Land’s Mondrian towards real scenes in non-uniform illumination.

[7528-2]

John J. McCann, Carinna E. Parraman, Alessandro Rizzi,

“Pixel and spatial mechanisms of color constancy”,

Color constancy remains an important subject of research on color standards, computer imaging, and human color vision. There are many different theories and algorithms that interpret and predict constancy. This paper analyzes three different approaches that are frequently discussed separately in the literature: pixel-based colorimetric standards of appearance; computer imaging calculations of an object’s reflectance; and calculation of appearance using spatial comparisons. This paper compares and contrasts these approaches. Further, it reviews experiments that measure appearance in color constancy in a variety of situations. A pivotal tool in analyzing models of constancy is the correlation of object’s reflectance with appearance. Each approach has different interpretation of this correlation. Using measurements of constancy with particular attention to reflectance, illumination, and appearance helps us to see the successes and limitations of each constancy approach.

[7528-31]

John J. McCann,

“The appearance of illusions in the delusion of reality”,

Physicists born in the 17th century still influence our impressions of reality. Take for example, the work at the Royal Institution, London around 1800. Sir Humphrey Davy and Josiah Wedgwood developed a precursor to silver-halide photography. Thomas Young taught at the Royal Institution at the time and proposed that three types of retinal receptors at the same location could explain our color response to all visible wavelengths. It is tempting to think that vision behaves the same as silver-halide film. We tend to think that the response of a single pixels can successfully model the response to the entire image, with curious exceptions, that we call illusions.

However, by 1800 there were the shrewd observations of da Vinci, von Guericke, Count Rumford, and many others. They showed that vision was different from film. All the neurophysiology of the second half of the 20th century has shown the visual pathway is a sequence of spatial operators. The pixel model of vision is a delusion.

We need to free our thinking from the pixel models of these physicists. If we look at a display, we apply our spatial image-processing pathway to the image on our retinas. Our spatial transforms of targets is the reality of vision.

2009

November, 209

John J. McCann, Carinna E. Parraman and Alessandro Rizzi,

“Reflectance, Illumination and Edges”

Proceedings of the Color Imaging Conference, Albuquerque, CIC 17, in press,

November, 2009

09CIC 3DMond.pdf

October 1, 2009

John J. McCann, Carinna E. Parraman and Alessandro Rizzi,

“REFLECTANCE, ILLUMINATION, AND EDGES IN 3-D MONDRIAN

COLOUR-CONSTANCY EXPERIMENTS”

Proceedings of the 2009 Association Internationale de la Couleur 11th Congress, Sidney, in press, 2009.

09AICf.pdf

September, 11, 2009

Exploring the Limits of HDR Capture
Workshop Moderator: Ricardo Motta, Pixim
John McCann, McCann Imaging

Dick Lyon, Google
Howard Rhodes, Omnivision
David Cardinal, CardinalPhoto

2009 Electronic Imaging, San Jose

C. Parraman, A. Rizzi & J. J. McCann,

“Colour Appearance and Colour Rendering of HDR Scenes: An Experiment”, 7241-26

09Parraman.pdf

J. J. McCann & A. Rizzi,

“Preservation of Edges: The Mechanism for Improvements in HDR Imaging”,

09McCannEDGES.pdf

J. J. McCann,

“Adaptation... What adaptation?”, 7241-23

In almost ever conversation with vision scientist one hears the statement “ the eye adapts…”. Always, this statement is true. The problem is that there are so many ways that the visual system “adapts’ that the words have no meaning. The visual system exhibits chemical dark-adaptation, neural light-adaptation, diurnal melatonin-adaptation, pupil adaptation, chromatic adaptation, von Kries adaptation, Blakemore spatial-frequency adaptation, McCulloch colored-stripe adaptation and many more kinds of adaptation. All neurons adapt. There are more than 106 retinal receptors that adapt, and potentially 1010 cortical neurons that adapt. What do we mean when we say “the eye adapts”?

Keywords: vision, adaptation, dark adaptation, light adaptation, melatonin adaptation, pupil adaptation, chromatic adaptation, von Kries adaptation, spatial-frequency adaptation, McCulloch adaptation.

2008

John J. McCann and Alessandro Rizzi,

“Retinal HDR Images: Intraocular Glare and Object Size”

Proceedings of the Color Imaging Conference, Portland, CIC 16, 24, 2008.

November, 2008

08CICMcR.pdf

A. Rizzi & J. J. McCann, “Simultaneous Contrast and Intraocular Glare:

Opposing Image Dependent Mechanisms in Appearance”, 2008.

08 AIC Rizzi019F.pdf

J. J. McCann, “Color Matches in Dim Narrow-band Illumination”, 2008.

08 AIC McCann035F.pdf

2008 CGIV Terrassa, Spain

J. J. McCann & A. Rizzi, “Appearance of High-Dynamic Range Images in a Uniform

.Lightness Space”, pp. 177-181, 2008.

08CGIV.pdf

2008 Electronic Imaging, San Jose

A. Rizzi, M. Pezzetti, & J. J. McCann,

“Separating the effects of glare from simultaneous contrast in HDR images”, 6806-9

08EI Rizzi 6806-09.pdf

J. J. McCann,

“Perceptual rendering of HDR in painting and photography” 6806-30

08EI 6806-30.pdf

J. J. McCann,

“Color gamuts in dim illumination” 6807-2

2008EI 6807-2.pdf

2007 CIC, Albuquerque, NM

J. J. McCann

“Colors in Dim Illumination and Candlelight”

07rodMatch.pdf

A. Rizzi, M. Pezzetti, and J. J. McCann

“Glare-limited Appearances in HDR Images”

07 CIC Rizzi.pdf

2007 CREATE, Bristol

J. J. McCann

“The Interaction of Art, Technology and Consumers in Pictures Making”

07 CREATE.pdf

2007 ECVP, Arezzo

J. J. McCann

Rod – Lcone color matching in complex images

Rod and L-cone interactions generate color appearances. This paper measure these appearances in complex scenes above and below-M and S-cone thresholds. The test target was a ColorChecker viewed in tungsten light and 1 wax candle. Firelight is an ideal illuminant for Rod-Lcone color. The observers’ task was to adjust RGB digits in LCD computer display to match the appearance of the ColorChecker. With the tungsten illumination, above L-,M-,& S-cone thresholds, the L*a*b* values for the reflective ColorChecker and the emissive LCD were reasonably close. With 1 candle illumination, the below M- and S-cone threshold ColorChecker showed matches marked different in L*a*b* values. A 4-D color space is not required because all colors were matched to above cone threshold colors, sharing information with other color channels. The color appearances are not consistent with rods sharing S-channel alone, or M-channel alone. The colors are not consistent with the rods desaturating all three channels. Under these conditions, the colors are consistent with the rod spatial comparisons sharing both the M- and the S-cone channels.

07ECVP.pdf

A. Rizzi, M. Pezzetti, J.J. McCann,

Measuring the visible range of High Dynamic Range Images (HDRI)

We made pairs of identical film transparencies. We viewed one (single-contrast), then two superimposed in registration (double-contrast). Single-contrast images have 2.7 log 10 dynamic range; double contrast 5.4 log10 range. Observers estimated the appearance of 40 gray areas surrounded with various size white and black blocks. First, the surround had equal white and black areas (average single-contrast luminance=50.01%max) and (double-contrast=50.00%max). Doubling the contrast had minimal effect on retinal glare. Magnitude estimates show nearly the same plot (appearance vs. log luminance) for both contrasts in the range of 0.0 to 2.3OD, and no discrimination at higher optical densities. Second, with a (8%white&92% black) surround appearances covered 0.0 to 2.7. Increasing the stimulus range had little effect on appearance. Decreasing the surround’s white area, decreased veiling glare and increased the range of usable densities. These, and other experiments, measure how veiling glare controls the range of appearance in HDRI.

07ECVP Rizzi.pdf