iiinova — where your digital self keeps evolving

Geoffrey Aguirre @gkaguirre.com · 02/07/2026

We placed our camera on a tripod in the dead center of the space, pointed at the zenith, and recorded as the camera rotated on its optical axis. This gave us exactly the measurement we needed. Thanks to Derrick Pitts, Chief Astronomer for the Franklin (right) and the Fels staff. 6/6

A group photo. In the front in a pinkish shirt is Geoff Aguirre. On the left is Sophia, a UPenn undergrad who led this measurement. On the right is Derrick Pitts, Chief Astronomer and Director of the Fels Planetarium at the Franklin Institute. In the back row are three members of the technical crew that run the Fels. Their help in setting the lighting conditions of the dome was invaluable.

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Geoffrey Aguirre @gkaguirre.com · 02/07/2026

The fielding function measures variation in pixel intensity across a camera sensor due to the optics and circuitry. This is one of many calibrations we are performing on our sensor array to support measurement of visual experience in physical, radiometric units. 2/6

The fielding correction we ultimately calculated for our camera. The value at each point is the multiplicative correction that is applied to each pixel across the sensor. The “thickness” of the surface is due to the intermixing of the R, G, and B sensors in a Bayer pattern, each of which has a different correction surface due to variation in radiometric sensitivity and the effect of chromatic aberration.

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Geoffrey Aguirre @gkaguirre.com · 02/07/2026

This week we completed an elusive measurement: the flat fielding function of the wide-angle camera on our wearable light-logger. To do so, we visited the Fels Planetarium at the @franklininstitute.bsky.social. 1/6

Sophia, a UPenn undergrad, takes measurements with a to-be-calibrated camera while standing in the center of the Fels Planetarium.

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Geoffrey Aguirre @gkaguirre.com · 29/06/2026

In honor of Mel Brooks turning 100, I would like to again note that young Dr. Frankenstein gives a pretty good brainstem lecture.

A still from Young Frankenstein, with Gene Wilder gesticulating in front of a chalkboard with labeled components of the brainstem.

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Geoffrey Aguirre @gkaguirre.com · 07/04/2026

Very cool. The white matter connectivity of early visual cortex recapitulates the polar angle variation of retinal structure. One look at this figure and you know you are in the world of retinal meridians and that Marisa Carrasco will be making an appearance.

A portion of Figure 3a of Amorosino et al that has the signature of polar angle retinal variation.

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Geoffrey Aguirre @gkaguirre.com · 01/04/2026

The mega-author biz has been falling off. As of 2015 we were on a good trend to hit a 100k author paper by 2041, but then the physics community became more insular and retreated to 3000 author papers.

Plot of the maximum number of authors on a paper in each year from 1970 to current day, with an exponential fit to the data between 1970 and 2015 (log y-axis). Plot generated using Gemini, so that this with an AI-sized grain of salt.

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Geoffrey Aguirre @gkaguirre.com · 20/06/2025

The next macOS version is bringing the bouba.

macOS Sequoia pointer is sharp and kiki. The macOS Tahoe pointer is soft and bouba.

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Geoffrey Aguirre @gkaguirre.com · 20/03/2025

We are building a gaze calibration apparatus. The observer positions their head at the center of a large hemisphere. They fixate on LEDs displayed at 3 foot distance at various visual angles while we record from a pupil camera. Today, I found the perfect structure to use for the hemisphere.

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Geoffrey Aguirre @gkaguirre.com · 20/02/2025

Overall sensory “diet” may influence visual discomfort. We made an all day, wearable light-logger with a fast “world” camera, eye camera, and a “mini spectrometer” that measures wavelengths of light. Do people with migraine and photophobia have different exposure to light wavelengths and flicker?

The left panel shows a mannequin head wearing custom spectacles with sensors attached to the frame. On the right the spectacles are shown resting on a recording pack that is worn by the participant.

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Geoffrey Aguirre @gkaguirre.com · 20/02/2025

We think ipRGC signals may alter trigeminal (face) sensation. These integrating spheres present the light. Nozzles puff air at the corner of each eye, and hidden IR cameras measure the blink reflex. We are testing if light alters blinking and psychophysical touch perception.

Two, black, light integrating spheres receive light via fiber optic cables from ports below. The interior of the spheres are reflective white, and hide infrared cameras. A little tube is visible on the side of one sphere. Air puffs from this tube evoke a blink reflex.

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Geoffrey Aguirre @gkaguirre.com · 20/02/2025

The melanopsin-containing ipRGCs are part of why bright light is uncomfortable. We control the spectral and temporal (“flicker”) content of light to selectively target these cells. The CombiLED has 8, narrow-band LEDs and can produce very bright light.

A CombiLED device from Prizmatix Inc combines light from 8, spectrally narrow-band LEDs. A fiber optic cable carries the light from the device to the eye of the participant.

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Geoffrey Aguirre @gkaguirre.com · 18/09/2024

This is not just a @zviroth.bsky.social "vignette" effect, but instead reflects the environmental "conditional prior". This is the why of it all: a visual system that efficiently leverages the statistical regularities of the environment will be subject to the tile illusion.

In natural images, the orientation of spatial structure in one patch of space will be similar to that of an adjacent patch.

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Geoffrey Aguirre @gkaguirre.com · 18/09/2024

An oriented surround biased responses, and increased FI at the surround orientation. Using the retinotopic map, we found that the change in neural encoding occurs just at the center-surround stimulus boundary. This is where tilt illusion “happens”!

If we derive FI from patches of cortex that subtend different parts of the tilt illusion stimulus, we see that the change in neural FI that reflects the illusion happens just at the boundary between the center and surround.

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Geoffrey Aguirre @gkaguirre.com · 18/09/2024

People performed *hours* of orientation estimation during fMRI. We derived neural FI from early visual areas. With a noise surround, encoding accuracy (FI) from behavioral and neural measures was higher for the cardinal orientations, reflecting natural image statistics.

Vertical and horizontal lines appear more frequently than oblique angles in natural images. Fisher information derived from behavioral and neural data show this same distribution, with increased encoding accuracy for the more frequently encountered stimulus orientation.

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Geoffrey Aguirre @gkaguirre.com · 18/09/2024

This is the tilt illusion. In a new study we can provide a satisfying answer to how and where this effect arises in the brain, as well as the teleological "why" a well-designed visual system might have this property. 🧪

The center grating on the left appears tilted due to the presence of an oriented surround. The same center grating on the right appears vertical, as the surround is un-oriented noise.

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Geoffrey Aguirre @gkaguirre.com · 14/07/2024

You may already know that the rate of change of acceleration over time is “jerk”. I was surprised to learn the identities of the 4th through 6th derivatives of position. 🧪

Cereal mascots Snap, Crackle, and Pop, who lent their names to higher-order temporal derivatives of position.

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Geoffrey Aguirre @gkaguirre.com · 29/06/2024

The use of a sphere to measure light and reflectance was formalized by Friedrich Richard Ulbricht in 1900 in the publication "Determining the average spatial light intensity by only one measurement [translated from German]".

A painting by Diana Lyn Cote of FR Ulbricht and his integrating sphere for the centennial of Ulbricht’s work (1994)

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Geoffrey Aguirre @gkaguirre.com · 21/05/2024

Adrien Chopin (INSERM) has a new way of presenting a scientific poster. He used DALL•E to create a stylish comic that describes his study of how stereo vision influences hand coordination in daily activities. #vss2024 docs.google.com/document/d/1...

A scientific poster by Adrien Chopin of INSERM that describes a study of stereo vision. The poster is in the form of a noir comic, with the panels describing the methods and results.

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Geoffrey Aguirre @gkaguirre.com · 22/03/2024

The House just passed 2024 appropriations. NIH budget numbers can be extracted from the PDF. $$ are in thousands; the last column gives the delta from 2023 value enacted by the House (As the Final 2023 appropriations differed, this is actually a cut to NIMH; HT @markhisted.org)

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