By Sara Goodnick
A Sensitivity Revolution Is Coming Our Way
Recently my husband handed me a copy of the magazine, “Spectrum”, a magazine published by IEEE for Electrical Engineering and Computer Science professionals. He is one of them, but I, most decidedly, am not. However, I spied the article which he knew would pique my interest: “Snapshots by Quantum Dots”, by Peter Palomaki and Sean Keuleyan. It was full of promise for that which we photographers crave: an image sensor with a greater dynamic range, including infrared!
I’m not going to go into the physics, but this is the basic concept: most of our cameras feature typical CMOS sensors which absorb given visible light wavelengths but cannot absorb the infrared nor very bright light ranges. They are made from silicon wafers. Light is absorbed by the sensor’s pixels after passing through red, green or blue filters on the CMOS chip. The sensors just can’t cope with very dark or extremely bright light. Your histogram will confirm this every time you see the bar creep up the left or the right side of it.
Quantum dots (QD) are extremely tiny particles, smaller than those in the silicon chips, that also absorb light in various wavelengths. However, QDs can be manufactured in differing sizes, and in this way be fine-tuned to absorb a greater range of wavelengths. According to the article, “…this thin, highly absorbent layer of QDs excels in both low light and high brightness, giving the sensor a better dynamic range.” It must be noted, though, that the smallest sizes are limited by the smallest wavelength of light. Any smaller, resolution becomes another issue.
If you’ve ever had a camera converted into an infrared-capable camera, you know the sensor has been irreversibly altered. These cameras can make beautiful infrared images but are limited, so you might have to carry two cameras for versatility. Imagine having one camera that could handle all—infrared, low light, and extremely bright light—producing detailed, clear images with no noise. We could easily use low ISOs and fast shutter speeds. Besides creating beautiful surreal IR images and stopping star movement in Milky Way captures, you could easily photograph at night, high contrast scenes, and stop action with low noise and low ISOs.
Right now, specialized QD cameras are in use for commercial applications such as detecting flaws in packaging, hidden bruises on fruit, etc. The tech giant Apple has expressed interest in QD cameras for their phones so we can probably expect to see them in use in future iPhones.
Currently, there are still some hurdles to making QD sensor cameras available for the consumer photography market. Production of the various QDs has not been uniform nor consistent in quality. But this is new technology, and the motivation is strong to bring it up to new standards. The latest estimate is about 5 years until we see them being common in our cameras, but what a great new way to make our images!
Disclaimer: the top and bottom images are not true IR images, but were created in Lightroom and Photoshop for illustration purposes.
Sara Goodnick is a Photo Guide with Arizona Highways PhotoScapes.
