Orion Rising

[Steaphany]

Out of my advancement with The Bear, I'm continuing my push to achieve a successful Foveon astronomical landscape:

Orion Rising
Sigma SD14 18-55mm @ 18mm, 16s, f/2.8, ISO 800

Here is the cowboy Orion, astride his trusty cutting Jackalope Lepus as they rise from the sky glow of the Dallas/Fort Worth Metroplex, hell bent on roping the Longhorn Bull Taurus.

For the astronomically minded, The 18mm on the SD14 yields a field of view of 59.80° x 41.95° and I shot this on 10-25-2011 @ 4:33:31 UT, 10-24-2011 @ 11:33:31 Texas time, when the Moon was near New. The single unstacked exposure was done similarly to that of The Bear, which not only allowed me to capture this image, only minimal noise reduction was needed. The 16 Second exposure meant that the stars are slightly trailed, but my goal was for the landscape and not an astronomically accurate image. This image exemplifies the Foveon's dynamic range. Clearly visible even here, scaled for CiC, is Aldebaran, a visual magnitude 0.99 star, while in the actual image 85 Tauri,TYC 1265-1173-1 , a visual magnitude 6.01, star can easily be seen against the dark sky. Even fainter stars can also be seen.

Pixel Peeper's Special - Taurus Close up ( 13.59° x 9.53° @ 100% )


Pixel Peeper's Special - Taurus Close up Aldebaran & 85 Tauri Identified ( 13.59° x 9.53° @ 100% )

Another surprise was the brilliance of the Orion Nebula. The image was taken with the SD14's IR blocking filter in place, yet there was sufficient Hydrogen Alpha sensitivity for the Orion Nebula to shine right through the Dallas/Fort Worth sky glow:

Pixel Peeper's Special - Orion Close up ( 13.59° x 9.53° @ 100% )

[Donald]

Out of my advancement with The Bear, I'm continuing my push to achieve a successful Foveon astronomical landscape:

Following this journey has become and will continue to be, I'm sure, fascinating.

I don't know, Steaphany, if it would help for you to insert text, or make a link to text in each of your posts in this series relating to the sensor, that would explain to the reader what the Foveon sensor is. This would, perhaps, help understanding of your quest.

I look forward with great anticipation, towards the next instalment, even though the science is beyond my understanding. The desire to strive to explore and discover is, thankfully, not.

[Steaphany]

I don't know, Steaphany, if it would help for you to insert text, or make a link to text in each of your posts in this series relating to the sensor, that would explain to the reader what the Foveon sensor is. This would, perhaps, help understanding of your quest.

First, some background:

As most who follow my activity here know, I started in photography back in the days of film. Whether working with negative or reversal film, the architecture of color film is three spectrally dependent layers each responding to wavelengths in the Red, Green, and Blue regions of the spectrum. For example, here is a diagram taken from the FUJIFILM FUJICHROME PROVIA 100F Professional [RDP III] data sheet of the Film Structure:

Of particular note, each and every location across a sheet of film records the full spectrum that the film is sensitive to. Now, is this how digital camera imagers look ? No, and this is clearly explained in the CiC tutorial Digital Camera Sensors.

From the advent of digital camera technology, I had one particular requirement: The imager MUST sense the whole spectrum at every photo site. I do not consider the on chip Bayer filter mask as a viable technological direction. The reason for my stance comes from video camera technology where color video cameras, as far back as the 1950's, employed three imaging tubes. The scene was imaged through a single lens, the light then passed through a prism to split the light into three paths, each passing through a particular color primary filter before being sensed by the imaging tube. WOW, the full spectrum is sensed at every location. Even today, high end digital video equipment is based on this same three imager design and you can even buy high end consumer grade three sensor digital video cameras.

Now, to the main topic:

What brought me really into digital photography was Sigma's line of digital cameras which are all based on imager technology developed, designed, and manufactured by Foveon. The key feature of a Foveon X3 imager is their application of a characteristic of how photons interact with the atoms of a Silicon crystal. We all know, well we should all know, that a photon entering a Silicon crystal will interact with an atom liberating an electron. Well, a property that is rarely acknowledged is that the depth of the interaction is proportional to wavelength. Blue liberates electrons near the surface, green a bit deeper, and red and infrared even further into the crystal. The Foveon X3 imager design utilizes this property to create a digital imager where the full spectrum is sensed at every photo site. Unlike high end three imager video, Foveon pulled it off in a single chip !

Foveon was so critical to Sigma that Sigma purchased Foveon just to ensure that they have exclusive access to this technology.

As you can imagine, a digital imager with a layered film-like photo site design has some clear advantages. Gone of the need for any in-camera antialiasing filter which does nothing more than soft focus every image whether you want it or not. Gone is the Bayer demosaicing necessary with every other imager which amounts to guessing two of the three primaries that should be at each image pixel. Foveon has a wonderful writeup on their technology which demonstrates the technological differences to Bayer imager designs with even less techiness than I have written here:

Foveon X3 Technology

and they also have a gallery of example photography:

Foveon Gallery

Why Low Light is a Challenge:

Most photographers would be fine with the presentations on Sigma's site and be potentially border line at cognitive overload with the Foveon site, but for me, that just scratches the surface. I sought out, found, and read Foveon's US issued patents. US Patent 5,965,875 is particularly enlightening. There is where you get into the real technical details of the design:

I will keep this simple, well as simple as possible.

As with any technology, there are tradeoffs. In the Foveon imager, you are dealing with quantum probabilities. At the depth where the blue photons liberate electrons, the blue photons liberate electrons most of the time. The rest of the blue layer electrons come from lucky green and red photos which just happened to interact with an atom early on their journey into the Silicon crystal. The green and red layers have similar problems:

Spectral sensitivity of the three Foveon Layers

It's obvious that there is a huge overlap between the three channels. In post processing, whether in-camera or by computer, it is a simple matrix multiplication operation to isolate the RAW sensed measurements into image appropriate primaries. When the light levels are sufficient, this is a very quick and effective process yielding spectacular images of huge dynamic range and wonderful expanse of color. The problem comes in when the light level is low. A night or astronomical scene such as "The Bear" or "Orion Rising" means the matrix multiplication operation ends up working with small numeric values which means the potential for errors, i.e. image noise, becomes more significant. If not handled corrently, the results can be a image with fine pixel to pixel noise overlayed with magenta and green blotches that no software is able to correct.

Since one of the main areas of photography that I challenge myself with is astronomical, night, and low light scenes, bringing into view what a person at that setting would see as featureless darkness, the low light noise characteristics of the Foveon imager, fortunately, was a major area to learn through. I found it very interesting that even supposedly open professional photographers working with Foveon based cameras kept the secret to themselves, so I had to research, experiment, and analyze my way through.

[Steaphany]

Here are some links I thought anyone interested in learning more about Foveon imager based cameras:

The model I have is the Sigma SD14

This was followed by the Sigma SD15

Their latest offering is the Sigma SD1

If you do not want to go the SLR route, Sigma also has Foveon based Point & Shoot that create RAW and JPG format files starting with the Sigma DP1

If you want to play with this technology, I'm sure you an find bargains on ebay.