Camera Conversion Types Guide

DIGITAL CAMERA CONVERSION TYPES

A digital camera spectrum sensitivity modification consists of the removal of the internal ultraviolet and infrared light blocking sensor filter and the Low Pass Anti-Aliasing sensor filter. Removing these filters opens the sensor sensitivity to the ultraviolet and infrared wavelengths, including the Hydrogen Alpha and Sulfur II deep space nebulae emissions as well within the visible spectrum near the infrared wavelength. Consumer digital cameras manufacturers install the UV/IR blocking sensor filters at factory because the color imaging sensors are sensitive to ultraviolet and infrared light and at the same time, they have installed the Bayer Matrix (Red, Green and Blue) Colors Filters Array (CFA). The CFA is composed by RGB micro filters fitted over each pixel. To reproduce “human vision” like images, the UV/IR blocking sensor filter needs to be installed at factory because the RGB pixel filters create false colors cast of the ultraviolet and infrared light, and these wavelengths focus on a different distance from the visible light focal plane causing out of focus hues when using optics with refractive elements like lenses and refractor telescopes.

SENSOR FILTERS ASSEMBLY DIAGRAM

The internal sensor filter assembly is comprised by the following elements:

• Retaining clip plate (support material)
• Low pass filter (also known as LPF1, Anti-Aliasing or dust removal filter)
• UV/IR Blocking filter* (LPF2, Hot UV/IR, Color limiting filter, Bluish filter)
• Filter gasket seal
• Sensor filter frame housing
• CMOS Sensor

STOCK UV/IR BLOCKING SENSOR FILTER

Among all the sensor assembly elements listed above, to open the sensor sensitivity to ultraviolet and infrared light and for a substantial increase of Hydrogen Alpha and Sulfur II deep space nebulae emissions, *the UV/IR blocking bluish sensor filter must be removed. This is where the digital cameras spectrum conversion starts from. As can be seen in the graph below, the stock sensor sensitivity transmission starts at 400nm (violet) light and on the red wavelength spectrum is greatly reduced after 500nm towards the infrared spectrum. This is why the original UV/IR blocking sensor filter is also called color limiting filter. It is the culprit for suppressing most of the H-alpha and Sulfur II emissions.

LOW PASS FILTER

Also known as LPF1, Anti-Aliasing filter or Dust removal filter, it also blocks Ultraviolet and Infrared light and has the piezoelectric device that triggers vibrations to shake off dust particles. The main purpose of the Low Pass Filter is eliminating the moire effect but at the cost of sacrificing sharpness slightly introducing a little blur effect. Digital cameras without low pass filter have the piezoelectric self-cleaning device attached directly to the UV/IR blocking filter.

Full Spectrum conversion (Ultraviolet + Visible + H-Alpha + Sulfur II + Infrared)

This is the most versatile type of conversion. It is suitable for ultraviolet and infrared photography with selective UV and IR band pass filters, regular photography with an original white balance filter (OWB) and Astrophotography. The camera will capture ultraviolet, infrared and the entire visible spectrum including Hydrogen Alpha and Sulfur II deep space nebulae emissions.

1. UV/IR blocking bluish filter and LPF removal


This is the most unexpensive conversion, most recommended to save money. Cameras without the LPF or when it is removed having the sensor bare or "naked" will become Full Spectrum sensitive. Without any glass above the sensor there are no internal reflections coming from a replacement filter. When the stock UV/IR blocking filter is removed, the surface of the sensor is not really naked. There is a layer of glass protecting the micro-lenses and the Bayer matrix RGB microfilters on top of the pixels.

Autofocus and focus to infinity: to allow the camera reach focus to infinity with lenses, the sensor needs to be repositioned closer to the lens mount. In many situations, there is not enough room for this adjustment. If this is the case, the camera may not or will not focus to infinity with lenses after the conversion. The sensor repositioning travel range can be verified once the camera is disassembled. It varies even among different samples of the same camera model. Perfect focus of subjects closer than infinity will always be achieved in Live View Mode, but for guaranteed focus to infinity with lenses including perfect autofocus in Pentaprism/Pentamirror mode using DSLR cameras, options 2 is the appropriate choice. Telescopes will always reach focus to infinity without any problem.


2. Astronomik or Optolong Anti-Reflective Clear Glass

Both Low Pass Filter with self-cleaning feature and the original UV/IR blocking bluish filter are replaced by the non-detachable Astronomik or Optolong Multicoated Anti-Reflective Clear filter which is permanently installed. With the Low Pass Anti-Aliasing Filter removed, the Camera Sensor performs at native maximum sharpness. With this Full Spectrum conversion option, the DSLR camera Pentaprism/Pentamirror mode autofocus and focus to infinity with lenses will work as before the conversion.


Daylight Infrared photography with a Full Spectrum converted camera

When the digital camera sensor becomes sensitive to ultraviolet and infrared light after the Full Spectrum conversion, specific infrared bandpass isolating filters can be used as camera lens filters or camera body clip filters. Infrared filters with different wavelengths are suitable to create artistic expressions with altered color tones or dramatic contrast effects with black and white images produced by deeper infrared filters.

Astrophotography with a Full Spectrum converted camera

The Full Spectrum modification is the best conversion for planetary astrophotography because the usability of infrared isolating filters like the Astronomik ProPlanet 742 IR-pass and 807 IR-pass . The infrared wavelength is significantly less susceptible to poor seeing (atmospheric turbulences) and consequently the resulting images are considerably sharper. Expert planetary imagers process planets photos with images taken with single line infrared filters as a luminance channel.

Regular photography with a Full Spectrum converted camera

For daylight or regular photography an additional UV/IR block or Original White Balance filter is required. The Astronomik L-2 and OWB Clip filters can be used to correct White Balance (Subject to lens and camera model compatibility). Clip filters can be used with Canon EF Lenses (EF-S Lenses are not compatible with clip in filters).

Out of focus Infrared: An additional UV/IR cut filter is required to capture the pictures in visible light. This filter is a must when imaging with telescopes using refractive elements (refractors, catadioptrics, reducers/flatteners, coma correctors, etc.) If light frames are captured without an UV/IR blocking filter you will get bloated stars, because UV and IR light rays focus on a different distance from the visible light focal plane. A luminance filter, or any narrowband filter will cut off ultraviolet and infrared Wavelengths. With a Ritchey-Chretien Telescope and no flattener/reducer there is no need of an additional UV/IR Blocking filter.

Astrophotography or “H-Alpha” Conversion (Enhanced Spectrum: Visible + H-Alpha + Sulfur II)

On the Astrophotography camera conversion, the spectrum sensitivity is enhanced to increase Hydrogen Alpha wavelength bandpass transmission at the 656nm emission line and the Sulfur II wavelength transmission at both 671.7nm and 673nm emission lines. The original UV/IR Blocking filter present on stock DSLR or Mirrorless Cameras only allows over 25% transmission of H-alpha emission line and over 15% of Sulfur II emission lines. An Astro-Converted DSLR or Mirrorless Camera is about 4 and 6 times (H-alpha and Sulfur II respectively) more sensitive to the deep reddish nebulae structure tones. H-alpha objects/sections are also present in all the other galaxies besides the Milky Way. The hydrogen element is present in the entire universe, and many emission nebulae visible on the night sky emanate hydrogen alpha emissions. This conversion does not require an additional or external UV/IR Cut filter.

1. UV/IR blocking bluish filter removal with LPF preserved


This conversion preserves the Low Pass Anti-Aliasing filter with self-cleaning function on cameras with Low Pass Filter. The spectral sensitivity of the camera sensor will be Enhanced Spectrum, allowing Hydrogen Alpha and Sulfur II wavelength emissions pass but still blocking UV/IR light.

Autofocus and focus to infinity: With the Low Pass Filter only preserved, in most cases the sensor distance to the lens bayonet can be adjusted accordingly to allow the camera reach perfect focus to infinity with lenses. The sensor repositioning travel range can be verified once the camera is disassembled. It varies even among different samples of the same camera model. If there is not enough room to bring the sensor closer to the lens mount, the camera may not reach focus to infinity with lenses. Perfect focus of subjects closer than infinity will always be achieved in Live View Mode, but for guaranteed focus to infinity with lenses including perfect autofocus in Pentaprism/Pentamirror mode using DSLR cameras, options 2 or 3 are the appropriate choices. Telescopes will always reach focus to infinity without any problem.

2. Baader or Optolong Luminance Filter and LPF

For this conversion, the non-detachable Baader or Optolong UV/IR Cut Anti-Reflective filter (Depending on filter availability) with enhanced H-alpha and Sulfur II transmission is permanently installed preserving the Low Pass Anti-Aliasing Filter with self-cleaning function. The sensor filters configuration of this modification is the same of the Canon EOS 60Da and Canon EOS Ra. With this conversion option, the DSLR camera Pentaprism/Pentamirror mode autofocus and focus to infinity with lenses will work as before the conversion.

3. Baader or Optolong Luminance Filter only

On this conversion both Low Pass Anti-Aliasing filter with self-cleaning function and the UV/IR blocking bluish filter are removed and replaced by the non-detachable Baader or Optolong UV/IR Cut Anti-Reflective filter (depending on filter availability or camera model) with enhanced H-alpha and Sulfur II transmission range. With this conversion option, the DSLR camera Pentaprism/Pentamirror mode autofocus and focus to infinity with lenses will work as before the conversion. With the Low Pass Anti-Aliasing Filter removed, the Camera Sensor performs at native maximum sharpness, which is also great for solar and planetary astrophotography. Astrophotography dedicated cooled cameras have the same sensor filter configuration of this conversion having an UV/IR blocking filter with the same transmission range without any low pass filter.

Regular photography with an Enhanced Spectrum converted camera:

The camera can be used for daylight photography setting the custom white balance with a gray card shot under the specific light source for "In-Camera" white balance correction or with Adobe Camera Raw. To make the automatic white balance work as before the conversion, the Original White Balance (OWB) Clip filter can be used to correct White Balance (Subject to lens and camera model compatibility). Clip filters can be used with Canon EF Lenses (EF-S Lenses are not compatible with clip in filters).

Out of focus NIR: With the Enhanced Spectrum modification, depending on the lens, telescope or optical corrector used, some imagers might experience a little bit bloated stars due to the near infrared light slightly out of focus when a refractive optical system does not have at least one ED (Extra-Low Dispersion glass) element. This chromatic aberration could be mitigated with post processing correction using computer software.

To browse our Astro Conversions options click here.