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Color-Temperature-Balancing Colored Glass Filters


  • Increase the Color Temperature of a Visible Light Source
  • Conversion Value: -132 or -160 mireds

FGT05165

Ø12.5 mm
-160 mireds

FGT165M

Ø25.0 mm, SM1 Mounted
-132 mireds

FGT200S

2" Square
-160 mireds

FGT200 Ø25.0 mm
Filter Shown Mounted
in the Filter Holder of
the SLS201L Stabilized
Broadband Light Source

Related Items


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General Specifications
Clear Aperture 80% of Diameter (Circular Filters)
80% of Dimension (Square Filters)
Surface Quality 40-20 Scratch-Dig
Transmitted Wavefront Error Ø12.5 mm: <λ/4 at 632.8 nm
Ø25.0 mm: <λ/2 at 632.8 nm
Ø2" and 2" Square: <λ at 632.8 nm
Dimensional Tolerance +0.0/-0.4 mm
Parallelism <3 arcmin

Click to Enlarge

Click to Download an Excel File of Raw Data
The graph above shows the measured transmission curve for a filter with a conversion value (V) of -132 mireds and a filter with a conversion value of -160 mireds. For details on the mireds unit, please see the Conversion Values tab.

Features

  • Pass Blue Light and Attenuate Red Light
  • Available in Ø12.5 mm, Ø25.0 mm, Ø2", and 2" Square Sizes
  • Ø25.0 mm Size Also Available Pre-Mounted in an SM1-Threaded Lens Tube
  • Use with Our Broadband or Stabilized Broadband Light Sources

These Color-Temperature-Balancing Colored Glass Filters are designed to increase the color temperature of broadband light sources by attenuating light on the red end of the visible and near-IR spectrum and transmitting light on the blue end. The amount of increase depends on the original color temperature of the source and the conversion value (V) of the filter. Filters with a more negative conversion value will increase the color temperature by a greater amount. We offer filters with conversion values of -132 mireds and -160 mireds. Given their conversion values, these filters are particularly useful in imaging applications for color correcting a tungsten light source to more closely match natural light. For an explanation of conversion values and the mireds unit, please see the Conversion Values tab.

Unmounted filters are available in Ø12.5 mm, Ø25.0 mm, Ø2", and 2" x 2" sizes. The Ø25.0 mm filters are also available pre-mounted inside SM1-threaded (1.035"-40) lens tubes, which are each engraved with the Item # and conversion value of the filter. For easy integration with our broadband stabilized light sources, the Ø25.0 mm size can be mounted in the filter holder included with each source, as shown in the photo at the top of the page. For storage of our Ø25.0 mm or 2" square filters, we offer the KT01 and KT03 storage boxes, sold below.


Click to Enlarge

The photo above shows light from an SLS201L 2796 K tungsten-halogen source with no filter installed. For a plot of the power output with and without a filter, please see the Conversion Values tab.

Click to Enlarge

The photo above shows light from an SLS201L 2796 K tungsten-halogen source with an FGT200 Ø25.0 mm filter installed. For a plot of the power output with and without a filter, please see the Conversion Values tab.
Colored Glass Selection Guide
Bandpass Longpass Color-Temperature-Balancing
Mounted Unmounted AR Coated Mounted Unmounted Mounted and Unmounted
Color Temperature of Light Sources After Filter
  Light Source Item # (Unfiltered Temperature)
Conversion Value SLS201L (2796 K) SLS202L (1900 K) OSL2 (3200 K)
-132 mireds 4432 K 2536 K 5540 K
-160 mireds 5059 K 2730 K 6557 K

In the table above, the values highlighted in green give the resulting color temperature of each source when used with a filter of the conversion value given in the first column.


Click to Enlarge

Click to Download an Excel File of Raw Data
The graph above shows the measured spectum of the SLS201L light source with and without a -132 mired filter or -160 mired filter installed.

The color temperature of a light source can be expressed in mireds (micro reciprocal degrees), given by 106 divided by the temperature in kelvin. For example, the color temperature of our SLS201L stabilized broadband light source is rated at 2796 K, which equates to 358 mireds. The SI unit of mireds is reciprocal megakelvin (MK-1).

The filters on this page offer a negative conversion value, meaning that they will decrease the mireds color temperature of light and thus increase the color temperature in kelvin. The filtered color temperature of a source can be calculated from the formula below, where V is the conversion value of the filter in mireds, K1 is the color temperature of the source in kelvin before the filter, and K2 is the color temperature in kelvin after the filter.

The table above and on the right gives calculated values for the color temperature of a selection of our white-light sources after being filtered. For example, the color temperature of the SLS201L light source when used with our -132 mireds conversion value filters can be calculated by first solving for K2, such that K2 = (106) / (V + 106/K1), and then by plugging in the initial color temperature (K1 = 2796 K) and the conversion value (V = -132 mireds) to produce K2 = 106 / 226 = 4432 K. The graph to the right shows the measured power output curve for the SLS201L source with and without the -132 or -162 mired filters.


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Posted Comments:
Poster:tomerg
Posted Date:2014-08-05 09:15:34.103
I have a Thorlabs hologen lamp OSL2 and I want to use the FGT200M color balancing filter with it (put in front of the source). Is it Ok from themral point of view (i.e. deformation, breaking, etc.)? Thanks, Tomer.
Poster:jlow
Posted Date:2014-08-08 08:35:53.0
Response from Jeremy at Thorlabs: We have not tested this with the OSL2 but this should be fine if you mount it in a metal holder and use the full aperture of the optic.

Unmounted Temperature-Balancing Filters, -132 mireds

  • Fabricated from 2.0 mm Thick LB-165 Hoya Glass
  • Conversion Value of -132 mireds
  • Ø12.5 mm, Ø25.0 mm, Ø2", and 2" Square Sizes

These unmounted, temperature-balancing, colored glass filters each offer a conversion value of -132 mireds.a By attenuating more red than blue light, they increase the color temperature of a given light source by an amount determined by the equation on the Conversion Values tab. For compatibility with our lens tubes and filter mounts, we offer these filters in Ø12.5 mm, Ø25.0 mm, Ø2", and 2" x 2" sizes.

a. The conversion value is dependent on the thickness of the filter.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
FGT05165 Support Documentation
FGT05165Customer Inspired!Ø12.5 mm Temperature-Balancing Filter, -132 mireds
$88.75
Today
FGT165 Support Documentation
FGT165Customer Inspired!Ø25 mm Temperature-Balancing Filter, -132 mireds
$93.00
Today
FGT20165 Support Documentation
FGT20165Customer Inspired!Ø2" Temperature-Balancing Filter, -132 mireds
$118.00
Today
FGT165S Support Documentation
FGT165SCustomer Inspired!2" x 2" Temperature-Balancing Filter, -132 mireds
$118.00
Today

Mounted Temperature-Balancing Filter, -132 mireds

  • Fabricated from 2.0 mm Thick LB-165 Hoya Glass
  • Conversion Value of -132 mireds
  • Ø25.0 mm Filter Mounted in an SM1-Threaded Lens Tube

This mounted, temperature-balancing, colored glass filter offers a conversion value of -132 mireds.a By attenuating more red than blue light, it increases the color temperature of a given light source by an amount determined by the equation on the Conversion Values tab. The Ø25.0 mm filter is pre-mounted inside an SM1-threaded (1.035"-40) lens tube for ease of integration into our SM1-compatible optomechanics. For quick identification, the lens tube is engraved with the Item # and conversion value of the filter.

a. The conversion value is dependent on the thickness of the filter.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
FGT165M Support Documentation
FGT165MCustomer Inspired!Ø25.0 mm Temperature-Balancing Filter, -132 mireds, SM1-Threaded Mount
$114.00
Today

Unmounted Temperature-Balancing Filters, -160 mireds

  • Fabricated from 2.0 mm Thick LB-200 Hoya Glass
  • Conversion Value of -160 mireds
  • Ø12.5 mm, Ø25.0 mm, Ø2", and 2" Square Sizes

These unmounted, temperature-balancing, colored glass filters each offer a conversion value of -160 mireds.a By attenuating more red than blue light, they increase the color temperature of a given light source by an amount determined by the equation on the Conversion Values tab. For compatibility with our lens tubes and filter mounts, we offer these filters in Ø12.5 mm, Ø25.0 mm, Ø2", and 2" x 2" sizes.

a. The conversion value is dependent on the thickness of the filter.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
FGT05200 Support Documentation
FGT05200Customer Inspired!Ø12.5 mm Temperature-Balancing Filter, -160 mireds
$91.00
Today
FGT200 Support Documentation
FGT200Customer Inspired!Ø25.0 mm Temperature-Balancing Filter, -160 mireds
$97.00
Today
FGT20200 Support Documentation
FGT20200Customer Inspired!Ø2" Temperature-Balancing Filter, -160 mireds
$135.00
Today
FGT200S Support Documentation
FGT200SCustomer Inspired!2" x 2" Square Temperature-Balancing Filter, -160 mireds
$135.00
Today

Mounted Temperature-Balancing Filter, -160 mireds

  • Fabricated from 2.0 mm Thick LB-200 Hoya Glass
  • Conversion Value of -160 mireds
  • Ø25.0 mm Filter Mounted in an SM1-Threaded Lens Tube

This mounted, temperature-balancing, colored glass filter offers a conversion value of -160 mireds.a By attenuating more red than blue light, it increases the color temperature of a given light source by an amount determined by the equation on the Conversion Values tab. The Ø25.0 mm filter is pre-mounted inside an SM1-threaded (1.035"-40) lens tube for ease of integration into our SM1-compatible optomechanics. For quick identification, the lens tube is engraved with the Item # and conversion value of the filter.

a. The conversion value is dependent on the thickness of the filter.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
FGT200M Support Documentation
FGT200MCustomer Inspired!Ø25.0 mm Temperature-Balancing Filter, -160 mireds, SM1-Threaded Mount
$118.00
Today

Filter Storage Boxes

If you purchase individual filters and would like a safe, convenient place to store them when not in use, consider our KT01 and KT03 Storage Boxes. The KT01 is designed to hold up to ten mounted Ø25 mm filters, while the KT03 can hold up to ten unmounted 2" x 2" filters.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
KT01 Support Documentation
KT01Storage Box for Mounted Ø1" (25 mm) Round Optics (Max. Capacity: 10)
$88.50
Today
KT03 Support Documentation
KT03Storage Box for Unmounted 2" Square Optics (Max. Capacity: 10)
$83.25
Today
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