DSLR IR Filtering Modification - New Lower Prices!
| So why should you modify a perfectly good DSLR for astrophotography? All DSLR's have sensors that are naturally sensitive to infra-red light. The manufacturers install IR filters to keep most IR energy from reaching the imaging chip to maintain a correct color balance similar to what our eyes see. Unfortunately, these filters also attenuate hydrogen-alpha light which is very important for capturing nebulosity in astronomical photographs. By removing the stock IR filter or replacing it with clear glass or another IR filter that is transparent to hydrogen-alpha, the camera's sensitivity for astrophotography is greatly increased. | |
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Photos courtesy of Mike Reid http://mikesastro.com/analysis/IRmod/ |
| While stock DSLR's are fine for capturing galaxies,
reflection nebulae and star clusters, they are woefully lacking in
sensitivity to hydrogen-alpha energy. This is the light from
glowing hydrogen that gives emission nebulae their characteristic red
color. However, that sensitivity is already built into your
camera...you only need to release it. All digital cameras have a
filter in front of the imaging chip which greatly attenuates infrared
energy which skews the natural visual color balance and does not focus
at the same point as visible light...and DSLR's are no different.
Unfortunately, the camera manufacturers didn't have astronomy in mind
when they designed these filters since they greatly attenuate
hydrogen-alpha light which falls in the spectrum between deep red
visible light and infrared. In the Canon DSLR's, the response to
hydrogen-alpha is down to about 20% of the sensitivity to other
colors. This causes astronomical photographs of emission nebulae
to appear washed out. As in the picture from the unmodified camera
above, the object of interest may be almost completely absent!
Unfortunately, it is virtually impossible to make up the difference by
simply exposing longer or stacking more images since the signal-to-noise
ratio at the critical hydrogen-alpha wavelength is so low. The solution is to remove the camera's IR filter. This opens up the imaging chip's full sensitivity to hydrogen-alpha and also makes the entire spectrum almost one f-stop more sensitive. However, as in all good things, there is a price to pay. Since removing the filter removes a section of glass in the light path that is behind the lens but in front of the imaging chip, the auto-focus mechanism becomes un-calibrated as well as the optical viewfinder. The back focus also changes preventing normal camera lenses from focusing to infinity, and since the balance of colors arriving at the imaging chip has changed, the auto-color balance is no longer calibrated. However, for a camera that will be dedicated to astronomical photography through a telescope and focused by software (DSLRFocus, ImagesPlus, MaximDSLR, AstroArt, etc.), these issues are of little concern and the simple filter removal provides the most economical path to a sensitive astronomical camera. For those wanting to retain the capability to use normal lenses for astronomical work, as well as the ability to do daylight terrestrial work with an external IR blocking filter such as the X-Nite CC1 filter from MaxMax (www.maxmax.com), a replacement section of clear optical quality glass can be fitted into some cameras. This also has the added advantage of replacing the protective cover for the expensive imaging chip previously provided by the IR filter. NEW! I now
offer modifications (Options 3 only) on the Canon 50D and 1000D/XS DSLR's - See below... "Like WOW...and not to sound
to corny ...but I only wish I would
have done this earlier." - GG "BTW - The service provided by
Hap was top notch and he was great to deal with." - CA |
| The options are as follows: Option 1 - IR Filter Removal Only for Canon 10D, 20D, 300D, and 350XT - $200.00 (was $250) plus return shipping cost of customer's choice This option is for those who will use their camera for astronomical use only with a telescope. It will provide the most hydrogen-alpha sensitivity. However, in refractive optical systems, an external longwave IR block filter must be inserted in the imaging chain such as a Baader UV/IR Block ( http://www.alpineastro.com/filters/filters.htm#UV-IR-Cut%20Filter ). On the 300D's and 350XT's, the camera's autofocus and optical viewfinder will be out of calibration. However, for software focusing tools, this is of no concern. Normal camera lenses will not be able to come to focus at infinity and therefore cannot be used for astrophotography.
Please be aware that this or any other modification to your camera
voids any remaining factory warranty. |
| Ship the camera and payment to: Hap Griffin Southeastern Laser Center 1250 Wilson Hall Rd Sumter, SC 29150
Clear skies!
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