CANON EOS 350D
IR-CUT FILTER REMOVAL OPERATION,
PERFORMANCES
AND
IMAGE SAMPLES
Some
view of the operation...
Quelques
vues de l'opération...
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Spectral characterisation
Caractérisation
spectrale
The
LISA spectrograph is used for the measures
Le spectrographe LISA est utilisé
pour les mesures
The standard spectral response of an unmodifier
Canon 350D on an halogen lamp. The peak response of each spectral
bands is normalized to unity (so, the relative response is not here
conserved). |
The spectral response after filter removal operation.
The source of light is an halogen lamp. The peak response of each
spectral bands is normalized to unity. The increase of the sensibility
in the red part is very significant (not only in the Halpha vicinity
at 6563 A).
The colored dye of the bleue and green pixels filters are also nearly
transparent in the infrared. For wavelength greater then 800 nm
the CMOS detector sensitivity is nearly the same for the R, G and
B pixels, i.e. detector behaves like a black and white sensor.
It is a very useful properties, for example for high resolution
study of Jupiter like planets in the IR methane bands or for spectroscopic
works. The global detectivity is improved (ideal for wide-field
survey, like search of novae, comets, ...). The increase of the response in the bleu part of the spectrum
is also significant. Photons of wavelength lower to 400 nm can be
now detected (H&K lines images of the Sun are now possibles). |
Same figure, but now the color temperature of the
source is lower. The result is clearly depend of the source used.
More infrared radiations further increases the apparent response
in the infrared. |
A
2D spectrum. Up to 800 nm the spectrum rendition is nearly neutral (same absolute
response for R,G and B pixels).
Un
spectre 2D. Au dessus de la longueur d'onde de 800 nm le rendu de couleur est
approximativement neutre (même réponse absolue pour les pixels R, V et
B).
The absolute measured transmission of the Canon
EOS 350D IR cutoff filter. In a surprising way, the attenuation
is still very sensitive in the yellow part of the spectrum. |
The compared measured transmission of the Canon
EOS 350D IR cutoff filter and of the Nikon D70 IR cutoff filter.
The attenuation at the Halpha level is respectively 0.195 and 0.158.
In the infrared part, the Nikon filter is more transparent compared
to the Canon filter (a well know properties of the Nikon DSLR). Download Canon filter
transmission curve (two column ASCII file) |
Internal filter removed and use of an external KG3 filter for suppress infrared radiation (a low cost solution). Note the transparence at the Halpha line level. Filtre interne enlevé et utilisation d'un filtre externe KG3 pour supprimer les photons infrarouge (une solution bas coût). Noter la transparence au niveau de la raie Halpha. |
Internal filter removed and use of an external BG18 filter for suppress infrared radiation. Filtre interne enlevé et utilisation d'un filtre externe BG18 pour supprimer les photons IR. |
Download KG3 transmission
curve - Download BG18 transmission curve |
Focusing
Focalisation
A solution for insert a filter
in the optical beam (because the small size of the 350D flip mirror).
Up to 2.7-mm thickness for the glass plate is possible. The goal is a partial
or total compensation of the optical
path reduction induced by the IR-cutoff removal (clear plate).
Une
solution pour placer une lame claire ou un filtre coloré dans le chemin optique (en
raison de la petite taille du miroir
reflex dans le cas du 350D). Un verre jusqu'à
l'épaisseur de 2.7 mm peut être disposé de cette manière dans le 350D. Le but
est une compensation partielle ou totale de la réduction du chemin
optique suite au retrait du filtre de rejection IR interne.
The
physical thickness of the IR rejection filter is 2.48 mm. The corresponding
optical path is near 0.8 mm. The out of focus is easily compensated for the majority
of Canon lenses (the "out of infinity" position).
L'épaisseur
physique du filtre de rejection infrarouge est de 2.48 mm. L'épaisseur optique
correspondante est proche de 0.8 mm. Le défaut de focalisation produit par le
retrait du filtre peut être aisément compensé sur de nombreux objectifs
de la gamme Canon (position au-delà de l'infini possible).
If the focus problem is fixed, standard photography is nearly possible...
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Images
Full
frame view of the field of Messier 97 + Messier 108 full frame field of view.
Canon 350D + KG3 filter + Canon 200 mm f/2.8 L lens. Exposure: 6 x 120 sec.
Suburban condition.
Champ
des objets Messier 97 + Messier 108. Canon 350D + filtre KG3 filter + objectif
Canon 200 mm f/2.8 L. Exposition : 6 x 120 sec. Conditions urbaine. Suburban
condition.
Crop
of Messier 97 / Messier 108 field at original scale.
Détail
du champ Messier 97 / Messier 108 à l'échelle originale.
A
crop of a Canon 200 mm f/2.8 image - NGC7000 nebula. For the G and B channel:
stack of 5 x 120 sec. exposures (modified 350D + KG3). For the R channel: stack
of 10 x 300 sec. exposures (Lumicon Halpha filter + KG3). Suburb conditions.
Un
détail d'une image Canon 200 mm f/2.8 autour de la nébuleuse NGC 7000. Pour
les canaux V and B accumulation de 5 x 120 sec. exposures (modified
350D + KG3).
pour le canal R on a accumulé de 10 x 300 sec (Lumicon
Halpha filter + KG3). Ciel pollué (magnitude limite de 2)..
The infrared sky / Le ciel infrarouge...
Infrared
photography with the modified 350D. A Wratten 87 is added for this purpose to
a 17-40 mm Canon zoom lens (equivalent to a Schott RG780).
Imagerie
infrarouge avec un 350D modifié. Un filtre Wratten 87 (équivalent à un filtre
Schott RG780) est ajouté pour cela à
un zoom Canon 17-40 mm L.
RY
Dra region
B & G channels: Modified Canon 350D + KG3 filter
+ Canon zoom 17-40 mm f/4 @ F = 40 mm - 12 x 10 sec. - Suburban
R channel:
Modified Canon 350D + W87 filter + Canon zoom 17-40 mm f/4 @ F = 40 mm -
6 x 30 sec. - Suburban
Canaux
B & G : Canon 350D modifié + filtre KG3 + Canon zoom 17-40 mm
f/4 @ F = 40 mm - 12 x 10 sec. - Ciel pollué
Canal R : Canon 350D modifié
+ filtre W87 + Canon zoom 17-40 mm f/4 @ F = 40 mm - 6 x 30 sec. - Ciel
pollué
Commented
field. Some IRAS source are pointed. Note the presence of the Be star Kappa
Dra
Champ commenté. Quelques
sources IRAS sont indiquées. Noter la présence de l'étoile Kappa
Dra, de type Be
Typical comparaison between classical vegetation view (up) and IR view (350D
+ W87) (down).
The infrared image is nearly black and black because the similar
R, G and B response of 350D pixels for wavelength up to 800 nm.
Une
vue typique de la végétation, standard en haut et dans l'infrarouge en bas (30D
+ W87).
L'image infrarouge est quasiment du type noir et blanc en raison
de la similitude de réponse des pixels R, V et B du 350D pour des longueurs
d'onde supérieures à 800 nm.
Thermal
emission of a soldering iron (demonstration of Planck law of a black body -
fine for pedagogical purpose). Obscured ambiance - Canon 17-40 mm lens +
Wratten 87 filter - 20 seconds exposure / ISO 200.
Emission
thermique d'un fer à souder (démonstration de la loi de Planck pour les corps
noir - bonne application pédagogique). Ambiance obscure - Objectif Canon 17-40
mm + Wratten 87 - exposition de 20 secondes / 200 ISO.
SOME USEFUL INFORMATIONS
Gain @ ISO 400 |
2.2 e-/count |
RMS noise @ ISO 400 |
6 e- |
Mean offset level |
256 counts |
Dynamic |
12 bit (4095 counts) |
Detector |
CMOS |
Dark
signal aspect. 300 seconds exposure @ 15°C. Visualisation threshold: hi = 400
- lo = 200
Very
high contrast image of the dark map. 300 seconds exposure @ 15°C. Visualisation
threshold: hi = 270 - lo = 250. The amplifier light glow is very limited
(significant progress compared with the 10D/300D family DSLR or D70). Possible
shutdown of some CMOS power during long exposure.
Crop
of the offset map (mean of 18 successives frames). The aspect of the image is
very clean (severe threshold under Iris: hi = 280 - lo = 240). The faint fixed
pattern amplitude is equal or inferior to 0.5 count RMS and constant (easy
to remove after a standard preprocessing).
QuickAPN:
a low cost and powerful wired remote control for DSLR (include intervalometer
function)
QuickAPN:
une interface de commande à fil bas coût et puissante pour reflex numérique
(inclue une fonction d'intervalomètre)