Canon EOS

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EOS 350D

EOS 5D Mark II


Digital photography & Linux

Misc links for EOS


Hand-made trigger for 350D

Hand-made trigger for 350D & other Canon models (look for "C6" here:
The external trigger is composed of a jack 2.5mm, three wires, an on/off switch and a push button
Shortcut of ground and right (the middle ring) is equivalent to half-press, here wired to a simple on/off switch which provides the housing
Shortcut of ground and left (the tip) is equivalent to full press, here wired to a simple red push button

AV to stereo cable for 5D Mark II

The 5D has an AV output connector accepting a TRRS 3.5mm jack.
With Magic Lantern you can use it to plug a headphone and get the sound feedback directly while recording a movie, nice!
But you can't just plug the headphone into the camera, you would get only sound on the left ear and, worse, you would be busy short-cutting Ground and Right signals!

On the Canon side, the AV port is a female 3.5mm TRRS jack, TRRS means it has 4 connectors where T=tip, R=ring (so two rings), S=sleeve.
On the headphone side, it's a simple stereo 3.5mm TRS jack.

We have:

canon               stereo jack
=====               ===========
T left              T left
R video             R right
R common            S common
S right             S common

I've shown the TRS as TRSS to show that physically the second ring of a TRRS meets the sleeve of a TRS.

To build an adapter, I bought a cheap 50cm 3.5mm jack TRRS cable (so a TRRS male at one end and a TRRS female at the other end). I didn't want any adapter cable because there is a high chance it's not properly wired. Even the popular TRRS to RCA have a great chance to have the ground on the TRRS sleeve which means you'll get the Right signal on all three cinches instead of the Ground. If you use a TRRS-RCA make sure to use the one provided with your EOS!! But that solution is bulky and we need an additional RCA(male)-TRS(female) to hook a headphone. With a TRRS extension cable, we've full control.

Cut the cable somewhere and check its color code. Here also electrically check it, don't make any assumption on the color codes! Mine was like this (with color conventions, to show you it's arbitrary and you can't trust it):

T naked cable  (usually naked=ground)
R white cable  (usually white=left)
R red cable    (usually red=right)
S yellow cable (usually yellow=video)

We want to wire left-left, right-right and common-common. We'll leave the video signal from EOS disconnected. As common on the TRS is wide, we'll connect both R&S of the female connector of the cable to the common.

So it will look like this:

canon       cable           stereo jack
=====       ============    ===========
T left      T----------T    T left

R video     R     +----R    R right
R common    R---/--+---R    S common
               /    \
S right     S-+      +-S 

My cable just before soldering, with the thermo retractile tubes ready: (colors of your cable may be different, beware!!)

With this cable you can also use a mobile headset with TRRS & Mic, it won't hurt (and obviously the Mic won't be used by the camera). It would look like this:

canon       cable           OMTP jack
=====       ============    =========
T left      T----------T    T left

R video     R     +----R    R right
R common    R---/--+---R    R mic
               /    \
S right     S-+      +-S    S common

Even an iPhone headset should work:

canon       cable           CTIA jack
=====       ============    =========
T left      T----------T    T left

R video     R     +----R    R right
R common    R---/--+---R    R common
               /    \
S right     S-+      +-S    S mic

Misc hacks

IR photography

If the lens allows to focus "further" than infinite, it'll be enough to compensate for the absence of filter refraction: focus needs to be (~1/3 * (0.55+0.58)) = 0.375mm shorter. Else, this could be compensated by removing the spacers or adding a clean filter of about 1.1mm.

Create custom white balance on picture of green grass/foliage, with possibly some exposure compensation (+2?)

Live View With Auto Focus (best method) : be sure your camera set to use the direct (also called Live) focus mode, not Quick mode. Press and maintain AF-ON till liveview AF square becomes green (a few seconds).


Modding 350D

A bad idea... Choose a camera with LifeView instead!!

Modding 50D

There are several guides on how to open the 50D but most suggest to dismantle more than needed. Here are minimalist instructions:

  • Remove the battery, CF card and eyepiece
  • Bottom:
    • Remove 2 screws holding the *back* panel
    • Remove the seal on the Wireless Grip port (looks like HDMI connector)
  • Back:
    • Remove 1 screw hidden under grip below the magnifiers logos
    • Remove 2 screws under eyepiece
    • Remove 1 screw with the small eyepiece wheel
  • Left:
    • Remove grip
    • Remove 2 screws under grip
    • Remove 1 screw under PC plug seal
  • Remove back
    • Beware of 2 FPC
    • Beware of U-shaped shield around the Wireless Grip port
  • Remove left
    • Beware of metal piece around HDMI
  • Desolder
    • 2 points holding the metal shield in the middle of the PCB
    • Remove shield
    • Remove FPCs
  • Unscrew PCB
    • 4 screws (leave the 2 holding the CF reader)
    • 1 screw accessible from hole at bottom of CF reader
  • Remove PCB
    • Beware of 2 cable connectors at back
  • Unscrew sensor
    • Remove 2 screws
    • Remove 3 screws with triangle tool, beware of their spacers and springs
  • Remove sensor

To defilter sensor:

  • Remove dust-cleaning filter (it's also an IR filter, so don't put it back)
  • Remove blue filter on top of sensor


  • main filter: 26.6x19.2x0.55
  • dust-cleaner: 37.8x26.8x0.58


Deep B&W IR:    830nm+  -> B&W mode 
Standard IR:    720nm+  = Hoya R72 = Wratten 89b
Enhanced IR:    665nm+  = Extra Color                                  dark red
Super Color IR: 590nm+  = Ultra Color -> yellow/blue                   red
                550nm+   IR portraits                                  yellow
Hyper color IR: 470nm+
Blue + IR       300-450 + 720+       = NDVI =Schott BG3          ~ 590nm + channel swap
UV-IR Cut       445nm-670nm     Aliexpress "FOTGA UV-IR CUT filter"
adjustable      530nm..750nm    Aliexpress "Adjustable Infra-Red Lens"

Digital photography


I was wondering why in bulk mode over 30s the camera was busy after the shot for about the same time.
Now I got the answer!
When taking long exposure shots, we can have what's called hot pixels, red, green or blue. To remove them automatically the SLR takes a picture of the same duration with the shutter closed (called "dark" in astrophoto) and substract it from the previous. [1]