EOS 550D out of focus after astromodding

[Mike_in_Freo]

Hey people, my very first post so be gentle with me... :)

I've just modded my old EOS 550D according to the superb instructions found here http://dslrmodifications.com/rebelmod450d4.html

Now, my camera is out of focus. The instruction clearly stated that the spring loaded screws (3) for the level of the CCD should be positioned accordingly, (preferably with a micrometer that I didn't have...) so is there an easy fix maybe? I don't mind disassemble one more time...

Cheers fellas
//Mike

[sunslayr]

Bad news I'm afraid, the distance to the sensor must be pretty precise for camera lenses to focus properly. I can see only three possible fixes.

1. Don't use slr lenses just use it for prime focus astrophotography in a telescope.

2. Buy the clip in filter version of this (https://www.bintel.com.au/product/astronomik-mc-clear-filters/?attribute_pa_astronomik=eos-clip%2F%3Fv%3D6cc98ba2045f&gclid=CjwKCAjwsO_4BRBBEiwAyagRTYqQg MB1Jt72DQ9TEoiHeEB5GN7pToIAVRX6QlPU 6IOH83_K7NCspxoCQu0QAvD_BwE&v=322b26af01d5) clear filter or something similar and hope that it moves the focal plane enough to get focus.

3.Buy a caliper and shims from your local hardware/auto shop and follow the guide again and setting the correct distance for the sensor.

[SteveInNZ]

Live view focus will still be correct. You just can't use the viewfinder any more.


Steve.

[Merlin66]

The mod to the camera changes the distance for the auto focus sensor.


The only way of retaining the auto focus function is to either re-set the position of the sensor or replace the removed filter with a clear or UV-IR filter.


To use standard EF lenses with a mod you need at least a clip in filter to reach focus. Adding a clip in filter allows you to manually focus using the Liveview or viewfinder.
HTH

[Mike_in_Freo]

Thanks a lot you all.
Although it was not all good news, I know a bit more...

[Paullus]

Hi Michael,

It is possible to adjust the micro focus with some Canons; not sure if the 550D supports it (my 50D does). The link below gives the gist of it or search for "Autofocus Microadjustment".

https://contrastly.com/autofocus-microadjustment/

PS when I modded my 50D I didn't measure the screws either (d'oh), but when I reassembled I tightened the 3 so that the sensor board was resting on the pegs/stops to at least make the sensor as square as possible to the light path. Surprisingly my AF isn't knocked around much.

Cheers

[Mike_in_Freo]

Really good info there Paul! Thanks for that

[Mike_in_Freo]

After doing some tests, I can focus very good using live view but only from about 65-250mm on my 55-250mm lens. Does this mean that, after I astro-modded my camera, the CCD is too far or too close to my lens?:question:

[bojan]

It is too far, it should be closer.

[AstroJunk]

Did you replace that glass with a baader clear glass or not? Without the replacement glass I have read that it can't reach infinity with a camera lens. I did mod a similar camera and all was fine.

Like Paullus, I screwed mine all the way down, but then slackend each screw by 3 turns and called it a day. Worked a treat (I used replacement glass)