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Old 25-07-2020, 06:41 PM
Mike_in_Freo (Michael)
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EOS 550D out of focus after astromodding

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
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Old 25-07-2020, 09:34 PM
sunslayr (David)
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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 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.
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Old 26-07-2020, 06:31 AM
SteveInNZ
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Live view focus will still be correct. You just can't use the viewfinder any more.


Steve.
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Old 26-07-2020, 06:47 AM
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Merlin66 (Ken)
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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
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Old 27-07-2020, 05:47 PM
Mike_in_Freo (Michael)
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Thanks a lot you all.
Although it was not all good news, I know a bit more...
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Old 31-07-2020, 09:40 PM
Paullus (Paul)
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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
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Old 12-08-2020, 05:32 PM
Mike_in_Freo (Michael)
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Quote:
Originally Posted by Paullus View Post
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
Really good info there Paul! Thanks for that
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Old 20-08-2020, 04:09 PM
Mike_in_Freo (Michael)
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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?
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Old 20-08-2020, 04:59 PM
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It is too far, it should be closer.
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Old 20-08-2020, 07:00 PM
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AstroJunk (Jonathan)
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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)
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