focus issue with modded 1000d (not what you may think)

[kaiserdave]

Hi all,

firstly i have modded my 1000d  - the lpf2 filter removal (no replacement).

I also have a uhc clip filter fitted. With this setup i am able to achieve normal focus without problem - I can achieve focus with the APT focus tool and back out before the lens hits the "stop" so no poblem there ( i think).

However when I take some test shots the stars look pretty terrible - which is particularly evident when an imaging session is stacked and the image separated into RGB mages.

The red chanel is rubbish whilst the green and blue are not bad (roughly stretched images for examples)

this was taken with the modded 1000d and a super takumar 200mm f4 lens.

 

I guess my question is what can i do to deal with this issue? 

 

Thanks! 

Adam

[michael8554]

Hi Adam

I assume the APT Focus Tool uses the LiveView image, so should give good focus, even if the UHC Clip Filter isn't compensating perfectly for the removed LPF #1 ?

Also the UHC Filter spec says it removes out-of-band IR, so that shouldn't be a factor in the poor Red focus.

So that only leaves the lens.........

Michael

[kaiserdave]

Michael - Correct it uses live view and FWHM to determine the focus. 

I guess I could use bahtinov mask to give me a visual representation and try to focus either side of the sweet spot, take some exposures and see what I can make of it.

Thanks

Adam

 

On 01/12/2020 at 23:40, michael8554 said:

Hi Adam

I assume the APT Focus Tool uses the LiveView image, so should give good focus, even if the UHC Clip Filter isn't compensating perfectly for the removed LPF #1 ?

Also the UHC Filter spec says it removes out-of-band IR, so that shouldn't be a factor in the poor Red focus.

So that only leaves the lens.........

Michael

 

[si717]

i found with modding my 650d i hadnt leveled the sensor chip on the camera when i did the mod i used a bahtinov mask and focused everytime for months and imaged away thinking i was doing ok until someone pointed out my stars were not sharp accross the image ,i re leveled the sensor on the camera and now stars are pin sharp just a thought

the extra level of red will be from the mod and can be aligned in software after imaging 

bubble neula image when sensor was off odd looking stars

and ngc 869 after leveling the sensor

[kaiserdave]

When you modded did you move the sensor in order to compensate for the missing glass? 

In theory when I did it I left the position alone and replaced the sensor as was knowing that I had a bit of "extra" focus on my lens. Also when I added the clip filter it brought the focus in my favour more. That's not to say I haven't reinstalled the sensor wonky of course! 

How did you check the level? Was it something obvious once you opened up the camera? 

[bottletopburly]

Did you know you can auto focus with a canon lens using APT .

Edited December 4, 2020 by bottletopburly

[kaiserdave]

6 minutes ago, bottletopburly said:

Did you know you can auto focus with a lens using APT .

That I did not know! I haven't really dug into APTs toolset properly yet! I have a slower 70 - 300mm tamron lens I could use that with, however I'm currently using an old pentax 200mm f/4 so no auto focus on that. 

I'll have to look into that and see what I can do with the tamron lens 👍

[Alien 13]

On 01/12/2020 at 20:11, kaiserdave said:

Hi all,

firstly i have modded my 1000d  - the lpf2 filter removal (no replacement).

I also have a uhc clip filter fitted. With this setup i am able to achieve normal focus without problem - I can achieve focus with the APT focus tool and back out before the lens hits the "stop" so no poblem there ( i think).

However when I take some test shots the stars look pretty terrible - which is particularly evident when an imaging session is stacked and the image separated into RGB mages.

The red chanel is rubbish whilst the green and blue are not bad (roughly stretched images for examples)

this was taken with the modded 1000d and a super takumar 200mm f4 lens.

 

I guess my question is what can i do to deal with this issue? 

 

Thanks! 

Adam

This is always an issue when using a modded camera with a camera lens, the best solution is to replace the removed filter with one that has a slightly wider bandwidth..

Alan