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Hi Eric - given the questioning I've put to you on modded Canon's, you would imagine me as the last person to be responding to your post!?!
However, your question has caused more re-reading of the requirements of Astro-imaging with DSLR's so I thought, in the absence (yet) of any other responses to your questions, I'd articulate my thoughts - if only for my own erudition!
As I understand it, modifying these units with UV/IR filters allows for the passing of wider bandwidths of both the infra red and ultra violet light spectrums - clearly demonstrated in the graphs you provide. This complements the sensitivity of the camera's chip's ability to register and record these particular colours' (ie, more of their bandwidths/wavelengths'.)
This is demonstrated by the blue graphics in your first graph - this being what the "normal" unmodded Canon passes of the infra red spectrum - less than the bandwidth of the fuller bandwidth pass of the filter used in a modded camera.
Although the graphs you show do not reveal the ultra violet response, from what is seen of them and extrapolating from the infra red graphs it is reasonable to presume it performs a similar job.
Thus, taking a normal day shot is going to reveal more of the infra red or ultra violet without any external moddifying filters - as your pictures 3 and 5 would seem to attest.
Have no idea what your Hutech LPS2 filter is, but from the logic I am educing it would seem that it is of a similar type to the original Canon internal filter that was removed during modifications.
This would cut the extended bandwidth pass of the modified internal filter and revert it to the response (or closely similar) of that of an unmodified camera - as picture 4 and 6 seem to attest.
I hope you won't take offense at my presumptions, but logically the above seems to hold water!
Cheers, Darryl.
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