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Old 20-06-2014, 06:09 PM
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traveller (Bo)
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DSLR full spectrum pros and cons

Hi all, I have been happily using a Baader modified canon 40d.
Now I am tempted to get the canon 1100d and modify that as well.
I am tempted to do a full spectrum mod for the 1100d, either with a replacement clear glass or just leave the sensor exposed.
Obviously if I replace with a clear glass I preserve the refractive index and therefore the auto focus function, the other advantage being keeping the sensor clean.
What are the other advantages are there?
A naked sensor is more vulnerable but also cheaper, but misses out on the auto focus.
Are there anything else I should be aware of?
What brands clear glass replacement filters would members recommend?
Cheers,
Bo
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Old 21-06-2014, 12:24 AM
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Full spectrum mod doesn't actually leave the sensor exposed as you might expect, the sensor still has a protective clear glass cemented directly to it. In the 1100D this has proved virtually impossible to remove. Earlier bodies can be removed with little or some effort. You will not need to remove this glass unless you wish to attempt a mono conversion too.
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Old 21-06-2014, 07:41 AM
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Merlin66 (Ken)
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Bo,
I have and use a FULL full spectrum modded 1000D camera. Both filters removed.
There's no real issues with a "bare" chip..
I use a Clear Astronomik clip-in filter to maintain focus with the standard EF lenses. It also keeps the dust out!
Great for spectroscopy.....
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Old 21-06-2014, 01:58 PM
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traveller (Bo)
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Thanks ken and Simon,
I intend to use the 1100d as a dedicated astro cam, so was only worried about the exposed sensor. Didn't know about the glass protector over the sensor, I take it is a full bypass glass and not filtering out any IR or UV.
Judging by your comments, I just need to remove both the clear IR/UV bypass filters and the blue filter and that should do the trick.
Bo
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Old 21-06-2014, 02:53 PM
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MrB (Simon)
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Quote:
Originally Posted by traveller View Post
I take it is a full bypass glass and not filtering out any IR or UV.
That is correct.
There is some debate about potential star bloat from refractive optics and UV/IR, so you may want to try with the UV/IR filter left in and removed and then choose which works best for you

Edit: Just re-read and realised my comment could be misinterpreted....
"from refractive optics and UV/IR"
By this I meant that some optics(including reflectors with corrective optics) may not be well corrected at the UV and IR ends of the spectrum and may cause bloat without the filter. Not that bloat was caused by the UV/IR filter

Last edited by MrB; 21-06-2014 at 04:33 PM.
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  #6  
Old 21-06-2014, 03:49 PM
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rcheshire (Rowland)
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Like Ken, both filters removed, plus an Astronomik clip-in UV/IR filter for use with camera lenses - maintains focus - 1000D.
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Old 23-06-2014, 09:42 AM
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rustigsmed (Russell)
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i have clear glass modified 600d, definitely degraded captures of the planets and introduced star bloat (powermate or coma corrector induced), but mostly corrected with a clip in eos UV/IR filter.
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Old 06-09-2015, 02:22 PM
amitk75 (Amit)
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Canon 1100D

Quote:
Originally Posted by MrB View Post
Full spectrum mod doesn't actually leave the sensor exposed as you might expect, the sensor still has a protective clear glass cemented directly to it. In the 1100D this has proved virtually impossible to remove. Earlier bodies can be removed with little or some effort. You will not need to remove this glass unless you wish to attempt a mono conversion too.
I have some confusion: I modified my EOS 1100D yesterday. I just removed the filter assembly which was screwed in on top of the sensor (i.e. I didn't use knife etc to remove anything stuck). Even I have doubts on the clear glass stuck on the sensor. If it's not blocking anything, am I safe to assume that I have full-spectrum modification? One doubt is that most of the posts say that auto-focus wont work without a replacement filter/glass, but its working fine in my camera.
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Old 07-09-2015, 08:23 AM
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Amit,
It sounds like you have only removed the front filter element, there is a second colour correction filter mounted on the chip.
For the full spectrum mod, this also needs to be removed.
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Old 07-09-2015, 08:50 AM
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The blue cast filter is the one to remove for full spectrum mod, you do not have to remove the clear anti-alysing filter. Suggest you have a look at Gary Honis' excellent online tutorial on how to mod your camera. Gary's instructions cover many of the popular Canons and all of the filter setups are the same.
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  #11  
Old 07-09-2015, 09:06 AM
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Glen,
To achieve a FULL full spectrum mod both the AA filter (which blocks the UV/IR) and the colour correction filter need to be removed
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Old 07-09-2015, 10:00 AM
glend (Glen)
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Quote:
Originally Posted by Merlin66 View Post
Glen,
To achieve a FULL full spectrum mod both the AA filter (which blocks the UV/IR) and the colour correction filter need to be removed
Merlin, that is not true according to Gary Honis' information. The AA filter (also known as Low Pass 1) is clear and can be left as protection for the sensor and in terms of the spectrum has negligible effect. The AA filter is not a UV/IR block, that function is performed by the IR Cut filter (the blue cast one). In fact Gary recommends that you install a Baader IR Cut which has the cut point down below the Ha frequency (this can be done with a clip-in or with a 2" screw in on the T-adaptor - which is the one I use. Details on this page undre Filter imaging chip disassembly.



http://dslrmodifications.com/rebelmod450d4.html
Attached Thumbnails
Click for full-size image (xsmod028.jpg)
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Last edited by glend; 07-09-2015 at 10:12 AM.
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  #13  
Old 07-09-2015, 11:30 AM
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Quote:
Originally Posted by Merlin66 View Post
To achieve a FULL full spectrum mod both the AA filter (which blocks the UV/IR) and the colour correction filter need to be removed
Hope this is not too much of a thread hijack but I was wondering if removing the AA filter is a worthwhile mod in itself?
Would you get any worthwhile increase in resolution on astro targets?
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Old 07-09-2015, 12:18 PM
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Quote:
Originally Posted by Retrograde View Post
Hope this is not too much of a thread hijack but I was wondering if removing the AA filter is a worthwhile mod in itself?
Would you get any worthwhile increase in resolution on astro targets?
IMHO you will lose the sensor cleaning protection that the coating on the low pass1 provides. Normally the auto piezo vibration is tuned off when imaging but you can manually do it from the menu. The surfac coating is suppose to repell dust. If you have nothing there then you risk getting the sensor face dirty at the very least.
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  #15  
Old 07-09-2015, 01:19 PM
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Merlin66 (Ken)
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Glen, et al,
I 've previously posted detailed spectral data on both the filters used in the Canon cameras.
I can assure you that the front AA filter does indeedv act as a UV/IR filter, no matter what Honis says.
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Old 07-09-2015, 01:43 PM
amitk75 (Amit)
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I am confused

I have attached picture of the filter assembly I took out.

If the glass I left inside is indeed a UV/IR filter, any idea which wavelengths will it block? Is there any test I can perform to measure what I have achieved and what I am missing?

I was checking the IR sensitivity earlier just to see if I have really unblocked IR, I pointed the camera to a TV remote with and without filter and it appears like a flash without the filter.

I need to weigh now if it is worth opening the camera again to take that glass out or no.
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  #17  
Old 07-09-2015, 01:52 PM
glend (Glen)
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Quote:
Originally Posted by Merlin66 View Post
Glen, et al,
I 've previously posted detailed spectral data on both the filters used in the Canon cameras.
I can assure you that the front AA filter does indeedv act as a UV/IR filter, no matter what Honis says.
Perhaps reposting the link to that your spectral data would be useful. Rudy Kokich tested one of Gary Honis' full spectrum modded Canons and compared to stock early this year using the GRISM spectroscope and published the spectral performance here:

http://dslrmodifications.com/DSLRcomparison.html

just scroll down to spectral chart on that page.
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  #18  
Old 07-09-2015, 02:32 PM
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Just thought I'd chime in here. I'm about to mod a 450D for astronomy only duties and intended to remove all the filters (aa and uvir hot mirror.) I do however intend to image primarily with my 300/2.8 (nikon mount with adapter focused via home made ascom stepper focuser.) lens. Will I not be able to reach focus with this setup? I will also be imaging with my 5" newt a bit..

My other intention was to get an astronomik clip in ha filter for imaging in the suburbs.


Anyone got any tips or advice.
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  #19  
Old 07-09-2015, 03:50 PM
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I can't seem to link to a previous post with the iPad......
You will need a clear clip in filter to maintain focus with standard lenses.
Glen see the post on uv -ir imaging
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Old 07-09-2015, 04:58 PM
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To maintain af accuracy or to retain the ability yo reach focus at infinity?
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