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removing the mirror in a canon DSLR

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#1 pfile

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Posted 11 March 2013 - 01:56 AM

from time to time i've noticed DSLR images here and there that seem to have a strong horizontal gradient only near the bottom (or top) of the long edge of the frame. i've often wondered what causes this.

it seems perhaps that with certain fast optics, due to the steepness of the light cone, the mirror is casting a shadow on the sensor.

check out this link - this guy has removed the mirror from his DSLR. the first flat shown on the page shows the gradient i'm talking about. certainly not for the faint of heart but pretty interesting.

http://www.markshell...50mirrorless...

#2 mmalik

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Posted 11 March 2013 - 03:34 AM

I wonder if any of the modifiers (Brent/Hap/Gary, etc.) would do this or have done this?


I presume there would be better/simpler way to accomplish this with open camera during typical sensor mod? Thx

#3 bilgebay

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Posted 11 March 2013 - 04:22 AM

This was one of my dreams for a long time. I was worried that there would be some sort of sensor to check if the mirror was in place before letting the shutter go off. It appears there is not.

Rob, thank you for sharing this link.

Clear skies.

#4 JPGriffin

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Posted 11 March 2013 - 08:10 AM

Thanks for posting this information. I was wondering why I kept getting such obvious vignetting on the bottom of my pictures using relatively fast optics (f/2.8 300mm lens and f/3 OS Veloce RH200 astrograph).

#5 fishonkevin

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Posted 11 March 2013 - 08:21 AM

I'm excited about this.

#6 Rankinstudio

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Posted 11 March 2013 - 09:35 AM

That makes perfect sense. I think I am going to try this.

#7 pfile

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Posted 11 March 2013 - 10:15 AM

I wonder if any of the modifiers (Brent/Hap/Gary, etc.) would do this or have done this?


I presume there would be better/simpler way to accomplish this with open camera during typical sensor mod? Thx


well, the link was originally posted on DSLRModifications after gary gave some advice to the guy who removed the mirror, so at least gary H. knows about this. most likely the other modifiers are on that list.

#8 Rankinstudio

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Posted 11 March 2013 - 10:30 AM

I would like to hear if the camera works right with BackyardEOS before I do this.

#9 Rankinstudio

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Posted 11 March 2013 - 06:23 PM

Easy mod. I'll post before and after flats when I shoot some tonight. That hot screwdriver went through those hinges like they were not even there. Took 5 mins.

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#10 piaras

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Posted 11 March 2013 - 06:31 PM

I have always seen this on my 350D. This mod is only viable with a body that has Liveview, just remember thats 450 and newer.
Pierre

#11 guyroch

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Posted 11 March 2013 - 06:32 PM

Genius idea, permanent mirror lock!

I have a few spare DSLRs... that usually means I'll try it on one of them :)

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#12 zerro1

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Posted 11 March 2013 - 06:41 PM

Genius idea, permanent mirror lock!

I have a few spare DSLRs... that usually means I'll try it on one of them :)

Guylain



I think this is what I was seeing that I emailed you about. It's a pretty profound shading in some instances. Don't have anything on hand to show but if I locate an image I'll post it.

#13 nofxrx

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Posted 11 March 2013 - 08:26 PM

I wonder if any of the modifiers (Brent/Hap/Gary, etc.) would do this or have done this?


I presume there would be better/simpler way to accomplish this with open camera during typical sensor mod? Thx


Yes, I for one would definitely offer this on "AP dedicated" DSLRs! ;)
And re: being easier/simple while performing the filter mod...the filter mod only really requires removal of the rear parts of the camera..we do not touch the front(on most DSLRs) for filter mods.
But, it could be done at the same time.
And could be cheap.


And no, there are ZERO sensors on/in the camera that have anything to do with the position of the mirror...so should be simple and cheap to add this to the mod services. (now, I say this, but I have not tested to see if any errors would come up on the AF system, metering system, etc, which is all used by the mirror...in theory, I see no side effects of the mirror being removed, OTHER THAN losing the features of the camera that come with the mirror..)


What I find weird however, is that this issue is not common on ALL cameras, or even a set model. it seems to really vary between camera model, scope, FF/FR(if applicable), filters, etc, etc..
So, I would STRONGLY advise people to test their cameras for this issue BEFORE sending out for a mod to see if you even need it.
Since this mod would be 'sorta' permanent, I would not recommend it IF you ever plan to use the camera for daytime, or even sell it in the future.
People may not want a camera that has no: viewfinder, AF system, metering, etc...which are the reasons we buy DSLRs in the first place(besides for AP use lol) ;)

Cheers!

#14 Rankinstudio

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Posted 11 March 2013 - 10:34 PM

I have noticed the light meter doesn't work now. I can live without it. Everything else works fine.

Before (Definitely had the problem)

Both Shot on my 8" F3.9 with the Paracorr II

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#15 Rankinstudio

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Posted 11 March 2013 - 10:35 PM

After:

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#16 pfile

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Posted 11 March 2013 - 11:08 PM

amazing. that really confirms it. except for camera lenses i don't have any optics that fast so i'll probably leave my 50D alone. i figure that canon bodies probably already work properly with canon lenses.

congrats on the mod!

#17 Rankinstudio

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Posted 11 March 2013 - 11:25 PM

amazing. that really confirms it. except for camera lenses i don't have any optics that fast so i'll probably leave my 50D alone. i figure that canon bodies probably already work properly with canon lenses.

congrats on the mod!


I actually noticed this over a week ago when I had first light with my new scope, the F3.9. I figured it had to be the mirror blocking the light path but wasn't sure what to do about it. This thread* came just in time! I'm set now.

:)

#18 guyroch

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Posted 11 March 2013 - 11:43 PM

amazing. that really confirms it. except for camera lenses i don't have any optics that fast so i'll probably leave my 50D alone. i figure that canon bodies probably already work properly with canon lenses.

congrats on the mod!


I actually noticed this over a week ago when I had first light with my new scope, the F3.9. I figured it had to be the mirror blocking the light path but wasn't sure what to do about it. This threat came just in time! I'm set now.

:)


WooHoo :bow:

#19 LeCarl

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Posted 12 March 2013 - 08:03 PM

100% agree, I done this to my 2 T3i since last year, really better, and dedicated astro cam is a dedicated astrocam...

I used force instead of heathen screwdriver, but this is a good idea

(I removed all pentaprism part too, this add weight and not needed at all now...)

#20 Daniel Oliva

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Posted 07 April 2014 - 12:38 AM

I earned an EOS 20D from a friend and decided to remove the IR filter. I have no Canon lenses, so could not test the camera before the mod. I only checked the sensor and mechanism taking some pictures without a lens.
After the procedure, I attached it to my Orion 6" f/5 for test and noticed a dark shade on the bottom of the pictures.
The first thing I tought was I had made any mistake during the mod, but later I detected the mirror was not completely lifted. As this is an old and very used camera, possibly the mechanism was already faulty.
Reading this post, something came to my mind: why not only stick the mirror lifted with a black tape? Isn't it enough? In my case it solved the issue.

#21 Hilmi

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Posted 07 April 2014 - 02:17 AM

I have a very easy but delicate procedure for removing the mirror, anybody should be able follow this process if they have access to the correct tools.

First of all you will need the following items:

-Anti-static strap
-set of precision screw drivers
-Table top mounted magnifying glass
-A hard impact resistant, fire proof work surface
-gas torch
-Hammer
-Blendtech blennder




Honestly, some of the things we do to our DSLRs to make them Astro-friendly are just plain scary. The way I see it, soon as somebody comes up with a half respectable dedicated Astro-camera within $800 range, one that also accepts camera lenses out of the box, the appeal of all this butchering we perform on DSLRs will drastically go down.

The only reason I would see to continue these practices is if you already have a camera body not getting utilized for any purpose.

The way I see it, I am surprised there are no dedicated Astrocameras on the market that can compete with a 450D in picture quality at a price of around $800. It doesnt need regulated cooling, it doesnt need the latest and greatest sensors, just a large APC style sensor, unregulated cooling, no shutter, less backfocus and optimized for continuous fast shooting to assist in focusing. No need for high res LCD, just a low res screen for control and all excess hardware, buttons and switches of no use to Astro-photography removed.

#22 tazer

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Posted 07 April 2014 - 08:39 AM

> The way I see it, soon as somebody comes up with a half respectable dedicated Astro-camera within $800 range, one that also accepts camera lenses out of the box, the appeal of all this butchering we perform on DSLRs will drastically go down.

Some combination of Canon & Sony NEX would do. Small, light, mirrorless, APS-C, great live view, fully controllable via USB tether including live view export, etc.

#23 end

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Posted 07 April 2014 - 09:02 AM

I clearly see this vignetting when doing hyperstar imaging at ~f/2. On the other hand, a good flat eliminates the problem. Obviously I'm still losing a bit of sensitivity in the periphery, but I can live with that. My guess would be that people with full frame sensors have even more difficulty with this shadow than those of us with APS-C sensors.

The other issue that this eliminates is the annoyance of having to do "mirror up" mode to avoid vibrations. Not a big deal, but it would save me 5 seconds on every exposure.

#24 calypsob

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Posted 08 April 2014 - 08:15 PM

I only have this problem with camera lenses, F1.4-F5 and I get the gradient.






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