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Modified Camera Lens Ghosting

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#1 DavidInTheSky

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Posted 10 October 2019 - 07:33 PM

I recently had my Canon T5 modified to Full Spectrum (all filters removed) and I've been using it with my telescopes without issues.  However, when using my 18-55mm lens with high ISO, I get a weird "ghosting" in the photos. It's also there when doing Darks (dust cap on) and it's worst at 18mm.  But, when I remove the lens and put the camera body cap on, I don't get the ghosting in the Darks. I even blocked the eyepiece of the camera, thinking lights were getting through, but no change.  I also put the camera in total darkness inside a hard case, but nothing changed.

 

I thought maybe the camera's red LED may be leaking inside the camera and reflecting on the lens, but that seems far fetch.

 

Any thoughts?  I was thinking of getting a 50mm f/1.8 lens, but I'm wondering if I'll get the same issue. 

 

18mm.JPG

55mm.JPG

noLens.JPG

 

Orion at 55mm, f/5.6, ISO1600 (40x30sec + 5 Darks). The ghosting is clearly visible over Bernard's Loop:

Orion.jpg
 



#2 OldManSky

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Posted 10 October 2019 - 07:50 PM

I used to think the outside red LED leaking light onto the sensor was far-fetched, too.

Except it's not:

 

https://www.cloudyni...roubleshooting/



#3 DavidInTheSky

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Posted 10 October 2019 - 08:59 PM

I used to think the outside red LED leaking light onto the sensor was far-fetched, too.

Except it's not:

 

https://www.cloudyni...roubleshooting/

Interesting, but after trying BackyardEOS with no red light on, I still get the same issue.  I don't know if there's another light inside, for when a lens is connected.  Thanks for the suggestion.



#4 nofxrx

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Posted 11 October 2019 - 09:11 AM

David are you using LiveView at all? Or is the rear screen displaying a counter/timer while the shutter is open?
Either of these can cause this issue as well.
You have you disable the screen with the DISP button and in the menu there is an option to "use last setting" for the screen between sessions so when you turn the screen off and then go to use the camera the next day it doesn't just come back on by itself.

Good luck

#5 nofxrx

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Posted 11 October 2019 - 09:16 AM

If that is not the issue then the lens must be the issue. Do you have any other lenses you could test this theory? I have never seen canon use this kind of tech before but then again wouldn't surprise me. Which model 18-55 is it? There have been many versions. Did it come with your T5?

#6 DavidInTheSky

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Posted 11 October 2019 - 09:06 PM

If that is not the issue then the lens must be the issue. Do you have any other lenses you could test this theory? I have never seen canon use this kind of tech before but then again wouldn't surprise me. Which model 18-55 is it? There have been many versions. Did it come with your T5?

Yes, the LiveView, Display and Timer light are off. When using BackyardEOS, all of these are turned off automatically and I get no lights that I can see from the outside. The lens is the default lens that came with my Canon and I wish I had another lens for testing.  The light seems to be coming from the top, when looking at the 18mm Dark.    I think I will call the shop where I got the job done and ask.  I appreciate the help!



#7 KLWalsh

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Posted 12 October 2019 - 09:21 AM

Could it be ‘amp glow’?

#8 nofxrx

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Posted 12 October 2019 - 03:13 PM

Since it doesn't happen with a scope attached it must be the lens.

Very interesting..

I think the only way to know would be to test another lens. 

The Canon 50mm 1.8 can be had for less than $100 on the used market. 

It is a decent lens so you can't really lose money with it. 

Not sure what the shop could do for this issue but I suppose it doesn't hurt to ask. 

Makes me want to test my kit lenses for this issue..

 

Good luck



#9 sharkmelley

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Posted 12 October 2019 - 05:49 PM

Since it doesn't happen with a scope attached it must be the lens.

It's worth pointing out that it doesn't necessarily mean the lens is the source of the light (or IR).  Maybe the lens rear element reflects an in-camera light (or IR) source back onto the sensor, which doesn't happen when using a body cap because it is non reflective.

 

Mark


Edited by sharkmelley, 12 October 2019 - 05:59 PM.

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#10 KLWalsh

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Posted 12 October 2019 - 08:42 PM

It's worth pointing out that it doesn't necessarily mean the lens is the source of the light (or IR). Maybe the lens rear element reflects an in-camera light (or IR) source back onto the sensor, which doesn't happen when using a body cap because it is non reflective.

Mark

This could be tested by removing the lens and laying the camera down on a mirror in a dark room; then laying the camera down against black cloth in a dark room. Repeat the exposure sequences and see if the glow shows up. If it shows up only when placed against the mirror, it’s a reflection (of amp glow?) off the mirror.
If it doesn’t show up at all, or if it shows up in both trials, well that’s a puzzler.

Edit:
Another thought - Instead of ‘amp glow’ it might be a reflection of the viewfinder data off the rear lens surface. Perhaps at the high ISOs you’re using the viewfinder data is just bright enough to appears as a faint diffuse reflected glow off that lens.
If so, maybe running the camera using Backyard EOS from a laptop would disable the viewfinder screen and thus eliminate the viewfinder glow.

Edited by KLWalsh, 12 October 2019 - 09:02 PM.

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#11 nofxrx

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Posted 12 October 2019 - 10:29 PM

The view finder *should* be blocked by the mirror when the shutter is open (and mirror up), and AFAIK there is nothing "on" in the viewfinder during bulb exposure... it *should* go black.

This definitely requires a more in depth test to verify source or at the very least determine whether it is internal to the camera or not (lens).
Obviously I think you have the control aspect down im just trying to help spawn ideas and TS.
What I would do:
Verify whether it does this with the first image after power up or if it is after a period of time or after multiple exposures (heats up).
Happens on all exposures? (With that lens attached)
Is the pattern captured consistent when settings remain the same and cameras orientation stays identical? Does it change is orientation changes?

Are you absolutely positive it does not happen with a scope attached (or body cap)? Ever? Try max ISO possible and several minutes of exposure just to humor us and see if it's there but at a much lower level like Mark suggested it being a reflection. Given enough time you should see it start to glow if it's from the sensor (amp). It should not be amp glow but could be a defective component heating up and causing glow, doesn't have to mean typical amp glow.

Im assuming this is your only camera capable of long exposures? If possible, try setting up another camera to take a picture of this camera during bulb exposure without a lens cap or lens on it. This would require a camera sensitive to IR so a long shot I know.

Last thing I can offer is I would be willing to help out in some way. Either take a look at it for you or offer a lens or two for testing.
Where abouts are you located? Maybe someone in the local area could offer a lens for testing or another camera?

Shoot me a PM if you want to discuss offline. I will follow this thread with interest either way.

Good luck!
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