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Deciphering light anomalies, Glow, Leak, Internal Pollution, etc.

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#1 mmalik

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Posted 30 March 2017 - 03:32 AM

I think we need to set the baseline by defining/explaining exactly what these terminologies mean in terms of light anomalies we see in stock and modified DSLRs/MILCs. Lately I have come across some light anomalies myself, and have seen enough confusion in terms of injudicious use of such terms lately.... Here is my take to get the discussion started:
 
 
Amplifier (Amp) Glow (Referred to as Amp. Glow): Simply put it is sensor circuits emitting light when operating. I need more clarity and definition around it? Is it a thermal anomaly or a separate category?
 
 
Thermal Glow: This would be where sensor unevenly heats up with source inside the sensor or components around the sensor. Not sure if this needs to be separate category or merged with amp glow?
 
 
Light Leak (Technical): I would like we start using terms like leak and pollution differently to avoid confusion; take for example, I consider leak a leak when light is slipping in through openings, crevices around the sensor once default milieu around sensor gets disturbed in a modification. I consider it more of workmanship related deficiencies or breaches where brackets, framings, moldings, etc. around the sensor let the light in as default filter/s are removed and/or replaced.
 
 
Internal Pollution (Internal Light Source): I would like we start calling all light that makes it to sensor either directly or through filters that let it in. Take for example an LED around area whose light is otherwise blocked when all default filters are in place; remove those filters in a mod and sensor starts getting internally polluted. In this case it is not a leak technically in framing/molding around the sensor, just that light now has a straight path to sensor with filters not being there and light source being there all the time.
 
Another example of internal pollution would be a modified Canon where an exposure is invoked from within the LiveView; in such a scenario LED would internally pollute the sensor by being ON and default filters not being there to block it. So technically it is not a "leak"; it is an internal source polluting its own sensor.
 
Another internal pollution example would be a reader module LED that may pollute a modified camera.
 

External Pollution (External Light Source): This would be any light whose source is outside the camera; for example light polluting through the eyepiece, lens cap, etc. I would like we don't refer to this as a leak to preserve the concept of a (technical) leak defined above, and rather call it external pollution.


Reflections (Internal or External Light Sources): I hesitate to put this as a separate category here but a category nonetheless; this again would the result of disturbing the default milieu around sensor in a mod for example. I consider this an outcome of one of the above... for example a internal light pollution source may also be a source of secondary reflections. Or a leak causing secondary reflections.

 
Sensor Artifacts: Some manufacturing processes may create discernable oddities; stay tuned for examples in coming posts.

 
Other: Please add if I have missed any…


Edited by mmalik, 31 March 2017 - 02:05 AM.

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#2 sharkmelley

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Posted 30 March 2017 - 06:32 PM

As I understand it, the effect known as "amp glow" has traditionally had a thermal cause but not necessarily on the sensor itself.  Sometimes the heat might come from a chip sitting on a circuit board in close proximity to the sensor or maybe heat generated by the battery pack.  Cooling the camera down will reduce this thermal amp glow.

 

This kind of glow will appear purple in the jpg because although the R,G & B pixels pick up equal quantities of thermally released electrons, the R&B channels are boosted to give daylight white balance.

 

The Sony A7S camera and many other cameras with Sony sensors have a glow on the edge of the sensor that is not thermally related.  There's an example here that I carefully investigated:  https://www.cloudyni...ting/?p=7594209  I have heard from more than one source that this is likely to be circuitry on the sensor itself that emits IR radiation which is subsequently captured by the sensor elements.  It is noticeable if you take night-time video using the Sony A7S at very high ISO (e.g. ISO 100000).  Most commenters and reviewers assume it to be heat related but my tests demonstrate this not to be the case.  I don't know if this kind of glow has a name to distinguish it from "traditional" amp glow.

 

Again this kind of glow will appear purple because R,G&B pick up more or less identical amounts but the R&B channels are boosted to give daylight white balance

 

Some cameras have optoelectronic components (typically infrared) involved in the shutter timing. Unmodified cameras cut out this IR but modifications that remove the IR filter or remove shielding can allow this IR to reach the sensor.  Here's an example, again with my Sony A7S:  https://www.dpreview...s/post/56215295

I would put this in the category "Internal light source".  Again it appears purple for the reasons above.

 

Mark


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#3 mmalik

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Posted 20 May 2017 - 07:41 PM

Amplifier (Amp) Glow examples: T5i (700D), 5DIII, 6D

 

 

I have an unmodified T5i (700D) that I used for normal daytime photography, and recently used it for some deep-sky and found that my camera has some amp glow...
 
post-49575-0-54273800-1463687928_thumb.j


Here is the 5D III glow from a 20 minute dark:

JZECTyW.jpg


I went and dug up some darks that I had from a different 6D body and it has the brightening / amp glow on the left side in the same place...

This is 10 min at 1600 at room temp (probably about 75F)
 
post-49575-0-27461800-1463847309.jpg


Edited by mmalik, 21 May 2017 - 03:42 AM.


#4 mmalik

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Posted 21 May 2017 - 03:32 AM

Amplifier (Amp) Glow example...

 

...By the way, amp glow looks like (upper/lower left corners and bottom edge):

DSC08529-2.jpg


Edited by mmalik, 21 May 2017 - 04:14 AM.


#5 mmalik

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Posted 21 May 2017 - 04:16 AM

Light Leak (Technical) example: a7S

...I have since re-modded the A7S by putting clear class in front of the sensor (so normal lenses can achieve infinity focus). This caused the artefact to move. Here it is with the camera's own daylight white balance:

post-216852-0-14560600-1437905215.jpg

Without any white balance applied, it looks like this:

post-216852-0-41670800-1437905227.jpg


post-216852-0-34066100-1438024938.jpg


I've now blackened the raw edges of my clear glass replacment in my Sony A7S...

After edge blackening:

post-216852-0-90829300-1438127165.jpg


Edited by mmalik, 21 May 2017 - 04:25 AM.


#6 mmalik

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Posted 21 May 2017 - 04:17 AM

Light Leak (Technical) example: a7S

 

post-234567-0-95284200-1437857715.jpg

post-205769-0-25193900-1437857928_thumb.


Edited by mmalik, 21 May 2017 - 04:32 AM.


#7 mmalik

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Posted 21 May 2017 - 04:33 AM

Anomaly position interpretation...

 

 

Note: Flip image vertically 'only' [no horizontal flipping] for anterior position interpreting (looking at front of the shutter as shown below)

 

Comparison of Greg and Mark's leaks and their locations...

post-205769-0-29251800-1438039087_thumb.

Attached Thumbnails

  • DSC08502.JPG
  • DSC08532.JPG

Edited by mmalik, 21 May 2017 - 06:24 PM.


#8 mmalik

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Posted 21 May 2017 - 04:45 AM

Internal Pollution (Internal Light Source) example: a7SII

 

 

 

Here's my first test shot with the full spectrum modified A7sii...

Please taka a 3min ISO2000 dark and share the in-camera JPG (i.e., after enabling in-camera JPG); I am curious if there are any lR leaks in a7SII after full-spectrum mod? Regards

 

41b90739574362391a5bb7e26f8bd563.jpg

 



#9 mmalik

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Posted 21 May 2017 - 05:45 PM

Internal Pollution (Internal Light Source) example: a7RII

 

 

Note: Full-spectrum mod sample

Attached Thumbnails

  • DSC00022-3Min.JPG

Edited by mmalik, 21 May 2017 - 06:05 PM.


#10 mmalik

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Posted 21 May 2017 - 06:07 PM

Internal Pollution (Internal Light Source) example: 6D

 

 

Note: Full-spectrum mod, LiveView execution sample

 

Attached Thumbnails

  • 6DAnomaly_FullSpectrum.jpg


#11 mmalik

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Posted 21 May 2017 - 06:10 PM

Internal Pollution (Internal Light Source) example: 6D

 

 

Note: 'Removed LPF-2' mod, LiveView execution samples

 

Attached Thumbnails

  • 6DAnomaly_RemoveLPF-2.jpg
  • 6DAnomaly_RemovedLPF-2.JPG
  • 1MikeMalik2332-3329-4362.jpg

Edited by mmalik, 21 May 2017 - 06:30 PM.


#12 mmalik

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Posted 21 May 2017 - 06:18 PM

Anomaly position interpretation...

 

 

Note: Flip image vertically as well as horizontally for posterior position interpreting (looking at the back of the shutter as shown below)

 

Attached Thumbnails

  • DSC08087w.JPG


#13 Alex McConahay

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Posted 22 May 2017 - 08:11 AM

Not commenting on the above, but responding to the original question about "deciphering," I would suggest the following to help isolate.

 

1. Rotate the camera in the tube and check if the  anomaly stays in the same place on the sensor. If so, you know it has something to do with the camera itself--either electronically or mechanically (how it is mounted).

 

2. If the anomaly moves when the camera is rotated, rotate the various other elements in the imaging train. When you find one that gets the anomaly to appear in a different place, you have your culprit.

 

3. Cover the whole imaging rig in an opaque cloth. Let no light in anywhere, and take a picture. If the anomaly disappears, you have light leak in the system (as opposed to an electronics issue).

 

4. If your opaque cloth over the whole rig eliminates a leak, progressively place the cloth over different parts of the rig (Around the OAG, for instance, but everything else in the open) until it disappears.

 

This kind of experimentation helps.

 

Remember that your sensor can record "heat" as well as "light."  So, you could have something in your imaging train giving off an infrared heat signal that later shows on your sensor. You cannot see it visually. But it is there.

 

Alex


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#14 t_image

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Posted 22 May 2017 - 05:33 PM

Great point Alex,

except this statement needs to be more precisely qualified:

Remember that your sensor can record "heat" as well as "light." So, you could have something in your imaging train giving off an infrared heat signal that later shows on your sensor. You cannot see it visually. But it is there.

It is improper to use the word "heat" when referring to near-Infrared light (700nm-1000mm wavelength, which usually start to become invisible to humans) that CMOS and CCD sensors without a "NIR" block filter covering it can detect.

This just-past-red light is nowhere close to long-wave thermal infrared radiation given off by "heat" sources that ONLY thermal cameras like FLIR cameras can detect with special types of sensors....Or temperture guns that also have detectors very different from optical sensors...

Otherwise dew shields would be an issue, but since they emit long-wave thermal (heat) and not just-past-red light, CMOS/CCD camera sensors CANNOT see this "heat" part of the spectrum of electromagnetic radiation....

 

The NIR light leaks inside a camera are due to intentional photodiode/phototransistor coupled pairs (like an invisible electric eye) that are utilized for purposes like accurately timing shutter activation, etc..

for example:

http://photographyof...s-to-spoil.html

..I seen some mention camera lenses may contain some?

The EVF eye proximity sensor on some cameras also contains some,

and the (N)IR remote communicator on some cameras is also a source.

Like tv remotes, normal cameras aren't supposed to see this light.

Most camera users don't take long exposures in the dark, nor do many modify their cameras to see near-infrared light.

Therefore camera manufacturers don't worry much about this "like leak" that doesn't apply to the majority of their customers......


Edited by t_image, 22 May 2017 - 05:37 PM.


#15 Alex McConahay

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Posted 22 May 2017 - 06:34 PM

I put "heat" and "light" in, as the President says "quotes."

 

But you still got what I meant!

 

Alex



#16 mmalik

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Posted 23 May 2017 - 12:00 AM

Thanks Alex/t_image.
 
Sensor Artifact example: a7S

  

What is the weird change is brightness/vertical banding happening about halfway across your darks?


The same 20min dark as it appears in PixInsight's defatul STF stretch (no debayering). Regards

post-205769-0-73675200-1438062668_thumb.


Allan, while the split may be apparent more at higher temps than lower..., a better explanation below, courtesy of ccs_hello.... Regards


Note: For all practical purposes this is s NON-issue; effect is not seen in lights and darks showing this manifestation is more of an academic discussion.

It seems to be related to the known artifacts over full-frame sized image sensor manufacturing process.

FF sized sensor being large, has known to be exceeding the Nikon photo-lithography's lens' maximum "sweetspot" area coverage in the light-mask stepper.
(Yes, SONY fab uses Nikon lens based photo-litho stepper. Canon fab uses Canon lenses.)
This causes a full frame sized image sensor being exposed in two steps (one left and one right.) It is known as stitching.
It is very hard to maintain sub-micron precision when a mechanical component (microstepping stage) is involved.
Obviously there will be chip that will be more obvious than other due to manufacturing tolerance.
See this post on the wafer picture: http://www.cloudynig...m/#entry6909037


post-205769-0-83117400-1438029516_thumb.
 
post-205769-0-91660800-1438029520_thumb.

Edited by mmalik, 23 May 2017 - 12:09 AM.


#17 tsk1979

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Posted 16 April 2019 - 05:41 PM

Thanks for this amazing thread.

I am planning to go full spectrum on A7SII

 

From the posts, to get light leak 30min exposure in ISO12800 was needed.

 

For regular astro exposures at high ISO even with worlds darkest skies you can never hit this time. It will usually be 30S at ISO 20,000-40,000 max

 

Do we have light leaks for that too?

Any A7SII users care to comment?



#18 mmalik

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Posted 17 April 2019 - 08:01 AM

From the posts, to get light leak 30min exposure in ISO12800 was needed.

Where are you getting this? a7SII full spectrum WILL have internal light pollution even at 30sec. Are you confusing sec with min? Regards



#19 tsk1979

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Posted 18 April 2019 - 02:42 AM

Where are you getting this? a7SII full spectrum WILL have internal light pollution even at 30sec. Are you confusing sec with min? Regards

You are right. I contacted Kolari Vision

They sent me this sample 30S ISO 8000

 

My question to you is, if I am using Full spectrum with Light pollution filter, will it still be a problem, or only with narrowband Ha Alpha kind of filters? Is A7S better in this regard?

 

i-jx5bv27-XL.jpg


Edited by tsk1979, 18 April 2019 - 02:42 AM.


#20 mmalik

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Posted 18 April 2019 - 03:14 AM

Here is the sum total; all 2nd generation onward alphas have heavy internal light pollution sources. Full spectrum is out of the question; you'll need to put something on the sensor. Baader mod may be able to get you by with really short exposures (10-20 sec) at lower ISOs, and if mod was done right.

 

 

All first generation alphas are a good bet; best of all is a7S (...the first generation that is). Regards


Edited by mmalik, 18 April 2019 - 03:14 AM.


#21 tsk1979

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Posted 19 April 2019 - 11:17 AM

Here is the sum total; all 2nd generation onward alphas have heavy internal light pollution sources. Full spectrum is out of the question; you'll need to put something on the sensor. Baader mod may be able to get you by with really short exposures (10-20 sec) at lower ISOs, and if mod was done right.

 

 

All first generation alphas are a good bet; best of all is a7S (...the first generation that is). Regards

Thanks! I will got for first generation A7S.

I see you are a vendor. Can you private message me your website?



#22 mmalik

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Posted 21 April 2019 - 02:55 AM

a7S mod info here...; please PM me for mod needs. Regards



#23 tsk1979

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Posted 31 July 2019 - 04:33 PM

I was looking at A7RII. It has internal LED which causes the leak. Has anybody located where is it? What happens if you disable this led (paint/wire cut).

 

Has anybody tried it?



#24 mmalik

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Posted 01 August 2019 - 02:50 AM

Read here....

 

 

I intend to do much deeper research into the matter if upcoming a7S III were to be internally polluted? Read more here.... Regards


Edited by mmalik, 01 August 2019 - 02:51 AM.


#25 t_image

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Posted 02 August 2019 - 12:58 AM

Read here....

 

 

I intend to do much deeper research into the matter if upcoming a7S III were to be internally polluted? Read more here.... Regards

????Your immediate post after the post you link to is incorrect.

Old times were simple; first gen neither had IR source nor the IBIS.

If you remember more clearly, the issue was seen in 2015 with the Sony a7s, first gen. with IR source. You were there.

https://www.cloudyni...lpha/?p=6699037


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