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What is Going on With my Sensor?

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#1 DanielJStein

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Posted 27 May 2020 - 07:27 PM

This some freaky stuff here. I have owned and used a H-alpha modified Nikon Z6 by Lifepixel for over a year now. I have never had a problem with the images this camera produces.

 

My girlfriend and I just came back from a four night extravaganza of shooting the Milky Way. 4 nights in a row of clear skies in upstate NY— crazy, right! Keep in mind she has the exact same camera, lenses, tracker, and adapter as I do. The only difference is hers is stock, not modified at all. What is happening in my camera is not happening with hers.

 

It seems several of my images contain this awful reddish gradient depending on where/what I am shooting. This is the first time I have ever seen such an anomaly, and I am completely baffled. I fear I am losing valuable data and many of my shots from our adventure are completely ruined…

 

I cannot seem to pinpoint the problem, but given the example shots I feel like it may be the Canon 24-70 2.8L II I am using in conjunction with a Fringer Canon EF to Nikon Z mount adapter. I have never seen this happen with any of the Sigma ART primes with the Nikon FTZ adapter I have used in the past, and I have yet to find it an issue with the Canon 70-200 f/2.8L II coupled with the Fringer adapter. But as you will later see the 24-70 is perfectly capable of producing no gradient shots when there is no light pollution (I am assuming this is a factor).

 

What I do know is that it is not amp glow. The gradient changes when I zoom, it is not in the same spot on the sensor. It is also not an internal sensor light polluter like on the Sony bodies, the Z6 sensor does not have such a thing. I can also add in that while I have tested for a light leak on the Fringer adapter, it does not appear to be the culprit given I did the same test for the Nikon FTZ and the results were the same.

 

The gradient does not show up in dark frames if taken in a dark area. If taken in a more well-lit area, there are some light leaks, but I believe it is just coming from the lens cap of the 24-70.

 

I am stumped, so hopefully someone on here can help me out! Let’s get to some samples:

 

Figure 1: this is the first ever shot I noticed the gradient in. It happened shortly after I swapped a memory card. I thought it was the card so I replaced it with another one and recomposed. It seemed to have fixed the problem for the night and I thought I had found the culprit. The next night of shooting I found out I was wrong… Note that the settins are different for each shot but regardless the gradient isn’t visible in the shot post card swap. What happened?

 

xdxAtUT.png

 

Figure 2: this was the last night of the extravaganza. I was preparing to shoot a pano. I had my UV/IR cut filter on for the shot on the right. The shot on the left it was off. Settings were exactly the same. Obviously, the shot with the filter on is well more controlled, but the gradient is STILL there!! There is even a friggen lens flare in BOTH of these shots albeit more subtle in the shot with the filter on. What in the world?????

 

yQ4Kt87.png

 

Figure 3: 2 shots. Same exact settings and focal length, different composition (panned only). Gradient is in the exact same location.

 

fcArW53.png

 

Figure 4: 2 shots, same settings, slightly different composition, same focal length BUT different lens. On left is the Canon 70-200 f/2.8L II, on right is the 24-70 f/2.8L II. Only the 24-70 has the gradient.

 

LdVXXk0.png

 

Figure 5: a shot that I took at another location with the 24-70 and no immediate light pollution in the foreground, no gradient!

 

b86KrUX.jpg

 

Figure 6: another shot with the 24-70 zoomed to 35mm taken from a different location. You can see the gradient in the bottom right.

 

uT5SQ4z.jpg

 

So, what is going on here? Any help is much appreciated. Hopefully we can get to the bottom of this.


Edited by DanielJStein, 28 May 2020 - 10:18 AM.


#2 sharkmelley

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Posted 28 May 2020 - 01:55 AM

Was the moon shining by any chance?

 

They all look like internal reflections to me. It's very obvious in Figure 2 where the lens flare appears to be caused by a bright object, possibly just out of shot.  It's causing internal reflections within the lens and/or within the camera just like when taking a daylight shot towards the sun.

 

Do you know exactly what was done during the modification?  Was a replacement filter put in the camera?  In any case, it's entirely possible the end result has created an additional set of internal reflections that don't exist in a stock camera.

 

Do you see the same effects in the daytime e.g. pointing in the general direction of the sun with the sun just inside or outside the field of view?  It is much easier to "debug" a problem during the day.

 

Mark


Edited by sharkmelley, 28 May 2020 - 05:41 AM.


#3 james7ca

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Posted 28 May 2020 - 06:19 AM

I don't know. With the clouds, the vignetting, the many external light sources, the differences in the exposures and f-stops, and the JPEG compression I'm not sure what I'm seeing. Could you produce one example (A to B) where you think there is a clear difference and then identify exactly what artifact you are referring to (with a selection around the difference, one set without the markup and another with the markup)?



#4 DanielJStein

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Posted 28 May 2020 - 09:48 AM

Was the moon shining by any chance?

 

They all look like internal reflections to me. It's very obvious in Figure 2 where the lens flare appears to be caused by a bright object, possibly just out of shot.  It's causing internal reflections within the lens and/or within the camera just like when taking a daylight shot towards the sun.

 

Do you know exactly what was done during the modification?  Was a replacement filter put in the camera?  In any case, it's entirely possible the end result has created an additional set of internal reflections that don't exist in a stock camera.

 

Do you see the same effects in the daytime e.g. pointing in the general direction of the sun with the sun just inside or outside the field of view?  It is much easier to "debug" a problem during the day.

 

Mark

I appreciate your insight Mark, I have followed your content for quite some time and seen the mod you did yourself to your Z6. While I cannot specify what exactly Lifepixel did to my camera, I can see they did remove possibly 1 or 2 of the stock filters in front of the sensor. I am unsure if they replaced a clear filter in place of the removed filters. I know from your findings the Z6 kind of has its AA filter bonded to one of its other blocking filters. 

 

I was shooting all of these during new moon, so I do not think it is that. Rather given the set of examples above I think the reflection is being caused by the light pollution in the immediate foreground as well as off in the distance. In figure 5 there is no light pollution in the immediate foreground and thus there seems to be no reflection/gradient. However in figure 1 there is no LP in the immediate foreground but tons off in the distance. Still, even moving the camera a little bit seemed to have mitigated the gradient.

 

It is just strange I have used this camera for a year now and have never had an issue—shooting in similar skies no less... All of these shots were taken during new moon, but here are a few examples of shooting towards the sun.

 

In this first shot, the sun was just below the mountains, I do not see any reflections. I had the UV/IR cut filter on the 24-70.

 

lgeYBHM.jpg

 

Here is another shot taken towards the sun, this time with it visible above the horizon. You can see reflections, but it just looks like lens flare to me. This was with the 70-200 and UV/IR cut filter on the lens.

 

TDupSBS.jpg

 

If the sun comes out here today I can try some test shots with the 24-70 and camera pointed towards the sun and see what comes up.



#5 DanielJStein

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Posted 28 May 2020 - 10:15 AM

I don't know. With the clouds, the vignetting, the many external light sources, the differences in the exposures and f-stops, and the JPEG compression I'm not sure what I'm seeing. Could you produce one example (A to B) where you think there is a clear difference and then identify exactly what artifact you are referring to (with a selection around the difference, one set without the markup and another with the markup)?

Here is a dropbox link to higher resolution files, maybe this will help... I have annotated a few as well. Below are also a few that have been annotated, albeit with some compression. You can see where the gradient starts and how this magenta hue is cast throughout the image from the start point.

 

UG9xASR.jpg

 

om7whkR.jpg

 

iNjg3yR.jpg 

 

GSWDVdh.jpg

 

pZaj2tV.jpg

 

klk1Ic3.jpg



#6 YAOG

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Posted 29 May 2020 - 12:47 AM

Does the 24-70 do this on the other camera? I had an original EF28-70 2.8L USM suddenly start making yellow looking images that happened overnight and got much worse and then stopped degrading but remains consistent. I sent the lens to CPS who said the issue was that there is a degraded lens pair, apparently the cement between lens elements had failed. The lens was.fully functional but made odd yellowed images. CPS said it was not repairable.



#7 nofxrx

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Posted 29 May 2020 - 06:23 AM

Daniel,

 Do you know if LifePixel performed an "H-Alpha" modification or a "Full Spectrum" modification? 



#8 DanielJStein

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Posted 29 May 2020 - 06:41 AM

Does the 24-70 do this on the other camera? I had an original EF28-70 2.8L USM suddenly start making yellow looking images that happened overnight and got much worse and then stopped degrading but remains consistent. I sent the lens to CPS who said the issue was that there is a degraded lens pair, apparently the cement between lens elements had failed. The lens was.fully functional but made odd yellowed images. CPS said it was not repairable.

Funnily enough my Mark I 24-70 did some weird things over time where it would no longer achieve infinity focus eventually. However I have no experience with the Mark II degrading in some way. My 24-70 II is also only a few months old... My girlfriend’s 24-70 does not seem to be doing any of these weird things with her unmodified body, so I guess you could say there are 2 factors at play now.

 

1. Different copies of the same lens. 2. Her Z6 is unmodified. Regardless, her images do not have these gradients despite shooting at the same time, same nights, same locations.



#9 DanielJStein

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Posted 29 May 2020 - 06:46 AM

Daniel,

 Do you know if LifePixel performed an "H-Alpha" modification or a "Full Spectrum" modification? 

I just checked the invoice, it was definitely the h-alpha mod. I know from Mark’s findings the Z6 has 2 LPF filters. LPF2 should have been the one they removed since it blocks 75% of HA, potentially replacing it with a clear filter. LPF1 should have been placed back. I believe removing both LPF1 and LPF2 would make it a full spectrum mod, based on Mark’s findings (unless I am misunderstanding his results).

 

Lifepixel does not go into detail on how they modded my Z6, just that it was specified for the h-a mod only, not full spectrum. I also reached out to them with these sample images. 



#10 erictheastrojunkie

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Posted 29 May 2020 - 09:32 AM

I just checked the invoice, it was definitely the h-alpha mod. I know from Mark’s findings the Z6 has 2 LPF filters. LPF2 should have been the one they removed since it blocks 75% of HA, potentially replacing it with a clear filter. LPF1 should have been placed back. I believe removing both LPF1 and LPF2 would make it a full spectrum mod, based on Mark’s findings (unless I am misunderstanding his results).

 

Lifepixel does not go into detail on how they modded my Z6, just that it was specified for the h-a mod only, not full spectrum. I also reached out to them with these sample images. 

Realistically Lifepixel removed both and replaced them with some form of a UV/IR Cut glass that was closer to the combined thickness of LPF1/LPF2. I would even wonder if Lifepixel has any idea that the mod can be performed by just removing LPF2. FWIW I also modded my own Z6, at first I removed both filters and used a piece of astronomik UV/IR Cut glass as a replacement, it worked fine, but I had some sensor tilt that I could not seem to fix with it in (I think the glass was not sitting level over the sensor), so I pulled it apart again and used just the LPF1 with the supporting frame and rubber holder. After a bunch of adjustments I have the sensor mostly flat, perhaps a slight amount of tilt on the extreme right edge. I have not noticed any strange gradients or light leaks like you are experiencing, to my eye they look like internal reflections with some kind of hard edge casting that "shadow" in some of the images. I wonder if it's related to the glass that Lifepixel used as a replacement for the LPF1/LPF2 filters they removed. 



#11 DanielJStein

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Posted 29 May 2020 - 01:52 PM

Realistically Lifepixel removed both and replaced them with some form of a UV/IR Cut glass that was closer to the combined thickness of LPF1/LPF2. I would even wonder if Lifepixel has any idea that the mod can be performed by just removing LPF2. FWIW I also modded my own Z6, at first I removed both filters and used a piece of astronomik UV/IR Cut glass as a replacement, it worked fine, but I had some sensor tilt that I could not seem to fix with it in (I think the glass was not sitting level over the sensor), so I pulled it apart again and used just the LPF1 with the supporting frame and rubber holder. After a bunch of adjustments I have the sensor mostly flat, perhaps a slight amount of tilt on the extreme right edge. I have not noticed any strange gradients or light leaks like you are experiencing, to my eye they look like internal reflections with some kind of hard edge casting that "shadow" in some of the images. I wonder if it's related to the glass that Lifepixel used as a replacement for the LPF1/LPF2 filters they removed. 

You are one brave soul for modding your Z6 yourself! I am not great with small electronics, so I left it to the pros. Given I purchased the camera over a year ago, Lifepixel seemed to be the only company who would mod it at the time. Again I have no idea what they did, and I only know about the LF1, LF2 situation thanks to your and Mark's findings of your own behalf.

 

What still boggles my mind is why is this the first time I am having these issues. Like I said, I have been using this camera for a year, much of which has been in upstate NY which is decently light polluted. I have used it in even more light polluted skies than this one. It seems to be a problem in conjunction with the 24-70 2.8L II. None of my other lenses seems to cause these flares. Why is this lens doing it then? 



#12 Huangdi

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Posted 29 May 2020 - 03:10 PM

I get those flares with my refractor when overexposing things (for example photographing earthshine, bright side will cause lens flares) and with my sigma 50mm F1.4 as well, for example when photographing a sunset.

This happened after modifying my Nikon D3300. I didn't replace the filter I took out, so it's essentially lacking a millimeter of glass.

I am 99% sure that this is caused by the missing glass.

Perhaps, when modding your cam, they didn't get the exact glass thickness right and it's off by a small amount.

As we all learned through astrophotography, a small difference at one scale, can make a huge difference at another scale.

If a missing millimeter of glass can deny you the ability to reach focus, then 1/3rd of a millimeter might just cause some flares.

Of course this is still just speculation..

#13 Noobulosity

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Posted 31 May 2020 - 04:30 PM

Those definitely look like internal reflections.  By removing the additional layer of glass, I wonder if there's some anti-reflective coating on the removed filter that's no longer blocking some of these lens flares and such.

 

If they didn't replace the missing filter glass with anti-reflective glass, or if they only replaced with plain glass, that might explain the new issues.



#14 DanielJStein

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Posted 01 June 2020 - 08:10 AM

Realistically Lifepixel removed both and replaced them with some form of a UV/IR Cut glass that was closer to the combined thickness of LPF1/LPF2. I would even wonder if Lifepixel has any idea that the mod can be performed by just removing LPF2. FWIW I also modded my own Z6, at first I removed both filters and used a piece of astronomik UV/IR Cut glass as a replacement, it worked fine, but I had some sensor tilt that I could not seem to fix with it in (I think the glass was not sitting level over the sensor), so I pulled it apart again and used just the LPF1 with the supporting frame and rubber holder. After a bunch of adjustments I have the sensor mostly flat, perhaps a slight amount of tilt on the extreme right edge. I have not noticed any strange gradients or light leaks like you are experiencing, to my eye they look like internal reflections with some kind of hard edge casting that "shadow" in some of the images. I wonder if it's related to the glass that Lifepixel used as a replacement for the LPF1/LPF2 filters they removed. 

Ok I just heard back from Lifepixel. You pretty much hit it spot on, this is exactly what they do. The Owner did bring up a good point though... How come I am only seeing these reflections with just one lens?



#15 DanielJStein

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Posted 01 June 2020 - 08:12 AM

Those definitely look like internal reflections.  By removing the additional layer of glass, I wonder if there's some anti-reflective coating on the removed filter that's no longer blocking some of these lens flares and such.

 

If they didn't replace the missing filter glass with anti-reflective glass, or if they only replaced with plain glass, that might explain the new issues.

According to the Lifepixel Owner, both LPF 1 and 2 were removed (the OEM filter stack) and their filter was replaced to act as a UV/IR cut with h-alpha pass through. Whether or not that filter has an anti-reflective coating is beyond me, but it’s strange that I have not seen this happen with any other lens.



#16 DanielJStein

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Posted 01 June 2020 - 08:13 AM

I get those flares with my refractor when overexposing things (for example photographing earthshine, bright side will cause lens flares) and with my sigma 50mm F1.4 as well, for example when photographing a sunset.

This happened after modifying my Nikon D3300. I didn't replace the filter I took out, so it's essentially lacking a millimeter of glass.

I am 99% sure that this is caused by the missing glass.

Perhaps, when modding your cam, they didn't get the exact glass thickness right and it's off by a small amount.

As we all learned through astrophotography, a small difference at one scale, can make a huge difference at another scale.

If a missing millimeter of glass can deny you the ability to reach focus, then 1/3rd of a millimeter might just cause some flares.

Of course this is still just speculation..

True, another good point.



#17 erictheastrojunkie

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Posted 01 June 2020 - 01:14 PM

Ok I just heard back from Lifepixel. You pretty much hit it spot on, this is exactly what they do. The Owner did bring up a good point though... How come I am only seeing these reflections with just one lens?

Probably has something to do with the focal length, aperture, angle of light entering the lens and angle of incidence of light leaving the lens and entering the glass over the sensor. Unfortunately it seems you've found some combination of equipment which is creating it, related to the lens optics and the modification of the camera. 


Edited by erictheastrojunkie, 01 June 2020 - 01:14 PM.

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#18 Noobulosity

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Posted 03 June 2020 - 12:15 AM

Probably has something to do with the focal length, aperture, angle of light entering the lens and angle of incidence of light leaving the lens and entering the glass over the sensor. Unfortunately it seems you've found some combination of equipment which is creating it, related to the lens optics and the modification of the camera.


Have to agree. Perhaps the lack of filters and possibly AR coating, plus that particular lens design, is causing this.

#19 DanielJStein

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Posted 03 June 2020 - 05:40 AM

Have to agree. Perhaps the lack of filters and possibly AR coating, plus that particular lens design, is causing this.

Darn, I really like using the Canon 24-70 with the Z6 as it has minimal coma and is pretty sharp even at 2.8. I guess I will try the S line primes...



#20 happylimpet

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Posted 03 June 2020 - 05:59 AM

My only observation regarding this is that the mauve colour you are seeing is identical to the colour seen when imaging NIR sources (like a remote control) with a digital camera - corresponding to the relative infrared leaks in the different bayer filters.

 

Could there be a strongish infrared source nearby? Or even in the FOV?

 

The one with the flare (5205) seems to suggest that the bright object in the FOV could be a strong NIR source. 

 

You dont have some kind of infrared remote control do you?

 

I'm putting money on this being the general issue...in some way!!!


Edited by happylimpet, 03 June 2020 - 06:03 AM.

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#21 DanielJStein

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Posted 03 June 2020 - 06:39 AM

My only observation regarding this is that the mauve colour you are seeing is identical to the colour seen when imaging NIR sources (like a remote control) with a digital camera - corresponding to the relative infrared leaks in the different bayer filters.

 

Could there be a strongish infrared source nearby? Or even in the FOV?

 

The one with the flare (5205) seems to suggest that the bright object in the FOV could be a strong NIR source. 

 

You dont have some kind of infrared remote control do you?

 

I'm putting money on this being the general issue...in some way!!!

Hmmmmmmmm. That makes sense BUT—

 

My remote is the radio frequency type, with a little 2.4 GHz box sitting in the shoe and a DC-2 cable plugged into the body. 
 

Could it be the use of red light behind the camera? Still even so I can insure that most, if not all of these shots our lights were off.



#22 happylimpet

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Posted 03 June 2020 - 08:35 AM

Curses. I hoped I had it there! I still think the IR thing is worth pursuing though - maybe its some other source?



#23 calypsob

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Posted 03 June 2020 - 08:42 AM

Id be curious if a nikon mirrorless lens would do better than the Canon. It will sit much closer to the sensor than an aEf lens so reflection may not be an issue.

#24 erictheastrojunkie

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Posted 03 June 2020 - 09:09 AM

Id be curious if a nikon mirrorless lens would do better than the Canon. It will sit much closer to the sensor than an aEf lens so reflection may not be an issue.

I can't test Daniel's setup, but I can test my modified Z6 (I only removed LPF2 and left LPF1) with something like the 50mm f1.8s and see if I get similar reflections. I have not seen any reflections of the similar type with any of the lenses I've used, however, so I may not have the issue to begin with (but neither did Daniel until now). 



#25 DanielJStein

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Posted 03 June 2020 - 01:09 PM

Id be curious if a nikon mirrorless lens would do better than the Canon. It will sit much closer to the sensor than an aEf lens so reflection may not be an issue.

This is going to be my next test. Given that none of the F mount Sigma ART lenses I have used (with the FTZ adapter) have had this issue. I wonder if it has something to do with the Fringer adapter + Canon lens. Still, the issue is not prevalent with my Canon 70-200 using that same adapter so again I wonder...




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