What causes stripe noise on a7iii?

Started Mar 1, 2018 | Discussions
sybersitizen Forum Pro • Posts: 14,921
Re: was wishful thinking, too bad....
3

BBQue wrote:

JimKasson wrote:

BBQue wrote:

(sorry the all caps and triple exclamation marks)

Probably not. Happens in the a9, too:

http://blog.kasson.com/a9/pdaf-striping-on-the-a9/

hmmm... that's too bad. But probably not a big deal in "real life".

It (or something very similar) has been happening in a number of E-mount bodies since at least 2014; and no, camera anomalies are not a big deal ... until people decide they are. Then the petitions start.

Horshack Veteran Member • Posts: 8,184
Re: A9 sample from Jim using round light source

JimKasson wrote:

Horshack wrote:

Jim sent me some great A9 raws he shot using a Godox Flashpoint XPLOR 600PRO as the light source. This creates a perfectly circular light source, which allows us to better delineate the axis of where the G vs G2 banding begins and ends.

Here is an animated GIF I created from the raw (click on image, then on "100% zoom" in the dpreview gallery viewer to animate, panning around if necessary). I darkened out the center of the strobe to make viewing of the stripes around the outer of the circle easier.

Very nice.

I'm embroiled with taxes today, but I'm thinking about writing some code to do heatmaps for this artifact.

Jim

That would be cool Jim. Here's a blend I create to further highlight the transition point between the G/G2 banding. I inverted the G bands so that they're black, while the G2 bands are white. If you follow around the circle you can see where one begins and the other ends, which is almost exactly at 45°. Click on the image to see the full-size.

Horshack Veteran Member • Posts: 8,184
Illustration of theory
5

Here's an illustration I created to depict how and why the G1 bands are only visible above/below the light source and G2 bands only left/right. In my theory I indicated this might be because of the axis of light relative to the angle of light that the micro-lenses are designed to absorb - in reality I think it may be much simpler. If we assume that light is reflecting off the PDAF pixels radially in all directions (due to the property of the lens optics/aperture), and this is reaching the microlenses at an angle which can be absorbed into the pixels, then the explanation of why the G1/G2 bands taper across their respective axes is just a function of the radial falloff of light (ie, the distance from the center of a circle to its horizontal/vertical edges is shorter than the distance to its diagonal edge).

This also would mean that both G1/G2 are "striping" in the center areas of the light glare - we just can't see it because the luminance values are at/near clipping. We however can see both G1/G2 striping around the circular perimeter of the light glare, where the luminance levels have dropped off enough to reach a tonal area where the stripes would be visible.

I depicted everything described above in the following illustration. Click on the image for the full-sized version.

bclaff Veteran Member • Posts: 9,034
Re: I still believe it's related to PDAF pixels.
8

bclaff wrote:

JoFa wrote:

Bill, can you post a link of your other analysis showing that same pattern?

Here are a couple of links to older posts:

ILCE-9 (A9) PDAF Row Locations

Re: PDAF

And here's summary of the research I did at that time:

The color code at the bottom indicates sensor with identical PDAF layouts

BTW, this analysis was performed on black frames. Light isn't required to detect the pattern.

So, I looked at the ILCE-7M3 and it has the identical pattern as the ILCE-9 except shifted down 8 rows.

But, there does look like a surprise.

In all my earlier investigations the PDAF pixels were distingished by lower Read Noise.
For example, here's the ILCE-9:

But my initial ILCE-7M3 investigation shows this:

Dramatically (3 stops) higher Read Noise in the PDAF blue pixels.

As they say ... interesting !

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Horshack Veteran Member • Posts: 8,184
Re: I still believe it's related to PDAF pixels.

bclaff wrote:

bclaff wrote:

JoFa wrote:

Bill, can you post a link of your other analysis showing that same pattern?

Here are a couple of links to older posts:

ILCE-9 (A9) PDAF Row Locations

Re: PDAF

And here's summary of the research I did at that time:

The color code at the bottom indicates sensor with identical PDAF layouts

BTW, this analysis was performed on black frames. Light isn't required to detect the pattern.

So, I looked at the ILCE-7M3 and it has the identical pattern as the ILCE-9 except shifted down 8 rows.

But, there does look like a surprise.

In all my earlier investigations the PDAF pixels were distingished by lower Read Noise.
For example, here's the ILCE-9:

But my initial ILCE-7M3 investigation shows this:

Dramatically (3 stops) higher Read Noise in the PDAF blue pixels.

As they say ... interesting !

That is interesting, thanks. I wonder what the distribution of pixel values for those A7III PDAF rows look like.

KKnipser Regular Member • Posts: 210
Re: Illustration of theory

Does that apply to all models with on sensor PDAF or is it A7III specific?

Entropy512 Senior Member • Posts: 4,780
Re: A7rII observation - PDAF bands on G rather than G2

Horshack wrote:

The banding on the G2/B channel of the A9/A7III is somewhat logical considering they're on the same Bayer row (even though we don't yet understand why the G2 pixels would be affected since PDAF uses the blue pixels).

At least for this particular item - it was my understanding that the PDAF sensels "stole" a blue pixel to create a dual-pixel site under a single microlens - with the other pixel being one of the green pixels.

As a result while the green pixel might still have data, that data is going to be impacted by the different optical arrangement of the microlens for that sensel - to the point where it would be very difficult to do anything other than simply interpolate THAT pixel out too.

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JimKasson
JimKasson Forum Pro • Posts: 27,462
Re: I still believe it's related to PDAF pixels.

bclaff wrote:

bclaff wrote:

JoFa wrote:

Bill, can you post a link of your other analysis showing that same pattern?

Here are a couple of links to older posts:

ILCE-9 (A9) PDAF Row Locations

Re: PDAF

And here's summary of the research I did at that time:

The color code at the bottom indicates sensor with identical PDAF layouts

BTW, this analysis was performed on black frames. Light isn't required to detect the pattern.

So, I looked at the ILCE-7M3 and it has the identical pattern as the ILCE-9 except shifted down 8 rows.

But, there does look like a surprise.

In all my earlier investigations the PDAF pixels were distingished by lower Read Noise.
For example, here's the ILCE-9:

But my initial ILCE-7M3 investigation shows this:

Dramatically (3 stops) higher Read Noise in the PDAF blue pixels.

As they say ... interesting !

Good work, Bill! Could this mean that the blue pixels are split and aren't interpolated over? Do those particular blue pixels taken as a group have lower FWC?

Jim

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AlexPhotoPT New Member • Posts: 1
Re: What causes stripe noise on a7iii?

Hello everyone.

First of all, I would like to point out, I am nowhere near you guys as far as these technical issues are involved. I am an amateur photographer, with no background on these matters. As such, and having become quite taken at the prospect of the A7III, I read this thread from end to end, and realized that most of what is said is simply lost on me.

As such, after reading all that has been written, I was unable to understand one thing: were these photos taken by Rishi using the electronic or mechanical shutter? And if they were taken with the electronic shutter, would the banding have been “avoided” by simply using the mechanical shutter? I know that electronic shutters can be more prone to issues (such as banding) due to how the sensor preforms the readout, and even electronic first curtain shutters are more likely.

If my question borders on barbarity, I ask you to be patient, as I said, it comes from a place of ignorance looking for knowledge.

Regardless of how much (or little) I was able to take from this thread, I thank you all for all that you have shared here.

JimKasson
JimKasson Forum Pro • Posts: 27,462
Re: What causes stripe noise on a7iii?
1

AlexPhotoPT wrote:

Hello everyone.

First of all, I would like to point out, I am nowhere near you guys as far as these technical issues are involved. I am an amateur photographer, with no background on these matters. As such, and having become quite taken at the prospect of the A7III, I read this thread from end to end, and realized that most of what is said is simply lost on me.

As such, after reading all that has been written, I was unable to understand one thing: were these photos taken by Rishi using the electronic or mechanical shutter?

Mechanical close, electronic open:

And if they were taken with the electronic shutter, would the banding have been “avoided” by simply using the mechanical shutter? I know that electronic shutters can be more prone to issues (such as banding) due to how the sensor preforms the readout, and even electronic first curtain shutters are more likely.

If my question borders on barbarity, I ask you to be patient, as I said, it comes from a place of ignorance looking for knowledge.

Regardless of how much (or little) I was able to take from this thread, I thank you all for all that you have shared here.

And welcome to DPR!

Jim

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JimKasson
JimKasson Forum Pro • Posts: 27,462
Complete EXIF -- warning, may be TMI
3

AlexPhotoPT wrote:

were these photos taken by Rishi using the electronic or mechanical shutter?

In case anyone's interested, here is the complete EXIF from Rishi's file:

ExifTool Version Number : 10.68
File Name : DSC00082.ARW
Directory : C:/Users/jim.KASSON/Desktop
File Size : 24 MB
File Modification Date/Time : 2018:03:06 08:36:27-08:00
File Access Date/Time : 2018:03:06 16:24:16-08:00
File Creation Date/Time : 2018:03:06 16:24:16-08:00
File Permissions : rw-rw-rw-
File Type : ARW
File Type Extension : arw
MIME Type : image/x-sony-arw
Exif Byte Order : Little-endian (Intel, II)
Image Description :
Orientation : Rotate 270 CW
Image Width : 6048
Image Height : 4024
Bits Per Sample : 14
Compression : Sony ARW Compressed
Photometric Interpretation : Color Filter Array
Samples Per Pixel : 1
Planar Configuration : Chunky
X Resolution : 350
Y Resolution : 350
Resolution Unit : inches
CFA Repeat Pattern Dim : 2 2
CFA Pattern 2 : 0 1 1 2
Sony Raw File Type : Sony Compressed RAW
Strip Offsets : 499712
Rows Per Strip : 4024
Strip Byte Counts : 24337152
Default Crop Origin : 12 12
Default Crop Size : 6000 4000
Preview Image Start : 147618
Preview Image Length : 350160
Y Cb Cr Positioning : Co-sited
Exposure Time : 1/125
F Number : 1.8
ISO : 250
Sensitivity Type : Recommended Exposure Index
Recommended Exposure Index : 250
Exif Version : 0231
Date/Time Original : 2018:02:26 19:13:18
Create Date : 2018:02:26 19:13:18
Offset Time : -04:00
Offset Time Original : -04:00
Offset Time Digitized : -04:00
Components Configuration : Y, Cb, Cr, -
Compressed Bits Per Pixel : 8
Brightness Value : 1.8921875
Exposure Compensation : -0.3
Max Aperture Value : 1.8
Metering Mode : Multi-segment
Light Source : Unknown
Flash : Off, Did not fire
Focal Length : 85.0 mm
Rating : 0
Brightness : 0
Long Exposure Noise Reduction : On (unused)
High ISO Noise Reduction : Off
HDR : Off; Uncorrected image
WB Shift AB GM : 0 0
WB Shift AB GM Precise : 0.00 0.00
Face Info Offset : 94
Sony Date Time : 2018:02:26 19:13:18
Sony Image Width : 6000
Faces Detected : 1
Face Info Length : 37
Meta Version : DC7303320222000
Face 1 Position : 2366 4069 788 788
Creative Style : Standard
Color Temperature : Auto
Color Compensation Filter : 0
Scene Mode : Standard
Zone Matching : ISO Setting Used
Dynamic Range Optimizer : Auto
Image Stabilization : On
Color Mode : Standard
Full Image Size : 6000x4000
Preview Image Size : 1616x1080
File Format : ARW 2.3.3
Quality : RAW + JPEG
Flash Exposure Compensation : 0
White Balance Fine Tune : 0
White Balance : Auto
Sony Model ID : Unknown (363)
Multi Frame Noise Reduction : Off
Picture Effect : Off
Soft Skin Effect : Off
Vignetting Correction : Auto
Lateral Chromatic Aberration : Auto
Distortion Correction Setting : Off
Lens Type : E-Mount, T-Mount, Other Lens or no lens
Lens Spec : FE 85mm F1.8
Auto Portrait Framed : No
Flash Action : Did not fire
Electronic Front Curtain Shutter: On
Focus Mode : AF-C
AF Area Mode Setting : Flexible Spot
Flexible Spot Position : 320 211
AF Point Selected : n/a
AF Points Used : (none)
AF Tracking : Face tracking
Focal Plane AF Points Used : 0
Multi Frame NR Effect : Normal
Focus Location : 6000 4000 4490 2750
Variable Low Pass Filter : n/a
Metering Mode 2 : Multi-segment
Exposure Standard Adjustment : 0
RAW File Type : Compressed RAW
Flash Level : Normal
Release Mode : Normal
Sequence Number : Single
Anti-Blur : On (Shooting)
Shot Number Since Power Up : 16449
Sequence Image Number : 1
Sequence File Number : 1
Sequence Length : 1 file
Camera Orientation : Rotate 270 CW
Quality 2 : RAW + JPEG
Sony Image Height : 4000
Model Release Year : 2017
Ambient Temperature : 26 C
AF Area Mode : Tracking
Focus Position 2 : 164
Camera Temperature : 38 C
Exposure Program : Aperture-priority AE
Intelligent Auto : Off
Sony ISO : 265
Base ISO : 100
Stops Above Base ISO : 1.4
Sony Exposure Time 2 : 1/128
Sony Max Aperture Value : 1.8
Sony Image Width Max : 6024
Sony Image Height Max : 4024
Picture Effect 2 : Off
Distortion Correction : None
Lens Zoom Position : 365%
Battery Temperature : 38.9 C
Battery Level : 86%
Lens Mount 2 : E-mount
Lens Type 3 : Sony FE 85mm F1.8
Camera E-mount Version : 1.70
Lens E-mount Version : 1.60
Lens Firmware Version : Ver.01
Flash Status : No Flash present
Image Count : 0
Sony Exposure Time : 51922.1
Sony F Number : 0.0
Release Mode 2 : Unknown (34)
Internal Serial Number : 10048602
Lens Mount : E-mount
Lens Format : Full-frame
Lens Type 2 : Sony FE 85mm F1.8
Distortion Corr Params Present : Yes
Lens Spec Features : FE
User Comment :
Flashpix Version : 0100
Color Space : sRGB
Exif Image Width : 6000
Exif Image Height : 4000
Interoperability Index : R98 - DCF basic file (sRGB)
Interoperability Version : 0100
File Source : Digital Camera
Scene Type : Directly photographed
Custom Rendered : Normal
Exposure Mode : Auto
Digital Zoom Ratio : 1
Focal Length In 35mm Format : 85 mm
Scene Capture Type : Standard
Contrast : Normal
Saturation : Normal
Sharpness : Normal
Lens Info : 85mm f/1.8
Lens Model : FE 85mm F1.8
PrintIM Version : 0300
SR2 Sub IFD Offset : 52822
SR2 Sub IFD Length : 56958
SR2 Sub IFD Key : 0x44332211
Black Level : 512 512 512 512
WB RGGB Levels : 1668 1024 1024 2296
Color Matrix : 1141 -205 88 -52 1229 -154 70 -225 1179
WB RGB Levels Daylight : 2292 1024 1624
WB RGB Levels Cloudy : 2472 1024 1492
WB RGB Levels Tungsten : 1432 1024 2852
WB RGB Levels Flash : 2508 1024 1444
WB RGB Levels 4500K : 2072 1024 1824
WB RGB Levels Shade : 2712 1024 1348
WB RGB Levels Fluorescent : 2124 1024 2368
WB RGB Levels Fluorescent P1 : 2200 1024 1740
WB RGB Levels Fluorescent P2 : 2432 1024 1604
WB RGB Levels Fluorescent M1 : 1660 1024 2836
WB RGB Levels 8500K : 2848 1024 1276
WB RGB Levels 6000K : 2448 1024 1508
WB RGB Levels 3200K : 1596 1024 2492
WB RGB Levels 2500K : 1248 1024 3404
White Level : 15360 15360 15360
Vignetting Corr Params : 16 0 64 432 1040 1808 2640 3552 4496 5472 6448 7440 8432 9408 10368 11296 12208
Chromatic Aberration Corr Params: 32 640 384 128 0 -128 -128 0 0 -128 -128 -128 -128 -256 -256 -256 -256 384 128 -128 -256 -256 -256 -256 -256 -256 -256 -256 -256 -256 -256 -256 -256
Distortion Corr Params : 16 -4 -2 2 5 11 16 23 30 36 40 44 44 40 31 17 -4
Subfile Type : Reduced-resolution image
Make : SONY
Camera Model Name : ILCE-7M3
Software : ILCE-7M3 v1.00
Modify Date : 2018:02:26 19:13:18
Thumbnail Offset : 43092
Thumbnail Length : 8100
Aperture : 1.8
Blue Balance : 2.242188
CFA Pattern : [Red,Green][Green,Blue]
Focus Distance 2 : 3.32 m
Image Size : 6048x4024
Lens ID : Sony FE 85mm F1.8
Megapixels : 24.3
Preview Image : (Binary data 350160 bytes, use -b option to extract)
Red Balance : 1.628906
Scale Factor To 35 mm Equivalent: 1.0
Shutter Speed : 1/125
Create Date : 2018:02:26 19:13:18-04:00
Date/Time Original : 2018:02:26 19:13:18-04:00
Modify Date : 2018:02:26 19:13:18-04:00
Thumbnail Image : (Binary data 8100 bytes, use -b option to extract)
Circle Of Confusion : 0.030 mm
Field Of View : 23.9 deg
Focal Length : 85.0 mm (35 mm equivalent: 85.0 mm)
Hyperfocal Distance : 133.59 m
Light Value : 7.3

TMI?

Jim

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bclaff Veteran Member • Posts: 9,034
Re: What causes stripe noise on a7iii?

AlexPhotoPT wrote:

... I was unable to understand one thing: were these photos taken by Rishi using the electronic or mechanical shutter? And if they were taken with the electronic shutter, would the banding have been “avoided” by simply using the mechanical shutter?...

The type of shutter might matter in a real photograph depending on the lighting but since I detect the PDAF pattern using black frames I'm sure they are always there.

If my question borders on barbarity, I ask you to be patient, as I said, it comes from a place of ignorance looking for knowledge.

I'm ignorant all the time; just try to be less so each day.

Regardless of how much (or little) I was able to take from this thread, I thank you all for all that you have shared here.

You are welcome.

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Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

Horshack Veteran Member • Posts: 8,184
Re: I still believe it's related to PDAF pixels.
3

JimKasson wrote:

Good work, Bill! Could this mean that the blue pixels are split and aren't interpolated over? Do those particular blue pixels taken as a group have lower FWC?

Jim

Someone posted this link in the comment section of today's SAR story about the striping. It implies a newer version of pixel structure for Sony's PDAF. It references smaller Smartphone sensors so we'll have to see if it also applies to the A7III. Excerpt from end of link:

Recent back-illuminated Sony chips have been found to use a new type of PDAF system that could be described as lossless. The 1.0 µm pixel generation Exmor RS chip in the Apple iPhone 7 Plus used a 1x2 microlens structure over two of eight pixel pairs in selected green-blue rows [16]. The wide microlenses cover a green filter in the Bayer pattern and a green replacement filter in the neighboring blue position. Two of 64 pixels in an 8x8 block use this lens structure and these blocks are distributed across ~95% of the active pixel array. A similar implementation of 1x2 microlenses were found in use in the Sony IMX398 from the Oppo R9s and have been dubbed “Dual PDAF”

JimKasson
JimKasson Forum Pro • Posts: 27,462
Verified with heat map
6

Horshack wrote:

I just switched from my continuous light source (LED panel) to a remote strobe with no modifiers (lots of glare). With this new setup I'm now able to get banding on both G and G2, but with a twist - G always bands above and below the light source, whereas G2 always bands to the left/right of the light source. This orientation holds true irrespective of where I place the strobe in the frame or whether I shoot in landscape or portrait. I verified this same orientation behavior on the A9 raw sample I have - I suspect the A7III will behave the same.

Here are G and G2 channel images with the strobe at the center, left, right, top, and bottom of the frame.

I took the center-strobe shot and applied some code that I wrote to find the artifacts. Here's what I saw in each raw plane:

Red

G1

Blue

Same results as you got, but you don't have to pixel peep to see them.

If anybody wants to see the Matlab code, PM me, but I warn you that it is extremely seat-of-the-pants heuristic.

Jim

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JimKasson
JimKasson Forum Pro • Posts: 27,462
In living color!
4

Here are the two green raw planes assigned to different planes of an sRGB image:

Jim

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Horshack Veteran Member • Posts: 8,184
Re: Verified with heat map
1

JimKasson wrote:

Horshack wrote:

I just switched from my continuous light source (LED panel) to a remote strobe with no modifiers (lots of glare). With this new setup I'm now able to get banding on both G and G2, but with a twist - G always bands above and below the light source, whereas G2 always bands to the left/right of the light source. This orientation holds true irrespective of where I place the strobe in the frame or whether I shoot in landscape or portrait. I verified this same orientation behavior on the A9 raw sample I have - I suspect the A7III will behave the same.

Here are G and G2 channel images with the strobe at the center, left, right, top, and bottom of the frame.

I took the center-strobe shot and applied some code that I wrote to find the artifacts. Here's what I saw in each raw plane:

Same results as you got, but you don't have to pixel peep to see them.

If anybody wants to see the Matlab code, PM me, but I warn you that it is extremely seat-of-the-pants heuristic.

Jim

Looks great, thanks Jim. Making the blue channel stripes so visible is very helpful. It's remarkable how directional the G1 vs G2/B light shading is. The bayer layout for visual reference:

Bayer layout. Red-Green1 on odd rows and Green2-Blue on even rows

If we visualize the high-intensity light source hitting the sensor from each direction we can see how the Blue PDAF reflections lead to the observed per-channel striping. For example, for light moving from the left, the reflection from the Blue PDAF pixel will leak onto the G2 adjacent to the right....and the inverse for light from the right. For light moving from above the blue pixel will shade the G1 pixel below it, and inverse for light from below.

The fact that the stripes are of a somewhat continuous tone even though there is variable horizontal spacing between the PDAF blue pixels tells us that the reflection is strong enough to reach and affect several sets of adjacent pixels...after which the next blue PDAF pixel "regenerates" the effect with its own reflection. It's surprising though how directional the reflection is, otherwise we would see shading on the G1/G2 pixels diagonal from each reflection. When I get the time I plan to see if there a gradient that can be detected within a given stripe...finding that would lend support to the overall theory and also give us an idea of how strong the reflections are per PDAF pixel.

JimKasson
JimKasson Forum Pro • Posts: 27,462
a7RIII does it, too
4

Here's a comparison of the a7RIII and a9 G raw planes (assigned to the sRGB G planes) and the G2 planes (assigned to the sRGB R planes) with a Godox 600 TTL strobe centered and a Batis 135/2.8 wide open.

a7RIII

a9

So this has been with us a while. It looks to be more severe on the a7III, though. If someone has an a7III and wants to run a test for me, please let me know.

Jim

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iso rivolta Contributing Member • Posts: 566
Re: Verified with heat map

The previous image in the A7 III's gallery is more suitable to the analysis. The purple flare in the upper right corner has a more uniform background and a gradient along the stripes can indeed be seen.

https://www.dpreview.com/sample-galleries/6769434587/sony-a7-iii-sample-photos/2140526984

JimKasson
JimKasson Forum Pro • Posts: 27,462
Re: Verified with heat map
1

iso rivolta wrote:

The previous image in the A7 III's gallery is more suitable to the analysis. The purple flare in the upper right corner has a more uniform background and a gradient along the stripes can indeed be seen.

https://www.dpreview.com/sample-galleries/6769434587/sony-a7-iii-sample-photos/2140526984

And see this:

https://www.dpreview.com/forums/post/60861606

Jim

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iso rivolta Contributing Member • Posts: 566
Re: a7RIII does it, too

All these cameras have BSI sensors. In FSI sensors, the masking of the PDAF pixels is done with the metal interconnects (copper or aluminium) that are anyway above the diodes. For PDAF with BSI sensors, a metal back aperture grid must be introduced and manufactured through either tungsten or aluminium metalization. More about it here.

Depending on the reflectance of this grid, the refractive index and shape of the microlenses, you can imagine that at certain incidence angles a reflection could propagate in the space between the metal grid and the microlens sheet above it, in a light guide fashion, like Horshack also suggested.

So the difference between cameras could be due to the use of tungsten vs. aluminium, the latter having a higher reflectivity: W, Al

The effect should be slightly reduced if one adjusts a linear polarizer in front of the lens.

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