Author Topic: Spotting  (Read 491 times)

Critters

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Spotting
« on: June 07, 2017, 01:47:40 AM »
What causes the mottled spotting in lower light? I've done multiple black calibrations but that doesn't seem to improve things.

Here's a gif showing it against a white door:


tesla500

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Re: Spotting
« Reply #1 on: June 07, 2017, 05:09:06 PM »
Hey Critters,

That's a calibration issue, we have contacted Luxima, the image sensor manufacturer, and they suggested adding 3-point calibration to fix the issue. We're currently using 2-point calibration. This is high priority on the list of things to fix.

Basically, due to variations in the semiconductor production process, some pixels have a response that is non-linear, with slightly less response when dark compared to in brighter light. As a result, they need more gain applied, but only in dark areas. The 3-point calibration will do this.

To minimize this for now, try to avoid using analog gain as the problem is worse at higher gain, and expose your images as bright as possible to bring up the pixel levels. Applying gain afterwards will also make the spots more noticeable.

David

Critters

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Re: Spotting
« Reply #2 on: June 07, 2017, 06:35:07 PM »
Great to hear it's a software fix, keep it up! :)

Camoit

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Re: Spotting
« Reply #3 on: June 08, 2017, 12:52:58 PM »
Please keep us informed on this fix.
This would be an issue my editor would see and ask me about it. Now that I know about it I have seen them in other youtube videos.

JamesB

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Re: Spotting
« Reply #4 on: June 08, 2017, 08:27:56 PM »
After some careful testing today it is clear the camera will show much fewer spots when over exposed or near over exposure. As David said above the 3 point calibration should fix it.

Image quality is the most important aspect of any camera and fixing this is top on the list, rest assured this is getting worked on. 

Some cameras will show more than others and there is an irregular pattern from each sensor.   I worked on After Effects to try to correct it and while cloning is a kind of fix, it introduced several hours of trial and error to get the shot to a place where I would be able to say it is acceptable.  It would take about 4-5 hrs of cloning to get a 30-second static shot clean which is what I did (Do not recommend it!).  The other fix I found where it was much faster is the "dust and scratches" filter in After Effects.  Only problem is resolution is decreased severely by applying it.  After it, however, it mostly cures the shot but makes it look posterized and water color like even at it's lowest setting.

After the dark dot issue is fixed and based on the incredible footage I was able to gather today, I would say the camera + sensor are extremely good in detail, color and dynamic range.

Some sample frames from today!




« Last Edit: June 09, 2017, 02:02:48 PM by JamesB »

nik282000

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Re: Spotting
« Reply #5 on: June 09, 2017, 06:02:47 AM »
Out of curiosity, is it always the same pattern (a sensor fingerprint), if so you might be able to map them for your particular camera and make an adjustment mask that lets you make a quick and rough correction.

JamesB

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Re: Spotting
« Reply #6 on: June 09, 2017, 01:48:59 PM »
In theory, you could but since the pixels are not dead but changing according to brightness levels you would have to adjust accordingly as the scene changes for them not to look odd. Depending on the scene the changes could be less apparent.   They are individual pixels but since the de-bayer process averages the neighboring ones you get a cross pattern that is much more apparent. My camera has around 173 pixels that exhibit this problem as far as I could tell by the cloning post I did. Here is an animated gif of the zoomed pixels and the cloning fix in After effects.


« Last Edit: June 09, 2017, 02:04:33 PM by JamesB »

Critters

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Re: Spotting
« Reply #7 on: June 09, 2017, 01:54:47 PM »
FYI: All the images you have posted are broken, probably only visible to you as they are on your google drive

imgur.com is your friend :)

JamesB

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Re: Spotting
« Reply #8 on: June 09, 2017, 02:03:26 PM »
Thanks Critters, I dusted off my photobucket account ;-) has been a while since I posted images in forums!

Critters

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Re: Spotting
« Reply #9 on: June 09, 2017, 02:09:19 PM »
Nice, which lens are you using?

JamesB

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Re: Spotting
« Reply #10 on: June 09, 2017, 02:41:48 PM »
Canon 100mm Macro 2.8 USM! It becomes like a 400mm due to the nearly 4x crop factor (3.93x) of the 2/3rds chip!  I sometimes have to step way back to get framing properly. Which is good as wildlife is more forgiving due to the distance.