Author Topic: Issue with horizontal darkening w/ bright things  (Read 1084 times)

Prehistoricman

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Issue with horizontal darkening w/ bright things
« on: March 29, 2020, 03:27:33 PM »
I've had this issue on my Chronos 1.4 since I got it. If there is a dark-ish scene with a bright light source/object, everything in the horizontal band of the highly exposed area gets darkened.
Here's a video to showcase the issue (see 10s and onwards):

https://www.youtube.com/watch?v=E7BHrx0BAM4

This was probably shot at 12dB gain on v0.3.1 firmware, 1024x576. Standard issue Computar lens.

I've done some testing to determine at what settings this does and doesn't happen:
1280xanything: Only happens with >0dB gain
All other resolutions are affected by this at 0dB and other gains.

Black cal doesn't seem to influence it.

Is this an issue with all 1.4s? I haven't seen anyone else here complain about it.

foobar

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Re: Issue with horizontal darkening w/ bright things
« Reply #1 on: March 29, 2020, 10:38:08 PM »
This is a known behaviour of the LUX1310 image sensor that powers the Chronos 1.4. It occurs under conditions of extreme overexposure which appear to degrade the sensitivity of the entire line as it is digitized. This is an analog characteristic of image sensor, and we don't have any way to avoid it other than to reduce the exposure or aperture until the image is no longer clipping.
« Last Edit: March 29, 2020, 10:40:29 PM by foobar »

Prehistoricman

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Re: Issue with horizontal darkening w/ bright things
« Reply #2 on: March 31, 2020, 07:56:40 AM »
So what's the reason for the effect not occurring on full width shots with no gain?
Does the 2.1's sensor suffer from the same effect?

foobar

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Re: Issue with horizontal darkening w/ bright things
« Reply #3 on: March 31, 2020, 11:15:53 AM »
This effect does occur at full width, or without gain it just takes a stronger exposure to cause it. The effect is caused by overexposing pixels way beyond their normal saturation point, which requires a lot more light when there is no gain.

I don't recall if this also affects the LUX2100 (Chronos 2.1) off the top of my head, I will need to test that.

foobar

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Re: Issue with horizontal darkening w/ bright things
« Reply #4 on: March 31, 2020, 11:49:10 AM »
This issue also appears to affect the Chronos 2.1 and the LUX2100 image sensor.

SergeyKashin

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Re: Issue with horizontal darkening w/ bright things
« Reply #5 on: March 31, 2020, 02:48:41 PM »
Use more light, because cameras like the Vision Research Phantom have noise when the sensor sensitivity is increased and use a lot of powerful light sources to compensate


Here is one example of the light:
https://www.bhphotovideo.com/c/product/1247485-REG/mole_richardson_6371_1600_watt_tener_led.html


As soon as I get my camera I will make myself powerful light sources for shooting to save on buying. At the moment, I found a 600W led chip, but I need to look for a more powerful one around 1000 watts

Nikon1

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Re: Issue with horizontal darkening w/ bright things
« Reply #6 on: April 01, 2020, 07:12:07 AM »
Use more light, because cameras like the Vision Research Phantom have noise when the sensor sensitivity is increased and use a lot of powerful light sources to compensate


Here is one example of the light:
https://www.bhphotovideo.com/c/product/1247485-REG/mole_richardson_6371_1600_watt_tener_led.html


As soon as I get my camera I will make myself powerful light sources for shooting to save on buying. At the moment, I found a 600W led chip, but I need to look for a more powerful one around 1000 watts
I only found those 500W white LED-Chips from China as the biggest thing on Ebay. If you find any bigger ones, like 1000W, please post a link or something, cause i would also like to get some.   
But for me ist the Same, i will build an array (Planing to do a few thousand Watt array), but only after i got the Camera. Have a Few 100W chips right now, but those arent bright enough if i want to get some Soft Light (Like Bounce the Light off an wall or something alike) in bigger Scenes.   

Nikon1

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Re: Issue with horizontal darkening w/ bright things
« Reply #7 on: April 01, 2020, 07:17:34 AM »
Use more light, because cameras like the Vision Research Phantom have noise when the sensor sensitivity is increased and use a lot of powerful light sources to compensate


Here is one example of the light:
https://www.bhphotovideo.com/c/product/1247485-REG/mole_richardson_6371_1600_watt_tener_led.html


As soon as I get my camera I will make myself powerful light sources for shooting to save on buying. At the moment, I found a 600W led chip, but I need to look for a more powerful one around 1000 watts
Also, wow, that is one expensive Lamp right there in the B&H Link.... just checked... 10k.   
I have an 1200W and an 600W HMI Lamp, but those will flicker for High Framerate Shots (anything above 50fps will Flicker pretty badly with that Lamp).So i will definatly need to get something powerfull with LED, cause Tungsten Lamps will just need crazy amounts of Power to be anywhere near as bright....

SergeyKashin

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Re: Issue with horizontal darkening w/ bright things
« Reply #8 on: April 01, 2020, 08:30:40 AM »
Use more light, because cameras like the Vision Research Phantom have noise when the sensor sensitivity is increased and use a lot of powerful light sources to compensate


Here is one example of the light:
https://www.bhphotovideo.com/c/product/1247485-REG/mole_richardson_6371_1600_watt_tener_led.html


As soon as I get my camera I will make myself powerful light sources for shooting to save on buying. At the moment, I found a 600W led chip, but I need to look for a more powerful one around 1000 watts
Also, wow, that is one expensive Lamp right there in the B&H Link.... just checked... 10k.   
I have an 1200W and an 600W HMI Lamp, but those will flicker for High Framerate Shots (anything above 50fps will Flicker pretty badly with that Lamp).So i will definatly need to get something powerfull with LED, cause Tungsten Lamps will just need crazy amounts of Power to be anywhere near as bright....


OK man
As soon as there is any news about the light, I will definitely let you know. Also, the led chips that I found at 600 watts are with a high color rendering index of 95, but I do not want to advise them yet, as soon as I do the tests, I will share links to them

Nikon1

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Re: Issue with horizontal darkening w/ bright things
« Reply #9 on: April 01, 2020, 08:40:33 AM »
Use more light, because cameras like the Vision Research Phantom have noise when the sensor sensitivity is increased and use a lot of powerful light sources to compensate


Here is one example of the light:
https://www.bhphotovideo.com/c/product/1247485-REG/mole_richardson_6371_1600_watt_tener_led.html


As soon as I get my camera I will make myself powerful light sources for shooting to save on buying. At the moment, I found a 600W led chip, but I need to look for a more powerful one around 1000 watts
Also, wow, that is one expensive Lamp right there in the B&H Link.... just checked... 10k.   
I have an 1200W and an 600W HMI Lamp, but those will flicker for High Framerate Shots (anything above 50fps will Flicker pretty badly with that Lamp).So i will definatly need to get something powerfull with LED, cause Tungsten Lamps will just need crazy amounts of Power to be anywhere near as bright....


OK man
As soon as there is any news about the light, I will definitely let you know. Also, the led chips that I found at 600 watts are with a high color rendering index of 95, but I do not want to advise them yet, as soon as I do the tests, I will share links to them
Thanks a lot!   
High CRI is always welcome, since those cheap ebay ones are mostly far from good.   
I bought a few pretty cheap 100W ones and those where somewhat decent, but still far from perfect in terms of color.   
Still, one of the best ways to get a ton of light for cheap.   
I also tried those 100W ones with integrated driver circut. Those will mostly flicker, but i did just feed them DC current @320V or something like that, and then they will give Flicker-Free Light even at 1000+fps.   
Really Like those integrated Driver ones, cause you can just build an Array with just connecting them All to Mains without need for some Crazy Power Supply (Speaking about an Multi-1000W Array...). But a few Bigger ones (1000W chips) will also just make the Setup very easy, cause then you wont need to wire up like 60 or 90 single LED-Chips.   
Absolutely looking forward to your testing if you manage to find something that Powerfull!Thanks!

Prehistoricman

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Re: Issue with horizontal darkening w/ bright things
« Reply #10 on: April 03, 2020, 03:38:42 PM »
As soon as I get my camera I will make myself powerful light sources for shooting to save on buying. At the moment, I found a 600W led chip, but I need to look for a more powerful one around 1000 watts
I was also planning on making my own high power light source. Currently I have a ~30W array that is adequate for slower frame rates.
I got about 40x 7W LED COBs, I just need something suitably sized and priced to mount them on. Basic extruded aluminium heatsinks are surprisingly expensive (compared to the price of these LEDs from aliexpress haha).

This effect does occur at full width, or without gain it just takes a stronger exposure to cause it. The effect is caused by overexposing pixels way beyond their normal saturation point, which requires a lot more light when there is no gain.
You're right! I had to use a laser pointer to get it overexposed enough.

Nikon1

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Re: Issue with horizontal darkening w/ bright things
« Reply #11 on: April 03, 2020, 03:51:50 PM »
As soon as I get my camera I will make myself powerful light sources for shooting to save on buying. At the moment, I found a 600W led chip, but I need to look for a more powerful one around 1000 watts
I was also planning on making my own high power light source. Currently I have a ~30W array that is adequate for slower frame rates.
I got about 40x 7W LED COBs, I just need something suitably sized and priced to mount them on. Basic extruded aluminium heatsinks are surprisingly expensive (compared to the price of these LEDs from aliexpress haha).
Unless you want it to be very Portable, you can build some Cheap Water-Cooling Setup for it very cheap.Just get some Used/ Old Car Radiator and Find a Way to water-Cool the LED-Chips.As some Experiments with DIY (not done by me, can link, if you want...) Watercooling for Computer CPUs Showed, even just a Flat Plate of Aluminum or Copper with water Flowing on the Back of it will do surprisingly well in cooling Powerfull Chips. So just find a Way to Seal the Backside of the Plate and connect some Tubes to it and a Pump.If you are not running it for very long, you could even steal the Idea from Krontechs Light-Setup and dont even use an Radiator. Just use a Bucket of cold water and change the Water, when it gets to warm for your Liking. See Here: https://www.youtube.com/watch?v=A4u2xmk5Qys      I still am not quite sure, what i want to use for my array, since i want it to be fairly portable. For now i use some Old Server CPU-Heatsinks with Heatpipes, those can be get for very low price and Can handle a ton of heat, even with little Airflow (Big, Silent fans!)