Low Light tuning for AR0234 in OAK-D-LR

Sachin

I noticed here that custom tuning is needed for the sensors such that exposure is increased instead of the sensitivity during AE when going above 33ms. I tried using the one defined for the color camera. it doesn't seem to work for the AR0234. so is it possible to generate one that can be used such that all 3 AR0234 cameras can increase the exposure up to 200ms before adjusting the sensitivity? @Luxonis-Alex

Luxonis-Alex

Hey @Sachin, I'll follow up today with a patched AR0234 tuning for this case.
We have an API now like camNode.initialControl.setAutoExposureLimit(200*1000) but it can set values only less than the tuning limit.

Sachin

Luxonis-Alex Thanks. looking forward to the patch.

I did try the camNode.initialControl.setAutoExposureLimit(200*1000) even with that enabled for 200ms. it was reaching max of 33ms. at least with the current tuning limit.

Luxonis-Alex

Pushed to develop on top of today's 2.28 release.
AR0234 tuning (embedded in FW) maximum exposure was bumped from 33ms to 890ms, which is the limit for the lowest FPS the sensor can stream at with the current config, 1.12fps.

The configured FPS will auto-limit the max exposure, for example 5fps will limit the max to 200ms. If less exposure is needed (to minimize motion blur) the above API can be used to set a lower value.

CI build: luxonis/depthai-pythonactions/runs/10462256853

I saw there is a small issue currently for the max exposure limit (which is internally implemented as an integer FPS range), when the configured FPS is fractional (not an integer), we'll try to fix this as well in the future.
For example currently:

-fps 1 -> 1.12 fps (minimum possible) with max exposure 890ms
-fps 1.12 same FPS, but max exposure is 1/ceil(1.12) = 1/2 = 500ms
-fps 2.5 same FPS but max exposure is 1/ceil(2.5) = 333ms instead of the expected 400ms

Sachin

awesome. Thanks. Does it also handle that all cameras use the same exposure when chained? (at least it looks that way from my initial test)

and how to change the order you have mentioned in this commit. Incase we are using only Left and right cameras or left and center. @Luxonis-Alex

and any possible of a sub-release with this tuning anytime soon ?

Luxonis-Alex

Yes, as in that commit, we implemented 3A (actually exposure & white-balance) sync for all enabled cameras on OAK-D-LR: A (center), B (left), C (right). The main camera that will drive exposure is currently hardcoded:

A for A B C
A for A B
A for A C
B for B C

Maybe we will add a new control to change this default with the merging of luxonis/depthai-python986 planned for this week.

As for a release, not sure how soon that would be, maybe depending on other fixes we might add, in a few weeks...

Sachin

Luxonis-Alex only white balance and exposure. not ISO?

Luxonis-Alex

ISO as well (closely related to exposure)

Sachin

@Luxonis-Alex when using the manual exposure I see that after the exposure setting crosses the 99ms. the image dims down. the overexposed parts are now looks underexposed. seems to be some sort of overllow and increasing the exposure above 100ms doesn't change anything it stays the same.

80 millisec Image

100 millisec Image

500 millisec Image

Luxonis-Alex

@Sachin, just checking, is the camera FPS set to a lower value accordingly, for example 5FPS (or less) to set up to 200ms exposure, or 2FPS for a max for 500ms exposure. Currently we don't have FPS auto-lowering implemented.

Sachin

Luxonis-Alex
Ah got it. from the fps explanation before. I thought it would scale when ExposureLimit was set.
And yes. I confirm it works on changing the fps.