I got one of the 16 MP Autofocus camera modules from the kickstarter project.
Sofar the installation on raspian OS went fine and the camera as well the autofocus works fine. I use the camera within an outdoor case to take pictures of the sky, the clouds and sunset. I create Timelapses mainly.
My issue is that I have difficulties to adjust brightness, ev or expose right to not have totally blown out images once the sun turns towards the camera.
I tried to adjust the parameters of libcamera-still to deal with the sunlight, but most of the pictures turn half white blown out in the upper part of the horizont where the sky is.
Is there no way to set ISO value like in raspistill? Or where can I get one of these tuning JSON files to maybe auto adjust the exposure some how?
I noticed the same issue.
It appears that the lowest achievable ISO (ISO 100 apparently?) and the shortest exposure time (it looks like it should be 100microseconds, but the shortest I saw was 150 us) combined with the rather large aperture just overwhelm the sensor in full daylight.
I ended up adding a ND8 filter, which allowed me to achieve properly exposed clouds in the sky. You could probably get away with a bit less density, something like ND4, 2 stops down should do it.
Downside is, I need a loooooot more time (or gain) for night time exposures now.
Question for Arducam:
Is this a limitation of the software, or actually of the sensor? I can’t remember ever having problems taking daytime photos with my smartphone, and the IMX is a common smartphone camera chip…
You can manually set shutter and gain:
libcamera -t 0 --shutter 100 --gain 1.0
–shutter is in microseconds.
I think it may be a related limitation of the sensor, when we set the exposure less than 20 lines (the unit of the exposure register is line length) the image is not normal. (IMX477 has the same problem)
So we limited the exposure register to a minimum value of 20 (for 2328x1748–preview resolution, the minimum exposure is around 270 microseconds)
Is there somewhere a sheet to view which gain value matches which ISO on the IMX519 ?
–shutter and --gain works, the exposure could be lowered, but without a sheet or documentation on the values it is a lot of testing required to get the right settings.
Also I wonder how to deal with exposure adjustment more or less automated to adapt unattended to the sunlight Leven outside.
There is currently no such table.
Maybe you can try the
--ev parameter, for example
--ev -2 will get a darker image than normal.
Also, can you provide relevant photos?
I’m not quite sure about the scene you’re photographing, generally the auto exposure algorithm will measure the brightness near the center area and try to adjust it to the proper range.
Seems to me the --ev parameter for manual exposure adjustment doesn’t do anything.
I had to wait until today where sky is clear blue again and sun is out.
You can see when the sun directly faces the sensor not even autofocusing works at all. Once the sun is about to move towards right side and dawn is approaching, then autofocus works again. Anyhow, i struggle badly to deal with the sun and get an focused image at all.
1st PIC is all defaults just autofocus enabled:
Hint: You have to download or click the images to see them in the full resolution. Otherwise you can not see that it is not well focused / balanced. The preview size here in forum rather looks clear / sharp / well focused, but it is not in the files from the camera.
here a pic with shutter 150 and gain 1.0 set.
And here additionally I added --ev -50.0 and it does nothing it all… of course I tried lower values aswell.
Last one - even trying to overexpose with --ev 50.0 does nothing - I expected a totally blown out mostly white image here.
I forget to reply to Wong what my objective here is. I want to do Timelapse’s from the sky. Usually I use the --roi to crop the image to 1920x1080 resolution but I did the test pics here without that parameter.
Thanks for your information,
From the picture of --shutter 150 --gain 1.0, even with the exposure down to very low, the picture is still very bright. This may be why --ev doesn’t work. I will take the time to test it further.
Just confirmed that if the minimum exposure register is 20, for 2328x1748, the minimum exposure time is 269us, and the maximum resolution is 492us. This exposure time is still too large for shooting the sun.
Unfortunately, if the value of the exposure register is set to less than 20, the image will be wrong, so there is currently no good way to improve this problem.
Tahnk you @wong . I think I will try what @frx suggested and fit an ND 4 filter on my outdoor case I use for the raspberry and the camera.
I will report back how that worked out.
Okay, ND8 fitted and it is pretty much to less light now with default values. Also like @frx wrote, as soon as you start to raise exposure / gain values noise starts and kills the footage.
Tomorrow I try an ND4. Its a bit tinkering here as I have to fix those filters with glue inside of the case.
Thank you very much for your sharing,
I think this will be helpful for someone with similar needs!!
@wong you’re welcome.
Currently I have fixed an ND4 Filter to the outdoor camera case and with default values it is now sort of under exposed and the autofocus can not set the focus right. At least I think it is because of the exposure.
OK, obviously the autofocus had issues when the ND4 filter was too close to the lens.
I removed the clear window glas of the outdoor case and now the ND4 filter is the only glas before the lens.
the image is now sharper with --shutter 300 on a cloudy day but when there will be bright sunshine again it will for sure be overexposed.
With --shutter 150 the autofocus will not work well and the image will not be sharp.
I have to figure out a mechanism to identify the right shutter / exposure values before each single image will be made. Maybe I need to make a test image, somehow figure out values and based on those auto adjust and shoot the image with the best fitting values. But this will be a pain for creating unattended Timelapse.
Sun came through a bit more and now with --shutter 300 autofocus not works well anymore.
Okay interesting. Obviously it is --roi values related how focus is set. If I do a full sensor image with --shutter 300 the image is sharp now.
@wong can you give some more information which values either set or automatically have influence on the focusing area?
The autofocus area is a large area near the middle and now we can’t modify it.
For automatic exposure, it calculates the central area by default.
Regarding automatic exposure, you can achieve different effects by setting different exposure modes.
For details, please refer to: