Wednesday 15 July 2020

Night photo update on Raspberry Pi HQ camera with 16mm lens

To continue from yesterday's post, yesterday evening I took some photos of near and far street lamps (heavy cloud so no stars...). The results show the same effects, but possibly more pronounced.

Overall the bloom is greatly improved by stopping down to 2.8. In some circumstances there may be a further slight improvement by going to F4, but the difference is pretty small.

All these photos are taken with 2 second exposure.
First here are the full images:
This photo used analogue gain set to 1
F1.4
In the subsequent photos I adjusted the analogue gain to achieve equal brightness of the road area. Even in this small view, the bloom on the near light is already significantly smaller.
F2
and a bit better again
F2.8
This looks much the same?
F4

Crop on the near lamp

Heavy blooming at F1.4. Even the nearby leaves on the tree are completely blown by the bloom. The blue cast around the outer edges of the bloom is probably because the lamp has a strong blue component, and has 'leaked' further.
F1.4
Improved at F2. The blown area around the lamp is smaller and the leaves show more detail and better defined.
F2
Still significantly better at F2.8. This is as good as it gets. The effect on the leaves is reduced and although they are still blown, at least the leaf shapes are more visible.
F2.8
F4 doesn't look any better than F2.8
F4

Crop on distant lamps

Even on these distant lamps, There is a significant area of bloom around each lamp
F1.4
As with the near lamp, much better at F2
F2
And better yet at F2.8
F2.8
There looks to be a further slight improvement at F4
F4

3 comments:

  1. Hi pootle.

    I'm interested in how you are taking these pictures. (Are you using SSH, or pressing a button on the pi itself, do you use a touchscreen/remote desktop)

    I'm putting a brand new PI HQ camera onto my telescope. I used to use https://elinux.org/RPi-Cam-Web-Interface with the old V2 pi camera board - and whilst this seems to work with the new HQ camera, I'm not convinced it's working at it's best.

    Many thanks

    ReplyDelete
  2. Hi Mike, I've written my own version of a web pi camera interface, set up to use multiple ports so it can process images in parallel in different ways. It's functional but a bit flakey still, but I use it to live stream using mjpeg. However I've found that with long exposures the lag gets really painfull ( the web browser view is typically 2 frames behind reality - OK at 30fps, but painful at .1 fps! So I have just started testing with a small screen connected direct to the pi with the camera and using preview, which gives instant response. I still use the web interface to control it all, including setting zoom - and the zoom setting shows up immediately on the preview screen. My software is at https://github.com/pootle/piCameraWeb. I'm doing a big rework atm, so the docs are out of date though

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