Hello Everyone.

Something weird is happening with the photos taken with the P4M.

They seem to have a higher brightness circle in the center, I compared to contiguous photos of the same band and there's a difference on the same objects (left objects in centero of photo, right objets in the lower part of photo

I don't undestand why this is happening.


Thanks

Hi,I think it's due to image distortion. The center of the camera returns the light directly, not to the side. Do you see what I mean? If your overlap is tight enough, it's not a problem. At least with Metashape.

What you are seeing is a natural phenomenon called Heiligenschein, see here: https://en.wikipedia.org/wiki/Heiligenschein

Geebax Posted at 6-10 16:43
What you are seeing is a natural phenomenon called Heiligenschein, see here: https://en.wikipedia.org/wiki/Heiligenschein

You put a name to what I had in mind. thank you

If it is Heiligenschein, these authors say there's not much of a solution from photogrammetry software:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5677353/

also look at:

https://www.asprs.org/wp-content/uploads/pers/1973journal/nov/1973_nov_1205-1214.pdf
https://www.researchgate.net/publication/239924417_Dodging_research_for_digital_aerial_images


is there a way to confirm if this is addresed by metashape?
It seems to be a 50yr old problem

Thanks for your help

dpicassom Posted at 6-14 11:15
If it is Heiligenschein, these authors say there's not much of a solution from photogrammetry software:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5677353/

There are two solutions, you send me your photo and I pass it in Metashape with the settings that go well for the P4M, so you can judge the result yourself. Otherwise you download the 30 day trial version and do it yourself.

LV_Forestry Posted at 6-15 12:07
There are two solutions, you send me your photo and I pass it in Metashape with the settings that go well for the P4M, so you can judge the result yourself. Otherwise you download the 30 day trial version and do it yourself.

Thanks for your offering LV_Forestry,  I did it locally and the images as displayed by agisoft definitely look better, although I'm not completely sure, wished there was a way to see more contrast.

You have to change the bands to a 0-1 format by dividing by 32768. After all the rest can be done in QGIS. It is not necessary to adjust the contrast but it is possible. If you are simply looking for a quality visual rendering then Metashape is sufficient. With the raster calculator you can perform all the transformations. If you want to process the results more precisely by applying filters for example, software like QGIS is essential (and free).