Brightness of a "long" rendered image from 49 UAV / drone images shifts from bright to dark

[johngithens]

I ran into the same problem, first when using MS Image Composite Editor, and now after using Affinity. After rendering, the composite image is bright at one end, then gradually becomes dark at the other end.

Here's some background. I have a collection of images taken with a programmed drone on which there is a camera aimed straight down (nadir). The camera has a quality, non-fisheye lens. The drone flies in a horizontal "lawnmower" pattern above a long drainage ditch. The images in the first row are taken at intervals to overlap by 80%, then the drone shifts over some distance and flies in the opposite direction. The images in this second row overlap the images in the first row by 70%. (note for the UAV/drone enthusiasts: the images are not geotagged)

Before you jump to conclusions, here's more background:  If I use 39 of the jpg images in the collection, the resulting composite image is just fine. Nothing to complain about.

However I needed to include more ground area in the composite image, so I added 10 more, adjacent images to the collection to be processed by Affinity. After rendering, the composite image is bright at one end, becoming dark at the other end. (By the way, the source images are excellent, with very little differences in overall brightness or color.)

Again, I encountered the same problem with both MS ICE and Affinity. 

I don't expect a quick fix for this problem. There appears to be a fundamental limitation in both products.

My next attempt will be to use Affinity with 40 images, then again with 10 more images, Then join the two composite images. Maybe that will produce a usable composite image.

I'm certainly open to suggestions!

[stokerg]

Hi johngithens and Welcome to the Forums,

Would you be able to upload the sources images used to our Dropbox so here and we can look into this further.

[johngithens]

Hi stokerg,  Thanks for responding. I have a DropBox account and am signed in. I rarely use DropBox. What should I do next to provide a folder with two sub-folders of image files? 

[stokerg]

5 minutes ago, johngithens said:

What should I do next to provide a folder with two sub-folders of image files? 

Just zip the 2nd group of images up and upload the zip file to the same link  

[johngithens]

Files uploaded. I appreciate your help. Would be great to have one reliable workflow to achieve even brightness. 

[johngithens]

Happy to upload a zip file with all 361 image files as the drone flew over the long channel in a serpentine pattern, if that would be useful. Affinity crashed on my Lenovo P70 when I attempted to construct a panorama from the full collection of images.

[johngithens]

As a followup, I captured the view in the attachment at some point. Note that the overall brightness from top to bottom is relatively even. I still have much to learn about using AP.

[Rocketdrive]

I'd copy the panorama to a second layer, and increase the brightness until the dark areas match the light areas of the original image. Then use a mask with a linear transparency gradient: the end with the now too-light areas should be 100% transparent, and the other end, now properly exposed, should be 100% opaque, covering the dark areas underneath.

The gradient can further be tweaked with intermediate steps.

[johngithens]

3 minutes ago, Rocketdrive said:

I'd copy the panorama to a second layer, and increase the brightness until the dark areas match the light areas of the original image. Then use a mask with a linear transparency gradient: the end with the now too-light areas should be 100% transparent, and the other end, now properly exposed, should be 100% opaque, covering the dark areas underneath.

The gradient can further be tweaked with intermediate steps.

Thanks! Sounds like that would be successful, once I learn more about creating the "linear transparency gradient". I would still like to discover the underlying reason why the panorama has that shift in brightness. Recently, I had more success with MS Image Composite Editor. MS ICE can stitch serpentine or zigzag image collections, which (so far), I haven't found a way to do successfully with AP.  Stitching many images of dense grasses and bushes in bright sun may be one or the more challenging situations. I will try the method you suggested. Much appreciated.