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Author Topic: Does adjust brightness actually change the data?  (Read 3917 times)

Rosy

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Does adjust brightness actually change the data?
« on: February 14, 2018, 07:30:49 PM »
My input data is 16bit uint and the intensity values are in the range of [197, 2338] instead of between [0, 255]. When the data is loaded into PhotoScan, I need to adjust the brightness to visualize it. But no matter how I adjust, automatic or not, the images look blurrer than those I load with imageJ.

Is this step ("adjust brightness") only for visualization or it changes the values of my input data for following stitching processing?

If it changes the intensity value of the original data? How exactly is this step is done? Is it simple scaling over all channels or it scales based on one master channel?

Maybe, do I need to change the format and scale of my input data? Which format and intensity range does PhotoScan prefer?

Many thanks!

Alexey Pasumansky

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Re: Does adjust brightness actually change the data?
« Reply #1 on: February 14, 2018, 07:35:39 PM »
Hello Rosy,

Brightness adjustment doesn't have any effect on the orthomosaic generation and export procedure. The operation "scales" the range for each band according to input scale-factor (percentage).
Best regards,
Alexey Pasumansky,
Agisoft LLC

Rosy

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Re: Does adjust brightness actually change the data?
« Reply #2 on: February 15, 2018, 11:39:09 AM »
Hi Alexey,

Thank you for your reply. I'm a bit confused about your sentense "Brightness adjustment doesn't have any effect on the orthomosaic generation". I got the feeling that if visualization of my data is better (brighter, shows more details and constrast) after brightness adjustment, the stitching works better.

In an extreme case that I've tested :  If I don't do any brightness adjustment, the visualization of my data looks completely dark, showing no objects/features at all. If I just do the ordinary workflow on such data, the alignment step fails completely. Is it normal?

Does it mean I should always adjust the brightness to the level which shows as good "quality" as possible? (I mean the results images should be sharp, have better contrast, clearer features, etc.)

Alexey Pasumansky

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Re: Does adjust brightness actually change the data?
« Reply #3 on: February 15, 2018, 12:43:31 PM »
Hello Rosy,

I mean that brightness option for the orthomosaic is only applied in PhotoScan Ortho view mode for the convenience, it wouldn't be applied to the exported results. Also brightness modification wouldn't affect the processing steps,  so it seems strange that you've go better results when aligning the images after brightness adjustment. Maybe the alignment is not stable and may fail or complete irrespective to the brightness?
Best regards,
Alexey Pasumansky,
Agisoft LLC