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General / Re: Alignment Experiments

« on: July 04, 2018, 10:37:30 AM »

I just ran some tests on a few existing images (of varying quality and content) and its seems the relationship between megapixels and maximum number of keypoints is approximately linear.

With 6MP Fujifilm S6500 i got ~35000 keypoints
With 12MP Nikon D90 i got ~70000 keypoints
With 16MP Nikon D7000 i got ~110000 keypoints
With 24MP Sony NEX7 i got ~150000 keypoints
With 36MP Nikon D800 i got ~240000 keypoints
With 50MP Canon 5DSR i got ~320000 keypoints

So the formula is that max no. keypoints ~= megapixels x 6400

i didn't include the fact that one of my nikon d800 images returned 280,000 keypoints as that ruined the graph and contradicted what Marcel posted. also his figure of 180,000 points for a 21MP camera doesn't fit either. i think this may be down to the fact that most of my images are not ideal, particularly with the lower end cameras, so there could be something more complex going on.

Also these were tests on JPG files, so TIFs or similar may give different results.

if you want to run the test on your own images, just make sure the console is visible when you run align images, with key point limit set to 0, and the console will display the number of key points detected in each image early on in the process.

Hey Mr James,
I'm rifki from Indonesia, I have any questions for you about alignment parameters. Someday you have statement that formula to get max no. keypoints ~= megapixels x 6400. How u can get 6400 from formula? It's constant? Can I use ur formula to align process of key point limit and tie point limit?
I'm newbie in agisoft and still studying for it.
Thank's before.

Rifki