Topics

1

General / estimate image quality

« on: March 26, 2014, 05:38:22 PM »

Hi,

Somebody know what exactly do Photoscan to define the image quality?
I did some tests with different textures and exposure parameters fixed. Results are better for a fine texture (sand than gravel) and always better for S size than L size of the picture. But this coefficient seems to be very variable according to exposure and the type of the object (for example, an aluminium paper will have a better coefficient in under exposure than in over exposure).

More over, I have a photo test with a quality coefficient of 1.06. I thought this coefficient varied between 0 and 1.

Someone can help me? 

Jules.

2

Camera Calibration / How to calibrate

« on: March 24, 2014, 12:53:39 PM »

Hi everybody,

I would like to know how to calibrate with Agisoft Lens. I have took some photos with a Canon 100D (fix focal length of 50 mm, fix focus and  exposition parameters fixed).
I took 6 then 12 photos and I calibrate with these two sets. Results are not the same. Errors are diminished with 12 photos but parameters are different.

Parameters should not they be the same for a camera with fix focal length and fix focus  

3

General / curvature of model

« on: March 20, 2014, 11:22:12 AM »

Hi everyone,

I'm a student who works on physical modelling of stream in a laboratory flume. I want to study the morphological evolution of stream bed by photogrammetry. I did several models by fixing some target at the edges of the flume to give a scale to my model.
My problem is that the resulting model is curved. I give the same elevation (z=0) to all targets that are on the same plane but Agisoft generates an error of several cm (in the z axis) on the central target which gives this curved appearance. I first thought to a distortion effect  so I realize an optimization of parameters but the error is sometimes diminished or increased.
What Agisoft do during this step of optimization and what is the influence of checked parameters?

I try to calibrate my camera with Agisoft lens but parameters changes when I calibrate with 3, 6, 36, ... photos.

Why parameters are different according to the number of photos?
Shouldn't they be constant for a given device and a fixed focal length?

Best regards

Jules