Stereo library 2012 pointers

Question

Dear programmers,
I am trying to evaluate the new Stereo Vision Library and since I am fairly new at this, I would greatly appreciate an advice or two.
My (simple) setup is:
- Two DSLR cameras (different models, Cannon 50D and 350D)
- Different lenses, but the focal lengths were the manually set to 35 mm
- Same lighting (outdoor)
- Baseline distance ~200 mm
I calibrated single cameras using a camera model and also corrected perspective distortion. I used a grid shown above in 20 different postitions. Here, I had no problem.
A static scene was considered, and the cameras were set on 10 s timer.
Moving on, I used the stereo library to calibrate the stereo system and saved the stereo calibration data.
 I used the semi-global block matching alghoritm to find the disparity image. Based on the equation
where f = 35 mm and b = 200 mm.
I calculated the minimum disparity and number of disparities for my working distance (approx. 500-3000 mm) -> min disp = 0, number of disp. = 16.
Using a small window size 7x7, I calculated the disparity for the following acquired images (an example of acquired image pair):
                                             Left image                                                                                                      Right image
The disparity image i get (non-interpolated) is:
The depth image isn't calculated (blank image) for some reason.
What am I doing wrong? I know I made some errors by my simplified system (the cameras are not fixed, the optics is not the same etc.), but what is wrong with the resulting disparity?
Is the problem in the  vertical misalignment of the images? From what I can gather, the biggest problem is the texture matching. I expected more segmented images (more areas of equal depth). Is there not enough texture to match both images?
If i try the example which is shipped with the Vision Module (Stereo Vision.vi) it works ok.
Please help with an explanation. And if I made a mistake, please be patient with me.
Thank you and best regards,
K
https://decibel.ni.com/content/blogs/kl3m3n
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Answer 1

Ohh.. I forgot to mention that I reduced image sizes to 600x400. My fault. Also, I made them gray-scale. I am passing your images (rescaled and gray-scaled) in the attachement (Grid as well as object images, again for this set also make left as right and vice-versa). Use them. For calibration, I did the same thing (rescaled and gray-scaled the grid images). Finally, I used the Calibration Interface to calibrate the images. I passed the stero calibration file to you in the last response; use that along with the images I have sent. You will then have to change the number of disparities and see whether you can get the disparity and depth properly or not. I have tried here but due to different sensors, responses are different. So, while it gives something; it is not too clear. For example, for image-set 18, I am getting depth of the table starting from 57 inches to ending at 76 inches, if I take distance between two dots in your grid as 1 inch. I would recommend the following things for your future endeavours:
1). If possible use the similar sensors (similar cameras).
2). Capture smaller images (600x400) for your convenience.
3). You do not require 20 grid images. 6-7 grid images with sufficient translation and angle coverage should do.
4). Work in monochrome mode.
5). Use textured images (or use patterned lighting, if possible).
While it is slightly involved to setup stereo, it is very easy thereafter. So, bear with the process for now. Typically, for an informed user (having already set the system in past), it takes 15-20 minutes to set-up, capture images and calibrate.
Regards,
Ronak.
Attachments:
Images.zip ‏4403 KB