[IGSTK-Users] Webcam question

[Yaniv, Ziv]

Hello Frederic,

Glad to see you are trying out our tutorial.

Short answer:
The tutorial will work with almost any webcam, no need to invest too much thinking into this.

The only differences will be in tracking accuracy (low quality optics --> low quality tracking). This is a tutorial, not a clinical system so we don't care that much.

Long answer:

1. If you are working on a laptop you can use the built in camera. The issue with using the built in camera is that you need to have your laptop half closed so that the camera can view the desktop. This works, but is really inconvenient. I am speaking from personal experience, as this is how I demo'd the tutorial in a class I taught.

2. Most webcams are either fixed focal length or come with software that allows you to disable auto focus. As a last resort, autofocus on + no way to disable, you can calibrate and work at about the same distance and then the camera will not change focus.

3. Webcams that we worked with:
a. Internal webcam of two laptops (we don't know their specs, just that one was a new Sony and the other a 4 year old Dell).
b. Logitech QuickCam Pro 9000.
c. Logitech HD Pro Webcam C920.

4. Tricks of the trade: the tracking accuracy also depends on the camera viewing angle. If you place the camera so that it views your working area "head on" you will get better tracking than an oblique viewing angle. The former is when you place the camera on the desktop on which you are working. The later is when you keep the camera on top of your screen (usual webcam configuration), and you have to tilt it sharply so that it sees your desktop.

5. For the most up to date code, use the git repository and not the source from the tutorial's web page. We have made some minor changes to the code.

        regards
          Ziv
--
Ziv Yaniv, PhD.,
Principal Investigator,
The Sheikh Zayed Institute for Pediatric Surgical Innovation
Children's National Medical Center
6th Floor Main Hospital, Room M7740
111 Michigan Ave., N.W
Washington, D.C 20010

Phone: 202-476-1288
email: zyaniv at childrensnational.org
web: http://isiswiki.georgetown.edu/zivy/

________________________________
From: igstk-users-bounces at public.kitware.com [igstk-users-bounces at public.kitware.com] on behalf of Frederic Perez [frederic.perez at alma3d.com]
Sent: Thursday, June 06, 2013 6:19 AM
To: igstk-users at public.kitware.com
Subject: [IGSTK-Users] Webcam question

Hello igstk-users,

I've downloaded the material for the nice “Introduction To Image Guided Navigation Using the Image-Guided Surgery Toolkit (IGSTK)”, Ö. Güler, Z. Yaniv (thank you both for your effort and for making it publicly available).

In order to reproduce the Image-Guided "Biopsy" (as it is called in the Presentations/IGI-Users.pptx document), a webcam is required, and it is stated that one should "Disable auto-focus if your webcam has this feature."

I plan to buy a webcam, but browsing through some webpages on different brands I cannot say which ones allow disabling auto-focus. Is that a general feature for those that offer auto-focus? Do you have any recommendation (so I don't end up buying a webcam that does not suit me)?

Thank you very much.

Best,  Frederic Perez

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