[IGSTK-Users] Webcam question

[Frederic Perez]

Hello Ziv,

thank you very much for your answer. Since I'm working with a desktop PC, I
bet we'll start by buying one of the Logitech webcams that work for sure.
In the future we'll purchase a laptop and take care of the hindrances you
mention.

Best regards,

Frederic


On Thu, Jun 6, 2013 at 3:40 PM, Yaniv, Ziv <ZYaniv at childrensnational.org>wrote:

>  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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