RE: Comments on Image Capture draft

Hello Cullen,
Sorry I am late in getting back to you on this.  I am trying to clear up all comments on Image Capture spec at one go.  It would be easier for me to track these requests in the future if you go ahead and post issues on the repo:  https://github.com/w3c/mediacapture-image/issues.

> ISO does not makes much sense without aperture and speed. What does an implementation do when the ISO gets changed? How can an application use these to get the desired effect. Suggestion to add aperture and speed. On many devices the aperture is fixed and trying to change it would fail.

Note that this specification was written with respect to handheld devices and what the specific camera drivers in native platforms support.  The model was the QC driver in AOSP:  https://android.googlesource.com/platform/hardware/qcom/camera/+/master/QCameraParameters.h.  This may not be the best way to design a camera API, but in my opinion given the footprint of this driver in Android devices it is as good a reference as any other HW driver.

Digital ISO setting seems to be generally accepted to have expected behavior for different numeric settings (see http://digital-photography-school.com/iso-settings/ for an example).  In the QC driver, you'll notice that the ISO Mode settings are primarily numeric.  The spec written to allow flexibility in defining that numeric range.

Regarding aperture/speed setting, I am open to specific suggestions.  As can be seen, the QC AOSP driver does not seem to currently support this.  Please feel free to create a pull request.

> For all the things like brightness, shapness etc, need to say what the range is and how the browser implements them. (BTW - I think several of these might be better as floats than longs)

See http://w3c.github.io/mediacapture-image/#photooptions.  The range should be provided using this mechanism.

> Need to be able to set manual focus distance.

Was hoping this setting would land up on the MediaStream itself, but this isn't happening.  There has already been an issue filed requesting this.  Note that https://tools.ietf.org/html/draft-ietf-rtcweb-video-00#section-3.1 only calls for auto-focus currently.  So the underlying MediaStream would have auto-focus supported (and I assume enabled by default), but photos can be taken with a manual focus if I am to understand you correctly.  Or is my interpretation incorrect?

> Having the zoom be in something that can be mapped a field of view instead of relative lens would be much more useful for application programmers. So for example, it could be specified in what it would be in mm relative to a 35 mm sensor. Or it could just be represented as a ratio of sensor size.

Did you have a specific suggestion as to how the zoom setting could be defined?  Do you think the relative setting should not be made available at all?

-----Original Message-----
From: Cullen Jennings (fluffy) [mailto:fluffy@cisco.com] 
Sent: Thursday, September 11, 2014 12:48 PM
To: public-media-capture@w3.org
Subject: Comments on Image Capture draft 


Need an attribute to set the white balance color as an integer in degree kelvin.

ISO does not makes much sense without aperture and speed. What does an implementation do when the ISO gets changed? How can an application use these to get the desired effect. Suggestion to add aperture and speed. On many devices the aperture is fixed and trying to change it would fail. 

Lots of camera support a "sport mode" vs "portrait mode" or something like that. I would be nice to be able to tell camera if it was doing aperture priority or speed priority. 

For all the things like brightness, shapness etc, need to say what the range is and how the browser implements them. (BTW - I think several of these might be better as floats than longs)

Need to be able to set manual focus distance. 

Having the zoom be in something that can be mapped a field of view instead of relative lens would be much more useful for application programmers. So for example, it could be specified in what it would be in mm relative to a 35 mm sensor. Or it could just be represented as a ratio of sensor size.

Received on Thursday, 16 October 2014 17:00:20 UTC