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Author Topic: Camera lets you refocus after photo is taken  (Read 6365 times)

NotABunny

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Camera lets you refocus after photo is taken
« on: June 23, 2011, 02:38:00 AM »
Since there is no particular forum to post this to, here it goes.

There is a company which has developed a camera that allows people to refocus photos after they have been taken. They have a lot of example that you can play with (note that not all spots allow refocusing; click full view for better detail).

From their wording, it looks like they are not using focus stacking.

www.lytro.com

Quote
The light field is a core concept in imaging science, representing fundamentally more powerful data than in regular photographs. The light field fully defines how a scene appears. It is the amount of light traveling in every direction through every point in space – it’s all the light rays in a scene. Conventional cameras cannot record the light field.



Also at http://www.nytimes.com/2011/06/22/technology/22camera.html
« Last Edit: June 23, 2011, 02:51:56 AM by NotABunny »

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Camera lets you refocus after photo is taken
« on: June 23, 2011, 02:38:00 AM »

Fleetie

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Re: Camera lets you refocus after photo is taken
« Reply #1 on: June 23, 2011, 02:57:01 AM »
Apparently it (or at least, a similar prototype from 2004-2005) uses a microlens array between the main lens and the sensor. I'm not clear on how that helps, but I'd like to have it explained to me.

It seems that they are somehow capturing the direction information about incoming light, as well as just its intensity.

It looks as though the computation to perform the "digital refocusing" is pretty heavy.
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TBenson

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Re: Camera lets you refocus after photo is taken
« Reply #3 on: June 23, 2011, 08:20:47 AM »
Here's another source of info.  If nothing else, watch the video at the bottom of the page.  It is not the best produced interview I've ever seen, but for me the demo gave a better idea of what the camera can do.

http://www.engadget.com/2011/06/22/light-field-camera-captures-unprecedented-images-lets-you-cho/


amarlez

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Re: Camera lets you refocus after photo is taken
« Reply #4 on: June 23, 2011, 08:57:24 AM »
If I had to guess, it looks like they ratchet up the ISO, shoot at a really high f-stop, then let you pick where you want to focus in post.

amarlez

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Re: Camera lets you refocus after photo is taken
« Reply #5 on: June 23, 2011, 08:59:59 AM »
Example: The picture on their website of the kid eating and making a face.

DoesNotFollow

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Re: Camera lets you refocus after photo is taken
« Reply #6 on: June 23, 2011, 01:16:31 PM »
The idea of a plenoptic camera has been around for awhile now; the technology is just beginning to catch up to make some prototypes possible.

Essentially, it's a consequence of super high megapixel sensors (like Canon's 120mp APS-H). There's no way that any lens can produce enough resolution to make these sensors, so many sensors (sometimes hundreds) are grouped closely and each sensor gets its own lens. Each of these lenses are focused to a slightly different distance. Post-processing allows for the photographer to decide which areas are kept in focus and which are allowed to remain out of focus by using, or discarding, information from various sensors. It's a bit like focus stacking except all of the information is from one exposure.

http://web.archive.org/web/20080117075834/http://www.time4.com/time4/microsites/popsci/howitworks/lightfield_camera.html

This same idea can be used for more complicated things like 3D photography, but it all revolves around the same principle of multiple lenses focused at different distances.
« Last Edit: June 23, 2011, 03:24:30 PM by DoesNotFollow »

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Re: Camera lets you refocus after photo is taken
« Reply #6 on: June 23, 2011, 01:16:31 PM »

Canihaspicture

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Re: Camera lets you refocus after photo is taken
« Reply #7 on: June 23, 2011, 02:25:54 PM »
Introducing the Canon 3D...

DoesNotFollow

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Re: Camera lets you refocus after photo is taken
« Reply #8 on: June 23, 2011, 03:23:58 PM »
« Last Edit: June 23, 2011, 03:26:31 PM by DoesNotFollow »

aldvan

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Re: Camera lets you refocus after photo is taken
« Reply #9 on: June 23, 2011, 05:08:42 PM »
Just one doubt. Playing with the example, it seems that you are able to focus on a single spot, everywhere you want, but will it be possible to focus the whole range?

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Re: Camera lets you refocus after photo is taken
« Reply #10 on: June 23, 2011, 05:21:30 PM »
Just one doubt. Playing with the example, it seems that you are able to focus on a single spot, everywhere you want, but will it be possible to focus the whole range?

you can probably create a few different '2d' or 'traditional' photos from all the data, then layer them together as easily as you can take multiple-focus shots with a normal camera and layer them today.

surely the software would be easily enough manipulatable to 'fake' a narrow aperture or high DOF (without the diffraction) though...?
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Re: Camera lets you refocus after photo is taken
« Reply #11 on: June 23, 2011, 06:37:20 PM »
Apparently it (or at least, a similar prototype from 2004-2005) uses a microlens array between the main lens and the sensor. I'm not clear on how that helps, but I'd like to have it explained to me.

It seems that they are somehow capturing the direction information about incoming light, as well as just its intensity.

It looks as though the computation to perform the "digital refocusing" is pretty heavy.


Most of the articles about it refer to a microlens array.
There is another write-up on Wired as well:
http://www.wired.com/gadgetlab/2011/06/ren-ng-lytro/

I think the important point that is being alluded to, but not addressed directly is that this technology takes one element of interpretation and moves it from the photographer to the viewer of the image:
Traditionally, the photographer chooses where he/she wishes to place the point of focus, in order to direct the viewer's attention. With this technology, the viewer takes on this control.
From an artistic point of view, this raises an interesting discussion about whether or not the artist wants the viewer to have control of the interpretation of a work. - While the utility of a happy snapper being able to choose the focus point after shooting is something that appeals too many consumers, the interaction of the viewer with the interpretation is a totally different discussion.  Some photographers may not like the idea, because they will choose focus in a way that suits their interpretation of a scene, and they may not want the viewer to interpret a scene differently!
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docrender

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Re: Camera lets you refocus after photo is taken
« Reply #12 on: June 25, 2011, 02:23:04 AM »
After post processing plenoptic source file on computer effective resolution of the image could be really low. I'm predicting around 1Mpx max or something slightly bigger. But it is very interesting anyway :) To generate high resolution plenoptic kinda "RAW" file they need to deal with 100Mpx CCD or even bigger. Not quite possible for consumer product. Not yet.

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Re: Camera lets you refocus after photo is taken
« Reply #12 on: June 25, 2011, 02:23:04 AM »

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Re: Camera lets you refocus after photo is taken
« Reply #13 on: June 25, 2011, 04:44:32 PM »
I think the important point that is being alluded to, but not addressed directly is that this technology takes one element of interpretation and moves it from the photographer to the viewer of the image:
Traditionally, the photographer chooses where he/she wishes to place the point of focus, in order to direct the viewer's attention. With this technology, the viewer takes on this control.
From an artistic point of view, this raises an interesting discussion about whether or not the artist wants the viewer to have control of the interpretation of a work. - While the utility of a happy snapper being able to choose the focus point after shooting is something that appeals too many consumers, the interaction of the viewer with the interpretation is a totally different discussion.  Some photographers may not like the idea, because they will choose focus in a way that suits their interpretation of a scene, and they may not want the viewer to interpret a scene differently!

I've read that the technology is considered to be best for security cameras.  You can capture the images in very low light with this technology, and, if it becomes necessary to review the images, you can then focus sharply on the subject of interest.  With a limited depth of field in ordinary low light situations, this is a boon to reviewing recorded security photos.

I'm not sure its all that desirable for artistic images where the photographer has a subject in mind.

A product photo might be another application, a viewer could zoom and focus on a feature that interested him.

macgregor mathers

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Re: Camera lets you refocus after photo is taken
« Reply #14 on: June 28, 2011, 06:27:35 AM »
I think the important point that is being alluded to, but not addressed directly is that this technology takes one element of interpretation and moves it from the photographer to the viewer of the image:

<snip>

While the utility of a happy snapper being able to choose the focus point after shooting is something that appeals too many consumers, the interaction of the viewer with the interpretation is a totally different discussion.  Some photographers may not like the idea, because they will choose focus in a way that suits their interpretation of a scene, and they may not want the viewer to interpret a scene differently!

I'm not sure I'm following you.

What in the technology prevents the photographer from setting the focus at a certain point, turn the result into a JPEG (or printed paper, etc), and pass that to the viewer ?

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Re: Camera lets you refocus after photo is taken
« Reply #14 on: June 28, 2011, 06:27:35 AM »