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Can one of you camera / video pro's explain this?

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Can one of you camera / video pro's explain this?

I found this on a website for a device I have and can't fathom out how it can be 5MP if it only records at 1.9 at the highest (for HD) - It doesn't make sense!
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Re: Can one of you camera / video pro's explain this?

That is one heck of a drop
The normal definition is total pixels count every pixel on the sensor surface. Usually the very edge pixels aren't used in the final image. Effective pixels are the number of pixels actually used in the image after the edge pixels have been dropped.
Is that referring to a specific image ratio
Which camera or mobile phone is it
pwatson
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Re: Can one of you camera / video pro's explain this?

Working backwards...
The 'effective' 0.921 Mpixel figure is the sample size (for luminance) of a 1280x720 video image.
The stills camera section can grab a 1600x1200 image and this equates to 1.92 Mpixel,but to be full resolution this would need to have 1600x1200x3 sensors to resolve red, green and blue correctly.  In reality there are fewer red and blue sensors than green.
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Re: Can one of you camera / video pro's explain this?

Quote from: Oldjim
Which camera or mobile phone is it

Samsung HMX-F90
http://www.samsung.com/uk/consumer/smart-camera-camcorder/camcorders/camcorders/HMX-F90BP/XEU-spec
I need a new signature... i'm bored of the old one!
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Re: Can one of you camera / video pro's explain this?

so the effective resolution in this case is when using it as a video recorder
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Re: Can one of you camera / video pro's explain this?

Yeah but still seems a bit daft (and low) considering it's a 5mp sensor!
Why do they chop off the side pixels? - Ok I'm assuming they loose a few just to make sure they don't have any black space but that is a lot of pixels to loose!
Seems a bit odd!
I need a new signature... i'm bored of the old one!
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Re: Can one of you camera / video pro's explain this?

About 14 years ago I had a 'spy' camera (looked like a pen- I needed it as security/leverage, that's another story).,This camera took vge 640x480, but also  1.3mp INTERPOLATED.  Never did understand what this meant,but these figures nothing to do with that?
nanotm
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Re: Can one of you camera / video pro's explain this?

interpolation is best described as it records in squares, each square is 100 pixels by 100 pixels, but the sensor only actually records a fraction of that and adds in the missing pixels through using side by side copy over, its a gash technology that often makes things look strange and totally messes up the colour quality, its very common for video resolution to be less than 10% of the total still picture level because of the speed of image capture cycling across the sensor face, in reality this is performed by switching pixels on the sensor face as each frame is captured, if your camera can take stills at a rate of 1 every 20 seconds then your video frame rate will likely be 1/20th of the quality of still images which accounts for the low rating of the camera still section Smiley
forgive me if that doesn't make total sense but trying to explain it without the use of actual pictures of what I'm saying is a wee bit difficult
just because your paranoid doesn't mean they aren't out to get you
pwatson
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Re: Can one of you camera / video pro's explain this?

There's pixels and pixels...  My brief explanation above clearly wasn't sufficient.
The sensor pixel count has red, green and blue sensitive sensors of which you need a contribution from all three to provide a 'display' pixel. A full resolution 1600x1200 image would therefore actually need a 5.76 megapixel sensor to generate the image.  In reality, there are twice as many green sensors as red and blue, arranged in a bayer filter so a 1600x1200 image can be generated by a 3.84 megapixel sensor and interpolated.
Using this sensor as an example:
The basic resolution is 2592x1944 (5 mega pixels) arranged in a bayer filter.  This is therefore generates an approximately 1832x1374 (2.5 mega pixels) image.  A 1600x1200 image can simply be cropped from this.
The sensor has a 4:3 (16:12) aspect ratio but HD video has a 16:9 aspect ratio so, straight away, 25% of the image isn't used,  The video is therefore created from, at most,  a 1832x1030 (1.9 mega pixels) but possibly a 1600x900 (1.44 mega pixels) section of the image.  
This is then downsampled to the desired 720p HD video resolution of 1280x720 ('Effective' 0.921 mega pixels)
[Moderator's note by Jim (Oldjim)  unnecessary sniping removed ]
Apologies Oldjim - I felt it correct to point out that the explanation from nanotm was completely wrong but could have been nicer about it Smiley