8th January 2010, 10:49
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#48
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Registered User
Join Date: Sep 2006
Posts: 42
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Quote:
Originally Posted by Manao
I wasn't able to find any equivalence between lw/ph and effective resolution in pixels. What I was able to find, however, was that the IPhone has a lw/hp of 866 horizontally and 897 vertically. Which makes me doubt the quality of this camera. Care to explain ?
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That camera was in fact one of the highest effective resolution consumer 1080 cams (it fails in other areas such as low light performance though).
It would seem that their "video sharpness" test does in fact factor in temporal aspects such as interlacing/deinterlacing, temporal lossy compression etc (my assumption was wrong. Always delightful to improve understanding):
Quote:
Video Sharpness
The sharpness that a camcorder actually produces is rarely the same number that the manufacturer advertises. For instance, camcorders that output a 1920 x 1080 picture are not actually capturing one thousand nine-hundred and twenty horizontal lines of information. That's simply the size of the "container" that the camcorder outputs (also known as the resolution). In fact, there are lots of ways that manufacturers can play with the numbers, emphasizing capabilities of the lens, or the sensor, or something else. The simple fact is, you don't buy a sensor, and in most cases, you don't buy a lens. You buy a camcorder – a complete, pre-assembled camcorder, so that's how we test them.
We light a DSC Labs Multiburst chart at an even 3000 lux. The camcorder is stationed in a fixed position on a tripod. We aim the camcorder, aligning with the chart's 16:9 guideframes. We then pan the camcorder slowly left and right for about 30 seconds. Then we re-align the camcorder and tilt slowly up and down for about 30 seconds.
After the shooting is complete, we connect the camcorder to our HDTV using the camcorder's highest quality connection, typically either composite-out, S-video, component-out, or HDMI. We examine the playback footage, looking for the point at which the lines on the chart become indistinguishable.
The reason we test sharpness with the camcorder in motion, rather than a static shot, is simple. When was the last time you shot a video with nothing moving? The inherent nature of video is movement. This may not be the method manufacturers would prefer, but we think it makes the most sense.
The final score for this section is based on the horizontal and vertical sharpness as recorded in auto mode in the 60i frame rate. We may also examine the sharpness in other frame rates, but it does not factor into the score.
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http://www.imatest.com/docs/sharpness.html
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The use of Picture Height gives a slight advantage to compact digital cameras, which have an aspect ratio (width:height) of 4:3, compared to 3:2 for digital SLRs. Compact digital cameras have slightly more vertical pixels for a given number of total pixels.
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