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Author Topic: Why 2/3" Sensor only 8.8mm x 6.6mm (11mm diag.)  (Read 7136 times)

abcdefghi_rstuvwxyz

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Why 2/3" Sensor only 8.8mm x 6.6mm (11mm diag.)
« on: January 12, 2009, 02:33:02 am »

It seems all P&S sensor is over spec-ed.
You might think a 2/3" sensor is 16mm in diagonal, like a TV or monitor, but it'd actually 8.8mm x 6.6mm.
Same story for the 1/1.65" sensor.

The DSLR don't play this trick. It would say 1.5x or something like 24mm x 16mm or close.

Can you find whereabout is that 2/3" (same as 1/1.5"?) or 1/1.65" dimension?


 

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Yoram from Berlin

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Why 2/3" Sensor only 8.8mm x 6.6mm (11mm diag.)
« Reply #1 on: January 12, 2009, 03:41:58 am »

Uuuhhh... what?

I think you need to consider a sensor's size not only in terms of how it compares to a single frame of 35mm film, but also the effective size in relation to the lens - the distance from lens-back to sensor plane, and the size of the lens opening.
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Johnny_Johnson

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Why 2/3" Sensor only 8.8mm x 6.6mm (11mm diag.)
« Reply #2 on: January 12, 2009, 10:27:02 am »

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JeffKohn

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Why 2/3" Sensor only 8.8mm x 6.6mm (11mm diag.)
« Reply #3 on: January 12, 2009, 11:51:57 am »

Quote from: Iron Flatline
Uuuhhh... what?

I think you need to consider a sensor's size not only in terms of how it compares to a single frame of 35mm film, but also the effective size in relation to the lens - the distance from lens-back to sensor plane, and the size of the lens opening.
Uuuhhh... what?
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Jeff Kohn
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Yoram from Berlin

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Why 2/3" Sensor only 8.8mm x 6.6mm (11mm diag.)
« Reply #4 on: January 12, 2009, 06:19:11 pm »

Quote from: JeffKohn
Uuuhhh... what?
My assumption was the OP was wondering about "focal length equivalent" claims of P&S cameras... where it is not just the size of the sensor that determines what creates a "28-70mm equiv." (for instance)
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BJL

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Why 2/3" Sensor only 8.8mm x 6.6mm (11mm diag.)
« Reply #5 on: January 16, 2009, 12:14:03 pm »

Names like 2/3" for a sensor that is 11mm [0.43"] on the diagonal are a weird anachronism, even if they are an accepted standard industry-wide.

The frustrating thing is that sensor manufacturers like Sony use a more rational and accurate measure, the diagonal in mm. See for example this spec sheet:
http://www.sony.co.jp/~semicon/english/img...01/a6805284.pdf
where a so-called 2/3" sensor is described with

Image size: Diagonal 11mm (Type 2/3)


Why on earth do camera makers not change to this simple use of diagonal size in mm which is right there on the sensor maker's spec. sheets? Is it fear that folks in backwards, non-metric system countries (just Myanmar, Liberia and the USA last time I checked) will find measures like 8mm harder to understand than weird and inaccurate measures like 1/2.3" ?
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Ray

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Why 2/3" Sensor only 8.8mm x 6.6mm (11mm diag.)
« Reply #6 on: January 16, 2009, 06:57:55 pm »

Quote from: BJL
Why on earth do camera makers not change to this simple use of diagonal size in mm which is right there on the sensor maker's spec. sheets? Is it fear that folks in backwards, non-metric system countries (just Myanmar, Liberia and the USA last time I checked) will find measures like 8mm harder to understand than weird and inaccurate measures like 1/2.3" ?

I suspect that manufacturers are happy to continue with this archaic method of describing sensor size to ensure that most buyers of P&S cameras remain ignorant about the actual size of the sensor in their P&S camera. If the issue of size is obfuscated, then the customer will be less concerned with the fact that size really does matter when it comes to a camera's sensor, if image quality is a concern.

The typical pocketable P&S is 1/2.7" format size with a sensor diagonal of 6.72mm. The larger variety of P&S, the 2/3" format, has a diagonal of 11mm. The difference between these two formats is equivalent to the difference between the Canon cropped format DSLR, such as the 50D, and the full frame 35mm format such as the Canon 5D. The crop factor is approximately 1.6x in each case.
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