Sony follows Panasonic's lead

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tom hardwick
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Joined: Apr 8 1999

Interesting to note that the new Sony FX1 HD camcorder takes a leaf out of the Panasonic DVX100A book. Sony have replaced the 6mm to 72mm (f1.6 to f2.4) on the PD170 with a 4.5mm to 54mm (f1.6 to f 2.8) lens on the new hi-def FX1 and Z1 - exactly the same spec as the Leica lens. The Zeiss comes with their justly famous T* multi-coating which can do the image nothing but good.

So now Zeiss and Leica match perfectly, although the Sony lens covers (presumably) a smaller 1/3" chip. Smaller? Well, a native 16:9 shape cut out of a 1/3" chip presumably does it within a smaller circle. Are my trigonometry thoughts correct here?

tom.

tom hardwick
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Joined: Apr 8 1999

I'm an idiot (there - I beat you to it). The Panasonic is only a 10x zoom and tops out at 45mm. Tom - engage brain before tapping keyboard.

infocus
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Joined: Jul 18 2003
Quote:
Originally posted by tom hardwick:
So now Zeiss and Leica match perfectly, although the Sony lens covers (presumably) a smaller 1/3" chip. Smaller? Well, a native 16:9 shape cut out of a 1/3" chip presumably does it within a smaller circle. Are my trigonometry thoughts correct here?

I think not quite. Allowing for a safety margin, the 1/3" refers to the diameter of a circle (the coverage of the lens). Hence 1/3" is the distance from corner to opposite corner of a rectangle with 4:3 or 16:9 ratio of sides. Therefore, compared to 4:3, I'd expect the 16:9 chip to be a little wider horizontally, but not as tall. Much easier to understand when you can draw it out.....

Alan McKeown
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Joined: May 9 2001

Diameter of circle = diagonal of rectangle = 0.3333”

Using the theorem of Pythagoras:

The width of the 4:3 sensor is:
(4/5) * 0.3333” = 0.2667”

The width of the 16:9 sensor is:
(16/18.3576) * 0.3333” = 0.2905”

Alan

Alan Roberts
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Joined: May 3 1999

Beware of trusting format sizes. Cameras quoting inch sizes are usually relating them to the image size of a standard 2"/3 tube, where the image diagonal is 11mm not 2"/3. So, for a 1"/3 image, that diagonal is 5.5mm, not 1"/3. Other than that the maths are exactly right.

It's only when the manufacturer quotes the image size in mm (e.g. 3.3mm x 4.4mm, which are the dimensions for a 1"/3 4:3 image) that you can believe them.

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infocus
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Joined: Jul 18 2003

All true - what's relevant to Tom is that for a "1/3"" (or 5.5mm) format, a true 16:9 chip gives a horizontal field of view that's nearly 10% wider than for a 4:3 chip, for the same focal length lens.

tom hardwick
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Joined: Apr 8 1999

For this extra covering power the lens itself has to be physically bigger, heavier and probably more expensive. Bigger gates require bigger image circles.

Alan Roberts
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Joined: May 3 1999

But just remember that when a manufacturer designs a camera with non-interchangeable lens, the optical design gets a lot easier. Quite a few of the design criteria are eased because there is no fixed point in the lens where an image has to be. So you get better optical performance for the same price, and so on.

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Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

infocus
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Joined: Jul 18 2003
Quote:
Originally posted by tom hardwick:
For this extra covering power the lens itself has to be physically bigger, heavier and probably more expensive. Bigger gates require bigger image circles.

Not true - we're working on the assumption that the lens coverage is a CIRCLE with diameter 1/3" in every case, with the imaging chip a rectangle all of whose corners just touch this circle. The proportions of the rectangle can then be anything you like. For 16:9 v 4:3 you're trading off vertical coverage for horizontal.