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Old December 13th, 2010, 11:49 AM   #46
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Adrian

Yep nice description and shows how the four thirds sensor could be different sizes as we already discussed. For 16/9 on the 101/100 though I'm 75% sure NOW the sensor is cropped!
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Old December 19th, 2010, 12:18 AM   #47
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From what i garnered from the IBC Vimeo clip, It's 4/3, 4:3 aspect ratio imager. I thought that's where I'd heard it! Go ahead and listen, carefully, to the description of the accommodation of the 16:9 "slice".

I'm glad that I do know the difference between the convention of a 4/3 and a 4:3 ratio, and here, unless somebody would like to correct me, on what I'd heard, was where I correctly got the comparison being made.

Listen carefully, it's around 9:38, on this Vimeo link, and starts as a result of a discussion around the ISO settings and 3200 which leads into this further discussion around the actual pixels being employed, listen carefully:-

IBC Vimeo clip

Now, for me, the real question still remains, is this 16:9 "slice" being achieved from the WHOLE 4:3 physical surface and then being electronically arranged as a 16:9 slice? Or is this 16:9 "slice" a physical masked area of the whole chip?

My opening post was about getting to grips about what I'd heard from this clip. And I'm still none the wiser as to which of these options holds for this camera, which, has to be said, from what I've seen makes amazing footage.*

I may not know much on this topic, but I do know what I don't know, and will continue to ask.*

Best regards

Grazie
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Old December 19th, 2010, 02:35 AM   #48
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Hi Grazie

When is a four third sensor not a four third sensor!

The four thirds system is not the shape or size but the spec and the size and shape can change within that spec. Specifically the DIAGONAL which can be 22.5mm on the 17.3 x 13mm which is a 4/3 aspect ratio. So if you physically lower that DIAGONAL 22.5mm to create a 16/9 the sensor on paper is wider and thats what they build.

However the suspicion is they have simply cropped a 17.3 x 13mm sensor and not made a wider but either a shorter sensor or just not using all the sensor area, or the 22.5mm diagonal spec. From all the evidence so far from Panny and reps it seems that's what we have.

Maybe they could make an anamorphic mode on it that could use the whole of the cropped sensor for max quality and would be compatible with a larger range of lenses than increasing the sensor size for 16/9. Wow that'd be something.
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Old December 19th, 2010, 03:25 AM   #49
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Originally Posted by Graham Bernard View Post
Now, for me, the real question still remains, is this 16:9 "slice" being achieved from the WHOLE 4:3 physical surface and then being electronically arranged as a 16:9 slice? Or is this 16:9 "slice" a physical masked area of the whole chip?
You don't need to physically mask the sensor, as you would a 35mm motion picture gate, they could just read out the 16:9 slice and leave the rest of the sensor unconnected, so that there isn't a full 4x3 option.

You'd need an anamorphic lens to use the full 4x3 as a 16:9 aspect ratio.
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Old December 19th, 2010, 03:44 AM   #50
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Well, I listened ... and I read your comments Grazie.

First, let me point out that Jan Crittenden is for all intents and purposes 'the horse's mouth' -- she has a firm grasp of her product and engineering, and though her answer was actually to a question a little different than the one you pose, I have no doubt that her answer was informed.

Second, and related -- Jan is a very active forum participant at another site; if you were to ask a technical question she would answer.

Third, I don't have a problem reconciling her comment with the slightly generic explanation offered in the Panasonic site I referenced earlier -- the one that shows a 4/3 sensor delivering 4:3, 16:9 and 3:2 from the same chip. If someone were to summarize that as offering a '16:9 slice from a 4/3 sensor' I'd say that was accurate ...

Fourth, I still don't really understand your question. Are you positing that the area of the sensor as used is NOT 4/3 standard? That would have implications for the lenses -- it would mean that the image in terms of depth of field, angle et cetera would not be the same in an AF100 when compared to a shot from a GH2 in 16:9 mode -- a suggestion that the camcorder would not follow the 4/3 standard. You seem to be asking if the camcorder is somehow anamorphic -- using the 'whole 4:3' sensor ... but that's just impossible. You can't have an anamorphic sensor like that without also having an optical lens creating a matching anamorphic image.

So I find I'm still where I was posts ago: A little unclear on your question, and suspecting the answer can found in the Panasonic brochure I linked.

Cheers,
GB
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Old December 19th, 2010, 04:16 AM   #51
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Quote by R Geoff Baker

the one that shows a 4/3 sensor delivering 4:3, 16:9 and 3:2 from the same chip. If someone were to summarize that as offering a '16:9 slice from a 4/3 sensor' I'd say that was accurate

I think there could be confusion in calling it a 4/3 sensor. Could be better to call it a four thirds sensor. That is what I wanted to know it is a slice from a four thirds sensor that has a 4/3 aspect ratio 17.3 x 13mm and not a 16/9 four thirds sensor.

Brian
Yes your right You'd need anamorphic lenses.
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Old December 19th, 2010, 06:34 AM   #52
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Originally Posted by R Geoff Baker View Post
First, let me point out that Jan Crittenden is . . . I have no doubt that her answer was informed.
Yes, I did and have read her credentials.

Quote:
Originally Posted by R Geoff Baker View Post
Second, and related -- Jan is a very active forum participant at another site; if you were to ask a technical question she would answer.
Would you care to share which site that is?

Quote:
Originally Posted by R Geoff Baker View Post
Third, I don't have a problem reconciling her comment with the slightly generic explanation offered in the Panasonic site I referenced earlier -- the one that shows a 4/3 sensor delivering 4:3, 16:9 and 3:2 from the same chip. If someone were to summarize that as offering a '16:9 slice from a 4/3 sensor' I'd say that was accurate ...
It's the word "slice" that I'm confusing myself over.

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Originally Posted by R Geoff Baker View Post
Fourth, I still don't really understand your question. Are you positing that the area of the sensor as used is NOT 4/3 standard?
I'm still confusing myself as to how one gets a 16:9 area from this sensor? How is it done? If you, Pannsonic and the rest of the team here have got it - good. I'm asking simple HOW this is done and still use the full area - or doesn't it? I used the word mask, one of our colleagues here says that it isn't a mask, rather that in those areas outside the 16x9 shape, the receptors wouldn't be connected. Sure, I can understand that, no problem.

Previously and in an attempt to understand this I was considering that ALL of the area was being used and that somehow the data from that sensor was being adjusted to fit a 16x9 shape. I was trying to fit a PINT into a HALF PINT pot. Can sensors be arranged in different ways to provide various shape configurations? Stranger things have happened.

So, and following the line of discussion, this would mean that not ALL of the sensor is being used, but what IS being used fulfills the HD convention, which for this sensor is what?

Grazie
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Old December 19th, 2010, 07:32 AM   #53
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Some Digibeta cameras use different areas of the sensor for shooting 4x3 and 16:9. The former doesn't use either side of the 16:9 sensor, the result being a narrower field of view when shooting 4x3.

This was a feature that was used during the transition from 4x3 to 16:9, now everything is shot using the latter.
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Old December 19th, 2010, 07:58 AM   #54
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I'm still confusing myself as to how one gets a 16:9 area from this sensor? How is it done?
OK. Take a piece of paper and draw a circle. Then draw a rectangle such that the corners are just outside the circle. The circle represents the coverage area of the lens, the rectangle represents the whole sensor area.

Now, you can draw a whole series of rectangles of different shapes (4:3, 16:9 etc) but all with their corners touching the circle. These represent the photosites that need to be read out to give the desired aspect ratio - no need for masking, it's just a case of selectively reading or not reading from the chip. The most obvious point that follows is that the diagonal dimension is ALWAYS the same - regardless of aspect ratio. It also should be obvious that some photosites will always be used (the ones nearest the sensor), others never will (the ones at the corner, outside the circle).

Not quite that simple in real life, but it gives the general idea. Most immediate fact is that for the 16:9 rectangle encloses about 12 million photosites. It's extremely unlikely that all are being read every frame, more likely one in three. In a DSLR, that's what gives the aliasing, in the AF101 a good optical low pass filter stops the aliasing. It's not as good as a purpose designed video sensor (as with Sonys F3), but is a lot better than a DSLR, whilst making use of off-the-shelf components.
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Old December 19th, 2010, 08:02 AM   #55
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Yes, I did and have read her credentials.

I'm still confusing myself as to how one gets a 16:9 area from this sensor? How is it done? If you, Pannsonic and the rest of the team here have got it - good. I'm asking simple HOW this is done and still use the full area - or doesn't it? I used the word mask, one of our colleagues here says that it isn't a mask, rather that in those areas outside the 16x9 shape, the receptors wouldn't be connected. Sure, I can understand that, no problem.

Grazie
I have posted this link earlier, it is Panasonic's own explanation, it includes a diagram. Perhaps if you indicate what in this specific explanation fails I'd have a clearer idea where you are going.

DMC-GH2 | PRODUCTS | LUMIX | Digital Camera | Panasonic Global

The Flash diagram that steps through three different aspect ratios includes an example of how Panasonic does it, and the 'wrong' way to do it.

It seems rude to Chris for me to identify the 'other' forum -- a Google of her name quickly turns up her posting habits.
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Old December 19th, 2010, 08:07 AM   #56
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Originally Posted by Mark David Williams View Post
Quote by R Geoff Baker

I think there could be confusion in calling it a 4/3 sensor. Could be better to call it a four thirds sensor. That is what I wanted to know it is a slice from a four thirds sensor that has a 4/3 aspect ratio 17.3 x 13mm and not a 16/9 four thirds sensor.
Unfortunately you are continuing the confusion in your own post:
4/3 = four thirds, not four to three
4:3 = four to three, not four thirds

A 4/3 sensor can be configured to have any aspect ratio, including 4:3, 3:2 & 16:9 -- the lens creates a circle, the aspect ratios are selected from an area within that circle.

HTH
GB
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Old December 19th, 2010, 08:32 AM   #57
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I beg to differ 4/3 or 16/9 have been used historically as ways that describe the 4:3 16:9 Aspect ratio. Maybe wrongly but never the less this is used through history. Certainly here in the UK.. NOW a new spec(Four thirds) for a digital sensor is using the same desctriptive term of 4/3 that many may or could associate with 4:3 and causing CONFUSION.

Just trying to help.

FOUR THIRDS SPEC
Rotate a DIAGONAL LINE 22.5mm with a hole in the middle rotate so the outside edge makes a circle Draw a 4:3 aspect ratio on its edges
NOW draw a 16:9 aspect ratio on its edges
Look at what youve drawn and you can see the 16:9 is wider.

HOWEVER
The camera uses the 4.3 aspect ratio and then cuts off the top and bottom So you are not using the full sensor and it is NOT close to being the same size as 35mm film It is about halfway between Super 16mm and Super 35mm. Panasonics claim that it is almost the same as 35mm frame is WRONG.
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Old December 19th, 2010, 09:14 AM   #58
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This is how the AF100 Manual describes the chip:
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Last edited by Olof Ekbergh; December 19th, 2010 at 09:45 AM.
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Old December 19th, 2010, 09:16 AM   #59
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My apologies if there is a regionalism at work here, though in my years in Hitchin, Hertfordshire it seemed to me the convention was followed -- a ratio was expressed with a : or occasionally (vernacularly) with an x as in 4x3 read as 'four by three' ... a / represented a divisor, so:
4/3 was four divided by three or four thirds
4:3 was four to three or four units compared to three units
4x3 was four by three, typically four somethings by three somethings -- so four inches by three inches as an absolute measure.

It is true that the American photographic convention of 8x10 was reversed to 10x8, but the American convention didn't follow through all examples so a small print was a 3x4 more often than a 4x3 for example.

But never, except in error, was a 4:3 ratio written as 4/3.

Again, if your corner of Herts was different my apologies, though I'd suggest the time has come to stand on the convention that expresses the least confusion. The 4/3 format is a fraction, as in four thirds of an inch, and may use 4:3 as a ratio, or 16:9 or 3:2 or, though I know of no examples, any other ratio as they will all fit within the circle cast by a lens designed to cover a 4/3 of an inch.

Cheers,
GB
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Old December 19th, 2010, 09:31 AM   #60
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FOUR THIRDS SPEC
Rotate a DIAGONAL LINE 22.5mm with a hole in the middle rotate so the outside edge makes a circle Draw a 4:3 aspect ratio on its edges
NOW draw a 16:9 aspect ratio on its edges
Look at what youve drawn and you can see the 16:9 is wider.

HOWEVER
The camera uses the 4.3 aspect ratio and then cuts off the top and bottom So you are not using the full sensor and it is NOT close to being the same size as 35mm film It is about halfway between Super 16mm and Super 35mm. Panasonics claim that it is almost the same as 35mm frame is WRONG.
You express yourself with clarity, but I see no reason to believe accurately. Panasonic's documentation for the GH2 is very clear in this regard, and at odds with your description. In the GH2, the same imaging chip uses more pixels in width for the 16:9 than for the 4:3 -- the correct way.

As for 'using the whole chip' I can't see how this is important or significant. The size of a 4/3 imaging chip at 16:9 is an 'absolute' -- if the designers choose to derive it from something larger, that seems neither here nor there, so long as they get it right.

As for the proximity to Cine 35 in size, there does indeed seem to be some hyperbole here. The real numbers are these:
Super 16 is 12.4mm x 7mm if a 16:9 ratio is used;
4/3 is 17.8mm x 10mm in 16:9 mode;
Cine 35 is 21.2mm x 11.9mm in 16:9 mode.
So 4/3 is twice the area of Super 16 but only seventy percent of the area of Cine 35.

Cheers,
GB
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