Ignorant 16x9 Question?

[Graham Bernard]

This is me exhibiting my ignorance.

Panasonic have this truly very covertable new camera. Seen the footage, marvellous! OK, it has an almost "square" sensor plate. I would be videoing in 16x9. Does this mean that a central slice is the only part of the sensor that is uilized? If this is the case how much of the 4/3 is ignored?

Apologies for uninformed question, but I can't get my head around this one at all.

Grazie

[Brian Drysdale]

I wouldn't worry, quite a lot of the standard 35mm motion picture frame isn't used either when it's being used for most productions since they stopped shooting 4x3.

That's why 3 perforation pull downs became more popular now that digital post production has become common. It saves money on film stock.

[Graham Bernard]

Thank you Brian.

Ok, then how much of the HD reso, as this a central slice, is being made use of? Or putting it another way, how much reso is available on the whole sensor?

So, as this is be triumphed as a full 4/3 this has more to do with it coming from a stills dynasty. Is that correct?

Grazie

[John Wiley]

Graham, what makes you think the sensor is "almost square"?

There is nothing in the 4/3rds standard which stipulates the sensor must have a 4:3 aspect ratio (although most early ones did). The only measurement it has to adhere to is a diagonal of 22.5mm.

With the GH1, Panasonic actually made a chip that was larger than it needed to be in order to accommodate 16:9, 4:3 & 3:2 aspect ratios. So even though the chip was being cropped at every aspect ratio, you still always ended up with a diagonal of 22.5mm.

It seems Panasonic are being tight lipped about the actual sensor they've used but I hardly think they'd take a step backwards by going to a 4:3 sensor and cropping to a diagonal which is less than 22.5mm. Most likely they use a similar oversized chip to the GH1/GH2 so your diagonal is going to be 22.5mm.

A lot of people overlooked this fact when comparing crop factors between the GH1 and 7d - they failed to note that the GH1 was generating wider 16:9 images by adding pixels on the side, while the 7d was cropping it's 3:2 sensor. The result was that the crop factors of the two sensors in video mode was closer than the usal 2x vs 1.6x comparison.

[Brian Drysdale]

Looking at the IBC video in new thread, they're using a 16:9 "slice" on the sensor, that 4x3 won't be an option on this camera and a guesstimate is 11 mega pixels.

[Graham Bernard]

Thanks John.

What I was wanting to see is a 16x9 area clearly, diagrammatically laying on top of this 4/3 sensor. Tight lipped? OK.

Here is the video I saw and at 2:02 the 16x9 Graphic is slotted-in, but over what? I'm confused. Is this just to show the comparisons TO 16x9? But just how would that 16x9 look if it was placed over this new 4/3?

Taking careful note of the numbers, it looks like 1.15mm top and bottom (13mm>10.7mm). But then the width of 19mm (this for the 16x9) how does this then fit into the 17mm width?

YouTube - 4/3" Sensor vs 35mm comparison

Cheers

Grazie

[Brian Drysdale]

You'll find a multi aspect diagram here:

Panasonic Lumix DMC-GH1 Review: 1. Introduction: Digital Photography Review

[Adrian Frearson]

Graham, it is a little confusing, especially as Panasonic are being tight lipped on the sensor being used. John Wiley has given quite a good rundown of this. I think it is probably likely that they have used an oversize sensor, as in the GH1/2 and the diagram Brian has posted should explain how it fills more area horizontally.

[Brian Drysdale]

Looking at the diagram, I take it that more or less 16:9 sits in the centre of the 4x3 with bands top and bottom that are no longer used. Which is basically how the standard 35mm motion picture frame is used for various aspect ratios.

Panasonic are being tight lipped about the actual sensor, but Jan Crittenden's description of it a "slice" would seem to indicate this is how they're doing it.

Although, if the sensor is rounded either side, i suppose they could have more width wiggle room with 16:9 compared to using a straight edged 4 x 3 sensor.

[R Geoff Baker]

To be honest, I'm not really sure what the question is -- but maybe this link to Panasonic's description of the sensor in the GH2 will help. Look down the page for a flash comparison of Lumix aspect ratios and how the same imaging chip can handle multiple formats. Note too that the pixel count -- both horizontal and vertical -- changes for each of the three choices, i.e. the 16:9 does not simply drop lines top and bottom.

Aspect ratio:
DMC-GH2 | PRODUCTS | LUMIX | Digital Camera | Panasonic Global

Pixel count by aspect ratio (File size - still image):
https://panasonic.ca/english/audiovi...ries_specs.asp

HTH,
GB

[Brian Drysdale]

That makes sense, basically the sensor is oversized for 4 x 3 in width, which is used as the aspect ratio changes to a wider format, so that the image diagonal remaining pretty constant. A combination of cropping top & bottom and widening.

Seemingly this camera is only available as 16:9 anyway, so it could be an academic exercise in this case.

[John Wiley]

Thanks Geoff, I hadn't seen that diagram yet.

It's still difficult to find any info on what sensor is used in the AF100, but what you can see from that diagram of the GH2 is that even though every aspect ratio takes only a "slice" of the sensor, they all still maintain the maximum possible area allowed by the 4/3rds spec which dictates a 22.5mm diagonal.

I feel it's necassary, just to clear things up, to state that 4/3 is very different to 4x3 or 4:3. 4/3rds is a measurement of the sensors size diagonally. It is a measurement directly comparable to those of other sensors such as 1/3", 1/4", 2/3" etc. 4x3 and 4:3, however, are aspect ratios. They compare the relative width and height of an individual sensor or image. A 4/3rds sensor is not necessarily 4:3 or 4x3 - many early ones were, though that changed as the format grew and developed. So a 4/3rds sensor can be natively 16x9 or 3:2.

[David Heath]

Originally Posted by John Wiley

It's still difficult to find any info on what sensor is used in the AF100..........

When first announced at NAB, I seem to remember it was definitely announced as a 12.1 megapixel four-thirds sensor at the Panasonic press conference, so generally assumed to be adapting one of the sensors from the stills range - which seems highly logical. It seems to have been further confirmed that the adaptation includes an optical low-pass filter - so expect it to have overcome the worst of the problems that plague vDSLRs, even though still using a similar type of sensor.

What hasn't been commented on is how the sensor is being read, which tends to make me think the worst - that it's still having to pixel skip, rather than read out the entire sensor each frame and downconvert. That will mean that at very least the sensitivity is unlikely to be as good as may be expected from that size of chip, even if the OLPF gets over the worst of the DSLR problems.

However good it turns out to be, it won't be as good as a custom designed for video sensor with the "right" number of pixels. For 1080 video, "right" is likely to be around 4 megapixels - enough to give full resolution (4 megapixel = 2x1920x1080 total, so 1920x1080 green), but few enough to be easily processed, and large enough to give optimum sensitivity.

[John Wiley]

Exactly - they gave a number (12.1 megapixles) and a format (micro 4/3rds) but not much else to go off. Is it 12.1 megapixels total? Or effective? If it's the effective number of pixels, then which pixels are thrown away? ie how is it cropped? What is the aspect ratio of the sensor? Is it the same as the multi-aspect ratio in the GH1?

As for how the image is read off the sensor - well, that's beyond my level of undrestanding but so far the footage looks really impressive - less of the aliasing and moire which troubles the other DSLR's/hybrids. And in the end, all that really matters is that the picture looks great!

[Graham Bernard]

Yes John, quite. And I'm still around and still reading.

Sooooo, boys, what is/how many pixies=reso is the 16x9 slice finally, actually, in reality, reading on this 4/3 sensor? A 4/3" sensor is big, and placed against a 35mm plate, it is jolly impressive.

And yes, now I've seen much footage, I do want this camera - so far. Knowing something through the physics always guides and tones down my expectations. Having a good enough tool can go to satisfying my creative urges. Knowing the difference between these two tensions is for my bank manager to know!

When I know something, I know it. When I don't, I ask.

Interesting thread, huh?

Grazie