4/3?

[ernesto]

I wonder the meaning of 4/3...
4/3 is the same as 1 and 1/3, but I wonder of what.
Any hint will be greatly appreciated!
Ernesto

 

[rover]

Aspect ratio, 4x3

 

[user237428934]

4:3, 3:2, 16:9 all just ratios of the sides of a rectangle.

 

[ernesto]

Ah! I see!!!
Thanks Rover and Tom
So it is not a fraction, but a proportion.

Ernesto

 

[gdi]

I understand it is officially derived from the sizing of the sensor - 4/3" -, based on old video camera sizing. Probably better to consider this than the aspect ratio, particularly given the newer m4/3 multi-aspect sensors.

Quote from wikipedia:

"The name of the system stems from the size of the image sensor used in the cameras, which is commonly referred to as a 4/3" type or 4/3 type sensor. The common inch-based sizing system is derived from vacuum image-sensing video camera tubes, which are now obsolete. The imaging area of a Four Thirds sensor is equal to that of a video camera tube of 4/3" diameter. [3]"

 

[Dwig]

...
So it is not a fraction, but a proportion.

To a mathematician, the two are equivalent.

The 4/3rd's consortium chose to use fraction notation (long side is 4/3rds the length of the short side) instead of the more common ratio notation (e.g. 4:3). You see the same dual notation when discussing the speed of a lens. There is f/stop notation, where "f" stands for the focal length, on most markings and most discussions, but "focal ratio" notation is used on the lens barrel's markings (e.g. "50mm 1:1.4").

 

[Abbazz]

I understand it is officially derived from the sizing of the sensor - 4/3" -, based on old video camera sizing.

Yup. Nothing to do with the aspect ratio. The best proof is that the Panasonic GH1 has an oversized sensor allowing it to shoot natively in multiple aspect ratios (4:3, 3:2, or 16:9) with a similar angle of view. My E-P1 can also shoot in 1:1 (square mode), although with a slightly reduced resolution.

Aspect ratios normally use the proportion notation (4:3), while sensor sizes use the fraction notation (4/3"), so it makes sense that the 4/3rds format also uses the fraction notation.

Cheers!

Abbazz

 

[arwetheryet]

Hi
Just a dumb question. Is the 16:9 aspect ratio (and for that mater the other ratio's), just cropping of the 4:3?

 

[laptoprob]

Other sizes than 4/3 are crops, because 4/3 is the max. size of the sensor. Well, size is obviously not the right word.

 

[Photon42]

Hi
Just a dumb question. Is the 16:9 aspect ratio (and for that mater the other ratio's), just cropping of the 4:3?

The actual implementations differ. See e.g. here: Comparision LX2/LX3

 

[Abbazz]

Other sizes than 4/3 are crops, because 4/3 is the max. size of the sensor. Well, size is obviously not the right word.

In fact, 16:9 is a crop from 4:3 with most cameras, but not with the Panasonic GH1. The GH1 has a larger sensor, thus allowing three different aspect ratios (4:3, 3:2 and 16:9) while retaining the same image diagonal (image circle). Please refer to the Panasonic website for further explanations:

http://panasonic.net/avc/lumix/systemcamera/gms/gh1/high_image.html

Cheers!

Abbazz

 

[gdi]

The GH1 sensor is great - you can choose the aspect ratio you want and know you are not wasting any sensor real estate by cropping. Hopefully this will be implemented in the future new m4/3s models.

From DPReview:

 

[M4streetshooter]

Actually, the aspect ration is not scientific at all.
It really comes from what is much more common.

In the US and much of the world......

4/3 is what most Television screens are....
16/9 is what most HD TV is....
3/2 is what 35mm usually is.
By using the above relationships, the eye has a more natural native eye travel.

 

[Tuolumne]

So, to ask another stupid question: Is a 4/3rds sensor 4/3 of an inch in length, i.e. 1.33 inches?

/T

 

[JoeV]

So, to ask another stupid question: Is a 4/3rds sensor 4/3 of an inch in length, i.e. 1.33 inches?

/T

No, it's not. That's the problem I have with people claiming it's "4/3 inches." The attribution that it's based on the NTSC video format's aspect ratio may be true, but it ain't 4/3 inches (which would be 1 and 1/3 inches) in size.

According to the Wikipedia article: "The sensor measures 18×13.5 mm (22.5 mm diagonal), with an imaging area of 17.3×13.0 mm (21.6 mm diagonal)." This is roughly 1/4 of a 135 format film frame. The diagonal (22.5mm) is almost an inch, but not quite.

~Joe

 

[Abbazz]

According to the Wikipedia article: "The sensor measures 18×13.5 mm (22.5 mm diagonal), with an imaging area of 17.3×13.0 mm (21.6 mm diagonal)."

Let me add (also from the Wikipedia article):
The 4/3 inch designation for this size of sensor dates back to the 1950s and vidicon tubes, when the external diameter of the video camera tube was measured.

There's a very useful page on DPReview summarizing the sensor sizes:
http://www.dpreview.com/news/0210/02100402sensorsizes.asp

Cheers!

Abbazz