Really EASY 4/3 sensor question ???

First off, I PROMISE that I have looked for the answer to this question...without success. Secondly, feel free to laugh at my ignorance...here goes.

Just yesterday, my son asked me why a four thirds sensor is called a four thirds sensor. I quickly said, "I guess it is 4/3-inch diagonal, or maybe 4/3 square inches." I knew it was NOT because it has a 4:3 aspect ratio -- lots of sensors in many sizes share that. So, 4/3 of what?

So, being the good geometry student, my son did a little research and revealed there was really nothing about the 4/3 sensor (except aspect ratio) that was anywhere close to 4/3rds of, well, anything. Huh? Millimeter ratios, diagonals relative to other sensors, areas...you name it. Nada.

Would someone please chime in and explain exactly what the four thirds is referring to, PLEASE? Apologies to those who are not amused.

It has to do with old analog TV camera sensors. They were inside of a glass tube with a 4/3" diameter. The rectangular sensor is smaller than the diameter of the tube

PhilSouth said:

First off, I PROMISE that I have looked for the answer to this question...without success. Secondly, feel free to laugh at my ignorance...here goes.

Just yesterday, my son asked me why a four thirds sensor is called a four thirds sensor. I quickly said, "I guess it is 4/3-inch diagonal, or maybe 4/3 square inches." I knew it was NOT because it has a 4:3 aspect ratio -- lots of sensors in many sizes share that. So, 4/3 of what?

So, being the good geometry student, my son did a little research and revealed there was really nothing about the 4/3 sensor (except aspect ratio) that was anywhere close to 4/3rds of, well, anything. Huh? Millimeter ratios, diagonals relative to other sensors, areas...you name it. Nada.

Would someone please chime in and explain exactly what the four thirds is referring to, PLEASE? Apologies to those who are not amused.

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Contrary to your understanding, it's the aspect ratio.

PhilSouth said:

First off, I PROMISE that I have looked for the answer to this question...without success. Secondly, feel free to laugh at my ignorance...here goes.

Just yesterday, my son asked me why a four thirds sensor is called a four thirds sensor. I quickly said, "I guess it is 4/3-inch diagonal, or maybe 4/3 square inches." I knew it was NOT because it has a 4:3 aspect ratio -- lots of sensors in many sizes share that. So, 4/3 of what?

So, being the good geometry student, my son did a little research and revealed there was really nothing about the 4/3 sensor (except aspect ratio) that was anywhere close to 4/3rds of, well, anything. Huh? Millimeter ratios, diagonals relative to other sensors, areas...you name it. Nada.

Would someone please chime in and explain exactly what the four thirds is referring to, PLEASE? Apologies to those who are not amused.

Click to expand...

Extract from Wikipedia :

"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."

The same arcane "logic" leads to the "one inch" designation of sensors having a diameter of 15.9mm (as seen in the Panasonic FZ1000 and others).

It is also the basis for designations such as 1/1.7 inch and 1/2.3 inch etcetera.

It has nothing to do with the aspect ratio and nothing to do with the actual size of the sensor.

Cheers

Andrew

axlotl said:

PhilSouth said:

First off, I PROMISE that I have looked for the answer to this question...without success. Secondly, feel free to laugh at my ignorance...here goes.

Just yesterday, my son asked me why a four thirds sensor is called a four thirds sensor. I quickly said, "I guess it is 4/3-inch diagonal, or maybe 4/3 square inches." I knew it was NOT because it has a 4:3 aspect ratio -- lots of sensors in many sizes share that. So, 4/3 of what?

So, being the good geometry student, my son did a little research and revealed there was really nothing about the 4/3 sensor (except aspect ratio) that was anywhere close to 4/3rds of, well, anything. Huh? Millimeter ratios, diagonals relative to other sensors, areas...you name it. Nada.

Would someone please chime in and explain exactly what the four thirds is referring to, PLEASE? Apologies to those who are not amused.

Click to expand...

Extract from Wikipedia :

"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."

The same arcane "logic" leads to the "one inch" designation of sensors having a diameter of 15.9mm (as seen in the Panasonic FZ1000 and others).

It is also the basis for designations such as 1/1.7 inch and 1/2.3 inch etcetera.

It has nothing to do with the aspect ratio and nothing to do with the actual size of the sensor.

Click to expand...

Of course, it's very easy to misrepresent things by selective quoting.

In this respect, also from Wikipediia:

"The emphasis on the 4:3 image aspect ratio sets Four Thirds apart from other DSLR systems"

MisterBG said:

Contrary to your understanding, it's the aspect ratio.

http://en.wikipedia.org/wiki/Four_Thirds_system

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Strange. In that page I can only find one place where the origin of the name is described, and it says this:

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.

So the page directly says that the name comes from the size, not from the aspect ratio.

(I can see that you later quote from another section of that page, describing an emphasis on 4:3 aspect ratio. But there is nothing stating that this emphasis has founds its way to the naming of the sensor. Actually, that same section explicitly states that an 3:2 aspect ratio would be possible within the Four Thirds standard.)

MisterBG said:

axlotl said:

PhilSouth said:

First off, I PROMISE that I have looked for the answer to this question...without success. Secondly, feel free to laugh at my ignorance...here goes.

Just yesterday, my son asked me why a four thirds sensor is called a four thirds sensor. I quickly said, "I guess it is 4/3-inch diagonal, or maybe 4/3 square inches." I knew it was NOT because it has a 4:3 aspect ratio -- lots of sensors in many sizes share that. So, 4/3 of what?

So, being the good geometry student, my son did a little research and revealed there was really nothing about the 4/3 sensor (except aspect ratio) that was anywhere close to 4/3rds of, well, anything. Huh? Millimeter ratios, diagonals relative to other sensors, areas...you name it. Nada.

Would someone please chime in and explain exactly what the four thirds is referring to, PLEASE? Apologies to those who are not amused.

Click to expand...

Extract from Wikipedia :

"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."

The same arcane "logic" leads to the "one inch" designation of sensors having a diameter of 15.9mm (as seen in the Panasonic FZ1000 and others).

It is also the basis for designations such as 1/1.7 inch and 1/2.3 inch etcetera.

It has nothing to do with the aspect ratio and nothing to do with the actual size of the sensor.

Click to expand...

Of course, it's very easy to misrepresent things by selective quoting.

Click to expand...

His answer is honest.

The name does not come from the aspect ratio contrary to what you pretend.

BG454 said:

In this respect, also from Wikipediia:

"The emphasis on the 4:3 image aspect ratio sets Four Thirds apart from other DSLR systems"

Click to expand...

Allan Olesen said:

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.

So the page directly says that the name comes from the size, not from the aspect ratio.

(I can see that you later quote from another section of that page, describing an emphasis on 4:3 aspect ratio. But there is nothing stating that this emphasis has founds its way to the naming of the sensor. Actually, that same section explicitly states that an 3:2 aspect ratio would be possible within the Four Thirds standard.)

Click to expand...

From the same Wikipedia article:

Allan Olesen said:

Allan Olesen said:

In an interview John Knaur, a Senior Product Manager at Olympus, stated that "The FourThirds refers to both the size of the imager and the aspect ratio of the sensor".

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Click to expand...

Cheers

Christof21 said:

MisterBG said:

axlotl said:

It has nothing to do with the aspect ratio and nothing to do with the actual size of the sensor.

Click to expand...

Of course, it's very easy to misrepresent things by selective quoting.

Click to expand...

His answer is honest.

The name does not come from the aspect ratio contrary to what you pretend.

Click to expand...

So why does Wikipedia say otherwise?

READ THE QUOTE:

Member said:

Member said:

In this respect, also from Wikipediia:

"The emphasis on the 4:3 image aspect ratio sets Four Thirds apart from other DSLR systems"

Click to expand...

Click to expand...

Note that it says "emphasis on.. aspect ratio" NOT size.

MisterBG said:

So why does Wikipedia say otherwise?

READ THE QUOTE:

BG454 said:

BG454 said:

In this respect, also from Wikipediia:

"The emphasis on the 4:3 image aspect ratio sets Four Thirds apart from other DSLR systems"

Click to expand...

Click to expand...

Note that it says "emphasis on.. aspect ratio" NOT size.

Click to expand...

Bearing in mind your comments about selective quoting

If we quote more of the very same text (my italics):

BG454 said:

"The emphasis on the 4:3 image aspect ratio sets Four Thirds apart from other DSLR systems, which usually adhere to the 3:2 aspect ratio of the traditional 35 mm format. However, the standard only specifies the sensor diagonal, thus Four Thirds cameras using the standard 3:2 aspect ratio would be possible;"

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From the beginning of the same Wikipedia section:

BG454 said:

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.

Click to expand...

And below, complementing rather than contradicting:

BG454 said:

In an interview John Knaur, a Senior Product Manager at Olympus, stated that "The FourThirds refers to both the size of the imager and the aspect ratio of the sensor"

Click to expand...

Cheers

--
Alan Robinson

MisterBG said:

Christof21 said:

MisterBG said:

axlotl said:

It has nothing to do with the aspect ratio and nothing to do with the actual size of the sensor.

Click to expand...

Of course, it's very easy to misrepresent things by selective quoting.

Click to expand...

His answer is honest.

The name does not come from the aspect ratio contrary to what you pretend.

Click to expand...

So why does Wikipedia say otherwise?

READ THE QUOTE:

BG454 said:

BG454 said:

In this respect, also from Wikipediia:

"The emphasis on the 4:3 image aspect ratio sets Four Thirds apart from other DSLR systems"

Click to expand...

Click to expand...

Note that it says "emphasis on.. aspect ratio" NOT size.

Click to expand...

The old KonicaMinolta A200 had 4:3 (or 3:2 selectable) on a sensor described as 2/3" size.

The Kodak P880 had 4:3 (3:2 selectable) on a sensor described as 1/1.8" size.

By the way -- just a fun note given the way everyone "oohs" and "aahs" about high shutter speeds; while checking the P880's specs just now I noticed it had a top speed of !/4000. Never did notice that when I was using it for modest professional work! LOL.

After half a century in photography, I just took pictures and sold them!

It has the details .

The 4/3 sensor is twice the size of the 2/3 sensor on both dimensions, so actually 4x the area. And the 2/3 sensor is …

But check the link for the full story. It is interesting.

--
Geoffrey Heard
Down and out in Rabaul in the South Pacific
http://rabaulpng.com/we-are-all-traveling-throug/i-waited-51-years-for-tavur.html

MisterBG said:

Christof21 said:

MisterBG said:

axlotl said:

It has nothing to do with the aspect ratio and nothing to do with the actual size of the sensor.

Click to expand...

Of course, it's very easy to misrepresent things by selective quoting.

Click to expand...

His answer is honest.

The name does not come from the aspect ratio contrary to what you pretend.

Click to expand...

So why does Wikipedia say otherwise?

READ THE QUOTE:

BG454 said:

BG454 said:

In this respect, also from Wikipediia:

"The emphasis on the 4:3 image aspect ratio sets Four Thirds apart from other DSLR systems"

Click to expand...

Click to expand...

Note that it says "emphasis on.. aspect ratio" NOT size.

Click to expand...

Note that it says "emphasis on", not "name comes from".

of every other camera on the planet!

Not sure what everyone else is talking about.

4/3 is 4 UNITS (could be inches, Millimeters, Feet, miles, kilometers, WHATEVER) on the long side and 3 UNITS on the short side. So a sensor or a picture or a piece of film could be 4 x 3, 8 x 6, 12 x 9 or any combo divided by 4 UNITS in one direction and 3 UNITS in the other.

It has nothing to do with overall size. It is the Ratio between the long and short sides.

Edward Chatlos said:

Not sure what everyone else is talking about.

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But still you reply...

This is not a thread about the understanding of aspect ratios. We very well understand what an aspect ratio is.

We are talking about the origin of the naming of a sensor format called Four Thirds.

The question is whether the name of this particular sensor format came from the aspect ratio or from another property.

[No message]

Thanks for the link, but I couldn't find a direct answer the OP's original question "why is it called four thirds".

There is a rather oblique reference to size here:

Bobo Hodls said:

When the Four Thirds system was designed, special care was taken to avoid this problem and to achieve the optimum balance between high picture quality and compact size. The 4/3-type image sensor that resulted from this quest is where the Four Thirds system gets its name.

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From context "4/3 type" probably relates to size rather than aspect ratio, or more likely to a combination of size and aspect ratio as pointed out previously, but it is not made fully explicit in this section.

Cheers,

--
Alan Robinson

alanr0 said:

From the same Wikipedia article:

alanr0 said:

alanr0 said:

In an interview John Knaur, a Senior Product Manager at Olympus, stated that "The FourThirds refers to both the size of the imager and the aspect ratio of the sensor".

Click to expand...

Click to expand...

Click to expand...

I was a reporter at the unveiling of the 4/3rds format system in New York City in 2003, which was a joint production of Olympus and Kodak. At that time, the size of the sensor was the only reason cited for the name -- the aspect ratio was not mentioned.

As others have pointed out, the "4/3" type" nomenclature comes from vidicon tubes and refers to the diameter of the tube. It's unfortunate for us all that the engineering community decided to stay with the vidicon tube nomenclature for sensors even now, 50 years after vidicon tubes went the way of the dinosaur.

Not long after that initial launch, it became clear to Olympus, especially, that the name was confusing to people and had little meaning to them, a bad thing from a marketing point of view. So they began saying that the name referred to both the size and the aspect ratio. (I knew John Knaur and got several tech briefings from him back in those days, and I watched this adjustment in the marketing message as it happened.)

So, really, the answer is a little muddy. Aspect ratio was not originally a reason for the name, but very early on it was added as a reason by the companies who started the format. So I guess I would say that both reasons count, but one has a slight priority.

GOT it! THANK YOU ALL for chiming in, especially those with the reference to the link explaining the relationships to old TV camera tubes (Here: www.dpreview.com/glossary/camera-system/sensor-sizes); that is obviously what we were looking for.

Apparently, my son and I were not the only ones that were mystified. What remains a mystery is how using this "type-naming" technique stuck. Weird...sort of.

MANY THANKS!