Can you explain cropped sensor jargon?

dnme

Looking at image sensors on bridge cameras, I am wondering what the figures mean - 1/2.3” CCD or 1/2.4"CCD ?

I understand the crop factor of a sensor in all camera except the very high end, I had a 50D for a while which had a 1,6x cf. But can anyone explain the figures above please?

What does 1/2.4" mean? How do I even read this? Is it one half point four? makes no sense.

Many thanks

mdebets

Have a read in Wikipedia here and here.

Thecageyone

Not really, but Wiki can:

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

Diagrams to the right of all the common sized sensors. gives a pretty good idea.

[edit] beat me to it ^^

dnme

Ive read the above links before I came here to post. I need a simple explanation if possible, not a 4000 word academic article that I cannot absorb

Thecageyone

Looks simple to me. It's just a ratio. It's smaller than a Dslr sensor, what else do you need to know? And you should maybe say why you've already looked up in your initial post. Were not psychic. Just trying to help.

DaireQuinlan

dnme wrote: »

Ive read the above links before I came here to post. I need a simple explanation if possible, not a 4000 word academic article that I cannot absorb

Dude :-) If the wikipedia article isn't sufficiently dumbed down for you, here you go...

They're very small.

It's best not to worry about it, and most manufacturers give 35mm focal length equivalents anyhow. There you go.

dnme

Alright guys.

I was just hoping someone could explain to me what "one half point four" translates as.

I'll get my coat!

Effects

If it's just a ratio then why does it have the inch symbol? Surely it wouldn't make a difference? As for the 1/2.4", the longest side certainly isn't 2.4 times the short side`.

CabanSail

The following section seems to explain the terminology used in compact and bridge cameras.

The sensor sizes of many compact digital cameras are expressed in terms of the non-standardized "inch" system, as approximately 1.5 times the length of the diagonal of the sensor. This goes back to the way image sizes of early video cameras were expressed in terms of the outside diameter of the glass envelope of the video camera tube.

woody_2000

I wouldn't worry about it too much, as it appears to be based on an old standard from the 1950s - which just happened to stick. The actual area of the sensor in mm2 (can't do superscript) is the important thing to note, and to just recognise and learn off the main sensor sizes - methinks:)

From dpreview.com:

Sensor Type Designation

Sensors are often referred to with a "type" designation using imperial fractions such as 1/1.8" or 2/3" which are larger than the actual sensor diameters. The type designation harks back to a set of standard sizes given to TV camera tubes in the 50's. These sizes were typically 1/2", 2/3" etc. The size designation does not define the diagonal of the sensor area but rather the outer diameter of the long glass envelope of the tube. Engineers soon discovered that for various reasons the usable area of this imaging plane was approximately two thirds of the designated size. This designation has clearly stuck (although it should have been thrown out long ago). There appears to be no specific mathematical relationship between the diameter of the imaging circle and the sensor size, although it is always roughly two thirds.

More here:

http://www.dpreview.com/learn/?/Glossary/Camera_System/sensor_sizes_01.htm

dnme

CabanSail wrote: »

The following section seems to explain the terminology used in compact and bridge cameras.

That completely confuses me

dnme

woody_2000 wrote: »

I wouldn't worry about it too much, as it appears to be based on an old standard from the 1950s - which just happened to stick. The actual area of the sensor in mm2 (can't do superscript) is the important thing to note, and to just recognise and learn off the main sensor sizes - methinks:)

From dpreview.com:

Sensor Type Designation

Sensors are often referred to with a "type" designation using imperial fractions such as 1/1.8" or 2/3" which are larger than the actual sensor diameters. The type designation harks back to a set of standard sizes given to TV camera tubes in the 50's. These sizes were typically 1/2", 2/3" etc. The size designation does not define the diagonal of the sensor area but rather the outer diameter of the long glass envelope of the tube. Engineers soon discovered that for various reasons the usable area of this imaging plane was approximately two thirds of the designated size. This designation has clearly stuck (although it should have been thrown out long ago). There appears to be no specific mathematical relationship between the diameter of the imaging circle and the sensor size, although it is always roughly two thirds.

More here:

http://www.dpreview.com/learn/?/Glossary/Camera_System/sensor_sizes_01.htm

again hugely confused.
1/1.8 is not a fraction, it is some kind of mix of imperial and decimal which I don't even know how to word?

Is it 1 over 1.8?

CabanSail

dnme wrote: »

That completely confuses me

It is a system devised by Americans, so is bound to be confusing. It has a mix of inches, metric, fractions and decimal. As said in the articles it should have been binned years ago. The confused dimensions don't even refer to a real lengths. Just use the names as titles and look up the specs.

dnme

as advised by some of you, I'll just forget about it. It's utterly crazy.

woody_2000

dnme wrote: »

again hugely confused.
1/1.8 is not a fraction, it is some kind of mix of imperial and decimal which I don't even know how to word?

Is it 1 over 1.8?

My point is that it practically doesn't/shouldn't matter (i.e. there should be no need to try and make sense of it) - and to just just learn what the most usual sensor sizes are -- e.g. my compact camera has a 1/1.7" sensor (Canon PowerShot S90), which simply denotes a sensor 9.5 mm x 7.6 mm in size (according to the table on the linked page)...

Beyond that, unless you need to understand the particular reasoning behind this seemingly obscure designation scheme, then you may need to spend a bit of time reading up on the history of it...

woody_2000

dnme wrote: »

as advised by some of you, I'll just forget about it. It's utterly crazy.

Umm... Yeah.... But at least now you know...

5uspect

If lenses are round why are photos square?

woody_2000

5uspect wrote: »

If lenses are round why are photos square?

Because round photos/videos might not be practical or desirable... :eek:



I guess it's the most practicable nature of the technology...

TinyExplosions

In film, you have different formats, including 35mm and Medium Format (120) film. This have different physical film sizes, and different characteristics because of that (ie at the same focal length you will get different results from 35mm and 120 as the film size is bigger).

When digital SLR's came along, they wanted to keep as much of the jargon the same, so that people coming from film would be able to use their lenses and their knowledge, so a Full Frame sensor is digitally the same size as 35mm (so a 50mm lens on a full frame camera will behave in a similar manor as a 50mm lens on a 35mm Film SLR).

Now, for reasons of cost (I presume, along with physical size), a number of 'cropped' sensors came out. These are physically smaller than a full frame sensor, and so behave differently to how you would expect if coming from a 35mm camera. The 1.4 and 1.5 stuff is the amount by which they differ.

So, if you were used to 35mm cameras, and knew that a 50mm lens would give you a certain field of view, and make a certain picture, if you wanted to take the same one on a camera with a cropped sensor, you'd have to divide 50 by 1.4 or 1.5 (depending on the type of cropped sensor, broadly 1.4 for Canon, 1.5 for Nikon) to get the same 'effect'.

All lenses are sold (afaik) with the 35mm equivalent focal length, so a 50mm lens will behave like a 50mm on a full frame body, and like a 75mm on a cropped frame when compared with a 50mm lens on a 35mm film camera.

Clear as mud!

leche solara

This from dpreview might help.

http://www.dpreview.com/learn/?/key=sensor%20sizes

woody_2000

leche solara wrote: »

This from dpreview might help.

http://www.dpreview.com/learn/?/key=sensor%20sizes

I had referred to exactly the same information on dpreview.com in post #10 (the link address was a bit different, though)

Just to avoid confusion for the OP.

CabanSail

TinyExplosions wrote: »

All lenses are sold (afaik) with the 35mm equivalent focal length, so a 50mm lens will behave like a 50mm on a full frame body, and like a 75mm on a cropped frame when compared with a 50mm lens on a 35mm film camera.

Clear as mud!

The focal length of a lens does not vary depending on what it illuminates. A 50mm lens is just that it does not become a 75mm on a cropped body. The "equivalents" are approximations for full frame performance. If it has a circle of illumination large enough it will be wide angle lens on medium format, normal on full frame and telephoto on a crop body. This is because the different sensors are using more or less of the projection of the lens. The resolution will also be higher on the larger sensors.

TinyExplosions

CabanSail wrote: »

The focal length of a lens does not vary depending on what it illuminates. A 50mm lens is just that it does not become a 75mm on a cropped body. The "equivalents" are approximations for full frame performance. If it has a circle of illumination large enough it will be wide angle lens on medium format, normal on full frame and telephoto on a crop body. This is because the different sensors are using more or less of the projection of the lens. The resolution will also be higher on the larger sensors.

Yes indeed.. I should have said that I was dumbing it down a little to try and explain it better!