Sensors, Sizes and How to Decipher Them.

[skida]

I have a question for all you techies out there. This has been doing my head in for weeks now:

When I read reviews in magazines I look at the technical info and while I understand on dSLRs they normally give the size of the sensor in millimetres or as a ratio of a 35mm frame, the magazines present the info on compacts in a different format, ie. Canon Powershot A650 IS; Sensor = 12.1mp, 1/1.7inch CCD. Is that 1 inch by 1.7 inch, 1 over 1.7 inch (mixing a decimal and a fraction) or something completely different? Why do they not just present the sizes the same way as the dSLRs?:coffee:

[canonman]

I have a question for all you techies out there. This has been doing my head in for weeks now:

When I read reviews in magazines I look at the technical info and while I understand on dSLRs they normally give the size of the sensor in millimetres or as a ratio of a 35mm frame, the magazines present the info on compacts in a different format, ie. Canon Powershot A650 IS; Sensor = 12.1mp, 1/1.7inch CCD. Is that 1 inch by 1.7 inch, 1 over 1.7 inch (mixing a decimal and a fraction) or something completely different? Why do they not just present the sizes the same way as the dSLRs?:coffee:

Hi Skida ! It is the most ridiculous state of affairs, and one that you can be forgiven being horribly confused over.
I know that you have said that you understand DSLR sizing, but just to re-cap on this, a full frame digital sensor (is based on the size of a 35mm negative) but actually measures 36mm along the long edge and has a height width ratio of 3x2 making the height 24mm.
This is about the only denotation of sensor size that actually equates to a real physical dimension. Most non-DSLR cameras have a ratio of 4x3 (like the old TV sets), and it is actually inside early TV cameras where the origins of the nonsensical sizes stem from. Don't ask me how exactly because I don't have a clue.
But for example a digi compact denoted with 1.1/8" has a sensor measuring 5.32mm x 7.18mm giving a 4x3 hxw ratio !!!??? What this does show, is just how tiny the compact sensors are....I will leave you to work out the surface area differences from the dimensions I've given.
It is time that this was standardised, but I think there is a lot to gain for manufacturers keeping the masses confused.......especially given that more and more people are realising that image quality is far more sensor-size related than being about large pixel count.

[skida]

I might still be a bit confused here: I still can't work out the size of the sensor on my latest camera which the specs state is 1/2.5in.

Does it mean one over 2.5, ie it represents a fraction of an inch, which = two fifths of an inch = approx 10mm?

skida
head exploding

[lostmysnorkel]

1st Questio:

What's your camera?

2nd Questio:
If it's not a DSLR, does the sensor size really matter to you being unable to change lenses and have to worry about the crop-factor?


For those who may find it interesting:

The 'Compact' ration of 4:3 was brought in because the camera manufacturers realised that most people woiuld be viewing their new digital pictures on a computer monitor and not as prints. They therefore made the image dimensions 4:3 so that it would fit a 4:3 computer screen.

(I've lost count of the number of times I've had to explain to Mother-In-Law why her Nikon Coolpix pictures always end up cropped to nothing when she orders 6"x4" prints straight out of camera!)

A 16:9 widescreen has got them stumped though!

[skida]

Hi. I was interested in the size of the sensor because I am aware that larger sensors generally give better quality (something to do with heat generation being more severe on smaller sensors?). If I had been able to decipher the specs it may have had a bearing on my decision.

My latest camera:

http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=11594&pq-locale=en_GB

[lostmysnorkel]

MMMM...there are others here far better qualified than me (in that they understand it) but I believe that PIXEL size is the important factor here.

Larger pixels, I think, will create less noise for example, than smaller pixels.

So, a 10Mp camera will be noiser than an 8Mp camera with the same sized-sensor.

TBH though, the mid to high-end D-SLRS have little to separate them in terms of sensor performance, and much the same goes for the 'bridge' style cameras such as this one.

I wouldn't worry too much about the technicals of sensor size/material etc unless you are making images that need to be ultra-precise for noise and resolution and if that was the case, then I suspect you'd be looking at a Nikon D3 or Canon 1DS Mark-whatever-it's-up-to-now.

[canonman]

Hi. I was interested in the size of the sensor because I am aware that larger sensors generally give better quality (something to do with heat generation being more severe on smaller sensors?). If I had been able to decipher the specs it may have had a bearing on my decision.

My latest camera:

http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=11594&pq-locale=en_GB

Skida, once you start looking at sensor noise issues with regard to sensor size....the variables are far too great for anyone to arrive at a meaningful conclusion. Size alone is then influenced by the volume and construction material of the camera body (thus accelerating or reducing heat dissapation), layout of internal circuitry etc etc etc. As Snorks has said, unless you are into very technical and precise image recording, these details are pretty much insignificant. Snorks is also right about the reasoning behind the 4:3 aspect ratio, but it's ironic that most computer screens, as with modern TV's are now widescreen in varying aspect ratios, non of which are 4:3.

I am no mathmatician, but given the actual sensor sizes I posted, perhaps you can work out the "formula" for sensor size calculation.......if in fact there is one? From my understanding on this, I don't think there is a calculation. You can however find tables on just about every sensor size manufactured, which actually gives the "physical size" and saves a lot of head scratching and mathmatical pondering.

[copycat]

Ok if you have a read of this (http://www.dpreview.com/news/0210/02100402sensorsizes.asp) it should help clear up the ccd size question

[skida]

Ok if you have a read of this (http://www.dpreview.com/news/0210/02100402sensorsizes.asp) it should help clear up the ccd size question

I certainly understood all the words that were used!

Actually, it answered my first question very well, but I still don't understand why they use a different method of presenting sensor dimensions for compacts and for dSLRs.