Help with sensor size

Michele

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Aug 26, 1999
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I am currently using 2 very old digital cameras, bought in 2004, very behind the times. A digital rebel and an Olympus P&S, big and bulky. Mostly using the DSLR. However there are times when I just want one of those new P&S that I can carry in my pocket. Just for quick daytime pics, I'm not expecting alot.

My question is, I know that sensor size is important for good noise-free shots but I am not knowledgeable enough to be able to translate sensor speak. ;)

Went to dpreview and I see things like 1/2.5" or 1/3" or 1/17" for the sensor size on the P&S cameras so I thought well I'll see how that compares to a Dslr to know which would be better. Well they are all listed like 23.7 x 15.5 mm. Well how do those compare? What is a decent sensor size on a P&S going to be?

Also, I remember seeing some talk recently about how you don't want too many megapixels on too small of a sensor because that will give you alot of noise, so how many megapixels is too many?

They are listing things like effective pixels and sensor photo detectors, but I don't know what I'm looking for. Also, sensor type, what do I want?

Any help would be greatly appreciated. TIA!!! :thumbsup2
 
I did some quick research a few months back on the sensor size of PnS cameras.

Most of the PnS camera's out for sale today are 6x crop factor. That compares to a 1.3, 1.5, 1.6 or 2x crop factor on most dSLR's.

Some of the spec info on PnS camera's don't give the 35mm equilivent. But generally they are in the 6mm to 75mm focal length range which translates to about 36-450mm focal range on a film slr.

Even some of the better bridge camera's have the large crop factor.

I looked at my old Canon Powershot S30 and that has a crop factor of 4x. Yet its an older sensor. Today's sensors are much better.

Most of the sensor's on PnS camera's are around the same size. IIRC, Fuji has some models that are a bit larger. Groucho has an image of the different sensor sizes which really shows the difference.

I'm not really show how I would go about finding "the best" PnS. Best thing I guess would be to read the reviews of various models in the price range you want, then look for the features you want. Then look at sample images.

I would agree about the megapixel thing. Don't worry to much about how many it has. Generally speaking the larger the MP's, the more noise you'll get. That would be the last thing I look at. Though like I said, the technology is improving and things are better now than they were just a few years ago.
 
I hate to sound stupid....but I am ;) ...so if I am looking at 1/2.5", 1/3" or 1/1.7" which is bigger? I don't know how to read that.

Or do I have to apply that with some kind of crop factor? And how would I know what the crop factor is, that isn't listed on the spec list for each model. :confused3
 

For point and shoot cameras, or rather cameras on which you do not swap lenses, you don't worry about crop factor.

As far as zoom or telephoto or wide angle shooting goes, the most helpful number to compare one camera against another is the 35mm equivalent focal length.

For sensor size, one over a smaller number (for example 1/2.1) means a bigger sensor compared with one over a larger number (for example 1/3.2). If you feel more comfortable, use a calculator to convert the "one over" number into a decimal. (This is not the precise sensor size.) The rule of thumb is, the larger the sensor, the more sharp pictures are for the same number of pixels and the same choice of ISO. The same rule of thumb expressed in different words is, the larger the sensor the larger the number of megapixels you have without a grainier picture given the same choice of ISO. A sensor size difference of less than ten percent is probably not significant. I don't think there are any hard and fast rules (quantitative rules). DSLR's generally have much larger sensors than point and shoots so you can crank up the ISO more (to take pictures in low light conditions) before graininess becomes obtrusive. Similarly, ultracompact point and shoots will have smaller sensors than not so small cameras.

Digital camera hints: http://members.aol.com/ajaynejr/digicam.htm
 
Another quick question. So if I'm looking at two cameras, each with 1/1.8" as the sensor size, one with 8.0 megapixels and the other with 10.0 megapixels, should I go with the lower amount of megapixels, for less noise?
 
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Another quick question. So if I'm looking at two cameras, each with 1/1.8" as the sensor size, one with 8.0 megapixels and the other with 10.0 megapixels, should I go with the lower amount of megapixels, for less noise?
Hard to say. There are too many technical idiosyncrasies to make a quick statement one way or the other regarding whether the increased megapixels makes up for any added noise.

This question will need magazine reviews or other people's experiences to answer.

I would probably go with the higher megapixels.
 
Another quick question. So if I'm looking at two cameras, each with 1/1.8" as the sensor size, one with 8.0 megapixels and the other with 10.0 megapixels, should I go with the lower amount of megapixels, for less noise?

Some feel higher pixel density equals more detail, but IMO when printing small sizes one would not be able to see said detail. And then we get to the point where cheap/small lenses are unable to resolve that alleged extra detail.

IMO if two IDENTICAL in all other areas including price, I would get the one with the higher pixel count but I would not pay extra for it. Lets remember that yes higher pixel density results with more noise at higher ISOs, but if we downsize that image noise will also decrease to similar levels of those produced by the lower megapixel camera anyways.
 
In case Groucho can't get to this thread yet, here is the link to his visual example of sensor size. He's post it here many times in the past.

http://www.totalsham.com/gallery/misc/photography/Sensor+sizes.jpg.html?g2_imageViewsIndex=0

Sensor size is crop factor. That is how we get a crop factor because the size of a sensor is smaller than a frame of film (in the majority of cases).

4/3's is Olympus' sensor which is a 2x crop factor. You can see how a 1/1.8 and 1/2.5 is smaller. They are fractions, so 1/1.8 is bigger than 1/2.5.

I just find it easier to give it in a crop factor. Your not going to find much difference between the 1.5x and 1.6x crop. But there is a slight difference to the 2x crop (the 4/3's) and an even greater difference to the PnS camera's that have the 1/1.8 size sensor which is around a 5x or 6x crop factor compared to a dSLR at 1.5 and 1.6x.

IMO, if you want to compare the size of a sensor on a dSLR to a PnS, then one variable has to be the same. In my example, I use crop factor.
 
Thanks Kyle, you beat me to it. :)

Michele, I was confused a little too, until the lightbulb went off over my head and I remembered that these are no different than other fractions - ie, 1/2 a cup is bigger than 1/4 cup, 1/4 inch is longer than 1/8 inch, etc...

Finding exact mm measurements of PnS sensors can be difficult sometimes, but the vast majority are the 1/2.5" sensors. Anything bigger is generally a sign that you'll get better low-light ability. Fuji just announced a new PnS long-zoom, the S100FS, with a 2/3" sensor that sounds potentially very interesting (though probably pretty expensive.)

All other things being equal, more mp usually means worse low-light performance. I'm not quite convinced that PnS sensors have been advancing like DSLR ones have (where the latest 12mp sensors do better in low light than 6mp sensors of the same size), but the manufacturers do keep fiddling with the in-camera noise reduction settings, which can give a photo a cleaner look at high ISO, at the expense of detail.
 
Thanks so much. I guess it was the decimal that was throwing me off from seeing it as a fraction. Makes much more sense now.
 
Why crop factor?

Start with a 35mm film camera with a removable (interchangeable) lens. Unscrew the lens and install that lens on a camera with a smaller film frame or sensor.

The lens is still projecting the same image into the camera but the smaller sensor spans less of the image, that is, more of the sides and top and bottom are cropped. Coincidentally you are getting a more telephoto view compared with the same lens on the 35mm film camera.

The reference is the 35mm film frame, 24x36mm. The numerator of the crop factor, starting off as a fraction, is the diagonal of that film frame (43-1/4mm) and the denominator is the diagonal of the sensor you are actually using.

Another coincidence. Multiply the focal length numbers (for example 5.8 to 18 mm zoom) stamped on the lens barrel of a digital camera by the crop factor (let's say 6) and you get the 35mm film camera equivalents (here 35 to 108mm). Or divide the published 35mm equivalent focal length by the focal length stamped on the lens barrel and you get the crop factor.

It is possible to invent a crop factor for any sensor relative to any other sensor. But that would make too many permutations of crop factors. So crop factor is standardized using the 35mm film frame.

Rarely is a crop factor less than one discussed. If we screw the lens meant for a given a camera onto a different camera whose film frame is bigger, the same sweet spot of the same image, projected into this camera, might be smaller than the film frame i.e. the picture you get may be blurry at the edges. So this lens should not be used with this camera.

Sensor size as 1/2.5, 1/1.7, etc. is nominal (like a name) and only vaguely related to crop factor. There is no mathematical formula relationship. The real sensor size expressed as a decimal to the nearest tenth of a millimeter is not openly published.
 

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