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databoy

« on: 30 / December / 2008, 21:11:52 »
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I have been looking around for a cheap Canon credit card size camera for a while. I recently purchased a Samsung L201, 10.2 mega pixel camera purely because the price was right. In Australia the L201 sells between $175 & $225AUD. One of the nationwide franchise electrical chains was selling the camera in a sale for $99AUD.

My other camera is a 6 mega pixel Canon S3IS. How do the photos compare? There is no comparison. The L201 takes brilliant photos which are too sharp. It looks like there is some internal processing which sharpens the JPG images. Other images look too soft and out of focus. The S3IS photos are more natural; overall the 6 mega pixel S3IS is the better performing camera.

Which brings me to the title. Camera manufacturers are producing cameras with more mega pixels. The reality is while the sensors may contain higher digital definition, there are other factors involved in the photography equation. The end result is what you see, a digital photo. Just because the technical specifications are good, it does not equate that the end results are. The quality of the CCD; the lens is an important factor, so is the JPG processor chip.

Considering that the L201 package included a battery, charger and cables, for the price I paid for the camera, it was a bargain. The down side is that with all consumer goods that use a propriety battery is that when the battery fails it will cheaper to buy a new camera than replace the battery. For $99AUD, I cannot buy the parts to build a remote controlled camera. The L201 could be modified to use an external power supply, and wired with external switches; ie as a web cam, robotics or a fixed camera somewhere.

The software package is minimal; a driver which connects the L201 to a computer via a USB port and seen as a drive. Downloading to the computer is simple. The display on the camera asks you whether you want to download to a computer or print a photo. That connects you to the computer. Use your favourite file manager to do the rest.   

My recommendation to anyone contemplating purchasing a digital camera is: forget the mega pixel marketing hype and look at your individual application. The S3IS is cumbersome but it is my preferred camera. The L201 was purchased for situations where I need a camera in my shirt pocket. I would not have considered purchasing the L201 if it was selling at the normal retail price. I would have paid the extra and looked at a CHDK compliant camera.

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Offline fudgey

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« Reply #1 on: 31 / December / 2008, 08:05:31 »
High pixel count is generally a bad thing for today's CCD cameras.

The number of pixels has long since reached a point where they exceed or come close to the capabilities of low quality optics in many cameras, so increasing the count does not make much sense.

When the optics can't be improved due to size and cost restrictions, the sensor is small. So, to get more pixels, the pixels become smaller and smaller since the sensor size can't be increased. Smaller pixels get less light => high pixel count equals high noise unless the sensor can be improved. And noise is the #1 thing that needs fixing in digital point&shoot cameras, IMO.

« Reply #2 on: 31 / December / 2008, 08:41:27 »
the pixels become smaller and smaller

Any idea which (old) cameras have the largest pixel size and how many megapixels they are.

Ideally, I am looking for a fixed-focus non-zoom camera of any make.

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Offline fe50

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« Reply #3 on: 31 / December / 2008, 11:12:32 »


« Reply #4 on: 31 / December / 2008, 12:33:53 »
6MEGAPIXEL!

Yes, that is very similar to my 7MP A620 that has the same size sensor.

It looks easier to disassemble .. it depends if the lens-assembly sensors are static (just detect position) or dynamic (detect rotation) and how the firmware deals with them.


David

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Offline fbonomi

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« Reply #5 on: 01 / January / 2009, 17:00:23 »
In many cases yes, we have too many Mega Pixels.

Several factors are in game that might disturb more than the Megapixel count:

1) the practical precision of lens workmanship
The lenses are only made to be acceptable quality. Beyond a certain limit, having smaller pixels only means you are looking at the defects of the lens

2) the pixel-to-pixel noise
smaller sensors mean that each pixel is closer to its neighbouts, and noise "spill" from one pixel to the other more easily

But I want to speak about a very subtle limit, the thoretical optical resolution of a lens.

Especially with small apertures, there is a very strong THEORICAL limit to the resolution a lens can have, even having a perfect lens and a perfect LARGE sensor.

According to this page ( Do Sensors Outresolve Lenses? )
"Consider a 35mm system with a lens at f/11. At best, the maximum resolution you will get is equivalent to 16 MP, even if your camera has 22 or 25 MP. In the case of an APS-C based system the limit goes to 7 MP, and 4 MP considering a Four Thirds format."

This means that even having the perfect lens with the perfect sensor, there is a limit (depending on wavelength and aperture) on the number of pixels we can have per square millimeter...

Let's see if we can calculate this limit from the data on that page (can someone please check my calculations?):

Sensor: 35mm
Size: 24*36 mm
Area: 864 sq mm
Max theorical resolution: 16MP
18.5k kpixel per sq mm

Sensor: APSC
Size: 16*24 mm
Area: 384 sq mm
Max theorical resolution: 7MP
18.2k kpixel per sq mm

Sensor: Fours thirds
Size: 13,5*18 mm
Area: 243 sq mm
Max theorical resolution: 4MP
16.4k kpixel per sq mm

This is quite consistent: at f/11 we can have at most about 18kpixel per square millimeter.

Every aperture stop doubles (or halves) this value:
"stopping down to f/22 the limit of the effective resolution of the 35mm based system goes to 4 MP!"
That is, on a 35mm, going from f/11 to f/22 (two stops) brings the resolution down to 4MP.

Ok, let's see for example my a570IS

Sensor: 1/2.5"
Size: 5.76*4.29  mm
Area: 24.7 sq mm
Theorical limit in resolution at f/11 = 24.7*18kpixel = 0,4 Mpixel

If my camera had an f/11 mode (which thank god it hasn't) then I would have a resolution of 0,4 Mpixel

The smallest aperture the a570Is has is f/8, which is 2 stops higher than f/11, so the resolution is 2*2 times larger, i.e. 1.6 Megapixel ...

EDIT: actually F8 is 1 stop higher than F11, so the resolution is even lower!!!

HELP! someone please tell me I am wrong!

One stop up (at f/5,6) I am still at 3,2 Mpixel.
One other stop up (at f/4) I am at 6,4 Mpixel.

This means that even if my lens was a perfect lens, and my sensor was a perfect noise-less sensor even, up to f/4 my 7 Mpixel sensor would be useles, as no lens can give me 7 Mpixels on such a small sensor.



« Last Edit: 13 / August / 2009, 02:08:51 by fbonomi »

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Offline fudgey

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« Reply #6 on: 01 / January / 2009, 18:20:52 »
Don't know about the calculations, but keep in mind that a 7 megapixel a570 doesn't have 7M red pixels. It has around 1.75M red, 1.75M blue, 3.5M green.

« Reply #7 on: 01 / January / 2009, 19:44:12 »
keep in mind that a 7 megapixel a570 doesn't have 7M red pixels. It has around 1.75M red, 1.75M blue, 3.5M green.

That is not important, unless you are using monochromatic light.

The luminance information is at the camera's quoted resolution.
Overlaid on that, at lower resolution, is the colour information.

That is not a problem.

David


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databoy

« Reply #8 on: 01 / January / 2009, 22:43:17 »
I know from past experiences that specifications quoted by manufacturers do not equate to quality. I dismantle defective electronic equipment purely to find out what a manufacturer uses. Most of the time there are few salvageable parts; the equipment ends up in the rubbish bin.

It is my experience that most people purchasing consumer goods are swayed by manufacturer and sales hype. Ignorance is bliss; more mega pixels must be better.

I purchased the S3IS based on the available camera reviews in circulation. I compared the Sony, Panasonic and Canon cameras with similar functions and specifications. I spent months deciding on which to buy; ultimately what swayed me to the S3IS was price. The S3IS dropped $150 below the competitors and for the price it represented value for money.

Currently all my free resources are used in finding parts and building a motorised pan/tilt unit. Once completed, I will take some photos of objects and scenes for comparison with someone who owns a 10 mega pixel Canon camera. I never upload photos so I have no experience; what is a good size to upload? Is it better to take a full mega pixel photo and crop it, or can I get away with using one of the freeware resizing programs?   


« Reply #9 on: 02 / January / 2009, 05:30:32 »
If my camera had an f/11 mode ...  then I would have a resolution of 0,4 Mpixel
The smallest aperture the a570Is has is f/8, which is 2 stops higher than f/11, so the resolution is 2*2 times larger, i.e. 1.6 Megapixel ...
HELP! someone please tell me I am wrong!

You are correct   ;)

In terms of depth-of-field, f11 is equivalent to f66 and f8 is equivalent to f48.
Those apertures do not exist on 35mm lenses because of the massive diffraction.

With such tiny sensors on these cameras, you can hardly stop down at all, especially at the telephoto setting where the aperture wide-open is relatively small.

On some of the SDM OSD's, the aperture value is coloured red when the diffraction limit has been reached.

 

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