Noise at high ISOs: Does it increase as MP counts go up?

I have a Sony 717; like it. Kinda noisy at ISO 400-800, but considering the

camera's capabilities, I deal with it.

 

I bought a Canon G5; it was noticeably noisier at ISO 400 than the 717 is at

800, so I returned it.

 

I saw a mention that the downside of putting more pixels (8M now!) on a

given-size chip is increased noise. Is this true? And if it is, aren't there others

who would rather have less noisy images at ISO 800 than an extra couple of

MP (for instance, 6MP instead of 8)?

 

Granted, consumers like high pixel counts, but it seems to me that would be

more of factor in the <$500 market than in the $1000 market, where

presumably buyers take other factors into consideration.

 

(Btw, I know about Neatimage and other NR programs; I'd like an image that's

more noise-free BEFORE post-processing.)

 

Thanks for any light you can shed on this subject.

If you have a high-resolution image, you can always downsample it in Photoshop, decreasing noise to what it would have been if you had started with a low-resolution sensor.

signal to noise tends to decrease as pixel size decrease. More pixels in a given space means smaller pixels.

<I>I saw a mention that the downside of putting more pixels (8M now!) on a given-size chip is increased noise. Is this true?</i><BR><BR>

 

Not necessarily; if the physical size of the sensor is enlarged noise can actually decrease even if megapixels increase. I used to own the Sony F707 which has the same sensor as the F717 and the Canon 10D is <I>much</i> less noisy at six megapixels to the Sony's five. The 10D's CMOS sensor is quite a bit larger than the Sony's CCD sensor. With a small sensor comes a greater signal to noise ratio. Best wishes . . .

Generally the issue is pixel aperture size, or the physical dimensions of each pixel site.

 

If several cameras using the same sensor size have varying resolutions, theres a strong argument to be made that the lower "resolution" sensor may be capable of better image quality.

 

The 6mp Canon 10D sensor is far larger than the 5mp sensor in the Sony 707 and 717, and dwarfs the incredibly small photosites of the 828 for example. Noise at ISOs two or three stops higher may be noticeably better on the 10D than the 828 as a result.