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Digital Noise

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jerseyfinn
 
Posts: 56
Location: New Jersey USA

Digital Noise

Post Fri Feb 08, 2008 5:05 pm


OK, I understand why noise is always going to be an issue, especially with P&S cameras because of the smaller size of the CCD chips as manufacturers ratchet up resolution by cramming more pixels onto these chips.

Recently my trusty old P&S, a Sony DSV-1 dies on me. Ultimately I'm gonna migrate to the DSLR platform, but for the near future I elect to stay with a P&S replacement simply because I've gotten spoiled carrying around a pocket-sized manual P&S camera.

After researching things on dpreview, I choose the Canon G9 because I want a manual P&S and I'm drawn to the G9's ability to shoot RAW. Both dpreview and folks in the Canon forum there point to noise issues with the G9 at ISO 400 and above. Of course how this affects one is relative to how and what you shoot.

Personally, I'm happy with what I'm seeing from the G9 thus far ( though I've not really had it in the field yet doing my usual thing ). For me, I'm jumping from a 5.1 Mpx camera to a 12.1 Mpx G9. And yes, I can indeed produce the noise that folks at dpreview and elsewhere speak about if I ratchet up the ISO.

But shouldn't I also be able to reduce some of this noise effect by dropping down to lower resolutions such as 7 or 5 Mpx? Sure, one wants to shoot at high resolutions, but in certain light I'm willing to forgo high resolution if I can produce a little less noise as I'm not printing these images ( or if I do, it's a 5x7 or smaller ).

At this stage I'm just playing with RAW and JPG shots as I expand my skill set with RAW and Photoshop while I wait for the not too distant future when I talke the DSLR plunge. Are there any other techniques to minimize noise?

Barry

djwixx
 
Posts: 1360


Post Fri Feb 08, 2008 9:19 pm


Noise is a result of higher ISO or underexposure so reducing your pixel count won't help.

Don't use high ISO and assume if the shutter speed is too slow for the lighting conditions you will need to stabilise the camera. I rarely go over ISO 100/200 unless I have no choice other than to hand hold. If your shutter speed is slower than 1/25th then you either need to increase the ISO or stabilise the camera. Make sure you expose correctly (see histogram) in all situations and you won't get noise. If you need to introduce noise, i.e. higher ISO to get a quicker shutter speed then look to invest in NeatImage or Noise Ninja to effectively 'clean up' the noise.

Yes, this was taken with a DSLR, but the G9 is more than capable of matching it with no noise.
Image
http://www.pbase.com/djwixx/image/91069280

marxz
 
Posts: 282


Post Mon Feb 11, 2008 2:21 am


Noise will be less visible the smaller the print size (or screen display size).
the noise information will be rounded out with neighbouring pixels when it is re-scaled (and the human eye does much the same looking at pixels smaller than it can resolve)

Some shots that look noisy at full pixel peeping 100% on screen will end up looking smooth then printed at 5x8 or resized for web.

You'll still want to shoot at full resolution though.. use your computer to reduce file size for on screen images or let your printer/page setup "resize to fit page" option for prints.

for noise here's a not entirely fair shoot out between the G9 and the EOS D60 and 20D... G9 at 80iso the EOS's at 100....

http://www.pbase.com/marxz/sky_show_08

by not fair I mean that the G9's images, having a 12 MP resolution, have been resized down quite a lot more than the 6MP D60 and the 8MP 20D. But for your information the images from the EOS's all came out essentially noise free (though "pushing" exposure/levels in Photoshop has popped some slight shadow noise in to some), some of the the G9's images had to be Noise Ninja'ed and many still have (barely) visible noise at this much reduced size (though it is at a much reduced acceptable level)
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