Call me stupid but.....

[Travy]

But what is noise exactly..
Im very new to the digital SLR scene, have recently bought a 400D.
Now i hear lots of comments on pictures being noisy. (not mine as i havent taken many or showed anyone ) but in general..

Can some one show me some examples and explain what im looking for?
May a before and after (processing wise)

or some shots with explanations or links etc.

P.S i did a search but couldnt find any direct explanations...

Thanks in advance.

Trav.

[Yi-P]

Hi Trav, welcome to the forums

Take a look at the following posts:

http://www.dslrusers.net/viewtopic.php?p=275938

http://www.dslrusers.net/viewtopic.php?t=23932

You see the little 'dots' around the image? That is noise.

Generated from the sensor itself where it tries to capture detail of certain darker shadows at high sensitivity.


Enjoy your time here

[fishafotos]

The grainy stuff in the photo. It increases as you increase the camera's sensitivity (ISO) which allows you to shoot with faster shutter speeds in low light. Don't worry, you'll come across it soon enough.

[Travy]

ah yes thats pretty much what i was thinking it was.

So its only really a problem in low light? with higher ISO?

thanks guys

[wendellt]

more to do with underexposure

even in low light if the exposure is long enough may produce blur
at high iso you can still get a clean image

[Onyx]

more to do with underexposure

Quoted for truth.





It is a commonly held myth that increasing a digital camera's sensitivity results in more noise. The noise is a result of the lack of light and user error (underexposure).

In the ISO100 image, I had mistakenly left auto ISO turned off (which I will make a point of NEVER doing again). The camera was set on self timer, and I did not discover the chronic underexposed image until much later (it's had +2EV applied in post, which is the highest exp comp bias supported by NC4.4 - so granted, is not typical of images taken at ISO100 from the D200).

If you increase the ISO to achieve a proper exposure, the results are far better than underexposing at a lower ISO and then attempting to fix it.

The confounding factor is, people usually only increase the ISO when light levels fall, and the lack of light leads to a higher incidence of underexposure creating the noise, which is mistakenly attributed to the higher ISO setting.

[wendellt]

thanks bud

but got to correct you on

'The noise is a result of the lack of light and user error (underexposure). '

true

but if the light is so low and you have to compromise expsoure to get the shot you need what can you do

e.g 2 lux lighting situation lots of movement under the covers
ISO3200 boost and reciprocal shutter speed to focal length

thats not user error thats a forced situation

[Travy]

ok, im following you now a bit

the more info the better.

thanks guys

[obzelite]

yeah, I've shot at high iso during the day to aid in getting the fastest shutter speed possible and i don't see much noise.
then on the other hand i took some pics of my son a few weeks ago under the patio without flash, used 400 iso and the noise is disturbing. the mistake under the patio was due to leaving a polarising filter on and concentrating more on getting a smile and pose and less on what shutter speeds i was using