? High ISO level noise + Big Pixels

[julie21]

I was reading the very helpful threads for us newbies re ISO and found this point that Kym made re noise from high ISO levels...
Pixel size on the Sensor: Bigger pixels in general equal less noise
So...I re-read one of Rick's posts in the newbie thread re Digital zoom and turning it off ( as I did and have kept off since reading his post) because it causes big pixels compared to fine grain photos ( my interpretation, sorry)
My question is this...if using a higher ISO and using normal zoom on the camera for a shot, should I turn on the digital zoom to get the bigger pixels and if I do this will it cut down on the noise created via the ISO level?
Quite possibly barking up the wrong tree re all of this but am interested in learning so thought I'd ask anyway.

[ameerat42]

Julie...
The answer as I see it would be NO. The "bigger pixels" you get with digital zoom are just the same size pixels your camera has but "magnified". The "bigger pixels" in Kym's and Rick's threads relate to physically bigger pixels in larger sensor cameras.

With the "higher ISO" you set and digital zoom in play you'd probably end up with some sorry results.

Generally, IF you don't have some decent PP software AND you need a magnified shot straight away, digital zoom is not very useful.
Am.

[Kym]

To clarify ... we are talking about pixel density and as Am said, the physical size of the pixel.

A 35mm size (aka Full Frame or FX) sensor at 12mp and a APS-C (aka DX),
roughly half the area, at 12mp means the pixel on the 35mm sensor a physically bigger.

Now we delve into micro electronics ... in a very simplified form ...
First, all ISO means in Digital Camera terms is a level of amplification to a standardised scale.
(this scape http://en.wikipedia.org/wiki/Film_speed#The_ISO_12232:2006_standard )
Secondly, the larger the piece of silicon ship handling a flow of electrons (current) the more it can handle.
(this is an extremely gross simplification)

The signal to noise level (S/N ratio) after amplification (ISO gain) when there is more signal in
the first place (the bigger pixel can 'catch' more photons) means there is less noise in the final image.

Explained in more detail here: http://www.cambridgeincolour.com/tutorials/image-noise.htm

[julie21]

Thanks to both for clearing the 'bigger pixels' up for me...I understand a bit clearer now. :o

[Kym]

Re: Digital zoom... It is no different to cropping an image in Post Processing.
The more you crop the less pixels you have to play with.

You are better off cropping in PP as you have more creative control.
In other words, don't bother with digital zoom. ;)

[Mile]

i was told every time you double the ISO value you essentially half the picture quality. Is that the case?

I know sometime this effect can give the picture a certain quality but i wouldn't use it on high all the time.

[Kym]

i was told every time you double the ISO value you essentially half the picture quality. Is that the case?

I know sometime this effect can give the picture a certain quality but i wouldn't use it on high all the time.

No. It is not as linear as that.
Eg. ISO 100 - 800 not much noticeable difference (on my cam) when exposed properly.
At 6400 I can get acceptable images when slightly over exposing (ETTR)
"exposing to the right" ETTR helps reduce noise.
(Google it)

Underexposure will make noise more obvious.

[Mile]

thanks Kym, i will research and test a bit more when i get a camera again.