ISO, Grain and MegaPixels?! Question.

[SYZahran]

i have read about Camera functions and i understand most of what i have read, but there is a little thing bothering me..its Noise in High ISO settings.

when you take pictures at high ISO, your photos will get grainy..why is that? what is this noise? i know how it looks but i can't understand what is it and why does it happen at high ISO?

is there any association to MegaPixels? didn't read it anywhere and i'm guessing they have no relation at all but still...it sounds logical to me..megapixels should have some impact on grain.. :s

and last...how does those Noise reduction methods work in camera's?


thank you in advance.

 

[Plato]

First, the correct term is "noise." "Grain" is what you saw with film pics. The noise is electrical noise. Think of static. The noise is always there and it's somewhat constant. Consequently, the noise impacts small pixels more than large pixels. That's why a 10MP FX ("full-frame") SLR is affected less than a 10-MP DX (consumer) SLR which, in turn, is affected less than a P&S. With the same quantity of pixels spread over a larger physical area (in an FX camera), the pixels are larger and therefore are less affected by the noise.

Again, with the noise being somewhat constant, high ISO values result in a need to amplify the signal more than at low ISO values. Unfortunately, the amplifier can not differentiate between image and noise so both are amplified. Consequently, noise imacts high-ISO shots more than low-ISO shots.

I do not know how the in-camera NR functions.

 

[Village Idiot]

Keep in mind, exposure affects noise as well. You can pull off clean high ISO shots in most modern DSLRs. If you under expose the shot though, you'll see more visible noise; especially if you bring the exposure back up in post.

 

[Stosh]

Yes, think of how audio systems work. There is always some noise (hissing) whenever any type of amplification system is used. If you were listening to a recording and there was a very quiet part you wanted to turn up so you could hear it better, when you crank the volume you get more noise. Cranking up the ISO is analogous to cranking up the volume.

I'm no expert on noise reduction, but it's probably related to a smart algorithm used to selectively blur certain ares on the picture to achieve a reduced noise look. The only way to actually reduce noise is to have a larger signal to begin with.

 

[Big Mike]

Keep in mind, exposure affects noise as well. You can pull off clean high ISO shots in most modern DSLRs. If you under expose the shot though, you'll see more visible noise; especially if you bring the exposure back up in post.

Expose Right

 

[SYZahran]

Thanks All, it really helped - the answers and the links

Expose Right

from what i understand, you should Aim for the high exposure levels - without getting the picture blown out - but in the same time try to spread the pictures on most of the dynamic range if it is possible, all that to get minimal noise. and the over exposure an fixed later on with digital editing... am i right here?

excuse me if i'm not using the right terms - or the proper English to describe what i think...

thanks again.

 

[Village Idiot]

Thanks All, it really helped - the answers and the links

Expose Right

from what i understand, you should Aim for the high exposure levels - without getting the picture blown out - but in the same time try to spread the pictures on most of the dynamic range if it is possible, all that to get minimal noise. and the over exposure an fixed later on with digital editing... am i right here?

excuse me if i'm not using the right terms - or the proper English to describe what i think...

thanks again.

It depends. If you're shooting something where noise levels in a photo or dynamic range is critical, then yes. If not, I would expose normally. That can really add up to a lot of PP time. You just have to weigh your priorities when you shoot.

 

[Big Mike]

from what i understand, you should Aim for the high exposure levels - without getting the picture blown out - but in the same time try to spread the pictures on most of the dynamic range if it is possible, all that to get minimal noise. and the over exposure an fixed later on with digital editing... am i right here?

That is correct.

 

[SYZahran]

i don't know in what photos "noise levels/dynamic range" is critical...but i guess i'll get a hold of that in time, i'll just have to keep on reading.....

thank you both!

 

[Village Idiot]

i don't know in what photos "noise levels/dynamic range" is critical...but i guess i'll get a hold of that in time, i'll just have to keep on reading.....

thank you both!

In situations like trying landscape photography. Rarely do you create your own light and sometimes you need high ISO's to get the job done. Dynamic range is very important here because you'll generally be dealing with very contrasting exposures in one scene; like the sky, a sunlit section of the photo, and possibly a part of the photo in shadows.

Something where this would be less important would be in modeling photography. Normally, unless you're a natural light photographer, you're going to be shooting in controlled conditions where you controll the lighting and the scene. Generally you'll shoot at lower, if not you're lowest, ISOs and you'll control the outcome of the photo, not mother nature. Shooting the right would be less important to me in a situation like this.

 

[SYZahran]

i don't know in what photos "noise levels/dynamic range" is critical...but i guess i'll get a hold of that in time, i'll just have to keep on reading.....

thank you both!

In situations like trying landscape photography. Rarely do you create your own light and sometimes you need high ISO's to get the job done. Dynamic range is very important here because you'll generally be dealing with very contrasting exposures in one scene; like the sky, a sunlit section of the photo, and possibly a part of the photo in shadows.

Something where this would be less important would be in modeling photography. Normally, unless you're a natural light photographer, you're going to be shooting in controlled conditions where you controll the lighting and the scene. Generally you'll shoot at lower, if not you're lowest, ISOs and you'll control the outcome of the photo, not mother nature. Shooting the right would be less important to me in a situation like this.

modeling photography is not my thing, i'm more into nature landscapes and Architecture and indoor shooting like in cathedrals and churchs - (thats basicly what i have been trying to take photos of all those years) - under/over exposed pictures are my main problem, i'm trying to figure out ways to over come that and i think HDR's and using high ISO's and tripods should solve some of the problems. the other problem is that my photos are not interesting...shooting in the morning or the evening should help with the landscape shots,I will need to focus more on composition and looking for some way to improve my indoors shots.

Any links to such photography will be greatly appreciated..can't find them on the forum...

 

[icassell]

Thanks All, it really helped - the answers and the links

Expose Right

from what i understand, you should Aim for the high exposure levels - without getting the picture blown out - but in the same time try to spread the pictures on most of the dynamic range if it is possible, all that to get minimal noise. and the over exposure an fixed later on with digital editing... am i right here?

excuse me if i'm not using the right terms - or the proper English to describe what i think...

thanks again.

Here's a nice little discussion :

Expose Right


EDIT: OOOPS! Silly me ... totally overlooked Mike's posting of this link ... sorry ...

 

[SYZahran]

yeah, i have already read that, was really useful.

thanks anyways.

 

[Dwig]

... i think HDR's and using high ISO's and tripods should solve some of the problems. ...

No, no, no ... using high ISO aggravates the problem.

At high ISOs the sensor system's tonal range is severely reduced. A single low ISO shot can usually achieve a tonal range equal to a 3 shot HDR at high ISOs and produce better color rendition. This latter attribute is something that HDR, regardless of the number of shots, does nothing to improve.

Use a tripod and a low ISO to achieve the best results, period.

 

[peterbj7]

Consequently, the noise impacts small pixels more than large pixels

You'll need to explain that "consequently". I don't see the logical link. Perhaps you've missed out a few steps?