How to control noise levels?

[rawpaw18]

Besides using high ISO's, are there other camera settings that may increase noise, or combination thereof.

I realize that a camera itself has its own limitations, but if there is something that should be paid careful attention to, that might keep the noise levels down.

[aparmley]

I think what most people are going to say and agree with is that the single most important aspect of keeping noise to a minimum is a correct exposure. In general its better to expose to the right - read: over expose slightly [to the right is a phrase used when speaking in referrence to a histogram. The biggest reason is more information is record in the highlight area of a histogram than in the shadow area. . . I will have to reread that part in Bruce Frasier's real world camera raw book. But essentially when you underexpose and then bring back the exposure you are effectively brightening areas that have very little information recorded - and at higher ISOs you are amplifying the noise that has been captured in those low information shadow areas. And if I've interpreted his text correctly, at high ISOs more noise is present than detail information in the shadows areas - which is why under exposing and bringing the exposure back up reveals a lot of grainy noise.

Long exposures [30 seconds or more] produce a lot of noise as well. In general, the sensors physical temperature has some effect on how much noise is produced as well - a sensor from a camera thats been out in the sun all day is going to produce more noise than one that hasnt. Again, nothing I've proven scientifically just tips I've read online.

Something else I've noticed is that using a little bit of bounced flash in combination with high ISO helps left some shadows and improves the overall exposure resulting in less noise.

Maybe that helps, I know it wasn't a list of what creates noise but rather tips to help avoid more noise. . .

[rawpaw18]

Thanks Andy,
Your info might be right on the money for what I see sometimes. I do tend to under expose and then bring it back up a bit. I will have to watch that.
I thought there must be something I was doing to cause it sometimes, but could not put my finger on it.


Thanks much

[aparmley]

My pleasure Rich - Like I said I'll reread that part in Bruce's book and post that up here. . . and I'm sure the more techy guys are going to add to this. . .;)

[some guy]

Besides using high ISO's, are there other camera settings that may increase noise, or combination thereof.


Easy. Get a CMOS sensor camera. :D

[timmciglobal]

Correct exposure is key.

Noise ninja or neat image helps to remove noise.

Tim

[ReF's temporary account]

I think what most people are going to say and agree with is that the single most important aspect of keeping noise to a minimum is a correct exposure. In general its better to expose to the right - read: over expose slightly [to the right is a phrase used when speaking in referrence to a histogram. The biggest reason is more information is record in the highlight area of a histogram than in the shadow area. . . I will have to reread that part in Bruce Frasier's real world camera raw book. But essentially when you underexpose and then bring back the exposure you are effectively brightening areas that have very little information recorded - and at higher ISOs you are amplifying the noise that has been captured in those low information shadow areas. And if I've interpreted his text correctly, at high ISOs more noise is present than detail information in the shadows areas - which is why under exposing and bringing the exposure back up reveals a lot of grainy noise.

Long exposures [30 seconds or more] produce a lot of noise as well. In general, the sensors physical temperature has some effect on how much noise is produced as well - a sensor from a camera thats been out in the sun all day is going to produce more noise than one that hasnt. Again, nothing I've proven scientifically just tips I've read online.

Something else I've noticed is that using a little bit of bounced flash in combination with high ISO helps left some shadows and improves the overall exposure resulting in less noise.

Maybe that helps, I know it wasn't a list of what creates noise but rather tips to help avoid more noise. . .

yep


Correct exposure is key.

Noise ninja or neat image helps to remove noise.

Tim

and yep. if you take a shot at iso 800 and up but it is very well exposed or bright, you will notice very little noise. in fact it may look so good that you might think it was shot at a lower ISO. easier said than done eh? ;) i like noise ninja for cleanups

[aparmley]

Ref Whats up with the Temp account?

My noise removal tool of choice is Noiseware (http://www.imagenomic.com/detailsstandalone.asp).

[timmciglobal]

Wow nice pickup on noiseware, did a pretty good job to community download I tried.

I like neatimage since you can select the area to profile from too.

Tim

[ReF's temporary account]

Ref Whats up with the Temp account?

My noise removal tool of choice is Noiseware (http://www.imagenomic.com/detailsstandalone.asp).

oh, the temp account.. i changed my email address and needed to get a email notification to reactivate my account, but i never got one. i tried different email accounts but still didn't get anything, so i just opened a temp account

[aparmley]

Wow nice pickup on noiseware, did a pretty good job to community download I tried.

?? Whats that? LOL -


Sorry it took a while for me to remember:

Bruce Fraser writes:

"Asssuming a camera that can record 12-bit images and a 6 stop dynamic range;

[Paraphrasing]

Sensors count photons in a linear fashion. The linear capture is important to exposure. in an image half of the 4,096 levels are devoted the brightest stop. half of what remains [2,048] is 1,024, this is devoted to the next stop until the darkest stop, the darkest shadows, is represented by 64 levels. "

Shadow-------------------------------------------------------------Highlight
[64][.128.][..256..][....512....][........1,024........][................2,048................]

Thats just a rough little diagram I came up with. As you can see more information is recorded in the highlight side of the exposure than there is in the shadow part of the exposure. Lets call the 512 level, the middle stop, the midtones its not a highlight or a shadow. you want your midtones in your expsoure to fall at the very least in this range. Why, say you underexpose by a stop, now you have used 256 levels to recordyour midtones, when you bright back your exposure you are forcing 256 levels to be streched out to cover the 512 level area. now think about the shadow area, 64 levels were recorded there, now assume that you are shooting at a high ISO setting, most noise lies in the shadow areas, now you are going to stretch 64 levels into 128 and along with it you'll be increase the ratio of noise to shadow detail.

That is basically the understanding I took from it after reading this section in Bruce frasers book. Again I highly recommend you pick up a copy.

Remember before displaying the image histogram your camera has to convert the raw to a jpeg - in doing so it will blow highlights that aren't actually blown in your RAW file.

[rawpaw18]

Thanks again Andy for taking the time,

Wow that is very helpful and I will look to acquire his book.

It seems what I tried to do was all wrong, I was always careful (too careful), in trying to keep out blown highlights, because they could not be recovered.
It looks like I will have to work on proper exposure more, and less correction in pp.

Oh yeah nice diagram