"High ISO Noise Reduction" - What's the catch?

[Shacklebolt]

As one who has taken their share of noisy pictures and had to put up with it on my old camera, I say that this sounds quite nice. However, if "noise" is just "sporadic, brightly colored pixels caused by shooting at high ISOs", why would one even need an on-off switch for noise reduction? What's the trade-off?

Like, if I found out that my new Porsche 911 turbo came equipped with a switch that said, "Flip switch to activate Car-Won't-Crash mode" I would wonder, why wouldn't this just come standard?

So yeah, why is there even a choice between more noise or less noise?

 

[Westside guy]

Is this a camera option? I know my camera has "long exposure noise reduction", but I don't think it has "high ISO noise reduction".

At a minimum, I'd say the downside is your camera is making smoothing decisions based on an algorithm you have no access to nor control over (sort of like the jpeg versus raw arguments). It would probably do an okay job; but you'd get better results doing it with a separate application. Anyway, as with any noise reduction the cost is loss of sharpness.

 

[r.j.s]

Because with noise reduction on, you could end up losing A LOT of detail/sharpness that would be there in the noise. The camera/software doesn't know what is noise and what is detail for sure.

 

[Shacklebolt]

Yep, definitely a "High ISO NR" option on the D80

 

[seniorstinky]

As one who has taken their share of noisy pictures and had to put up with it on my old camera, I say that this sounds quite nice. However, if "noise" is just "sporadic, brightly colored pixels caused by shooting at high ISOs", why would one even need an on-off switch for noise reduction? What's the trade-off?

Like, if I found out that my new Porsche 911 turbo came equipped with a switch that said, "Flip switch to activate Car-Won't-Crash mode" I would wonder, why wouldn't this just come standard?

So yeah, why is there even a choice between more noise or less noise?

It's been said already about some reasons but artistic intent may be put in there as well.

The car analogy doesn't work for me. More like, if you have Image Stabilization in a lens why isn't it always turned on (which has almost the same answer... because sometimes sometimes technology causes more of a problem than it solves).

 

[baby duck monge]

There's also a slight loss of speed, though this really shouldn't be a big deal. If you're using the long exposure NR, most cameras take a second exposure after the first to determine where there are brights spots and then remove them. That makes it take longer to take your pictures. Not a huge deal about 99% of the time, but something to think about.

 

[ChrisA]

So yeah, why is there even a choice between more noise or less noise?

You can not reduce noise in a photo. What you can do and what the camera option does is change how the noise is distributed in the image. Remember the sensor has an RGB mosic filters over it and 2/3rds of the color information is gotten by interpolation. There are at these three different ways to do this that I can think of, there are likely many more. Each is best for different types of subjects. You trade off sharpness, digital artifats and apearent noise or grain

Wouldn't it be nice if there were only one subject in our photos but many of mine have both trees and the sky, to very different subjects.

You will always get the best results if you shoot raw format then carefuly do the raw conversion on the computers using software are you have control over the process and can try things several times.

 

[blackstone]

However, if "noise" is just "sporadic, brightly colored pixels caused by shooting at high ISOs", why would one even need an on-off switch for noise reduction? What's the trade-off?

More accurately, noise is random variation in sensor response. In bright light, the noise is too weak to interfere with the image you want to capture. But when the overall lighting conditions are low enough that the sensor is struggling to accurately capture the actual rays of light hitting the sensor, noise starts to become a real problem.

Because of this, there is no way to magically "remove" the noise -- you cannot, with 100% accuracy, distinguish the noise from the actual light variations you want to capture. Any time you remove noise, you also remove some detail. And if you over-aggressively remove noise, you start smearing the image in a very unattractive way.

 

[Macerture]

One trick to lower noise is to use multiple exposures.

Obviously, this doesn't work for action shots but, for all still shots, it's a very simple way to get near noise free photos regardless of a high ISO setting.

Also, reducing noise is as simple as lowering the ISO and increasing the shutter speed. Agian, not always feasible depending on the type of shot.