How many things cause NOISE?

[matthewkane]

Ok I understand that shooting at a higher ISO enables more noise.

But what about PS alterations? I know like oversharpening... But what

about like using the Curves function? Levels? Contrast adjusting?

List some PS adjustments that I should typically use very sparingly

if you would please. I typically use only the stuff under the

adjustment tab. Just in general what should I watch out for when

going from PS to print? I'm not looking for color mgmt advice, I

understand the concept but that's all still beyond me at this point.

I only ask this because I'm rather new to digital and haven't printed

after using PS much to take my own look on numerous different images!

Thanks

[rodolfo_negrete]

whenver you eddit a file . Even if you just copy and save.

 

I have learned 2 things that reduces it( noise) always use layers when you whenever you can, and either save your files in PSD TIFF or RAW .Also when you work on them try to do all your edditing in those modes.

 

I am also kind of new to this but that is what I have undestood sofar.

[beauh44]

Hi Matthew, What I call noise is generated in-camera, and usually not by your image-editor. Noise is simply the signal-to-noise ratio of the chip in your camera. When you crank up the ISO, the signal is essentially reduced and the noise becomes greater. The over-use of some PS tools can certainly cause image degradation, but I wouldn't define that as "noise" in the traditional sense. For the least amount of noise, shoot at the lowest ISO you can. Once in Photoshop, use Adjustment layers so that the background pixels aren't directly affected. There are many noise-removal tools available that work very well. Good luck!

[jbq]

You really need to define what you call "noise", because the definition varies from one person to the other.

 

Curves, levels, contrast, color, saturation (and all their friends, including sharpening and blur) all create a tiny bit of quantization noise, which progressively adds up (typically, two manipulations cost one bit of data, 4 cost 2 bits, 8 cost 3 bits, etc... Median filter is one of very few filters that doesn't generate quantization noise (but it generates it own kind of signal loss).

 

I do all my photoshop work in 16-bit (even when I shoot JPEG) so that I don't have to worry about it, because in that case the noise introduced by photoshop will be much much lower than the noise that was in the image initially.

[mark_herring]

What causes noise?

 

Small children, trash trucks, and any electronic system at a temperature above absolute zero. I think its the last category you're interested in....;)

 

The dominant noise in digital imaging is called the "readout noise" in the sensor. For most applications, it is a constant. The reason that higher ISO seems to increase the noise is that the gain is increased, placing the noise higher in the digital encoding.

 

For very long exposures, the variations in the dark signal may become dominant. These may appear as either random noise (indistiguishable from the read noise) or pattern noise---fixed patterns that appear the same in every image.

 

The other major issue is the so-called "encoding noise" associated with the Analog to digital conversion process.

 

Finally, you may see various artifacts associated with re-sampling and other imaging processes. The patterns in a low-quality JPG are a perfect example.

 

There are a lot of combinations of things that can happen when you process so it's hard to give a comprehensive answer. As you gain experience, you will see what's important and what's not.

[matthewkane]

Ok thanks.