[Ivo]

Hi everybody,

Is it normaly for k20d that there is presence of visible noise at ISO 400? In some shots noise is more visible in some shots - less visible.

[Ash]

G'day there.
Now you'll need to post some evidence of this 'noise' at ISO 400, as what's most likely happening is that you are under-exposing in camera and getting your software to 'push' the exposure up to make it look OK, which of course boosts whatever little noise there is. Indeed this can even happen at ISO 100 if you underexpose enough...

[Big G]

Need to see some examples.

ISO 400 is perfectly fine on the K20d, I shot a wedding at ISO 800 and the noise wasn't remotely noticeable on the prints. ISO 1600 definitely starts to get noisy, although it's not a show stopper unless you're a pixel peeper and looking at 100% crops in the shadows.

As mentioned, underexposure at high ISOs is gonna look rubbish.

[Marc Sabatella]

I'd say yes, if you pixel peep shadows at 100%, particularly if they've been pushed in PP, it would be typical to see *some* noise at ISO 400 with just about any camera. Enough noise to actually be visible in normal viewing situations? Not as likely - again, unless you've underexposed and pushed in PP. Use of the "D-range" feature has exactly that effect, BTW. Also, turning sharpening or contrast up too high in camera would also exaggerate noise.

---

Last edited by Marc Sabatella; 08-10-2009 at 04:07 PM.

[benjikan]

need to see some examples.

Iso 400 is perfectly fine on the k20d, i shot a wedding at iso 800 and the noise wasn't remotely noticeable on the prints. Iso 1600 definitely starts to get noisy, although it's not a show stopper unless you're a pixel peeper and looking at 100% crops in the shadows.

As mentioned, underexposure at high isos is gonna look rubbish.

exactly....pixel peepers!

[eyou]

theres noise in iso 100 if you want to pixel peep too.

There's a lot of great high-iso shots in that thread. many usable shots at 1600-3200. the only noise (from my k-m) that makes me mad is the blue chroma noise in the shadows of high-iso shots... its everywhere!

[PentaxPoke]

Are you sure that the pictures you are seeing don't have the sharpness turned up? It can greatly magnify the noise. This was the topic of another thread.

[WalterGA]

Somebody posted that they noticed some noise in some pics I took @ ISO800 of the Junior Nationals Diving. I had definitely underexposed some of the shots, which I "fixed" by adding fill light with Picasa.

[Gooshin]

this post is worthless without pics!

[KungPOW]

If you do the wrong things, you can get lots of noise at any ISO setting.

If you do the right things, you can get ISO 1600 to look better then ISO 400 done wrong.

Worst case: Underexposed JPG, with in camera sharpening maxed, then pushed to correct exposure in post process.

Best case: slightly (0.5 to 1.5 stops) overexposed RAW file, confirm no channels are clipped with the histogram, pulled back in PP, then add sharpening etc.

[Marc Sabatella]

the only noise (from my k-m) that makes me mad is the blue chroma noise in the shadows of high-iso shots... its everywhere!

I agree, it's pretty prominent on my K200D too, but luckily, very easy to remove with minimal ill effects by pulling the shadows back a bit via a curve and applying chroma NR. I'd say I do this with 95% of my concert shots.

[Ash]

Ivo, where are you?
We're all just speculating here trying to explain what's causing your 'noisy' images without having seen any.

[bymy141]

If you do the wrong things, you can get lots of noise at any ISO setting.

If you do the right things, you can get ISO 1600 to look better then ISO 400 done wrong.

Worst case: Underexposed JPG, with in camera sharpening maxed, then pushed to correct exposure in post process.

Best case: slightly (0.5 to 1.5 stops) overexposed RAW file, confirm no channels are clipped with the histogram, pulled back in PP, then add sharpening etc.

Yes, this is more or less right.
Noise is in every picture you take at any ISO value. Actually the noise level at any ISO value generated by the sensor is the same.
Noise however is linear with the sensor temperature. The only good way to lower the absolute noise level generated by the sensor is by cooling it.
The real question is: when can we see noise in our picture? Answer; when the signal to noise ratio is so low that the noise becomes noticable.

With higher ISO values you amplify all (analogue) signals coming from the sensor. It is the bad signal to noise ratio that makes you see noise then.
In black / dark areas of any picture the signal is very low, making the s/n ratio bad. Therefore in dark areas you are likely to encounter noise first.
So, under exposing a picture at ISO 100 and later cranking the picture up in post processing is almost the same as up the ISO value at picture taking (not quite, digital multiplication does not have the same resolution). It will make you see the noise all over the picture.
Using a high ISO value will amplify a weak sensor image signal together with the sensor noise signal, resulting in visible noise all the time.

I hope this helps you understand noise better.

- Bert

[GLXLR]

I heard that if you turn on the Noise reduction to the weakest setting, the detail remains basically the same as before but the noise speckles are gone at ISO 400.