Any coorelation between noise & in camera sharpening ?

[Raj]

Hi,

Is there any relation between noise & in camera image sharpening. I shot some pics in custom mode with increased sharpness & got noise (i used high iso also which think is more significant contributer). I was advised that too much sharpening also contributes to noise.
If this is true can someone explain why this happens ?

If I want to use high ISO, is "low sharpening" mode recommended ? will it help ?

Thanks

[tim]

Sharpening a noisy picture can make the noise worse, yes. You're better off doing noise reduction on the PC then running it thru a sharpener.

[Raj]

Thanks Tim.
Do you know the root cause of this ? i.e. why this phenomenon happens ?

Regards

[al606]

Raj, most articles on workflows I've seen recommend sharpening as the very last step.

One such article states "oversharpening in a camera's firmware can permanently damage an image causing undesirable results that can not be sufficiently removed later by any software tricks. So, it is thought by many that not applying too aggressive of a sharpening filter when processing the image internally, as is often the case with more consumer type cameras, is actually a much preferred practice, leaving final sharpening to you in a software program as the very last step. Many experts will tell you that most of your software fixes or tweaks such as changing color levels or luminosity, applying other filters or corrections etc. should be done first before sharpening is done because of the way sharpening changes the pixels in an image."

Another : "Sharpening can be easily added to any picture (and normally greatly improves it, if done right), but it can hardly be removed again. Once you've done it, you have so-called sharpening artefacts.

For this reason, sharpening normally is the last step in any workflow ... take the picture, download it, transform it to work with it in PS, do any modifications you might want to do, like change colours etc... then SAVE ... then resize for the web, then apply sharpening and then save as JPEG.

If you want to have the least in-camera sharpening, then RAW is the way to go."

I always do it last (usually USM), having found it's usually the best outcome.

Hope that helps....

[Jesper]

Thanks Tim.
Do you know the root cause of this ? i.e. why this phenomenon happens ?When you sharpen an image, the software looks for edges and details in the image and enhances the contrast of the edges (sharpening is sometimes called "local contrast enhancement"). To the sharpening software, noise looks just like other details in the image. When you sharpen the image, the contrast of the noise speckles will be enhanced and the noise will be more visible.

[Raj]

Thank you everyone !
This explains well !