Finer-grained noise profiling, and more
Posted: Mon Oct 27, 2003 3:55 pm
Hello NI staff,
I'm using NI since 2.4, now using 2.6 Pro.
Of course I love it and continuously recommending it on various forums; but having processed some thousands images of different kind (from scanner, from digicams and so on), I noticed a few shortcomings about noise profiling / noise filtering: maybe expressing them here, we may find workarounds, or maybe you may find suggestions for future developments...
First of all, I feel that the rectangular selection is quite a limitation in many cases. Let's present an example.
You did surely hear about new Fuji digicams: S5000 and S7000. Their new SCCD-HR sensors are very noisy, so Fuji implemented a very aggressive in-camera NR, that kills most surface details.
I worked on RAW CCD outputs from those camera with NeatImage, and obtained decent results (please see http://gundam.srd.it/PhotoPages/fuji_dcraw_02.html ); but the RAW CCD output from those sensors (when processed by free tools like DCRAW) is rotated by 45 degrees.
If you straighten it up *before* processing with NI, you'll end up modifying noise characteristics a bit (please see this thread:
http://forums.dpreview.com/forums/read. ... ge=6465075 ), maybe weakening NI action (?).
But on the other side, trying to build a noise profile on a 45-degree test target with a rectangular selection is difficult: you waste a lot of patch space.
Second comment: the noise equalizer has too few frequency bands in my opinion. Some profile have steep variations around low frequencies, i.e., noise is awfully high in deep shadows while quite OK in 1/4 shadows and bearable in midtones. As for now, my equalizer (after fine-tuning the profile with the test target) looks quite coarse, with the 2 lowest sliders to the top (150-200%) and the third one (for example) at 33%.
Now, considering how a frequency-domain filtering works, (you know, not-too-high-order filters and so), isn't a similar situation a bit imprecise?
In particular, I'm observing too much details killing and too few noise reduction in some cases (high ISO shots from newest digicams).
Maybe a finer-grained equalizer would help...
Third comment: High frequency / medium frequency / low frequency noise filtering... isn't it too coarse a subdivision, too?
Maybe more sliders would help figuring a better tradeoff between noise and details?
Fourth comment: sometimes it seems to me, that noise on test target is not modelling real-world pictures accurately enough, expecially for small-sensor digicams.
I build a noise profile (of course I follow your instructions very closely), figure out a noise filtering preset, then apply them to the test target image, and all goes very well & smooth; but when I try the same setup on real-world images (of course same ISO, same device, and so), noise is not cleared "well enough", expecially shadow noise; while quite a lot of surface details (textures) are washed out.
Even trying new values for noise filtering does not seem to help much: seems like noise was somehow too roughly profiled...?
Of course I apply NI on non-processed pics, often straight from RAW conversion (and did build the noise profile the same way).
Last comment: sometimes some kind of "pattern" is visible within CCD noise; expecially with "exotic" sensors like Fuji SCCD-HR. Does NI perform some kind of pattern recognition and suppression, or it's only frequency-based (Fourier-domain band-pass filtering)?
Please note that in the end I'm happy with NI; just noting that maybe with latest digicams I'm pushing it very much... so maybe some improvements could be handy.
Regards,
Fernando
I'm using NI since 2.4, now using 2.6 Pro.
Of course I love it and continuously recommending it on various forums; but having processed some thousands images of different kind (from scanner, from digicams and so on), I noticed a few shortcomings about noise profiling / noise filtering: maybe expressing them here, we may find workarounds, or maybe you may find suggestions for future developments...
First of all, I feel that the rectangular selection is quite a limitation in many cases. Let's present an example.
You did surely hear about new Fuji digicams: S5000 and S7000. Their new SCCD-HR sensors are very noisy, so Fuji implemented a very aggressive in-camera NR, that kills most surface details.
I worked on RAW CCD outputs from those camera with NeatImage, and obtained decent results (please see http://gundam.srd.it/PhotoPages/fuji_dcraw_02.html ); but the RAW CCD output from those sensors (when processed by free tools like DCRAW) is rotated by 45 degrees.
If you straighten it up *before* processing with NI, you'll end up modifying noise characteristics a bit (please see this thread:
http://forums.dpreview.com/forums/read. ... ge=6465075 ), maybe weakening NI action (?).
But on the other side, trying to build a noise profile on a 45-degree test target with a rectangular selection is difficult: you waste a lot of patch space.
Second comment: the noise equalizer has too few frequency bands in my opinion. Some profile have steep variations around low frequencies, i.e., noise is awfully high in deep shadows while quite OK in 1/4 shadows and bearable in midtones. As for now, my equalizer (after fine-tuning the profile with the test target) looks quite coarse, with the 2 lowest sliders to the top (150-200%) and the third one (for example) at 33%.
Now, considering how a frequency-domain filtering works, (you know, not-too-high-order filters and so), isn't a similar situation a bit imprecise?
In particular, I'm observing too much details killing and too few noise reduction in some cases (high ISO shots from newest digicams).
Maybe a finer-grained equalizer would help...
Third comment: High frequency / medium frequency / low frequency noise filtering... isn't it too coarse a subdivision, too?
Maybe more sliders would help figuring a better tradeoff between noise and details?
Fourth comment: sometimes it seems to me, that noise on test target is not modelling real-world pictures accurately enough, expecially for small-sensor digicams.
I build a noise profile (of course I follow your instructions very closely), figure out a noise filtering preset, then apply them to the test target image, and all goes very well & smooth; but when I try the same setup on real-world images (of course same ISO, same device, and so), noise is not cleared "well enough", expecially shadow noise; while quite a lot of surface details (textures) are washed out.
Even trying new values for noise filtering does not seem to help much: seems like noise was somehow too roughly profiled...?
Of course I apply NI on non-processed pics, often straight from RAW conversion (and did build the noise profile the same way).
Last comment: sometimes some kind of "pattern" is visible within CCD noise; expecially with "exotic" sensors like Fuji SCCD-HR. Does NI perform some kind of pattern recognition and suppression, or it's only frequency-based (Fourier-domain band-pass filtering)?
Please note that in the end I'm happy with NI; just noting that maybe with latest digicams I'm pushing it very much... so maybe some improvements could be handy.
Regards,
Fernando