Hello,This looks like you've got fine wire window screens over mini-blinds which is a perfect storm for moire formation even without a camera.
Did a road trip on the weekend to a beautiful little town called Te Aroha 2 hours south of Auckland. As I was looking at some of the old buildings I took this with the Nikon D800E. As you can see not having a AA filter does have it drawbacks.
Cheers
Simon
Hello,
Did a road trip on the weekend to a beautiful little town called Te Aroha 2 hours south of Auckland. As I was looking at some of the old buildings I took this with the Nikon D800E. As you can see not having a AA filter does have it drawbacks.
Cheers
Simon
Hello,
Did a road trip on the weekend to a beautiful little town called Te Aroha 2 hours south of Auckland. As I was looking at some of the old buildings I took this with the Nikon D800E. As you can see not having a AA filter does have it drawbacks.
Cheers
Simon
That can be fixed in Photoshop quickly. Healthy dosage of GB on both A and B channels in LAB should fix it in less than 20 seconds.
Did a road trip on the weekend to a beautiful little town called Te Aroha 2 hours south of Auckland. As I was looking at some of the old buildings I took this with the Nikon D800E. As you can see not having a AA filter does have it drawbacks.
Hi,
I wouldn't call that fixed. The false colors are gone, but the luminance moiré remains.
Cheers,
Bart
Hello,
The lens is a new Nikon 24-85mm VR lens which I bought as a walk around and for scouting. The F stop was F9.0.
I did a shot on Friday last of a business man and his very expensive suit also had some moiré in it as well as a a female athlete I shot a few weeks ago had moire in her Lycra suit around her breasts.
I'm not sure what you mean about the grass?
The raw converter I use is ACR CS6. I have had a look with Phase 7 but I could not see any improvement than what I got from ACR.
Off subject I did a comparison yesterday with a Leaf Aptus 75 image at 400ISO in the new Phase 7 and ACR CS6 and in my opinion the ACR did a better job in cleaning up the colour noise.
Cheers
Simon
...OK, so we still get color moiré at f/9....
... I took this with the Nikon D800E. As you can see not having a AA filter does have it drawbacks...
The lens is a new Nikon 24-85mm VR lens which I bought as a walk around and for scouting. The F stop was F9.0.
Simon
Bill I have only had the lens for a couple of weeks and I am very impressed with the resolution. I did however try a number of this lens and found they are not created equal so I would strongly recommend that you try before you buy.
The great thing of course is the VR. My lady and I went to the local museum in Te Aroha and hand holding inside at 8th sec I was still getting sharp images and the lens is just a nice size and weight.
Like you for my paying jobs I go for primes or the pro grade zooms from Nikon but 24-85mm VR is what it is and does a good job at it.
1st shot: 24mm F5.0, 8th Sec, 800 ISO
2nd Shot: 24mm F5.0, 30th Sec, 800 ISO
3rd Shot: 24mm F7.1, 500th Sec, ISO 100 4 shots stitched.
I wouldn't call that fixed. The false colors are gone, but the luminance moiré remains.
I'd like to suggest that the moiré in this scene is actually in the scene, and produced by the interaction of the venetian blinds with a mesh screen. The moiré in this case is not produced by an interaction with the sensor so much, but is there to be seen with the naked eye, just as you'd see when looking through two mesh screens. For that reason, I don't expect the moiré tool to be able to fix that, and I wouldn't fault the camera.
The luminance moire is another matter entirely. Some valid, un-aliased high-frequency information just cannot look right without some interpolation. This is because, in theory, digital images need a reconstruction filter to turn the individual pixels/samples back to the continuous, analog domain. Digital images often get away without the reconstruction filter step because they don't have a lot of very high frequency detail. The D800E with a good lens can certainly capture a lot of the highest image detail, as you have shown, and can easily produce images that need a little reconstruction filtering.
I used a pure sinc filter (done by FFT like described here (http://www.luminous-landscape.com/forum/index.php?topic=40809.msg340711#msg340711)).
A good Lanczos filter should give similar results. The key is that the filter has good response up to the highest frequencies.
That can be fixed in Photoshop quickly. Healthy dosage of GB on both A and B channels in LAB should fix it in less than 20 seconds.
I don't know of a Lanczos plugin for Photoshop :( - somebody needs to create one!(open source) Image magick contains one of the most extensive sets of linear scaling operators that I have seen:
Thanks. What do you recommend as canvas color in the step "Increase the canvas size on all sides."?
By any chance, would you know any Lanczos filter plugin for photoshop?
Lightroom moire brush:
(open source) Image magick contains one of the most extensive sets of linear scaling operators that I have seen:
http://www.imagemagick.org/Usage/filter/nicolas/
Board index ‹ ImageMagick ‹ Users < best downsampling method for DSLR photographs (http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=20992&sid=5418e6dc87f52b930666684ec9915aa5)
-h
Do you have a script that might work well with Simon's image?
The 8-lobe Lanczos command does give results very similar to my 2X zoom (FFT) example above. It is actually a little less ripply.I am not surprised that 8-lobe lanczos is visually similar to FFT-based scaling.
...
We have to come up with some ways to reduce the rippling, so D800e users can get the most from their cameras and in an easy way!
Thanks for the info, Bart.
The 8-lobe Lanczos command does give results very similar to my 2X zoom (FFT) example above. It is actually a little less ripply.
The 3-lobe and your general purpose one don't do the job on this image, however.
We have to come up with some ways to reduce the rippling, so D800e users can get the most from their cameras and in an easy way!
I am not surprised that 8-lobe lanczos is visually similar to FFT-based scaling.
For linear filtering, there is a relationship between frequency response (wide & flat passband, narrow transition band and lots of attenuation in the stop-band) and ringing. In order to approach a perfect lowpass filter (sin(x)/x), you need to have lots of filter coefficients, some negative and some positive. This means that an image edge will spread out in space and cause undesirable artifacts.
The common (linear) solution to this problem is to either sacrifice passband (blurriness) or stop-band (aliasing). A more advanced solution might be adaptive/non-linear processing.
Did you consider DCT-based scaling rather that FFT-based? I believe that the implicit periodic extension built into DCT might be more suited than the periodicity built into DFT (FFT).
-h
Hi Luke,
It's the camera, really, and it does exactly what it was designed for. The proof is in the detail, as shown here (a crop from Simon's image)
[...]
If it were scene detail that is already aliased because of two overlayed screens, then that wouldn't produce single pixel wide lines, and the angle of the single pixel lines would probably not be as horizontal.
Yes it boils down to, hard transitions in the frequency domain (MTF) cause ripples in the spatial domain, and vice versa. The Lanczos filter smooths the transition from full to zero response, with fewer lobes making for a smoother transition. The FFT filter has hard, straight transitions. The key to controlling ripples is the smoothing of the transitions.Yes, it can be described as a classical filtering problem. For many applications, you can even do the design (and thinking) in 1 dimension, extending that solution into 2d by straight separable processing (see image magick forums for dissenting views)
I think the DCT will help if the problem is hard transitions right at the border of the frequency domain. Since in the special case of image zooming the transitions end up farther in and away from the borders, the mirroring effect of the DCT probably won't help.Yes you are right, DCT will only affect the virtual padding outside the known image. If that is not the problem, then the DCT may not be the cure.
I see that the (choice of) demosaic process is being partially blamed for D800E issues. There are some nice papers decribing demosaicing in the spatial frequency domain, as a filtering process to separate luminance and color-difference channels. Did you consider taking the FFT of the raw bayer data, identifying various components and extracting them directly (or using the FFT magnitude as a guide to design an optimal spatial-domain filter)? Joint debayer-scaling might make things more complicated, but may be what is needed for optimal results when the camera lacks pre-filtering (and great care is put into maximizing the amount of recorded details).
E.g.:
http://white.stanford.edu/teach/index.php/A_Review_of_Frequency-selection_Demosaicing_Algorithm_by_Shuang_Liu
-h
Hi griffithimagePerhaps a Foveon-type sensor or a Bayer + multi-shot (as used by one of the MFDB manufacturers) is suited for your use?
As I'm shooting a lot of suits I would never consider the D800e. As you can see I even get moiré with the D800 (shot yesterday). Just to put things into perspective: there's no camera or back I shot that didn't produce moiré in fine fabric....
Just to put things into perspective: there's no camera or back I shot that didn't produce moiré in fine fabric....Try to use a consumer lens... well, it cures moire
Perhaps a Foveon-type sensor or a Bayer + multi-shot (as used by one of the MFDB manufacturers) is suited for your use?
I guess that closing the aperture to the point where fine pattern is smeared out is out of the question?
-h
Hi griffithimage
As I'm shooting a lot of suits I would never consider the D800e. As you can see I even get moiré with the D800 (shot yesterday). Just to put things into perspective: there's no camera or back I shot that didn't produce moiré in fine fabric....
Quick ImageMagick comments:
Bart: When you use -distort Resize, you do not need to specify -filter Robidoux when you want the Robidoux filter, because it is the universal default. Also, recent ImageMagick assumes sRGB unless there is something indicating otherwise, so you almost never need -set colorspace sRGB. (Things have changed a lot in the last year.)
I've not done any testing on this test image, and I'm still figuring things out, but I think that if you have issues with moire, you should immediately try resampling in linear light (linear RGB in ImageMagick, which also supports XYZ, although I don't know how accurately). You get get linear light by omitting the +sigmoidal-contrast and -sigmoidal-contrast commands (or setting the contrast to 0, which wastes flops, but indicates that the contrast is a sliding scale which you could use to balance aliasing against ugly over and undershoots).
Also: LanczosRadius would not be my first pick to reduce moire.
I'd use -filter LanczosSharp or the variant recommended at the site you already know: http://www.imagemagick.org/Usage/filter/nicolas (http://www.imagemagick.org/Usage/filter/nicolas) (which is already outdated, and suggests, IMHO, too high a contrast value: I think 6.5 is better all around with the Robidoux filter, for example, and going above 7 is probably not "safe" unless you always inspect the results). I'd leave it at the default 3 lobes.
I'm a bit hesitant to make too clear a pronouncement if this does not give you what you want, but maybe you should try Ginseng (if you have an HDRI version of ImageMagick, which my guess is you don't) or the suggested Quadratic Jinc (at the default 3 lobes) or Robidoux if you want even less ringing.
Anyway: I always learn from seeing what people like, so it was interesting to read what you liked.
For less specific images that require 'artifact free' upsampling, I get very good upsampling results with the following batch file entry:
Code:
convert %1 -set colorspace sRGB -colorspace RGB +sigmoidal-contrast 12.09375 -filter Robidoux -distort Resize 200%% -sigmoidal-contrast 12.09375 -colorspace sRGB -compress None "%~dpn1_200pct-CSpc+sigmoid.tif"
It can also do good downsampling, in this example to an uncompressed TIF format, with modified resize percentages below 100%.
Bart:
This really is a current favorite? (I'm not arguing: I just find it really really hard to sort out what's better from what's good, and I've programmed so many different schemes with strengths and weaknesses so I have a lot to sort through. This being said, my two very similar variants of EWA LanczosSharp with 3 lobe are winners in my book. And EWA Robidoux has been liked by a variety of people, even though I'm more than a bit iffy about this method. The big surprise is you liking high contrast sigmoidization really surprises me a lot.)
Would you be kind enough to explain what you compared it too, what you saw as good, and what you saw as bad? Here or elsewhere? And email me the link (nicolas.robidoux@gmail.com)?
I'm interested in knowing your favorite(s). I'm not specifically asking because this filter has my name. If you'd rather discuss another filter (I read that you like -distort Resize with the Mitchell filter, for example), I'm still thankful. I'm trying to figure out what to recommend. And what to program into the new GEGLized GIMP when I've put enough money in the bank to afford more pro bono work.
...this (assumed by me) bug. When I resize this file (http://bvdwolf.home.xs4all.nl/temp/LuLa/PerfectSlant_IJ.png) to 200%, I get a different/incorrect resampling for odd/even horizontal lines of the edge ... My conclusion stems from my research of sharpening mentioned earlier, and has existed for some time already in various versions of IM (so I'm starting to conclude it's not accidental but inherently a systematic flaw, until fixed). I know you are not to blame, I'm just giving some feedback (which probably should be given to Anthony Thyssen (or others) of IM instead)...When you have a minute, can you be a bit more specific w.r.t. what you expect to see/measure? It certainly does not jump at me.
When you have a minute, can you be a bit more specific w.r.t. what you expect to see/measure? It certainly does not jump at me.
It's only with -distort Resize, and not -resize?
P.S. This being said, if you use a filter with negative lobes in such a way that over and undershoot are clipped in a different way for the two values that are on the two sides of the interface, you will break the symmetry of the interface. In this case, sigmoidization may help because it limits over and undershoots (in a way that is symmetrical w.r.t. exchanging black and white).
... However, with upsampling it has an IMO nasty side-effect of exaggerating edge sharpness in an ugly way. I say nasty because we have no control over it, unlike post resampling sharpening...This agrees with http://www.imagemagick.org/Usage/filter/nicolas (http://www.imagemagick.org/Usage/filter/nicolas).
...On the other hand, when we want to reduce the risk of running into issues with limited bit depth images being converted into linear gamma and back, we might as well (QED !) skip the gamma and sigmoid conversions and just use (deconvolution) sharpening to control the edge sharpness...Provided conversion between colorspaces is sufficiently accurate (and, between linear RGB and sRGB, it is sufficiently in ImageMagick unless you use an 8-bit version), it is not the input or output bit depth that matters, it's what happens within the processing.
Provided conversion between colorspaces is sufficiently accurate (and, between linear RGB and sRGB, it is sufficiently in ImageMagick unless you use an 8-bit version), it is not the input or output bit depth that matters, it's what happens within the processing.For testing new ideas, and for passing back and forth algorithms/results for comments and tweaking, I much prefer something like MATLAB: it is double-precision float (pretty much by design), it is often "fast enough" (using libraries like FFTW, BLAS etc), and operations like scaling can be implemented with a fraction of the effort it is to do anything at all in C.
-----
Right now, ImageMagick has a split personality w.r.t. sigmoidal-contrast: it uses a clamping LUT in IM6, and a full double precision, but still clamping, version in IM7. When I have time (and money in the bank), I'll reconcile the two and remove the clamping, which should help a little when using an HDRI version of ImageMagick.
I had to rewrite the whole thing so that sigmoidization work properly, and unfortunately did not quite finish the job.
That can be fixed in Photoshop quickly. Healthy dosage of GB on both A and B channels in LAB should fix it in less than 20 seconds.I've yet to see any software fix for moire that removes moire, it might disguise it with a certain degree of success, chances are it leaves luminance banding behind.
I've yet to see any software fix for moire that removes moire, it might disguise it with a certain degree of success, chances are it leaves luminance banding behind.
Kevin.
Yes, aliasing artifacts are by definition permanently mixed with real detail, and as such cannot be separated afterwards.There is no general method to separate aliasing and signal once they are overlapping if we make no assumptions about the true signal and the aliasing.
There is no general method to separate aliasing and signal once they are overlapping if we make no assumptions about the true signal and the aliasing.
I believe there to also be no general method to separate signal and noise if we make no assumptions about the true signal and the true noise. The thing is, we can often make assumptions about signal and noise that allows us to do noise-reduction that really reduce the noise while not affecting the signal all that much. Many viewers feel that noise reduction can improve noisy images.
That's correct, for single images. Of course when we shoot multiple images of a stationary subject with sub-pixel offsets, then we can resort to things like super-resolution which will allow to increase the Nyquist frequency and thus shift the aliasing threshold. Likewise for S/N ratios we can use HDR exposure stacking, thus cherry picking from the lower shadow SNR levels of the longer exposures, or use exposure averaging which will reduce the noise threshold by the square root of the number of exposures.Sure.
Cheers,
Bart