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Moirée DP2M
- Thread starter koju
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- sigma dp2 merrill
Futax
Senior Member
I think it's colour moire that the Merrills (and other true Foveons) avoid. Any sensor with no AA filter and paired with an ultrasharp lens can suffer from aliasing, which is what causes moire patterns. Mind you, I think other forces are at play here!Why would you want to remove that? It looks SO cool.
I thought Merrill cameras were incapable of producing moiré (unless it is something happening in real life). I guess not, huh?
Not forthcoming, apparently?If it turns out to be a re-sizing artifact, which does seem likely, try applying a small amount of Gaussian blur before down-sampling, maybe 0.7px? The greater percentage of down-sampling, the more the blur amount needed.
How about posting a crop from a 100% JPEG? Then we can all play with it
Fraulain Uebermueller
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If resized, the resizing is likely the reason.
If crop, then it certainly looks ugly. Softer lens, tiny aperture (due to diffraction), vaseline on the lens, different distance to the offending subject all can help. Or using a camera with an anti-alias filter. Since there are AA, hotmirror etc. removal services, I wonder if there is AA-adding service (may change the optical stack height though so possibly PDAF and image edge quality issues).
If crop, then it certainly looks ugly. Softer lens, tiny aperture (due to diffraction), vaseline on the lens, different distance to the offending subject all can help. Or using a camera with an anti-alias filter. Since there are AA, hotmirror etc. removal services, I wonder if there is AA-adding service (may change the optical stack height though so possibly PDAF and image edge quality issues).
CatchAlive
Well-known member
mmm... I think you use full res TiFF or DNG for your test... So when you are in front of your screen and you zoom at 100% you see that kind of moiré?
It's new for me because shooting fabrics with DP2 and 3 I never have this problem. I also shoot with "no AA filter" cam such as Ricoh GR and PEntax K3 and that's the kind of problem I sometimes encounter.
Anyway you're more aware of this kind of things because you test a lot of different cam...
But for the submited shoot at the first post I'd be curious to have the original file. Because the really few times I had this behaviour on fabrics with DP, it was because of a "bad resizing". I really never had this on a DNG in the same situation... curious... :-/
It's new for me because shooting fabrics with DP2 and 3 I never have this problem. I also shoot with "no AA filter" cam such as Ricoh GR and PEntax K3 and that's the kind of problem I sometimes encounter.
Anyway you're more aware of this kind of things because you test a lot of different cam...
But for the submited shoot at the first post I'd be curious to have the original file. Because the really few times I had this behaviour on fabrics with DP, it was because of a "bad resizing". I really never had this on a DNG in the same situation... curious... :-/
RitterRunkel
Well-known member
That's what I thought, too; I'd buy one!
Moiré shirts could be a new trend ... maybe one should offer color moiré as well. 
RitterRunkel
Well-known member
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www.dpreview.com
And I think he's perfectly right. Here's a real world example from DP3M with a grid/lattice/trellis: http://wxyz.de/bilder/orte/Goettingen/DP3M0083_o.jpg See the right tower at its top left. U can see the grid from straight, but a little more left and tilted, the meshes become narrower ...
Well, you can see patterns with in the cables of a large bridge as well, but then you also see the asame with your eyes. See this photo
It is not taken with a DP, but I have taken photos of the same bridge with both DP2 and DP2M and you cannot avoid the effect, but then you also see the exact same effect with your bare eyes.
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Out lightwriting with Sigma dp2Q
August feast 2014 - one photo each day
Thanks, Ritter, excellent example of Foveon moire!
Here's the Foveon paper on the subject:
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Cheers,
Ted
TIFF.
If you go back and look again you will see that the images are zoomed 400% in FastStone Viewer. This shows certainly that the image moiré is caused by the sensor's geometric resolution and is not the moiré you can get on the screen when zooming in/out.
Moiré from repeating patterns in a scene become possible above a certain frequency of repetition, called Nyquist. In the simple case, think of a lens at infinite focus. The focus distance to the sensor for a DP2M is 30mm. One sensor pixel is 5um from the next one (horizontally) up to 7.07um (diagonally).
So any repeating pattern in the scene must not be closer together (at the sensor) than those numbers. If we shoot a shirt at 3m distance (3000mm) that is a factor of 100 times the focus distance. So . . . the threads must not be closer than 5um x 100 = 0.5mm (horizontally).
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Cheers,
Ted
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koju
Active member
In reply to all the posters taking time to look at the problem I'm supplying these pictures that support the idea that the problem occurs when downsizing i.e. picture not rendered at 100%. The artefacts are definitely not a (psychedelic) pattern on the shirt.
Image at 100%
Image at 82%
Image at 23%
Image at 100%
Image at 82%
Image at 23%
RitterRunkel
Well-known member
It's what most of us thought and guessed. The recommendation with blurring first is one possibility. The other one is using another algoritm for resampling. Below is cubic-spline ... 82% + 32% ... No moirè, but quite soft. It's always a tradeoff between sharpness and moiré ...
Cubic-Spline with IM (-filter Cubic -define filter:c=.25 -distort resize x%)
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Normallity restored. Try a netter resize algorithm and your problem should be solved --
Out lightwriting with Sigma dp2Q
<a href="https://www.flickr.com/photos/prebenr/sets/72157646094831602/" >August feast 2014 - one photo each day</a>
Damn that's annoying! (I mean those moiré patterns.) I'm SURE those were not visible by the naked eye. So sad. We need a higher resolution Foveon sensor, obviously!
The following are resized using different scaling methods from that larger 100% size crop of the patterned shirt:
Cubic downscaling sample.
Lohalo downscaling sample.
Nohalo downscaling sample.
I used GIMP 2.9 to create these from this sample image:
The image from above, in this thread, which I used to create my downscaled samples.
As you can tell, a different method of downscaling can make all the difference. The same goes for upscaling. Some methods of upscaling make jagged edges, while others don't seem to do that so much.
Cubic downscaling sample.
Lohalo downscaling sample.
Nohalo downscaling sample.
I used GIMP 2.9 to create these from this sample image:
The image from above, in this thread, which I used to create my downscaled samples.
As you can tell, a different method of downscaling can make all the difference. The same goes for upscaling. Some methods of upscaling make jagged edges, while others don't seem to do that so much.
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