Spring 2012

Spring 2012
by ani

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15

I actually wouldn't describe what you're seeing as a halo artifact. It seems to me to be posterization — there just aren't enough tones to smoothly represent the gradient of the sky. It just happens to be in a circular pattern because in this image the center is brighter and then diminishes evenly in all directions. In a different image, this same effect ...


10

The image has some highlights where there is some blue mixed in, where there is otherwise only information in the red and green channels. It's those highlights that doesn't balance well when you desaturate the image. You can use the Channel Mixer in Monochrome mode to convert the image, that allows you to balance the channels to avoid the posterising. ...


8

Horizontal and Vertical Banding Noise (HVBN) is caused by sensor readout, downstream amplification, and ADC. There can be multiple sources of HVBN, some of them cause a relatively fixed pattern, others can cause random pattern. External signal interference is often a source of softer and more random banding. Exactly which causes banding in which sensors ...


6

As you are taking this on a phone - it has no shutter, instead it scans the CCD matrix (i think top to bottom) to build an image. What you are seeing is the variation in the brightness of the CFL as the camera scans the CCD. these lamps have a running frequency of around 50-60 Hz, as does the picture on your CRT tv (scan frequency).


5

I think what you're seeing is called banding or posterization. This is where smooth, continuous tones are rendered in a stepwise manner because the bit depth (the number of bits used to represent each pixel) is limited and the jump between pixel values is large enough to be visible. Because the image is still in Darktable and hence is 16 bit (which is enough ...


5

It would be helpful to know exactly which tool you used to tweak the sky and to see how it looked before. The histogram of you sky looks like it has been posterized, ie. jumping values, and then blurred to fill up the gaps. the causes for this can be working in a 8bit image space, doing multiple operations that should have made decimal values but then ...


5

The banding is caused by limited information in the sky area. You can confirm this by using the dropper tool on each band - you will probably find only a limited set of RGB values. Edit: have had a look and the blue values are all 235, 236, 237. If there is limited information, blur will merely move the bands around. You have to add some random ...


4

These lines are very likely there because of the frequency at which your light flickers. This is most notably the case with fluorescent lighting or led lighting, especially when you dim the light. Led are dimmed by switching them on/off rapidly. The dimmer the light the longer the off periods which our cameras capture easily (and not only the X-T1) Another ...


3

The vertical refresh rate of the screen is around 60 Hz, but the horizontal refresh rate is much higher. Each line of the display is refreshed from left to right during the vertical refresh. With a vertical resolution of 1280 lines, it means that the horizontal refresh rate is about 76800 Hz. As the exposure time is about 5 times that, it makes sense that ...


3

The effective trick for this is to double the resolution of the photo, add a very small amount of stochastic hue-constrained noise, bring the resolution back to original, and THEN de-noise. There is already significant banding in the original, by the way...which I find way more annoying than any noise, which seems pretty minimal. Edit: These two photos ...


2

What you are seeing is the refresh of yur monitor, probably 60Hz. You can prevent that by shooting at a longer shutter speed, which means reducing the ISO value and/or your aperture (=bigger aperture number). Just try a few different settings. A tripod will probably be helpful, to prevent camera shake at those slow speeds. Edit: i'm just seeing that you ...


2

I have made a circular 8 bit gradient with sampled edge colour and center colour. This illustrates that it clearly is not the 8bit quantisation problem. I have also took a stare at the source, non-denoised image and I found posterisation there too! This posterisation is already there in first image, denoising only reveals it. There cannot be any ...


1

You have diferent issues here. Lets separate them. 1) You have a bright wall and dark people... It is the same case as if you have a bright window with people on an interior. Your options are limited. Use aditional ilumination, like firing a flash as fill light. If you are shooting from far away this could not work. But if you have permissions you can use ...


1

Your ways are: using any film to record images instead of digital technology using the camera with strong enough AA filter using the camera with surplus of resolution (medium format cameras, may be very expensive) using very tight aperture (big F number) so that image is blurred enough with diffraction for moire to disappear. 1,5x crop camera with F13 will ...


1

I noticed the same trouble with sony A77II. Now my camera is at Sony's repair center, so I can't do any test, but I think that the problem could be the e-curtain. Did you try turning it off? I'll try when my camera will be back from the repair center.


1

There horizontal lines are some kind of noise problem setting/reading the horizontal addresses in the camera array. So if it is a 10 bit address then bit 4 in the address is always set or never set. This would show up more clearly on the raw image. The compressed image would average out the problem to some extent.


1

AS the CFL has a flickering luminosity with frequency based on the input current (50/60 Hz or a multiple of this value) you may have some effect due to the interaction with the shutter. Try to set your camera in speed priority mode and push the speed up.



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