Episode #125 of the Stack Overflow podcast is here. We talk Tilde Club and mechanical keyboards. Listen now
49

This image shows a rather long exposure. The image in general is very dark, but a few spots are light. Probably some reflection on shiny surfaces like the door knob, the sink and the tap. If you take a long exposure shot without a tripod you always move the camera around a bit. While it is not visible for the dark areas you can clearly see movement trails ...


46

The reflection on the screen tells me you used a flash. The flash only lasts a very short time (at most 1/200 of a second), while the shutter was probably open for a much longer time (maybe 1/30 of a second). Since the frame of your CRT as well as the wall behind it do not emit light on their own, their appearance on the photo is mainly due to them ...


37

This is moiré. It occurs because a screen is actually a grid of squares that are being used to make the image. When it ends up trying to be mapped to another grid of pixels (either by being captured by a sensor or by scaling) points of light or pixel data don't line up exactly. Some pixels get 2 pixels of information, some get the border between pixels. ...


35

The variability you are seeing in your photos is due to the way many types of lighting convert alternating current into light. Although they look constant and steady state to our eyes, in reality they are flickering with the oscillations in the alternating current supplying them with electricity. When shooting under any kind of flickering lighting, ...


28

I would suggest that it might actually be a sensor fault (or firmware bug). My reason for suspecting this rather than JPEG artefacts or banding is that the surrounding sky has exactly the same gradient but is rendered correctly. Also, JPEG artefacts would tend to be noticed in areas of higher detail, but those look great. If this only tend to happen in ...


25

I think "several fluorescent fixtures that I use to light my studio" is the key here. I'm guessing that the very high ISOs are accompanied by very short shutter speeds. Fluorescent lights cycle, and there are color variations within the cycle. Repeat your test with incandescent light or sunlight (or a strobe with high-speed sync). See Do fluorescent ...


23

What you are seeing in the photo is a specific type of lens flare known as ghosting. It is an inverted and reversed reflection of the brightest highlights of the scene. If you were to draw an x and y axis intersecting in the center of the photo, then the bright light on top of the building just left of the vertical axis is reflected the same distance below ...


22

These look like JPEG compression artifacts, possibly caused by picking a lower-quality setting in the camera settings. On many cameras there's e.g. a Fine JPEG mode and a SuperFine mode, or something similar to that. Select the higher-quality option, or better yet, shoot RAW...


21

This looks like a stuck/hot pixel in the sensor. Due to the demosaicing algorithm, it has affected not just one pixel in the output image but also four diagonally adjacent pixels. I would be willing to bet there is a single red or green pixel on the sensor right there that is incorrectly reading too bright. The other faint dot to the right may be a blue ...


19

An example Using the current photo of the week image. This is the high-quality JPEG: re-saved in Gimp with JPEG quality 80 (low); please note the general loss of sharpness, "dots" around high-contrast edges, loss of detail in low-contrast areas: and re-saved in GIMP with JPEG quality 30 (very low); please note evident 8x8 blocks and severe loss of ...


18

Despite what it might look like, this is not a focal plane shutter effect. A focal plane shutter effect causes distortion because different parts of the frame are exposed at different times. For a spinning blade that moves a fraction of a rotation during the entire exposure, the blade would appear curved and its thickness wrong. However, that is not what ...


18

This looks like the effect of noise reduction at high ISOs. Heavy NR is common in compact cameras with small sensors. Fujifilm cameras of that generation did it very well compared to others of the time, but there's only so much blood you can get from a stone. On most modern high-megapixel point and shoot cameras, you'll see this even at low-ISOs if you ...


17

This is lens flare, where reflections within the lens end up showing on your photos. General guidance to minimise it includes: Avoid getting the sun in shot (and ideally, avoid having it just-out-of-frame too) Use a lens hood to shade the front element Try to use lenses that have anti-reflective coatings Keep the front element clean, but follow the lens ...


16

JPEG actually uses two types of compression, a lossly and a lossless one. Lossless compression doesn't cause artifacts, so we can ignore that part. The particular type of lossy compression in JPEG, called a discrete cosine transform for the math knurds, allows a tradeoff between compression ratio and fidelity. Most software sufaces this as a "quality" ...


15

What you're seeing is longitudinal chromatic aberration (otherwise known as axial colour), whereby the light at the edge of the bokeh disc undergoes a colour shift depending on whether it is in front of or behind plane of focus. The reason for this is that light of different wavelengths focus at different distances along the axis of the lens. This is very ...


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 ...


14

You're exactly right — it's the same thing as a monitor pixel error, but on your camera's sensor rather than on an LCD screen. * You can either fix it in post-processing (automatically, with many RAW-processing packages) or have it mapped out with the camera's firmware. If you're lucky, your camera model includes a built-in feature to do that yourself in ...


14

Looks like there was some dust or watter droplets or whatever in the air and that they reflect the flash light. The effect is not very present but as your background is black you can see them. Furtehrmore as they are out of focus they appear as disc rather than dot (in fact you got nice bokeh)


14

Those are almost certainly reflections from the UV filter. I recommend taking it off. This is a topic of much debate, but the fact is filters do cause artifacts visible in your photos — you've got the evidence right there. You can get better results from a more expensive filter, but then it'll cost almost as much as your lens. Lenses aren't as fragile as ...


13

I think the other answers may have missed the issue here. Seeing compression artefacts on a RAW file in Lightroom is quite a common issue and it drove me nuts when I first encountered it. It turns out what you're seeing is just regular JPEG compression in the preview image that Lightroom generates. For performance reasons, in the Library module Lightroom ...


12

Looks like a hair on the sensor. Use your camera's built-in sensor cleaning function to see if you can dislodge it. If that doesn't work, you may have to clean it manually or take it to a camera shop that offers such a service. Dust or hairs in the lens won't show up in photographs as they are too far from the plane of focus to be visible; have a look at ...


12

tl; dr. Blend a "panorama" from only slightly rotated exposures and make sure no flare is included in the final result. It's not possible to optically remove this type of flare when shooting into the sun (though different lenses have different levels of flare resistance). However, there are other effective ways to get rid of it. What you can do is take ...


11

Looks like a shutter malfunction (which fits with it only appearing at certain shutter speeds). The shutter is made of a series of metal blades, it looks like one of these blades is misaligned, which is exposing that part of the sensor for longer than it should be, hence the bright area. You can have the shutter replaced at a Canon service centre.


11

This looks to me like Newton's rings, an interference pattern that occurs from closely-placed surfaces. They are usually only visible when narrow-band filters are used, or when the light is inherently narrow-band. With wide-band illumination, the rings fall in different places for the different wavelengths of light, so the effect is largely canceled out. My ...


11

I agree with what Hermann said, but have a different answer as to how to avoid this. Expose properly. Notice that the blue smudge is much dimmer than the moon, which is so bright that it is totally blown out and even has a quite visible halo around it. Some of that may be caused by atmospheric effects, but I also suspect blooming due to extreme over ...


11

I have done three things in the past to deal with this. Compose the photo in such a way that the lens flare is attractive... that's a great choice for your example above because the sun is IN the photo. Some lenses have an attractive flare (many don't) Use lens hoods, paper, or your hand to block the light that is causing the flare. This works when the ...


11

What you are seeing in the photo is a specific type of lens flare known as ghosting. It is an inverted and reversed reflection of the brightest highlights of the scene. If you were to draw an x and y axis intersecting in the center of the photo, all of the artifacts in the photo have corresponding bright light sources at the same distance from center and at ...


11

It is either subject motion or camera motion. 1/80 second is pretty slow for human subjects not making a specific effort to be still. It is also pretty slow to use hand held if you are going to pixel peep at 100% magnification. The flash is much shorter in duration than the shutter, so the motion that is only illuminated by the ambient light is much dimmer ...


11

It looks like lens flare. It is an internal reflection inside the lens. It is caused by off axis light allowed to fall on the front surface if the lens from outside the field of view. For an example of such flare when the exposure is brightened please see: Can you photograph the milky way with a full moon out? It might also be sunlight reflecting off dust ...


Only top voted, non community-wiki answers of a minimum length are eligible