211 votes
Accepted

What does an unprocessed RAW file look like?

There is a tool called dcraw which reads various RAW file types and extracts pixel data from them — it's actually the original code at the very bottom of a lot of open source and even commercial RAW ...
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  • 140k
32 votes

Do smartphones suffer from degrees of chromatic aberration? If so, how is it possible?

Because the chromatic aberrations happen in the lens, not the sensor - the picture is already distorted by the time it reaches the sensor, so it doesn't matter if there is a Bayer matrix (or any other ...
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  • 19.7k
24 votes

How was photo data processed and transferred back to Earth from satellites before digital photography became commonplace?

Luna 3 did something as complicated as you thought: It took photos on a film, processed it in a kind of onboard minilab, and then scanned and radioed it back home in analog way not unlike an old fax. ...
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  • 2,040
21 votes
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What algorithm can I use to simulate bokeh?

I think the main problem is one of dynamic range, your algorithm is probably right but you're working on the wrong type of data. A point light source that would otherwise clip and go pure white gets ...
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  • 117k
20 votes

Why does my Canon 700D take so long processing when I take a long exposure?

To reduce the processing time for long exposures, you want to turn off Long Exposure Noise Reduction. However, you may not want to give up the benefit of LENR. Long Exposure Noise Reduction (LENR) is ...
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  • 167k
19 votes

How was photo data processed and transferred back to Earth from satellites before digital photography became commonplace?

Amongst the myriad online pages documenting the Viking series, here's one which states clearly The Viking Lander camera design was very different from vidicon framing or CCD array cameras. The ...
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19 votes
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Why don't cameras record light data throughout the entire shutter?

It's been done in X-rays. The TimePix is a 256x256 detector. It has three operating modes: the usual "total energy in this pixel since we started integrating"; Time-over-Threshold (TOT): the ...
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18 votes

Why don't cameras record light data throughout the entire shutter?

You are missing some obvious problems with this idea. You want to "continously" capture the light data, but that's already being done. Apparently you mean to have a series of images available after ...
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16 votes
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Is it possible to find out what compression ratio was used for a particular JPEG?

No, you can not and it does not make sense to do so, since there is no ubiquitous definition of the JPEG compression level. The actual result when saving a JPEG with compression level 60 in one ...
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  • 2,809
15 votes

How to auto-align a stack of head shots?

I don't know if it's the easiest but this works pretty well for my needs: $ align_image_stack -a aligned -C *.jpg 'align_image_stack' utility is part of hugin, and under Debian/Ubuntu (and other ...
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13 votes

How can I convert an Apple iOS HEIF image into JPEG?

Support for reading HEIF was added to ImageMagick 7.0.7-22, you have to install it with --with-libheif flag. e.g. on macOS with Homebrew: brew install imagemagick --with-libheif. If you have ...
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13 votes

What does an unprocessed RAW file look like?

It's a really really big grid of numbers. Everything else is processing.
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12 votes
Accepted

How can I detect upscaled photos?

Have a DOG sniff out blur in the photos. If you're going to be penalizing for digitally enlarged photos, you might as well penalize for out-of-focus photos too. The blurred edges and details in both ...
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12 votes

What algorithm can I use to simulate bokeh?

First of all, in optics, only light adds up and darkness does not. Make sure that your algorithm does not bleed dark pixels outwards their original location. Resulting pixels should rather resemble ...
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11 votes
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What would happen if a camera used entirely different primary colors?

Color photography is indeed based on the tri-color theory. The world saw the first color picture in 1861 made using red, green, and blue filters by James Clark Maxwell. Today’s color photography is ...
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11 votes

Why don't cameras record light data throughout the entire shutter?

You suggest "Or every time a photon hits a pixel on the sensor give it a timestamp" — this would be a huge amount of data. A quick search suggests that each pixel — or sensel — in a digital camera ...
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  • 140k
10 votes

Are award winning landscape images edited?

The short answer to the question is: it depends. Some award winning images are entirely shot in camera, some are enhanced in the darkroom, some are enhanced digitally. The ultimate question here is ...
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  • 2,942
9 votes

What does "frequency" mean in an image?

I will try to explain with the simplest math terms possible. If you want to skip the math, jump to part II, if you want to get the short answer skip to Part III Part I Frequency of a signal means ...
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  • 232
9 votes

Is there any way to fix the wavy lines that appear when photographing a striped dress?

There doesn't appear to be any moire in the image itself. What you are seeing are scaling errors when the image is resized by a particular application for display on a particular size screen or print. ...
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  • 167k
9 votes

Why doesn't PNG show more detail than JPEG in a converted NASA image?

For photographic images and when a not too high level of compression is used, the loss of quality in the JPEG format is negligible and invisible. You'll pretty much only be able to notice it by ...
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9 votes
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Why does the Canon 450D have only 14bit depth RAW images?

The 14 bit depth is the limit of the physical sensors capabilities, it isn't just that the engineers decided to throw away useful data. An increasing number of bits available in a sensor reflects an ...
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  • 1,174
9 votes

What would happen if a camera used entirely different primary colors?

Is this already being done? Sure. The Hubble Space Telescope senses the near IR, visible, and near UV spectrum. Any images you see from Hubble that contain information outside of the visible ...
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  • 31k
9 votes
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Why are my RAW images already in colour if debayering is not done yet?

This is actually really simple: your image is shown in color by Darktable because it renders the preview from the RAW file in order to show it to you — including demosaicing. (Or, depending on ...
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  • 140k
9 votes
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How do I correct the huge blue-shift in these images?

I'm not sure how much they can really be rescued - there's one heck of a lot of blue in there & very little of anything else. Applying a Levels Layer & pushing the mid-point of each colour by ...
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  • 19.6k
9 votes
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How do I fix the color in this photo using Darktable to match the out-of-camera JPEG?

While darktable is an increasingly powerful piece of software, one of its rough edges is the fact that it doesn't try very hard to produce a good default "vanilla" rendering of the RAW files from the ...
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8 votes

What is the difference between HSV and CIE-Lab color space?

A perceptual uniform color space ensures that the difference between two colors (as perceived by the human eye). It is proportional to the Euclidian distance within the given color space. You may ...
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8 votes

Is it possible to find out what compression ratio was used for a particular JPEG?

You can, sort of. ImageMagicks' identify command can show a estiamte identify -verbose image.jpeg will produce (a lot of) information about the image. One of the lines will be something like: ...
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8 votes
Accepted

It is correct to match light sources with the same color temperature?

It's roughly true that light sources with the same color temperature have the same appearance. In fact, matching light sources in this way is exactly the reason we use the Kelvin WB scale in ...
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  • 140k
8 votes

Is it common practice to apply identical processing effects to a batch of photos?

Many demosaicing applications (RawTherapee, for instance) can save the processing on a picture (aka recipe) to repeat on others. But this is typically restricted in practice to global editing (colors/...
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  • 16.1k
7 votes
Accepted

RGB colour correction of CCD camera images

To fix this, you need to decompose your image to RGB channels separately. R and G channels are vertically shifted from B channel by 5 pixels each. You need to align these channels vertically. For ...
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