191

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 conversion software. I have a RAW file from my camera, and I've used dcraw in a mode which tells it to create an image using literal, unscaled 16-bit values ...


44

I will only answer the first question: What are frequencies in images? Fourier Transform is a mathematical technique where the same image information is represented not for each pixel separately but rather for each frequency. Think about it this way. The sea has waves some of which are very slow moving (like tides), others are medium in size and still some ...


24

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. Funniest part was that Soviets didn't have the technology of radiation-hardened film, but Americans did. They used it against Soviets in high-altitude spy ...


20

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 spread over a larger area by a defocussed lens, so that it forms a disc that isn't as bright and therefore doesn't clip. That's why you get those nice circles ...


20

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 Canon's nomenclature for in-camera dark frame subtraction. When you take a photo the camera will expose the image normally and then use the same settings to ...


19

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 lander camera was a facsimile camera with a single, stationary photosensor array (PSA), and azimuth and elevation scanning mechanisms. A lander image was ...


19

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 detected pulse height is recorded in the pixel counter in the TOT mode; and Time-of-Arrival (TOA): the TOA mode measures time between trigger and arrival of the ...


18

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 the exposure, each exposed from the start to times advancing withing the whole exposure. The later images would have more detail in shadow areas, but might ...


15

All image processing packages should make this easy. I'll show you how to do it in Mathematica, if you have access to this system. Mathematica is a programming language, but it's really easy to do these kinds of manipulations, so if you have access to it (e.g. through a university site license), I recommend you give it a go! First, import the image: img =...


15

The simple recipe is to convolve with a Laplacian of Gaussian kernel (3x3, with 8 in the middle surrounded by -1 and take the abs(result)) . After this you get some artifacts if it is a jpeg image, and out of focus borders that have a high intensity difference will also "ping". The result you can threshold to detect the strongest edges and remove teh ...


15

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 derivatives probably) you acquire it by installing 'hugin-tools' package. In the command above: '-a aligned' sets prefix of the name of output images to 'aligned' ...


12

Aliasing is the result of repeating patterns of roughly the same frequency interfering with each other in an undesirable manner. In the case of photography, the higher frequencies of the image projected by the lens onto the sensor creates and interference pattern (moiré in this case) with the pixel grid. This interference only occurs when those frequencies ...


12

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 maximum of nearby source pixels than average. Or, to be even more exact, you'd be summing up logarithms of affecting source pixels. Another possible cause why ...


11

You can probably do this by creating an action and then batch processing: Create the action with an open file in photoshop start recording do File > Save As > and set file type to PNG or use File > Save for Web if you need to resize or make other modifications click Save stop recording and save action as "Save As PNG" (there may also be some built in ...


11

The physics simply doesn't work that way. Aliasing irreversibly transforms frequencies past the Nyquist limit to appear as frequencies below the limit, although those "aliases" aren't really there. No amount of processing a aliased signal can recover the original signal in the general case. The fancy mathematical explanations are rather long to get into ...


11

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 based on his method. In 1891, Gabriel Lippmann demonstrated full color images using a single sheet of black & white film, no filters, no colored dye or ...


11

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 software can differ significantly from what another software produces when set to level 60. If you use ImageMagick as suggested by Rolazaro Azeveires, it will indeed ...


11

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 previously installed imagemagick with Homebrew, you need to uninstall it by brew uninstall imagemagick first. One other option to convert HEIF → JPG on macOS is by ...


11

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 saturates at somewhere between 20,000 and 100,000 photons. Let's say that we're happy with a 12 megapixel camera and are okay with the lower side of sensitivity ...


11

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


10

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 cause the same bad experience for viewers, regardless of whether it is caused by a small original or poor focus. What you want to do is detect blur, which is an ...


9

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 the number of occurrences of a repeating event per unit of time. So if the unit of time is seconds then frequency is measured with Herz: 1Hz = 1/s. So a signal ...


9

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. To solve this you can create, optimize, and export different resolutions of the image for different display environments. For instance the display on a ...


9

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 directly comparing individual pixels around sharp edges or in very smooth color gradients. This is why JPEG is so popular. If it always resulted in noticeable loss ...


9

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 increasingly larger complexity of circuitry and precision needed to resolve those progressively finer and finer details. Complexity and precision don't come ...


9

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 settings, it may initially show you a low-quality JPEG preview actually embedded in the RAW file by the camera.) This is why I find the whole "RAW isn't an image; it'...


9

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 eye to where it's at its strongest will restore it a little, but it doesn't look very natural. Quick attempt, each colour set in the same way, just by eye &...


9

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 vast array of cameras that produce such files (understandable, being an open-source project with limited volunteer resources). By default, it applies a "base ...


8

For an image to be a valid measurement tool two criteria must be met: The objects must be exactly in the same plane. The plane must be parallel to the plane of the image sensor. Criteria one is easy to verify, are both objects sitting on a flat surface? Do any of the objects have a significant depth when compared to the distance between the camera and the ...


8

I know it's already been answered quite well by mattdm, but I just thought you might find this article interesting. In case the link goes down, here is a summary: The human eye is most sensitive to colors in the green wavelength region (coincidental with the fact that our sun emits most intensely in the green region). The camera eye (charge coupled device (...


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