213
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 ...
- 142k
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 ...
- 20.5k
25
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.
...
- 2,090
23
votes
Accepted
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 ...
- 118k
21
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 ...
- 173k
20
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 ...
- 1,887
20
votes
Accepted
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 ...
- 316
19
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 ...
- 17.3k
17
votes
Accepted
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 ...
- 2,883
14
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 the ...
- 282
13
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 ...
- 351
13
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 ...
- 31.7k
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 ...
- 2,278
13
votes
What does an unprocessed RAW file look like?
It's a really really big grid of numbers. Everything else is processing.
- 271
12
votes
Accepted
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 ...
- 37.7k
12
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 ...
- 142k
11
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 ...
- 211
10
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 ...
- 31.6k
10
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:
...
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 ...
- 3,053
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.
...
- 173k
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 ...
- 4,634
9
votes
Accepted
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 ...
- 1,192
9
votes
Accepted
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 ...
- 142k
9
votes
Accepted
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 ...
- 21.6k
9
votes
Accepted
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 ...
- 5,374
8
votes
Why does my Canon 700D take so long processing when I take a long exposure?
It's not actually processing for most of that extra time. It is taking a second exposure with the shutter closed, for dark frame subtraction. This removes sensor-based pattern noise. Of course, there ...
- 142k
8
votes
Why don't cameras record light data throughout the entire shutter?
What you're asking for, continuous light sampling, might be theoretically possible but practically too expensive. It might be possible to approximate it with a very high sampling rate. This could be ...
- 181
8
votes
What does an unprocessed RAW file look like?
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 ...
- 89
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 ...
- 142k
Only top scored, non community-wiki answers of a minimum length are eligible