186

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 ...


74

Sorry, but your basic premise is wrong: an image can be encoded as an array of RBG pixels with 8 bits per value, but there are a lot of other ways: one channel with one bit/channel (pure black and white), one channel with x bit/channel (grayscale formats, x will usually be 8 or 16, giving 256 or 65536 values), various palette-based formats (cf.GIF) full-...


50

If at the core, photos are just 3 channels of pixel values [0, 255] X RBG, But photos are not "just 3 channels of pixel values" even "at the core." Computer screens are typically made up of an array of RGB pixels, so if you want to display an image on a computer screen you must, at some point, map whatever image data you have into an array of RGB pixels, ...


38

To be frank, it is entirely anecdotal that a JPEG image should be exported at a certain compression level all the time. The amount of JPEG compression should really depend on the usage purpose for the JPEG, and the contents of the JPEG. The quality level one should choose when exporting an image to JPEG is highly dependent upon the kind of detail contained ...


35

In my opinion, none of the other answers addresses the obvious misconception in the question: There is no use in converting a JPG (comparatively low quality) to a RAW file (high quality), because you do not gain anything. The reason why people shoot in RAW is that, as others have stated, RAW captures all the sensor data and saves it in a file. JPGs have ...


31

Beyond the very obvious memory card requirement differences between RAW and JPEG images as noted in the question: JPEGs are compressed and typically have much smaller file sizes. For example a RAW file from a Nikon D800 can be 50MB and the JPEG may be a fraction at 10MB. This benefits not only memory card capacity but also editing workflow speed, archival ...


28

"we may require the originals of the awarded photographs to be submitted by the relevant participants, with a short side of minimum 2200 pixels and bit depth of 300 dpi." and " Contest photographs must be saved in the jpg/jpeg format, 150-300 dpi and 7-12 compression quality, with a short edge of minimum 1920 pixels and a long edge of maximum 3200 ...


26

I suspect the answer here is that the format is written as "RAW" to match other common file format names which are acronyms such as JPEG, GIF, MOV, MPEG, etc. Nikon, Canon, Pentax, Hasselblad, Olympus, Sony, and many other manufacturers all write the format in all caps, so at this point it's a de facto standard. There is a distinction to be made between a ...


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 ...


19

In addition to @remco's fantastic answer, I want to add why there are different codecs for (roughly) the same purpose. Codecs are designed to: Be lossless vs. lossy Encode fast vs. reduce filesize Asymmetric vs. Symmetric en-/decoding Be compatible with software Be perceptionally almost lossless in different compression levels / situations Have features ...


19

In the absence of real raw files, the JPG is your "raw". Most image editors, including Lightroom, can open or import JPGs. You may choose to save in another format while editing, but do not lose or destroy the original JPGs. Also take care not to save over the original files. It is possible to convert JPGs to DNG. But it's usually used to test and develop ...


18

It sounds like what you're looking for is JPEG2000. It has a range of options including a 16-bit lossy compression and better compression ratios than JPEG. It hasn't been as widely adopted as hoped (for a host of reasons) and may have some patent issues that might make it difficult to use in certain situations but otherwise it fits your needs. Personally ...


18

Short Answer No, decoding is not guaranteed to always be the same. However, the differences are guaranteed to be very, very small. ISO Specifications The International Organization for Standardization (ISO) specifications for JPEG has the following specifications for decoders (emphasis mine): A decoder shall a) with appropriate accuracy, convert ...


17

Going from JPG (which is a lossy format) to any lossless one (like PNG) does not. Going from any format to a lossy one, yes, including JPG to JPG. It could be too little to notice, and using the same compression ratio loses a lot less on the second saving than on the first one, but yes, it is cumulative. But beware... Some image formats store more ...


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

If this image were RAW, the color would still be there. But since it is JPEG, I'm afraid not. The fact that the image is in RGB format does not help, because I'd you look, you will find that in fact for each pixel, each of these values is set to the same thing: (0,0,0), (37,37,37), (221,221,221), or whatever. That is, they're all gray levels, just ...


15

I'm 99.99% sure that this is just a typo for "lossy". I've never heard of the term "losee" and can't find it in search, either. Especially if it just appears in a review question and not in the rest of the text — it's probably just an error. A lossy format, of course, is one which discards (hopefully mostly imperceptible) information in order to achieve a ...


15

Nothing makes raw files difficult to manipulate for someone with the right expertise and tools. It's just that there aren't many folks around who have those tools and expertise. The tools needed to manipulate a raw file into a jpeg are much more widespread and well known than those needed to manipulate a raw file into a different raw file. That is probably ...


14

Noting other answers, and having had a bridge camera that did TIFFs, I'd suggest that for DSLRs TIFF is pointless except as an add on if it can be managed. TIFF is a lossless way of saving an image, once an image is generated, BUT the image that it saves is an interpretation of what the sensor records. RAW gives you the maximum possible flexibility ...


12

I would say TIFF is probably the best format. JPEG 2000, like JPEG, is still a lossy compressed format when you really try to save space (the lossless version can compress a bit, but not nearly as much as the lossy form, and some forms of the "lossless" wavelet compression still can't fully reproduce the exact original image.) When scanning in an original ...


12

There are several reasons why this assumption is incorrect, and they all come down to one thing: What scale are you actually using? And that can be broken down a little further: What is 255? "Color" is not a property of the physical universe. It is a sensation that arises in the mind. And, that includes things like "blue", "green", and "red". A scale ...


12

RAW files no more deteriorate over time than a DOC file would. As long as you store them correctly (with backups of course) the file will be fine. It's true that the software that you use to process them will change but in general that is a positive. Files from older cameras often look much better in modern RAW processing software than at the time they were ...


11

In general, RAW file converters, including Photoshop, will only open RAW files from camera models they know about. There's nothing special about the 60D to 70D transition here; you don't say which version of Photoshop (to be specific, raw files support depends on Adobe Camera RAW plugin which is updateable either with Adobe's update tool or through installer)...


11

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


10

JPG compression is done in blocks of pixels. In a highly compressed JPG image the edges of those blocks can be seen: in the original image two pixels may have been very close in brightness and color, but if they are in different blocks, then after compression and decompression (when viewed) each of their values may differ from the original, so you lose ...


10

A RAW file is a container format which includes metadata (proprietary and standard), possibly a JPEG-compressed preview, and a digitized record of the value of each sensor photosite, possibly with some low-level noise reduction applied and with dead pixels removed. This is common across the class of file formats we call RAW. Pure, "raw" sensor data alone ...


10

The RAW formats store, well, the raw sensor data from the camera with information on how to decode that for image processors such as Adobe Camera Raw or similar. In that sense, the RAW format is not an image, you have to apply demosaicing algorithms to interpret the sensor data into a coherent image for display. Beyond the Adobe attempt to convince everyone ...


10

First - do you have a specific problem? The time to dump an image to the memory card varies a lot from camera to camera and the best solution for your problem is probably to try to investigate it yourself. Also why are you focusing on the time it takes dump the file to the memory card? With the often large buffers of modern cameras you can often continue to ...


10

Shoot in RAW, and export on whatever format you like. JPEG for example. For print it can be on TIFF. And you could export at grayscale at 16 bits. But that is only for specialized usage. For most users, JPEG is fine. An additional note. If you are editing your photo using Photoshop, keep your working files in Photoshop, masks, layers. And again, export to ...


10

A RAW file is little more than a container for the output of a camera sensor. It has to be processed into an image which gives it full color information at each pixel. As such there are no programs intended to manipulate a RAW file since it is meant as input to RAW conversion software. Since it is just made of bits like any other digital file one can of ...


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