dsnoke Loc: North Georgia, USA

I'm not trying to debate the value of RAW files. I shoot only RAW. But I have seen statement that one can not edit a raw file. I believe that is correct, but there are some nuances that need to be explained. So what follows is my more complete (I think) explanation.

A raw file is just the data collected by the sensor in the camera, nothing more or less. What one sees, whether raw or some other format, is a rendering of that raw data by some software program. That rendering may take the form of a jpeg file or TIFF file or GIF file or whatever file format your viewing program uses.

So when you open a raw file in ACR or Affinity Photo or any other program, what you see is that program's rendering of the raw data. If you then make changes and save the file, that saved file may or may not include the original raw data. If you save the changed file as a jpeg file, then the raw data is not saved. If you save a TIFF file, then the raw data is not save, but more data is kept than in a jpeg file. I'm not sure about other file formats.

Some programs may keep a record of changes as a sidecar file or other method. In that case, the program may keep the original raw data. Then, when you reopen the file, the rendering can start with the raw data and reapply the changes for you to see.

Make sense? Comments are welcome.

R.G. Loc: Scotland

The typical procedure for a raw editor is that it will keep a copy of the raw file plus a record of any adjustments that you make. In other words the raw file is still there unchanged. When you close the editor and then open it again the editor takes the raw file and applies the adjustments that you made previously, which brings you back to the point where you see the results of your edit on the monitor. Even after you export the results of the edit, the editor still has the original raw file plus the adjustments.

Bill_de Loc: US

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NPSlover Loc: Woodbury Minnesota

I appreciate these conversations. As one that is new to RAW and still debating my editing program of choice, they are very helpful. Even hearing the same thing in different words proves helpful. Thanks for opening the “can of worms”.

robertjerl Loc: Corona, California

That is why I use Light Room as my first stop for edits, then Photo Shop and save back to LR. It saves not only the RAW, but copies of every edit you did. Non-destructive all the way. At times the lists get so long on images I try multiple edit ideas on that I break the strings by doing a virtual copy of the original and start a new edit list.
Then on occasion I use Picassa for a quick change when I am posting. I save my edit from LR or PS as a JPEG on my desktop before the regular save just so I can open it to see if I want other changes before posting, plus I don't have to keep LR/PS open all the time. It does slow things a little when I am using multiple windows/multitasking. So the image on the desktop allows me to close LR &/or PS. And my "to post list" is right there on the desktop in the form of images.

Rongnongno Loc: FL

Edits made to a raw file are usually stored in a text file (XMP?). (*1) This file is usually named 'sidecar'. Delete it and the raw file returns to its default. Something few are aware of: You can have different raw edit states within the same sidecar. (Check ACR menus to use that feature).

When viewing a raw file, the software usually shows the JPG embedded inside the raw file. The quality of what you see then is determined by the JPG settings used in camera. Advanced viewers give you the choice to decode the raw file. It takes longer and what one sees might not be as good as the JG 'preview'.

Most raw editors using their own settings when opening a file. You have to pay attention to that because if you do not, it will open a 14 bit file as an 8 bit, by example. Also, the color space is determined by the raw editor, so if you want the best, set your raw editor to accept the largest you can tolerate. Just remember you can always go lower when editing, but when opening you can lose a ton of data by not using the proper setting.

Of note, to think that a raw is unprocessed is a fallacy. The analog image projected to the sensor is processed in order to create a digital file (raw) (*2). The way it is done differs from brand to brand and from model to model (*3). This in turn means there is a bias introduced not only by the hardware (sensor used) but also by the process (analog to raw). While some of the bias introduced can be changed, it not all that easy to change other.

Once a raw file is loaded into a program, the raw file ceases to 'exist' as far as most editors are concerned (*4). You can export the result as whatever said program allows you to, including the infamous DNG format.

Another thing... Some formats are so-called raw format when they are not. Acrobat DNG is the most infamous as while DNG protects the content of the file within, this file can be a JPG or whatever the heck you want inside as long as it is an accepted digital image.

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(1) Some software had the bad habit of appending their data to the raw file...
(2) Even if you use JPG as format in camera.
(3) Hence the need for a software update when the format is brand new. That can take anywhere from a few days (sometime hours) to a couple of months, depending on the software one uses.
(4) Adobe by example will allow you to reopen a raw file if it is open as a 'smart object'. Other software can use a link to instead of importing the image. Check your software for information.

Blenheim Orange Loc: Michigan

That is my understanding.

DirtFarmer Loc: Escaped from the NYC area, back to MA

A raw file is several different things. It contains a jpg preview of the image, generated by the camera using the settings applied by the user. It contains metadata: parameters about the camera, date, time, lens, settings, and other useful stuff. It contains the raw data from the sensor.

The raw data from the sensor is what you can't edit. When you use an editing program on the raw file, it takes some of the parameters from the metadata to use in demosaicing the raw data to generate an image. It then converts that image into something your screen can display. If you edit it with the program, you change the initial parameters and the software then displays the new version of the image. When you save the image it converts the image to the selected format, jpg, png, bmp, tif, whatever.



When you save the image as a jpg, tif, etc., the original raw data is not saved (separately). There is no need to save it. It still exists in its original form as raw data within the raw file. What is saved is the list of edits used to produce the desired image from the raw data. Some programs will save that in an XMP file. Lightroom saves it in the catalog (AND the XMP file if it is enabled).



It's not that the program MAY keep the original raw data, it ALWAYS does so. Unless you delete the raw file, which contains the raw data, the raw data is never changed by the editing program so it is always there to start applying the edit list to produce a new image.

cahale Loc: San Angelo, TX

Yes, it does. RAW files can be edited, however. Edit (Sony proprietary) will save your changes to the RAW (ARW) file. I'm not sure why anyone would want that, however. Once the original is overwritten, original data is changed. But not lost, because we all back up religiously, don't we?

CHG_CANON Loc: the Windy City

No. No. NO.

The image 'payload' of any and ALL -- A L L -- RAW files is read-only. Always is, always was ...

There is also EXIF data in a form of a 'header' in the same RAW file containing this image 'payload'. This EXIF data is completely editable, being only text. Sony, as well as Canon, can update this 'header' with edit instructions their own proprietary software can read and understand. These edit instructions are extensions to the existing data, not overwrite. Only software that can read and understand this extended data will react, all other RAW editors will 'see' just the original image payload and the unchanged EXIF values.

Adobe, trying to force themselves into the 'middle', gave us a DNG. This format mimics the RAW format, read-only image payload and wrapper EXIF. We've analyzed the differences between the Canon RAW and the DNG 'RAW'. Adobe erases all the original camera EXIF, replacing with a mixture of the original EXIF and Adobe's edit instructions. Only Adobe really and fully understands the edit instructions in the DNG wrapper. Other software understands more (or less) of Adobe's instructions in the DNG wrapper.

Linda From Maine Loc: Yakima, Washington

There are already misrepresentations and incorrect statements, including in the opening post, so tread carefully

cahale Loc: San Angelo, TX

I stand corrected - kind of. When I select "yes" to the save option, the resulting ARW appears as what I last had on the screen - not the original version. If this is due to EXIF changes, it still has been changed (edited) in some way.

CHG_CANON Loc: the Windy City

The software that sees / understands the 'extended' EXIF will show the 'edited' results. Everyone else -- who doesn't recognize those edit instructions -- shows you only the original RAW image (with possibly what that software does by its own defaults).

Ideally, the larger 'we' of RAW photographers will choose digital editors that store the edit instructions external from the RAW, such as an XMP sidecar or an edit database like LR. Letting the camera's proprietary software 'extend' the RAW with editing instructions presents little risk. The worst approach, unfortunately, is letting Adobe 'destroy' the RAW by stripping the original EXIF and creating a DNG, where 'worst' is a photographer's decision to discard the original RAW and keep only the DNG.

And 'worst' is relative. Most of us will never miss the EXIF Adobe removed. Myself, I like to investigate the AF configuration and the AF point locations, data in the original EXIF that Adobe does not retain in the DNG. Otherwise, a DNG is as good as an original RAW, when working within Adobe's edit software.

cahale Loc: San Angelo, TX

Thanks. This is what comes from doing everything myself and playing by "ear." That's the same way I play(ed) several musical instruments. Maybe well, but limited.

Blenheim Orange Loc: Michigan

What did I miss? I didn't catch any serious errors in the opening post.