# What is "RAW" mode?



## Sylvanite (Oct 14, 2013)

In the giving and taking of digital photography advice, I frequently see (or hear) someone assert that shooting in "RAW" mode is necessary for good results.  Unfortunately, I also see (and hear) a lot of misconceptions as to why.  I thought I'd describe how "Camera Raw" photos and photo editing actually work - and hopefully reduce some of the misinformation out there.

Let's begin with a description of what a digital camera does when it creates a digital image from an exposure.
First off, the camera's sensor records the amount of light (as seen through red, green, and blue filters) that falls on each picture element (or "pixel").
We see colors as we expect them, but the camera sensor sees them as tinted by the ambient light.  To correct that, the camera applies a formula for "white balance".  That way, color tints appear more like what the eye sees.
The camera also applies a "recipe", such as "landscape", "portrait", or "standard" to further adjust the image.  The "landscape" recipe, for example, typically adjusts colors to accentuate blues and yellows (so our photos have a prettier sky).  It also sharpens the image more to call out the details.  "Portrait" recipe shifts the colors to better portray skin tones, and sharpens less.  "Standard" recipe typically favors greens and reds more, and applies moderate sharpening.  Many cameras will have other recipes as well, and some allow the photographer create custom ones.
Then the camera converts the photo to the target file format, and stores the image.  Information can be lost two ways during this stage.  If the file format has less "color depth" than the sensor captured, then the image will lose some dynamic range.  If the file format is compressed, then (depending on the compression scheme and the amount of compression) image quality may be reduced.  A camera that stores images as 16-bit TIFF files typically suffers no loss, but a highly compressed JPEG image might show visible differences (in contrast and color depth).  It's a trade-off between image fidelity and file size.
So, what is RAW?  Simply put, a raw image is one that is saved straight off the camera sensor (from step 1 above, without any subsequent processing).  The camera usually includes additional data about the white balance and recipe it would have used - but that manipulation has to be done off-camera during post processing.  In essence, when editing a raw image, you have to do the photo processing that the camera does for a regular image.  Today's cameras are getting quite good at automatic image processing, but if you are proficient at using Photoshop (or other such programs), then you might be able to do a better job.  If not, then shooting in raw mode won't help you.

Some real advantages of editing RAW images:
My current DSLR has a 14-bit color depth in each color channel.  That is, it records over 16000 increments each in red, blue, and green.  JPEG images only store 8-bits per channel (or 256 levels each).  When converting from 14-bit color to 8-bit, you lose a lot of in-between shades.  Some editing steps are better done before this conversion.  If, for example, the exposure was slightly off, one could adjust brightness while more detail is present.  One can also adjust shadow or highlight detail so that they persist when converted.
With the right software, one can try out the camera's different recipes and see which one looks best.
With greater color depth, sharpening algorithms do a better job and produce fewer artifacts.  Therefore, judicious sharpening before converting to 8-bit color can yield better results.
If one is going to make large prints from an image, Photoshop allows editing in 16-bit color depth, so no detail is lost at all.  If the target media is web based, however, 8-bit conversion will be necessary at some point.
Again, it's a matter of being able to do a better job than the camera does.

Some fallacies about RAW images:
"_Raw images have greater resolution_".  That is just plain false.  My current camera, for example, can save both in RAW and JPG format in three sizes.  The number of pixels (i.e. resolution) is exactly the same whether saved in RAW or JPG format.
"_RAW images permit additional editing controls_".  That isn't true either.  In Photoshop (and Photoshop Elements), one can "Open As Raw", and all the RAW controls are present, even if the original image was in a different format.
"_RAW images can correct for improper exposure_".  That is only true to a limited extent.  I've seen people claim they can correct for a 2-stop exposure error, but in my experience highlight detail is gone with a 1-stop overexposure - and no amount of post-processing is going to retrieve it.  Trying to recover underexposed shadow detail introduces a lot of noise.
One last time.  Raw image manipulation is about doing a better job editing a photo in post-processing than the camera can do internally.  It doesn't otherwise provide a great advantage.

I hope that helps,
Eric


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## OKLAHOMAN (Oct 14, 2013)

Hmm, and all this time I thought raw was steak tartare.:wink:
Eric, all kidding aside thanks I did learn something.


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## crokett (Oct 14, 2013)

Thanks. I learned a lot.  My Kodak point n shoot does have a white balance setting, but it makes the picture too blue.  I've learned to just adjust white balance in post-processing.  I am thinking after reading another thread I am going to try shooting on a grey background and see what that does.


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## OZturner (Oct 14, 2013)

Thanks Eric, for your "technical explanation for non technicians". 
I could understand and follow most of your presentation.
It looks like I might have to study a little more, and perhaps invest in some new improved photographic equipment.

What a fool I have been, I thought that for my retirement that Pen Turning would be easy and a lay back task to undertake and a great way to use all those small pieces of timber I have accumulated.
I now find it has possessed me, I have to visit this site before I do anything else in the morning. 
Then due to the time difference, I visit last thing before I go to bed. 
I have so many web site to visit, so much information to absorb. 
Boy I am glad I'm retired, I would not have the time to go to work.
Thanks Eric for the excellent Information Exchange.
Brian


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## TurtleTom (Aug 21, 2015)

Didn't have that on Kodachrome.


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## farmer (Aug 22, 2015)

*For those who dont want to buy software*

*Free and open source software[edit]*

darktable is a raw-workflow tool for Linux and other open Unix-like operating systems. Features native 32-bit floating point processing and a plugin architecture.
dcraw is a program which reads most raw formats and can be made to run on operating systems not supported by most commercial software (such as Unix). Libraw[51] is an API library based on dcraw, offering a more convenient interface for reading and converting raw files. HDR PhotoStudio and AZImage[52] are some of the commercial applications that use Libraw. Jrawio is another API library, written in pure Java code and compliant to the standard Java Image I/O API.
digiKam is an advanced digital photo management application for Linux, Windows, and Mac OS X that supports raw processing.
ExifTool supports the reading, writing and editing of metadata in raw image files. ExifTool supports many different types of metadata including Exif, GPS, IPTC, XMP, JFIF, GeoTIFF, ICC Profile, Photoshop IRB, FlashPix, AFCP and ID3, as well as the maker notes of many digital cameras.
ImageMagick, a popular software suite for image manipulation and conversion, reads many different raw file formats.[53] ImageMagick is available for Linux/Unix, Mac OS, Windows, and other platforms.
LightZone is a photo editing program providing the ability to edit many raw formats natively. Most tools are raw converters, but LightZone allows a user to edit a raw file as if it were TIFF or JPEG. The project was discontinued in September 2011[54] and reinstated as an open source project in December 2012.
Rawstudio is a raw format developer.
RawTherapee is a raw developer supporting Linux, OS X and Windows operating systems. It features a native 32-bit floating point pipeline.
Shotwell is an image organizer available for all major operating systems with the ability to view and edit raw images and has built-in social networking upload capability.
UFRaw is a frontend which uses dcraw as a backend. It can be used as a GIMP plugin and is available for most operating systems.
*Proprietary software[edit]*

In addition to those listed under operating system support, above, the commercial software described below support raw formats.
*Dedicated raw converters[edit]*


The following products were launched as RAW processing software to process a wide range of raw files, and have this as their main purpose:

Adobe Photoshop Lightroom
Bibble Pro (now Corel AfterShot Pro)
Capture One[55]
DxO Optics Pro
Hasselblad's Phocus relies on operating system support to process non-Hasselblad files
Photo Ninja
Silkypix Developer Studio
*Others[edit]*

ACDSee Pro is photo management and editing software that supports the raw formats of 21 camera manufacturers.[56]
Adobe Photoshop supports raw formats (as of version CS2).
_DNG Viewer_ is a free Windows (32bit) viewer based on dcraw. The very simple viewer is installed as _RAW Image Viewer_, supports some lossless operations, and can save raw images as BMP, JPEG, PNG, or TIFF.[57]
FastRawViewer is a dedicated RAW viewer that runs on Mac and Windows, and currently claims to support all RAW formats except Foveon.[58]
Helicon Filter supports raw formats.
IrfanView is a freeware/shareware basic editor with support for raw files.
Paint Shop Pro contains raw support, although as in the case of most editors updates to the program may be necessary to attain compatibility with newer raw formats as they are released.
PhotoLine supports raw formats.
Picasa is a free editor and organizer from Google. It can read and display many raw formats, but like iPhoto, Picasa provides only limited tools for processing the data in a raw file.
SilverFast supports raw formats.
XnView support for raw formats is mostly based on dcraw.
A new class of raw file processing tools appeared with the development of HTML5 - rich Internet applications. Raw.pics.io is able to render and apply basic adjustments to raw and DNG files in a web browser


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## vtgaryw (Aug 22, 2015)

So, Eric, is a RAW image pretty much the same for a CCD as for CMOS?

And then, of course, there is the Light Field camera, where the stored pixels have a whole lot of different information in them yet again.

-gary


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## Flynny (Aug 22, 2015)

Eric

Thanks that was helpful.

John


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