RAW files. What are they?

[AndrewWG]

Could someone tell me what a RAW photo is? I understand that it is a file format of some sort that pertains mainly to DSLR's, but what processing needs to be done to them, and how are they superior in some ways to JPEG? At some point I will be in the DSLR world and will need this answered so I figured I would ask.

Andy

 

[Master Mason]

Andy,

A raw photo is ALL the information that your camera gathers at the time of the picture. It makes no assumptions for any of the settings you have in the camera. Basically as the name implies RAW data. To use this RAW data you must covert it to a usable format, so every picture must be processed either individually or via a batch process. This is very similar to the developement stage of film photography. They are then converted to a file format after processing that you can use for whatever purpose you trying to use them for.

The advantage is loseless pictures, you have all of the info to make your selections. The disadvantage is processing time.

Hope that helps

 

[Furgus]

Try here

Understanding RAW Files

 

[AndrewWG]

Thanks Master Mason and Furgus. That looks like a good informative link too. I will check it out.

Andy

 

[photo_chick]

I always looked at it as RAW is the data straight from the sensor, without being run through the cameras image processor. Much like a latent image on film. You can't do much with it until you process it, but a lot of changes can be made to it when you process it.

In addition to the DSLR's some of the advanced, bridge, EVF, or whatever you want to call that group of cameras can save RAW also.

 

[MarkBarbieri]

When a camera records an image, it is translating an analog signal (the light hitting the sensor) into a digital image. A RAW file is the data that came from the sensor with very little processing. When you shoot a JPG image, the camera does a lot of conversion work on the raw data in order to create the JPG image. Some stuff the camera does includes:

1) Translating the red, green, and blue dots on the sensor into full color dots
2) Sharpening the image (enhancing the contrast where it detects edges)
3) Reducing noise
4) Increasing contrast and saturation
5) Applying white balance
6) Reducing the range of possible color values from 4096 (12 bits) per color to 256 (8 bits) per color

These are all things that RAW shooters eventually do anyway, but they have more control over the process. There are advantages to having this control. Some advantages include:

1) If you got the white balance wrong, with a RAW file you can correct it without losing as much information in your picture.
2) You can selectively sharpen parts of your image rather than the entire thing.
3) When photographing very saturated colors (like flowers), it is easy to exceed the color range available in your image and lose detail. By controlling the saturation yourself, you can often avoid this problem.

As a general rule, if you nail everything, the JPG will be just as good as a RAW shot. Shooting RAW gives you more room for adjustments.

There are some downsides to shooting RAW. It takes more memory on your cards. It's slower. The images need to be processed. Most cameras use a proprietary format for their RAW files which, for new cameras, sometimes means that you need to upgrade your software to work with it. (Props to Pentax for using Adobe's DNG standard as a RAW format).

Photo workflow packages like Adobe Lightroom and Apple's Aperture have made dealing with RAW files very easy. In Lightroom treats RAW and JPG files the same way (not sure about Aperture), so they are no more difficult to work with.

 

[GrumpyOne]

Good info here and in the link.

 

[jenr812]

Thank you for asking this. And thanks to those that answered

 

[DueyDooDah]

...(Props to Pentax for using Adobe's DNG standard as a RAW format).

Groucho! HEY GROUCHO! Look, Mark is going to start buying Pentax gear! Your work is now complete.

 

[jann1033]

Try here

Understanding RAW Files

good article

 

[0bli0]

(snip)
1) If you got the white balance wrong, with a RAW file you can correct it without losing as much information in your picture.
2) You can selectively sharpen parts of your image rather than the entire thing.
3) When photographing very saturated colors (like flowers), it is easy to exceed the color range available in your image and lose detail. By controlling the saturation yourself, you can often avoid this problem.
...
Photo workflow packages like Adobe Lightroom and Apple's Aperture have made dealing with RAW files very easy. In Lightroom treats RAW and JPG files the same way (not sure about Aperture), so they are no more difficult to work with.

white balance is one of the best reasons to shoot raw. even though all modern cameras have 'auto white balance', they are generally 'templated' against sunlight, incandescent, flourescent, overcast, etc. the problem is these light sources are all different temperature values with varying amounts of green to magenta. i adjust the white balance for all of my shooting conditions and batch apply this to the appropriate images during a shoot.

the second is the abilility to avoid using the camera's sharpening routines (to make up for the anti-moire filter) and using a better sharpen technique such as Unsharp Mask or similar. as Mark points out, it can be selectively applied as desired

the 3rd point Mark raises regarding the application of saturation is also very important - as is application of contrast. by applying these to a .jpg in camera, detail can be lost and colour tone can be shifted, and this is not something that can easily be corrected in post processing.

one item that has not been raised is the lossy nature of .jpg files. averaging and smoothing are natural especially if the filters used to convert to jpg are not edge protecting or a decent algorithm. that detail can never be recovered and if the files are saved again, further loss is introduced. a '10' quality .jpg setting is often as large as a raw file (because most raw files have lossless compression built in) and yet they do not have all of the colour information.

ah, and yes... Aperture is like lightroom in that it treats all supported file formats the same - jpg, raw, psd, tif, etc.

 

[Groucho]

Groucho! HEY GROUCHO! Look, Mark is going to start buying Pentax gear! Your work is now complete.

He's actually said that before, so it didn't surprise me.

I agree that white balance is one of the big reasons to shoot raw. Nearly all DSLRs get that yellowish cast under tungsten lights.

There are plenty of other good reasons, too. And with memory cards, disk storage, and blank DVDs all being pretty cheap, I don't see much reason not to use RAW.

 

[PhotobearSam]

Great info...thanks