Help me understand RAW

[lapdwife]

After seeing all the posts here that have specifically said "Taken in RAW" I bought a camera that does just that. Now help me understand what I'm doing.. Went out to our pier and took some pics, it's a cloudy day so there was a bit of glare out there. Is the purpose of RAW just to tweak them after? Do I always keep it on that setting or use the Auto too? It's a Canon Powershot S95.

 

[lapdwife]

Here's a few I took today and then tweaked a bit on the computer.

But then look at this one....

 

[ssanders79]

A RAW file is a digital negative. It stores all the information obtainted from the sensor in the manufacturers raw format. The raw file more often then not will need post processing. When you shoot in jpeg your camera processes the raw information into a usable jpeg.

The main difference between letting your camera process the raw info and you doing it is that you get to make the decisions and you have the ability to change the white balance after the fact, recover shadow and highlights.

 

[photo_chick]

Jpeg is like sending your film out to a lab to be processed. RAW is like processing that film yourself in the darkroom.

The main reason most people shoot RAW (at least from what I've seen) is for that control after the fact. You can change more without degrading image quality when you process RAW files.

 

[Geoff_M]

JPEGs, and other non-RAW formats, are all processed images. The data from each sensor pixel is processed by applying things like the white balance setting, sharpening, tonal settings (like "vivid" mode), and new red/green/blue values are determined for each pixel and the original sensor data is lost. On top of that the data compression is applied. For this reason alone, the image quality of non-RAW images generally aren't quite as detailed as those from RAW.

With RAW, all of the unprocessed data from the image sensor is preserved and saved, along with all of the settings that the photographer wanted applied to it (white balance, sharpening, etc.). When you view a RAW image, the image viewing software will "apply" the settings when it shows you the image. The difference is that with RAW you can change your mind and change the way that the settings are applied. It's short of like using an "undo" in Photoshop when you change your mind and want to do something different.

 

[GrillMouster]

Cooking analogy:
Shooting in RAW format is like having the raw ingredients to cook a dish. You choose which ingredients to add, how much of each, and how you cook them. Jpg is the end result --the final prepared meal. While you can still make adjustments to the jpg, like adding "salt & pepper", "ketchup", or "dressing", you can't undo what has already been done to it, and the unused raw ingredients have already been thrown away. Once that chicken has been fried, you can't "unfry" it to make baked chicken. Once that steak has been burned on the grill to the point of becoming shoe leather, there's only so much you can do to recover it . You can add some steak sauce to try to mask the charcoal taste, but you won't recover the natural juices and flavors that burned off. Cooking a dish that has already been cooked can dry it out, just like re-saving a jpg from a jpg from a jpg, etc., will reduce the quality of the image (like sending a fax of a fax of a fax).

All cameras capture RAW, but not all of them allow you to save the RAW file to the memory card. When you shoot in jpg mode the camera is actually shooting a RAW image, and the processor in the computer "cooks" that RAW file with its own "recipe" of white balance, exposure, saturation, contrast, sharpening, etc., and spits out a jpg file. If you, the photographer, have command of your camera, exposure, and lighting, and achieeve consistent results, then you may not need the extra leeway that RAW gives in post-processing. You'd be fine shooting jpg.

When you shoot RAW, then you can process it on the comptuter. Basically you do what the camera would have done if you had shot jpg. However, instaed of a "stupid" computer chip in the camera making decisions you choose how to process it. When you shoot RAW, the image you see on the camera's LCD panel and the thumbnail you see on the computer is actually a tiny jpg preview that is embedded within the RAW file. That image represents what the shot would have looked like if you had shot in jpg mode. The proprietary RAW processing software that came with your camera recognizes the camera settings that were in place when you took the image, and it can spit out a jpg image that will look just like if you had shot jpg straight from the camera. If you open the RAW image in a third-party program, like Lightroom or Photoshop's Adobe Camera RAW (ACR), then what you'll likely see if a different rendition of the RAW file. It ignores, or cannot decode, the in-camera settings, figuring that if you wanted them you would have shot jpg.

RAW files, because they contain so much data, are usually much larger than jpg files straight out of camera. For this reason, they take longer for the camera to write them to the memory card. If you're shooting several frames in succession, the camera's buffer will fill quicker if you're shooting RAW files, and the number of frames you can shoot per second will be lower than if you shot jpg. For this reason it's not uncommon for sports photographers to shoot jpg. Additionally, pro sports and news photograhers need their images to be instantly ready for uploading; they don't have time to process RAW files. Minutes and seconds can be an eternity in that world. If someone scores an amazing touchdown, Sports Illustrated wants the shot on their web page the next minute. The same goes for news; if you're not first, you're last.

So, there are times that RAW may be more appropriate, and other times where jpg may be more appropriate.

 

[manning]

A RAW file is a digital negative. It stores all the information obtainted from the sensor in the manufacturers raw format. The raw file more often then not will need post processing. When you shoot in jpeg your camera processes the raw information into a usable jpeg.

The main difference between letting your camera process the raw info and you doing it is that you get to make the decisions and you have the ability to change the white balance after the fact, recover shadow and highlights.

Kind of akin to film. You develop the film and get a negative. What you see is what yu get. You can't change the negative. Where the change takes place is when you print a picure. You make the changes there.

The same is true with raw. One example is in raw you can change the color temperature. You can't in the other formats.

 

[boBQuincy]

I am not fond of the term "digital negative" as it does not really describe a RAW file very well. A negative is most often used to make a print while a RAW file usually is not.

What a RAW file is, is the least processed version of the data captured by the sensor that can be viewed by us. Some (actually a lot of) processing is done to the data, more by some cameras, less by others. The camera manufacturers are very tight-lipped about how much processing their RAW files get. Even so, it is *much* less processed than a JPG and contains much more data (12 or 14 bits compared to 8).

What does all this get us? A file that can contain more light values than a JPG and one that can usually have more dynamic range. If we are going to process our images (and almost all images can benefit from some processing) then we have more options and potential when starting with RAW than JPG.

 

[photo_chick]

I am not fond of the term "digital negative" as it does not really describe a RAW file very well. A negative is most often used to make a print while a RAW file usually is not.

I've always thought RAW is more like a latent image on unprocessed film. A jpeg is really a lot more like a negative than a RAW file is. The camera has done the lab work for you when you shoot jpeg. When you look at the entire process from taking the image to making the print when dealing with film, it really is inaccurate to say RAW files are negatives. But that's a distinction I've found only old school photo geeks seem to make.

Kind of akin to film. You develop the film and get a negative. What you see is what yu get. You can't change the negative. Where the change takes place is when you print a picture. You make the changes there.

The same is true with raw. One example is in raw you can change the color temperature. You can't in the other formats.

You can change negatives. You can sway the process in a number of directions when processing the film with temperature, chemicals, rinses, etc... And after the negative hardens and you go to make a print you're more limited to the changes you can make, but you still can when you expose the negative and develop the print.

And you can actually change a jpeg to achieve all the same results that you would a RAW file with negligible image quality loss if you know what you're doing. My husband did it to one of mine once just to prove his point. But it's much easier to change things when you process the RAW file. My photoshop skills aren't where my husbands are so when I change a jpeg too far you can see it and I take a huge image quality hit.

 

[manning]

I've always thought RAW is more like a latent image on unprocessed film. A jpeg is really a lot more like a negative than a RAW file is. The camera has done the lab work for you when you shoot jpeg. When you look at the entire process from taking the image to making the print when dealing with film, it really is inaccurate to say RAW files are negatives. But that's a distinction I've found only old school photo geeks seem to make.



You can change negatives. You can sway the process in a number of directions when processing the film with temperature, chemicals, rinses, etc... And after the negative hardens and you go to make a print you're more limited to the changes you can make, but you still can when you expose the negative and develop the print.

And you can actually change a jpeg to achieve all the same results that you would a RAW file with negligible image quality loss if you know what you're doing. My husband did it to one of mine once just to prove his point. But it's much easier to change things when you process the RAW file. My photoshop skills aren't where my husbands are so when I change a jpeg too far you can see it and I take a huge image quality hit.

I think my photosop level is about on the same level as yours. I haven't really gotten into raw yet. Right now mostly reading. I tried changing the shade of white once. Couldn't do it in jpeg/tiff but was easy in raw.

You're right on the negative. I think what I was trying to say is once you set the negative that's it. The changes have to be done in the printing.

In RAW what the camera sees is what is recorded with no/or little adjustment to the data, depending how the camera is programmed. With jpeg/tiff the camera takes the picture, then does adjustments before saving the image.

In other words in RAW the color blue is recorded as the blue (any color) that it is (saw). No data is removed. In jpeg/tiff the blue is another shade according to what the processor is programmed to think what it is. You would be hard pressed/ impossible to produce the true blue the camera saw when post processing as the camera removed/changed some of the data needed (jpeg/tiff).

That is what little I know about RAW.

 

[Experiment_626]

you can actually change a jpeg to achieve all the same results that you would a RAW file with negligible image quality loss if you know what you're doing.

Yes -- if, by "know what you're doing" you include knowing when this won't work. While it is possible to get more out of a JPEG than some people seem to believe, it isn't possible with every image.

Scott

 

[Luv2Scrap]

Cooking analogy:
Shooting in RAW format is like having the raw ingredients to cook a dish. You choose which ingredients to add, how much of each, and how you cook them. Jpg is the end result --the final prepared meal. While you can still make adjustments to the jpg, like adding "salt & pepper", "ketchup", or "dressing", you can't undo what has already been done to it, and the unused raw ingredients have already been thrown away. Once that chicken has been fried, you can't "unfry" it to make baked chicken. Once that steak has been burned on the grill to the point of becoming shoe leather, there's only so much you can do to recover it . You can add some steak sauce to try to mask the charcoal taste, but you won't recover the natural juices and flavors that burned off. Cooking a dish that has already been cooked can dry it out, just like re-saving a jpg from a jpg from a jpg, etc., will reduce the quality of the image (like sending a fax of a fax of a fax).

All cameras capture RAW, but not all of them allow you to save the RAW file to the memory card. When you shoot in jpg mode the camera is actually shooting a RAW image, and the processor in the computer "cooks" that RAW file with its own "recipe" of white balance, exposure, saturation, contrast, sharpening, etc., and spits out a jpg file. If you, the photographer, have command of your camera, exposure, and lighting, and achieeve consistent results, then you may not need the extra leeway that RAW gives in post-processing. You'd be fine shooting jpg.

When you shoot RAW, then you can process it on the comptuter. Basically you do what the camera would have done if you had shot jpg. However, instaed of a "stupid" computer chip in the camera making decisions you choose how to process it. When you shoot RAW, the image you see on the camera's LCD panel and the thumbnail you see on the computer is actually a tiny jpg preview that is embedded within the RAW file. That image represents what the shot would have looked like if you had shot in jpg mode. The proprietary RAW processing software that came with your camera recognizes the camera settings that were in place when you took the image, and it can spit out a jpg image that will look just like if you had shot jpg straight from the camera. If you open the RAW image in a third-party program, like Lightroom or Photoshop's Adobe Camera RAW (ACR), then what you'll likely see if a different rendition of the RAW file. It ignores, or cannot decode, the in-camera settings, figuring that if you wanted them you would have shot jpg.

RAW files, because they contain so much data, are usually much larger than jpg files straight out of camera. For this reason, they take longer for the camera to write them to the memory card. If you're shooting several frames in succession, the camera's buffer will fill quicker if you're shooting RAW files, and the number of frames you can shoot per second will be lower than if you shot jpg. For this reason it's not uncommon for sports photographers to shoot jpg. Additionally, pro sports and news photograhers need their images to be instantly ready for uploading; they don't have time to process RAW files. Minutes and seconds can be an eternity in that world. If someone scores an amazing touchdown, Sports Illustrated wants the shot on their web page the next minute. The same goes for news; if you're not first, you're last.

So, there are times that RAW may be more appropriate, and other times where jpg may be more appropriate.

Now this is a comparison I can understand! I'm just starting to learn about RAW since I just got LR3. I couldn't get CS3 to open my Canon T2i RAW files so I didn't bother. Now that I'm starting to understand it a little better I think I will prefer shooting in RAW.

I'm sure I'm going to have some questions, but this thread has been a huge help already! Thanks everyone!!

 

[photo_chick]

Yes -- if, by "know what you're doing" you include knowing when this won't work. While it is possible to get more out of a JPEG than some people seem to believe, it isn't possible with every image.

Scott

It is possible with any image if you have the photoshop skills. Graphics people have been working with photoshop since long before most photographers were, before digital cameras and RAW were commonplace, and can do some incredible things with jpeg images. It's a different approach than with RAW files, but it is possible to get the same end result with either format.

My point, that I think I got sidetracked from, LOL, was really that neither format is ultimately better than the other. Use what works for you, not what works for someone else.

 

[Groucho]

I am not fond of the term "digital negative" as it does not really describe a RAW file very well. A negative is most often used to make a print while a RAW file usually is not.

What a RAW file is, is the least processed version of the data captured by the sensor that can be viewed by us. Some (actually a lot of) processing is done to the data, more by some cameras, less by others. The camera manufacturers are very tight-lipped about how much processing their RAW files get. Even so, it is *much* less processed than a JPG and contains much more data (12 or 14 bits compared to 8).

What does all this get us? A file that can contain more light values than a JPG and one that can usually have more dynamic range. If we are going to process our images (and almost all images can benefit from some processing) then we have more options and potential when starting with RAW than JPG.

Don't forget about white balance, one of the biggest advantages that raw has over jpg. It's just just a little extra headroom in the brights and darks.

As for "digital negative", I'm afraid that term will stick as long as Adobe uses DNG!

 

[Experiment_626]

It is possible with any image if you have the photoshop skills. Graphics people have been working with photoshop since long before most photographers were, before digital cameras and RAW were commonplace, and can do some incredible things with jpeg images. It's a different approach than with RAW files, but it is possible to get the same end result with either format.

Sorry, I was in a hurry when I posted that. Yes, I know -- I am one of those graphics people -- been using Photoshop since version 2.5. But it depends on the image and what you're trying to do. There are times that you cannot get the same result from a JPEG that you can from a RAW file. The data just isn't there. Sure, you can get good results much of the time, and you can often get results close enough that the average person can't tell the difference, but to imply that you can always get the same results if you know what you're doing is just (sometimes) not true. Try pulling back blown highlights in a JPEG versus a RAW file -- you can get away with more in the RAW file. Try pulling a usable image out of a severely underexposed RAW shot -- one that looks black when you open it. Then create a JPEG from that "black" image (at the default settings), reopen that JPEG in ACR or whatever you like and see how much luck you have pulling the same results out of it. And even when it does work, it usually requires more work than starting with RAW.

In certain situations, shooting JPEG may mean getting a shot whereas trying to shoot RAW will cause you to miss it. Also, some who shoot heavy volume prefer to work with JPEG, get everything as right as they can in the camera, and deal with the results as they are because they don't have time to process 4,000 RAW files. That's fine and legitimate (especially since they aren't me ). I'll almost always stick to shooting RAW. I'm just sayin'.

Scott

 

[photo_chick]

My husband has been using PS as long as I've known him... that would be since 1990. So whatever version that was. I didn't belive him at first, but I've seen what he can do so I know you can get the same result with any image. I'm not saying it won't take a heck of a lot more work with a jpeg, but you can get there. Like I've said, that's why I shoot RAW...my PS skills are not what my husbands are and RAW is cleaner and faster for me.

RAW isn't magical. It's the same data, just unprocessed.

 

[MarkBarbieri]

RAW isn't magical. It's the same data, just unprocessed.

Sort of. It's a subset of the original data. The conversion to JPG throws away data that the converter thinks that you don't need. If it turns out that you wanted some of that data, there really isn't a good way to get it back. For most shots most of the time, JPG is just fine. The problem is that you don't know which shots it won't be just fine on until too late.

 

[Experiment_626]

Sort of. It's a subset of the original data. The conversion to JPG throws away data that the converter thinks that you don't need. If it turns out that you wanted some of that data, there really isn't a good way to get it back. For most shots most of the time, JPG is just fine. The problem is that you don't know which shots it won't be just fine on until too late.

Indeed. Most of the time, an experienced Photoshop user can get good results out of a JPEG. I have to do it all the time because I'm sent images where a JPEG is the best I can get. But the image is compromised -- again, a good Photoshop user can often hide that fact. But the further afield from the original settings one has to go, the more that missing data starts to reveal its absence.

Here's an imperfect analogy: It's like having a coffeepot with extra coffee in a hopper, versus a pot that has only its current contents from which to draw. You can serve more guests from the former because the extra coffee can be allowed to trickle into the pot. In the latter instance, you can serve the coffee you have. If you're very careful and your coffee is good, you can water it down a bit to make it go further, but even if the guests don't notice, that coffee isn't the same as it was. In the same way, the extra data in a RAW file can, in a sense, fill in the gaps made when the image is manipulated. In both cases, you'll eventually find a limit you cannot exceed. But you'll come to that limit later and usually more gracefully if the image is RAW.

Scott

 

[GrillMouster]

Imagine I gave you a box of legos. The box contains 256 different shades of blue, from light to dark. I ask you to use those legos to create a gradient line by putting lego pieces end-to-end. When you're done you have a pretty seamless gradient.

Now imagine that I take away half of those legos, so you only have half as many shades of blue available. You can still create a gradient, but with every other value now missing, the jumps from one shade of blue to the next is a little more noticeable. As I take away even more legos the jumps become even greater and more pronounced.

This is what happens when you push jpg processing too far, and it's called banding. It happens in skies and in skin tones when people go too far in processing a jpg. As Mark said, a jpg is not "...the same data, just unprocessed". A jpg is some of the data; the rest was thrown away.

There are things that can be done in photoshop that go beyond processing. At that point it's collage and digital painting. For example, if I get color banding in the sky because I pushed the jpg processing too far (combing in the histogram), I can use the gradient tool to paint in a blue gradient. That's adding something foreign to the image that wasn't there. It's no different than swapping heads or dropping in the sky from another image.

 

[photo_chick]

They're both a set of RGB values. At the heart of it, it's all data. You're not throwing out half of those values when you save as a jpeg. That's not the same as compression. The sensor gathers one set of values for every pixel. You have the same number of pixels with a jpeg saved at the highest quality your camera can as you do with RAW. When the RAW file is processed into a jpeg format those RGB values are changed to reflect whatever settings you, or the camera, may choose.

and tell me how then, if I have the same number of pixels, each with a set of RGB values, does a RAW file have more data for the RGB values than a jpeg with the same number of pixels and RGB values?

And who is to say what is beyond "photo processing"? That's a fairly limited point of view. Photographers have long pushed the bounds of what they can accomplish with thier tools. The bottom line, you CAN get to the same end result from either format if you know how.

I get that I'm sounding crazy and I wouldn't have believed me either a while back. But I was schooled not too long ago by a graphics geek who knows far more about this than I ever could hope to. It's an interesting discussion anyway!