rmalarz Loc: Tempe, Arizona

Jenny, It's not a matter of more pixels getting into a RAW file, it the amount of data lost when the original image is compressed to make a jpg file. So, it's not that pixels are added, it's that pixels are lost in the process of converting the data to jpg format.

For instance, if I have a completely blank, formatted memory card in my camera, I can photograph 303 images using a RAW file format. If I set my camera to use jpg format, at the highest resolution the camera can provide, image size at large, 4256x2832 12.0M, and jpg set to optimal quality, I can fit 731 images on the memory card. I can fit over twice as many images on my memory card in jpg as I can in RAW. It's not a matter of where those extra pixels came from, but, more. where did some of them go?

The answer is in the algorithm that compresses the data to produce the jpg image. That compression is a lossy compression, meaning some data is lost in the process.

Here's a good article simply comparing the two formats. It does not support either format, but compares the differences between the two. The title implies a competition between the two, but it's merely a comparison.

http://digital-photography-school.com/raw-vs-jpeg/

--Bob

jenny Loc: in hiding:)

* * * *
Aw shucks Bob, you disappoint me! You refer me to "a good article" - title of which is "raw-vs-jpeg", then say it only implies competition but is "merely a comparison"?
Actually the info in it is just about as expected. Thanks for directing me to the, "digital photography school", where they state - "many professional photographers do not shoot RAW because 1. they don't know how, or 2. they don't want to take the time to process them..." ???
But let's go back to your reply claiming,"it's not a matter of more pixels in a RAW file but data lost when original image is compressed to make a JPEG".

jenny Loc: in hiding:)

Ooooo cat jumped up on me and lost the thread! But let's go back to your reply claiming data is lost. When? Now, really, nothing is lost if shooting JPEG. You would lose nothing but what you gained in switching to RAW if you went back to the smaller file...which you probably will if you print. Where do you get more---of what? --for a RAW file?
You are down to describing your own camera as proof of...what? I get about 3X size file in RAW as a straight JPEG. Says nothing about either of us though....
You invited me to reply to your input in this thread, or actually was it to challenge me (?) and claimed to be neutral about the subject. So where did you get more of what to make a RAW file? Do they grow like bacteria or bean sprouts? Sorry, but I just don't feel this is going to turn into a productive discussion. Most people are on one side or the other of this fence and your lack of neutrality is showing. Back to square one, to each his/her own. :roll:

rmalarz Loc: Tempe, Arizona

Jenny, Ok, as you stated let's go back to square one. In addition, I'll provide this tidbit of background info on me. For the last 15 years, years or so, I've been involved with computer programming. Though my experience goes back some years prior to that, I spent the majority of the time prior designing aerospace equipment. I bring up the programming part as a basis for credibility on computer files. No, I'm not an expert, but I am comfortable discussing and explaining file structures.

My cat just jumped on my lap, which will provide a bit of difficulty in typing quickly. I have to do that over her back.

Going back to RAW files. Each of those captured by my camera are approximately 14 megabytes. In fact, I just took two photos of the same subject, tripod as to not change any bit of the subject.

The RAW file is 13,256 kilobytes or 13.2 megabytes. The jpg file is 3,484 kilobytes or 3.4 megabytes. That is a significant amount of difference in the amount of information stored in these files. The jpg capture was set for large file size, quality optimized. Essentially, this is the set to provide the largest image with the highest quality. The camera, by the way, is a Nikon D700.

I would suggest reading the articles in wikipedia.org

http://en.wikipedia.org/wiki/Jpg

http://en.wikipedia.org/wiki/Raw_image_format

Here is part of the reason the jpg file is smaller. The algorithm which is used to take the RAW data and render a jpg image from it, compresses the data.

The JPEG compression standard, which was originally specified in 1994, specifies a coding process which has several specified steps:

1. Image Preparation (Separating the Components)
The image is separated into components, which are adapted to fit the level of quality chosen.

A JPEG file consists of distinct components, which are processed independently from each other. Both teh contents and resolution of the components could differ depending on application and level of quality chosen.

Now we have some variables to specify, or declare. The most common format is YUV using the two colour components U and V and the brightness component Y. Depending on the desired image quality the resolution of the color components could be reduced, for example by the factor two or four; i.e. beside the full brightness information two or four pixels will be combined together to one value of color information.

This approach results from the selective sensitivity of the human eye for the perception of differences in color and brightness. This results from the anatomical structure of the human eye, specifically the fovea. The amount of rods and cones present. If I'm not mistaken, the rods are each sensitive to one color. The brain combines the amount of information transferred and combines it to render what we see. The digital camera sensor, along with the Bayer filter pretty much do the same thing.

The brightness is substantially of higher importance for the total perception of the image. If the brightness component of an image is removed the remaining colors form a meaningless abstract. Therefore it is recommended to provide a proportionally larger part of the data volume for the encoding of the brightness. These procedures are called 4:2:2 or 4:1:1 subsampling.

2. Transformation (DCT: Discrete Cosine Transform)
Each individual component is transferred into a format, that allows to make conclusions about the structure of the contents. This offers the option to distinguish between basic and more complex contents. It also involves a good deal of math, that I'd rather not go into here.

The requirements to an ideal format for image compression can be outlined as follows:

The image information should be differentiated according to their meaning for the qualitative impression.

The internal structure should offer the opportunity to decide, to what extent the omission of information deteriorates the image quality. This is crucial for a presentable jpg image.

Only relevant information should require data capacity. If a section does not contain information like monochromatic areas, this should be directly reflected within encoded data.

The pixelwise representation used for conventional data formats do not fulfil these requirements. For that reason the original data has to be converted by the help of the so-called Discrete Cosine Transform (DCT). After conversion the data show the following characteristics:

Simple structures are given low values; complex, more detailed structures, high values.

Values resulting from the DCT reflect the geometrical structure of the contents. Details, as horizontal or vertical patterns, not contained in the image will be given the value zero.

Monochromatic areas are given a single value. All other values become zero.

Each component is normally given 8 x 8 pixels. Each component will then be transformed.


3. Quantization (Weighting of the Contents)
The transformed data are weighted according to their meaning for the image contents.

The result of the DCT is a set of values also describing the image contents. In contrast to the original format they do not affect the image quality in the same manner. This is important. The reason is the subjectively different perception of details.

With the help of quantization more relevant values are described with a higher accuracy. Values influencing the subjective perception to a smaller extend will be devalued and represented with lower range of values.

Quantization is not reversible and substantially affects the image quality.

The quantization is processed with special tables which will be stored within the corresponding JPEG file. They are essential for decoding.


4. Entropy Coding (Huffman Coding)
Elimination of redundant information.

Data, which result from the preceding steps, are provided with a different quantity of redundancy, which does not supply any contribution for the quality of the image representation. This redundancy is reduced e.g. with the help of a Huffman coding.

The basis for this coding is a code tree according to Huffman, which assigns short code words to symbols frequently used and long code words to symbols rarely used.

Beside Huffman coding another procedure is specified, which does not have a practical meaning because of the patent situation (arithmetic coding).

Additionally a special form of Run Length Encoding is applied.

This describes the manipulation of the data into a file. Pretty much reverse the steps and that produces the data necessary to produce the image we either see on a screen or print on a printer. All of these mathematical machinations and compression transforms result in a smaller file. The purpose of this was to allow the transfer of data in the shortest amount of time possible. So, this compression results in a, still identifiable and recognizable, image, but with a much smaller "footprint" and thus a faster transmission time, to say nothing of the smaller amount of storage space required. This was done at the sacrifice of losing a substantial amount of data. However, the image is still of good quality and, when applied to image scan present a remarkable representation of the original scene.

So, we can all make our choices for format. I'll stick with RAW, as I like working with the maximum amount of data pertinent to the image.

Sources:
Encyclopedia of Graphics File Formats - James D. Murray and William vanRyper
Multidisciplinary Approaches to Visual Representations and Interpretations - edited by Grant Malcolm
Data Structures In C - Noel Kalicharan
The JPEG still picture compression standard G.K. Wallace (Digital Equipment Corp., Maynard, MA, USA)
The number of quanta necessary for the perception of light of the human eye - HA Van Der Velden
Data compression apparatus and method using matching string searching and Huffman encoding - C Mayers, DL Whiting
http://www.tedmontgomery.com/the_eye/

lighthouse Loc: No Fixed Abode

Yes, the point of the post was to show that raw provides levels of data capture that jpg cannot match.

But that is not all it showed and supported.
It showed the ability to expose to the right and recover the data into a very much less noisy image.
If this image had been shot at the normalised exposure settings in jpg, then that jpg image would have noticeably more noise than the image that Bobs mistake and recovery process roduced. IE Bobs stuff-up has actually produced a better image than a "get it right in jpg" would have produced.

lbrandt, you ignore a very key issue in coming to your conclusion. That "get it right in jpg" image doesn't actually "get it right" in many cases. It is an approximation, a "close enough to right" for your purposes.
Your "get it right in jpg" image for sports has less detail and dynamic range in the dark areas of the shot. That is just a fact of how digital exposure works.
Does it matter? In some cases no. As long as the subject is correctly exposed then all will be fine.
Your sports image is for what? A pixelated grainy newsprint item? A magazine shot where the quality is good enough as long as it is an exciting shot capturing the action? Heck, it doesn't even matter if it has a bit of movement blur, and who cares about the noise in the crowd?

BUT, in many cases and in different types of photography to the types you are talking about, it can matter. It can matter a lot.
A landscape photographer might want the absolute maximum amount of data possibly available in the image to wring out as much dynamic range as possible with the least amount of noise.

I don't understand why you don't get it.
You have not "been there and done all of that".
If you had, you would realise that your conclusion does not apply to many types of photography.
You are talking about shooting jpgs for your particular purpose and attempting to apply those rules and restrictions to all types of photography.
Your rules don't apply to photographing many different types of images where maximum data is paramount in gaining a qulaity image.
Shots that can only be achieved with post work, shots that need post work to produce an image that has the detail and colour and subtlety in the scene that our eyes saw.
For example -the myriad landscapes with a dynamic range greater than the sensor can capture, still shots of the Milky Way behind a spectacular landscape, any shot that would be noisy otherwise, sunsets and sunrises with detail in the foreground, and many other types of shot.

What actually IS your definition of "getting it right in jpg" lbrandt?

jenny Loc: in hiding:)

Thank you Bob! Your Wikipedia references certainly gave a complete clarification of the subject and the history of the development was interesting too. If this is the position from which you cut your teeth on the subject I can readily see why you would support it, even vehemently. So many anonymous people (to photographers) have contributed so much to so much improvement in such short time.

Now, if you can extricate yourself from all that detail, I'm going to have to ask you to consider digital photography from the viewpoint of the consumer. You will probably agree that the capability of a camera to properly expose an image is taken for granted. The buyer will compare brand, price, possible lens purchases, maybe build quality and whatever else motivates him/her to finally make a purchase, and all depending on the experience or lack of it that buyer has.

My guess is that not a whole lot of UH members would ask for the solid evidence I requested. Most photographers would look for simple answers. We don't question when buying a car whether the brakes are adequate. At some point in the long road to learning photography more thoroughly some people will begin to look into the subject of "shooting RAW". They will again be looking for simple answers probably browsing among the many articles such as the first ref. you mentioned with its irresponsible remarks about "professional photographers".

You realize that immediately those who had their curiosity raised have to take it on good faith that everything they shot up to that point in JPEG has been flawed or outright ruined by discarding "up to half" what was in any image. That would be a hard idea to grasp, Bob! It is very hard to accept an idea that something was "taken away" when not having anything before getting a picture.

Then, if they have become to any degree knowledgeable, and now subjected to puzzling explanations that don't make sense, they are shown articles and tutorials with comparisons of processed RAW pictures compared with
"straight out of camera JPEG". Now you know Bob, anything processed compared with anything NOT processed is NOT a fair comparison!

Many photographers have found peace in the "family" of other photographers by taking the thought to set particular features both before taking a picture and afterwards improving their JPEGS. They have thus found "RAW" not to be needed. We CAN compare a processed RAW picture with a well-done JPEG.

So I've been that route Bob, totally open-minded when first investigating any need or desire to wander into the world of RAW. BTW, to state that it is an extra step in a process is really erroneous since those "extra steps" can
be taken both before and after shooting JPEG. I would ask therefore, that all those who advocate the RAW procedure with such certainty, please take a long hard look at photography in general, not just one aspect of exposure, which we could possibly say in many cases has been over-emphasized. I don't look to be on the fence in opposition to those on the other side of it. A little more understanding would do wonders to clear up a long running controversy.

Let us consider therefore that all the people involved in manufacturing YOUR camera and mine really want to give us the best picture possible, after all they are in competition, and since probably the overwhelming majority of people do shoot JPEG, perhaps the industry has provided the "best possible" by two different but equal methods.
:roll: peace

Nightski

Jenny, would you be so kind as to provide us with a link to all your fabulous jpeg images? I for one, would love to see them.

lbrandt79 Loc: League City, Tx.

I really did not intend to respond to anymore post but thanks for yours. I some times cannot express my views as others

lighthouse Loc: No Fixed Abode

Interesting how you answered jennys post but ignored the points I raised Larry.
I just noticed a perfect example image that helps make my point.
Your much viewed Antelope Canyon shot, your profile shot - did you really want that shaft of light to be blown? Or would you have liked it bright with subtle detail in it?
I have no idea whether you used film, or raw, or jpg for that image, but I do know, that a raw is going to produce a much better image in those conditions than a "get it right in camera jpg", more detail and less noise in the shadows, and, more detail in the shaft of light.

lbrandt79 Loc: League City, Tx.

Thanks, I am sure you could have done better, thanks for the advice.

lighthouse Loc: No Fixed Abode

Cheers.
Yes, I am sure I could have done too.

lbrandt79 Loc: League City, Tx.

Again, I appreciate your expertise and help.

Ruthiel Loc: Las Vegas

It's really quite simple if you want all the data on your sensor your gear can offer- shoot raw and process it yourself creating your vision. If you are happy with letting your gear process your photo - shoot jpg. Yes you can post process a jpg but the data discarded by your cameras computer will no longer be there for you to use. My 2c

Moxie Loc: Pensacola, FL

They call it RAW for a reason.... it possesses all the info needed to mature it w/o being preprocessed and unable to reach maturity.

lbrandt79 Loc: League City, Tx.

Gosh, I only hope that I can be as good as you some day.