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OT Facts about Raw according to yours truly.
I'm a noob, so feel free to shoot me cuz this is somewhat simplified and therefore not exactly correct! It may actually be wrong..

The image on a sensor, after exposure is in an analog "Raw format"..

If you save the image in jpg, the cameras software digitalises it and converts it to to a jpg image, and sticks an Exif header on it..

If you save the image in Raw, the cameras software "only" digitalises it and sticks an Exif header on it..

The Raw "image" if you could see it is in Gray tone ie. monochrome..

When you open the jpg image in any image processing software, you see what the camera manufacturer thinks you were trying to do. Then you can save it in any format the software allows. The camera manufacturer usually does an excellent job..

When you open the Raw image, the image processing software must include a Raw converter, and you see what you actually did. (unless the converter is set to auto and it makes a best guess)..

It is important to understand that, if you can see an image, it is already converted to something and is no longer Raw..

However you can tell the converter to do it's job again the way you want it done, and again and again. Then you can save it in any format the software allows..

When saving in jpg in the camera, the first step of degradation takes place in the camera..

When saving in Raw in the camera, the first step of degradation takes place in the software, but you always have the true original..

People who say that their images are better saved in jpg are saying that the camera software does a better job than they can. Which can be true, but they need to know what they are talking about..

People who say that their images are better saved in Raw are saying that they can do a better job than the camera software can. Which can be true, but they need to know what they are talking about..

People who shoot and save in Raw and let their Raw converter run in auto mode are saying that the image processing software does a better job of converting Raw than the camera manufacturer does. Which may or may not be true..

Most post processing is better done and easier done in the image processing software on a PC..

Some post processing is better done in the Raw converter on a PC..

Shooting in Raw introduces an extra step in the workflow, but it can be automated for series of exposures, with a script..

I could have included a reccomendation here, but that always leads to a never ending discussion..

Tom..

Comments (10)

I shoot raw because then I don't have to worry about the WB during the shoot (one less thing to worry about when three ladies suddenly start doing jumping jacks and I'm supposed to be shooting that or when the camera accidentally got switched to something other than auto WB and I didn't notice). That and I can save over-exposed images and because of that I can shoot more to the right which is better for noise..

As I understand it, each raw converter will have it's own unique way of determining the colors so switching raw converters could be a bit like it was to switch film in the old days...

Comment #1

Onlywhite balance... nothing more from me.I want RAW just for that..

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #2

Again, this how I understand it..

The different manufacturers, Olympus Nikon Canon etc. all make their own Raw converter based on their own "algorithms". These are proprietary..

Olympus has made a "plug-in" which is compatible with Adobe software..

Adobe Camera Raw (ACR) is compatible with Olympus Raw(orf files)..

So, ACR includes an Oly algorithm, as well a Nikon and a Canon etc..

Do Adobe figure out the algorithms themselves, or do they get them from the manufacturer. I don't know..

I think the author of dcraw figgers it out himself..

Anyway, because of the above I asume that no two Raw converters are identical and provide slightly different results..

Let me asume that by tweaking the parameters the results from two different converters can be come more similar..

Changing White Balance for what ever reason, is an area where Raw Rules..

Tom..

Comment #3

You have made a wonderful, accurate summary..

One minor nit:.

Tnordahl wrote:.

The image on a sensor, after exposure is in an analog "Raw format"..

When it's "on the sensor" it's just a series of charged photosites. I wouldn't call this the "raw format" yet. These charged photosites report a charge level as analog signals through an analog/digital converter, and the camera stores the digital equivalent numbers into an internal memory buffer. This buffer arrangement is what I would call the beginnings of a "raw format.".

You are accurate about raw viewers in general. The RAW file is a combination of that memory buffer, and the camera's current RAW->JPEG converter settings. The raw viewer, if left to automate the process, should approximate the same RAW->JPEG results that the camera would produce (with some vendor differentiation), because they would default to use those camera conversion settings..

[ e d @ h a l l e yc c ] http://www.halley.cc/pix/..

Comment #4

Thanks Ed..

Your clarification is appreciated.A question if I may.Are the camera's current RAW->JPEG converter settings in the Exif?Tom..

Comment #5

All of the image settings for the camera are included in the raw file. The format of the file varies with the maker, and there might even be nothing that matches the EXIF format in particular. It's up to the raw converter to decide what to put (and what CAN be put) into EXIF format to attach to the JPEG file. For example, the raw file will usually describe which focus point was selected by the user or by the camera, but many generic raw converters don't know how (or don't bother trying) to interpret those fields since they vary greatly between camera models..

[ e d @ h a l l e yc c ] http://www.halley.cc/pix/..

Comment #6

Tnordahl wrote:.

The Raw "image" if you could see it is in Gray tone ie. monochrome..

This is not correct. The data from a pixel records the amount of light after the light has been filtered through a green, red or blue filter. To get something like monochrome, you would have to combine the results from red, green and blue pixels to get the final result. If you take a shot of something white, the red count would be approximately one half of the green count and the red count would be approximately one sixth of the green count (for sunlight)..

Also, most jpg processing only uses a portion of the dynamic range of the sensor. My camera has about a stop of "headroom" above the max jpg brightness that I can use if I wish to get a larger captured brightness by shooting to the right.Nice summary, otherwise.Leonhttp://homepage.mac.com/leonwittwer/landscapes.htm..

Comment #7

The Bayer color filters define a color space for the raw data. Both jpg and raw processing perform a color conversion from the camera color space to what you want, i.e., sRGB aRGB, etc.Leonhttp://homepage.mac.com/leonwittwer/landscapes.htm..

Comment #8

Thanks Leon..

You are ofcorse exactly correct on the issue of graytone, and it is one of the simplifications I made..

Its just my mind that thinks of the process that way. Is it an acceptable simplification? - I don't know!.

The next issue, headroom..

I'm on thin ice here cuz I don't quite understand what you mean when you say:" -most jpg processors only use.".

My Oly E-500 has 12 bit Raw, Some have 14. Saved in jpg you always end up with 8 bits. I think we agree on that. (is jpeg2k is different?)ACR lets you work in 8 or 16bits..

So, my E-500 Raw uses only 4096 bits out of the sensors total dynamic range, which I'm sure is larger, but it doesn't matter what format the processor saves it to..

Converted to jpg I "sort of" loose 2 bits, but that is not out of the sensors total dynamic range..

My point is: I think you have headroom in both directions - eh - or rather, both head- and footroom and it is not format dependent..

Tom..

Comment #9

Tnordahl wrote:.

Thanks Leon.You are ofcorse exactly correct on the issue of graytone, and it isone of the simplifications I made.Its just my mind that thinks of the process that way. Is it anacceptable simplification? - I don't know!.

Not really. I would confuse most folks..

The next issue, headroom.I'm on thin ice here cuz I don't quite understand what you mean whenyou say:" -most jpg processors only use."My Oly E-500 has 12 bit Raw, Some have 14. Saved in jpg you alwaysend up with 8 bits. I think we agree on that. (is jpeg2k isdifferent?)ACR lets you work in 8 or 16bits..

So, my E-500 Raw uses only 4096 bits out of the sensors total dynamicrange, which I'm sure is larger, but it doesn't matter what formatthe processor saves it to.Converted to jpg I "sort of" loose 2 bits, but that is not out of thesensors total dynamic range..

My point is: I think you have headroom in both directions - eh - orrather, both head- and footroom and it is not format dependent..

My camera captures in twelve bits providing 4096 possible values. The jpg processor uses 2048 as the highest value, that is, the brightest value. This is also known as the white point. In a raw converter like ACR, you can choose the white point and by going up to 4096 I gain about a stop in dynamic range. This varies from camera to camera. I'm not entirely sure what value is used in jpg as the lowest value, the black point.

In much photography, it is not a big deal but in scenes with a large brightness range, you need all the help you can get.Leonhttp://homepage.mac.com/leonwittwer/landscapes.htm..

Comment #10

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