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Flying Fossil May 15, 2011 8:22 PM

Sony software
 
Not sure where to post this question so will start here.

I have been using Sony's A700 and now the A580 for some time and for the most part have been very happy with the jpeg output.

Thought I would do some RAW shots and play with them as a learning experience and see what I get.

How do I tweak a photo in Image Data Converter SR and then save it as a jpeg?

If I open in FastStone image viewer I can save as a jpeg but none of the changes I made in RAW are kept.

How do I keep a modified RAW file as a jpeg?

Do I need different software?

Thanks folks

JimC May 16, 2011 5:39 PM

You can't modify your raw files. Some converters keep track of the changes you want to make (exposure, white balance, etc.) and apply them each time you view one. But, the raw file data captured from the sensor isn't being changed (and those changes are not transferable from one converter to another anyway).

Think of a raw file as an undeveloped negative.

As for converting them to another format using Sony's Image Data Converter SR, use the Output Button. See the software section in one of our recent Sony reviews for more info. For example, go here for the Software Section from our A33 Review (which is the same software you'd use with your Sony cameras).

http://www.steves-digicams.com/camer...oftware-5.html

Here's a screen capture from that review with some examples of Output Types available (set to JPEG in this example, using an sRGB color space, as you'd want to use when converting files for others to view online or using non color managed image viewers):

http://www.steves-digicams.com/camer...3Software7.jpg

The vast majority of digital camera use a Bayer type Color Filter Array. When you're shooting JPEG images, a digital camera's built in image processing performs the demosaic process from the RAW file so that you end up with a usable image format with red, green and blue values represented at each pixel location (even though each photosite is only responsive to one color, thanks to the color filter arrays being used over modern sensors).

In other words, a RAW file isn't even viewable until it's gone through a demosaic process (which is what you get on screen when viewing one with a raw converter).

Now, some raw converters will keep changes you apply in separate settings files (usually in a database of some type), and rarely, store changes in a raw file's header (Nikon does it that way with some .nef files). Then, each time you load the same raw file for viewing, it automatically applies those changes after the demosaic process.

But, it's not actually changing the raw data; and how that works will vary by raw converter, and the changes being saved by one raw converter are not going to be readable by a different raw converter.

Again, the RAW file is not being changed. Think of it as an undeveloped negative. You need to *convert* the raw file to a viewable format (TIFF, JPEG, etc.) if you want those changes to be permanent.

The raw file produced by a given camera model is somewhat unique (with different byte offsets for information included in the metadata and much more), and a complicated process is needed to convert the image into a viewable format (and different raw converters will have different approaches to giving you the best image possible, with some of them using better algorithms compared to others for this conversion). So, you have to use a raw converter that supports your camera's unique files to convert them into a format that is understood by image viewers and editors.

A camera's image processing when shooting jpeg is making decisions that may not always be what you want. Manufacturers have to decide on what kind of tone/contrast curves to use to make an image that looks good to most viewers, and sometimes they use processing that can be a bit too contrasty (causing loss of detail in shadows and highlights), in order to give cameras owners a more "punchy" image straight from the camera.

Ditto for things like sharpening, which is mostly increasing the contrast at color/brightness transitions in an image using edge detection techniques (which can destroy detail if overdone). The same thing is true for how the camera compensates for the temperature of the lighting you're shooting in (your White Balance settings handle that). You can easily modify things like White Balance later if you shoot in raw (basically, white balance is nothing more than a set of RGB multipliers that are applied during the conversion process).

The camera's jpeg processing is also limited by the speed of the cpu/hardware for image processing built into the camera, as to the sophistication of the algorithms used, since they are trying to process images in a split second between shots. As a result, you can often do better if you shoot in raw, using a high powered PC to process the data from the camera's sensor, without the limitations of needing to process it in a split second that the camera's image processing has to deal with.

The individual photosites in a sensor are only sensitive to one color each, and with most Bayer Pattern sensor designs, you have twice as many pixels that are sensitive to green. The raw conversion algorithms take the values from the red, green, and blue photosites and combine them via sophisticated interpolation techniques so that all 3 colors are stored at each pixel in order to give you a usable/viewable image.

The raw file has not combined the output of photosites in any way. That's what the raw conversion process does (or in camera processing if you shoot in jpeg). There are a number of different algorithms used, and some are better than others. You can see some of the common ones discussed here (requires Adobe Acrobat Reader):

http://www.ece.gatech.edu/research/l.../bahadir05.pdf

Here is another document discussing raw conversion techniques:

http://www.dalibor.cz/files/Ting%20C...erpolation.pdf

When you convert to TIFF or JPEG using a raw converter, you've gone through this demosaic process of combining the values from the red, green and blue sensitive photosites so that red, green and blue are stored at each pixel location. Ditto for shooting in jpeg (the camera is performing the raw conversion if you shoot jpeg).

Most raw converters are doing some additional processing, too (sharpening, contrast, etc.). Ditto for in camera processing (which is doing the raw conversion for you).

Personally, I'd save the raw files, no matter your preference in raw converter, as technology is continuing to improve and you may want to reprocess cherished images later using better tools.

Flying Fossil May 16, 2011 7:20 PM

Thanks so much Jim,
I along with many others I'm sure will find your explanation very helpful.
My novice brain found this to be just what I was looking for and I will put it to good use.


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