CHDK Results (and they’re awesome!)

(CHDK is a program that allows you to write 48-bit RAW files to your SD card on your compact Canon camera.  Compact cameras normally support only 24-bit JPEG format)

In the process of writing the commentary on using small compact cameras, I also completed my research on whether or not using RAW with these small compact cameras was useful at all.   I only know of CHDK, so this is limited to the small Canon compact cameras.  Using RAW in this fashion does create some work — you need to do many of the functions that the camera will do for you as it writes the JPEG.  This includes noise reduction (both color noise and other CCD noise, which is extensive on these cameras), smoothing, sharpening, lens correction, etc.   Thankfully, this is all available in Sagelight, either through native functions or through included filters.    

Well, let me get right to it: the epitomical example:    

Example 1 – Building Wall.

This image represents the tough choice faced when taking a picture.  I would show you the original, but it’s important to show two originals, because that’s the    

only way to look at it in this situation.  You’ll see what I mean in a second:    

Original Image (Adjusted for Shadows)


This is really the image you’d take if you just wanted the one image.  You would want to preserve the main subject (the wall) at the expense of the sky — which is very blue and cloudy.  This is what you’d get with the JPEG.    

Original Image (Adjusted for Sky / Highlights)


This image is adjusted for the sky.  This is why there are two originals, because it’s impossible to see the actual conditions because of the range limitations on the JPEG images.  Realistically, this is the type of image that would make you want to combine the two images in an HDR program to get the best of both.    

Enter CHDK.

Keep in mind this is from a small compact camera.  Here is the RAW image with just the default processing in Sagelight:    

Original RAW image


Here, you can see the areas of the wall becoming visible and that the sky and highlights of the clouds have been preserved.  It looks pale now, but since we have all of this data (and at at least 10-bits per-pixel or more), here is what we can do with this single image:    

RAW Result (click on image for full-size)


When I saw this, I became much more of a fan of CHDK.  Keep in mind, too, that with CHDK I get the RAW and Jpeg, so I don’t have to shoot only RAW and suffer the consequences with the other pictures where the quality isn’t suffering enough to care.  I can pick and choose when I want to use RAW — after the fact, when I get back to my computer — preferring to use the JPEG image most of the time.    

But, with this picture, there was no way to use the JPEG.  With the JPEG from the camera, I would have had to choose between the two original pictures and make the best of it.  With this small camera, there was definitely a noise issue in the shadows.  So, this picture is never going to be a high-quality picture at the original size. But, for wallpaper and even at 1600×1200, it holds up.  Click on the picture for the full-size (cut down to 50%, or 6MP).  You’ll see some noise in the shadows, but when you resize it with a bicubic or bilinear algorithm, the noise all but disappears and you’re left with a very nice picture that, at one time, had no hope of being interesting at all.    

Example 2 — Another hopeless (but more subtle) picture

This is an example of a picture that just wouldn’t make it without using the RAW.  Here is the original:    

Original JPEG


You may recognize this as one of the pictures I used in the article about using compact cameras with Sagelight.  In that article, I pointed out that I had to use the RAW.  Here, I want to show why.    

The white areas of the birds are completely blown out.  They cannot be recovered and completely mar this picture.  I would normally say that I should have set the exposure lower. But, that would have created noise in the darker areas that would have shown up with this small, noisy 12mp CCD.  For a JPEG output, this would have been the better choice.  

But, when I know that I have the RAW image at my disposal, these blown-out highlights are only in the JPEG and not the CCD image.  With RAW, then, this is the better picture because the blown highlights in the above picture are actually perfectly intact.    

No matter how I edited this picture as the camera-supplied JPEG, the blown out white areas would always be too prominent and keep this picture from being very nice.  Let’s look at the RAW image:    

Original RAW Image


As you can see, the RAW image — this is the exact same image, just brought from the cameras as a .DNG file — has the white areas in intact.  Here is the result I created on my Netbook:    

RAW Result (click on image for full-size - 12 Megapixel)



Well, that pretty much wraps it up about using RAW with CHDK.  It’s definitely worthwhile.   The icing on the cake with CHDK is that it also writes the JPEG.  With a lot of cameras, you have to either use RAW or JPEG, which means you always have to switch around or take the burden of editing every picture from a RAW source (i.e. more work!) even when the JPEG would be just fine.  When using CHDK, you can choose between RAW or JPEG.  I personally just use the JPEG unless there is a compelling reason to use the RAW.  Since both are there, I have that choice and it makes things easy.  With my 8 Gigabyte SD card (small by today’s standards), I really don’t run out of memory too quickly, and the results I’ve shown definitely make it worth it, even on these small cameras that don’t technically (or officially) support RAW.

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