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DNG on SX1 IS

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DNG on SX1 IS
« on: 26 / May / 2010, 06:58:51 »
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My SX1 IS is using firmware 2.0.1. When I create a RAW-image with CHDK (version 0.9.9-893 or 1.1.0), it cannot be read by any of the current PC tools: e.g. RAW Therapee 2.4.1, Canons Digital Photo Professional 3.8.1.0.
Producing a DNG-image with the same CHDK versions can be read, but CHDK produces an image with dimensions 1824 x 1368 pixel according to IrfanView, which is a 4:3 image, even if I am using wide screen mode.
What is even more irritating: The EXIF-info of IrfanView says ImageWidth 128, ImageLength 96. 
Why is the image not wide screen?     

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Re: DNG on SX1 IS
« Reply #1 on: 26 / May / 2010, 07:18:07 »
Hello & welcome, michael46 !

When I create a RAW-image with CHDK (version 0.9.9-893 or 1.1.0), it cannot be read by any of the current PC tools: e.g. RAW Therapee 2.4.1, Canons Digital Photo Professional 3.8.1.0.
CHDK RAW is a direct, unmodified data dump of the camera's sensor - it's not a "real" image file format.
Read more about CHDK RAW in the sticky threads in the RAW section:
--> http://chdk.setepontos.com/index.php/board,15.0.html

Quote
Producing a DNG-image with the same CHDK versions can be read, but CHDK produces an image with dimensions 1824 x 1368 pixel according to IrfanView
No.
IrfanView (like some other viewers) shows a thumbnail / half-size image by default - this behaviour can be set up in the settings of your viewer.
The SX200 RAW dimension is 4080 x 3048 pixels, the JPEG image is cropped to 4000 x 3000 pixels, the active area (for DNG) is 4052 x 2245 (values from camera.h).

The CHDK RAW image (native RAW and also DNG) is a 1:1 dump of the sensor data (pixels);
the sensor size is always the same (physical), the "Wide" setting is just a software cropping done by the Canon firmware...

Re: DNG on SX1 IS
« Reply #2 on: 26 / May / 2010, 07:34:53 »
According to Fast Stone Image Viewer 4.2 the image dimension is 3647 x 2735, which still is 4:3.
Please take into account that my camera is type SX1, not SX200.

Re: DNG on SX1 IS
« Reply #3 on: 26 / May / 2010, 09:00:41 »
Interesting is the info concerning a genuine (not CHDK) RAW-image: FastStone says it has dimension 3960x2760, the camera manual says that a LW wide-screen image (not RAW) has dimension 3840x2160.
So which is the real physical dimension of the sensor?


Re: DNG on SX1 IS
« Reply #4 on: 26 / May / 2010, 12:22:45 »
Sensor have dimensions of 4152 x 2772 pixels.
Image is then cropped during processing of RAW because of two reasons:
1. Sensor have black border around image
2. Interpolation from Bayer pattern will give artifacts near the borders.

Quote
camera manual says that a LW wide-screen image (not RAW) has dimension 3840x2160
I don't know from where did you get those manual, but the biggest possible JPEG resolution is 3648 x 2736.

Quote
genuine (not CHDK) RAW-image: FastStone says it has dimension 3960x2760
Don't trust FastStone and othe viewers/converters that uses dcraw - they lies.
RAW image in many formats have 3 set of parameters:
1. Real sensor dimensions
2. Active area of sensor (rectangle inside sensor without black borders around image)
3. Crop area - rectangle inside active area containing image itself, cropped to eliminate artifacts around borders.

When decoding, dcraw (and all software that uses it) DOES NOT perform cropping, they try to enhance picture dimentions a little.
So in fact FastStone shows you dimentions of active area.
Try to develop RAW with Photoshop, Lightroom or any other RAW convertion software that does not use dcraw and you will get the same image dimentions that camera gives you in JPEG.

Re: DNG on SX1 IS
« Reply #5 on: 26 / May / 2010, 13:44:14 »

Re: DNG on SX1 IS
« Reply #6 on: 26 / May / 2010, 16:42:03 »
Hello cppasm,

concerning
Quote
Sensor have dimensions of 4152 x 2772 pixels
, I have found by Exif Pilot 4.1.0 that you are right, the dimension of the the DNG-file is indeed 4152 x 2772.

Re: DNG on SX1 IS
« Reply #7 on: 26 / May / 2010, 17:40:37 »
I have found by Exif Pilot 4.1.0 that you are right, the dimension of the the DNG-file is indeed 4152 x 2772.
But keep in mind that this is NOT image dimensions.
This includes black border around image which is always there.

By the way, you can use PhotoME (photo metadata editor) to view all DNG tags and edit many of them.

Why does it say "approximate values of recording pixel"?
Because this values are not accurate.
3648*2736 will give you 9980928 pixels or 9.98MPixels - they rounded it to 10Mp
Same for 8Mp - 3840*2160 gives 8294400 pixels or 8.29Mpixels, rounded to 8Mp
« Last Edit: 26 / May / 2010, 17:47:06 by cppasm »


 

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