|
Re: RAW - ACR vs. Studio 2
In order to elaborate on the issue following some information I have collected from Luminous Landsacpe web site and Thomas Knoll, who is one of the original authors of Photoshop and the creator of Adobe Camera Raw.
" You may not realize it, but your digital camera does not give you every pixel that it records.
In most cases this is because the manufacturer masks off pixels at the very edges of the frame. This is done for a couple of technical reasons.
1. Many of the image processing algorithms (de-mosaicing, noise reduction, sharpening) that camera firmware (or raw conversion software) apply to raw sensor data are not "point operations", but instead "neighborhood operations". When computing the output value of that pixel, the algorithm needs to know not only the input value of that pixel, but also the input values of the pixels in the local neighborhood. The pixels at the very edge of the recorded image do not have a complete local neighborhood, so the algorithms need make some guess as to their value, which means that output results for these edge pixels will be not quite as accurate as the pixels a few pixels away from the edges. By trimming away these pixels, the camera manufacturers guarantee that all the output pixels are of maximum quality.
2. Sometimes image sensors do not have aspect ratios that exactly match the standard aspect ratios (3:2, 4:3, 16:9, etc.). In these cases, there are often different numbers of horizontal and vertical pixels hidden, to cause the final output image to have an exact ratio, When some users print digital camera images, they often do not bother to crop them, so having the camera output images with standard aspect ratios that exactly match standard paper dimensions is an advantage.
Solving this problem that few people knew even existed, Thomas Knoll, who is one of the original authors of Photoshop and the creator of Adobe Camera Raw, has written a free utility program which recovers all the pixels that any supported digital camera records, whether it's hidden edges or intentionally cropped formats. Called DNG Recover Edges, the utility application is unsupported, and it is not an Adobe product."
Another interesting comment came from a reader of my thread in DP Review web site forum:
" RAW images usually contain capture area of the entire sensor, while the intended viewing area is smaller. While capturing the image, both sets of dimensions are recorded with it. From what I have seen so far it is just a few pixels on each side, but your examples show quite substantial difference. The purpose of that is to simplify the conversion from RAW to Jpeg as the edges require different algorithms, as well as to discard the areas with the most quality issues (i.e. vignetting, CA, poor sharpness).
I've seen an utility that was making the full captured image available - simply by copying the tag describing the physical sensor dimensions into the image dimensions field, but I'm not sure if it would cover your camera's format. If I remember correctly it was working with .dng files only."
|
Linear Mode
