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"While ExifPro strives to extract preview JPEG it has to fall back on raw decoding in the absence of embedded JPEG. This decoding is experimental and may occassionally produce incorrect images (in respect to colors). So far it has only been tested with Nikon D1 NEF files."
Somebody is drawing invalid conclusions from what they don't know.
The Nikon D1 has an embedded PPM image used for preview, not a JPEG. It is not a tagged data entry either, so Exif display tools (even exiftool, the ultimate Exif utility) can't see the thumbnail. But [i]dcraw[/e] can most certainly extract it.
Mistaking what a program like exifpro can or cannot do for what Nikon has or has not done is a serious lapse of logic!
That is the file (or lack of) EXIF Pro made a note about. Personally, I don't see a need for it, not only is it inefficient writing and storage, but if the camera is using the preview file for providing information even when you're solely relying on RAW, then also at the expense of accuracy. But, it is a compromise most have clearly bought into. As I mentioned earlier, Leica hasn't.
That is a grossly inaccurate assessment! Nikon has a very different engineering approach than Leica... which is exactly the reason that Nikon sells multitudes more cameras to professionals than Leica (and never mind the consumer market!). Nikon makes a huge effort at systems engineering with the professional photographer in mind. They want an integrated system with smooth functionality.
The evolution of the preview images embedded in the RAW file is actually pretty obvious, though I'm not sure exactly what the third JPEG image in the Nikon D4 does. I have no doubt that if the feature set of the D3S were compared to that of the D4 it would be obvious.
Right from the Nikon D1 on the most important requirement in a DSLR has been the CPU speed and load while shooting and then displaying images. The D1 on board JPEG engine could not be run at the same time as NEF files were being generated! It was one or the other, never both. The NEF file has a PPM thumbnail embedded, not a JPEG.
Addition of embedded files is done for two specific reasons, one is to reduce the CPU load, and the second is to provide speed. Your claim that the images are not needed is vacuous, and ignores the essential efficiencies those file provide. Of course the image are not necessary... if one is willing to accept the sales volume that Leica has.
However, Leica (for example) has not adopted it. They adhere to the same algorithm that one expects out of RAW not JPEG.
I claim this is wrong. Here's a quote with reference:
"These are some snaps I've made with a LEICA M9. [LEFT]I've also provided real, original DNGs. If you want to see them, you'll need to download them and open them in Lightroom, Photoshop Adobe Camera Raw, Aperture, or whatever in order to see them. Your Internet browser can't see them, although Apple Mac OS 10.5 (Leopard) and newer opens DNGs in Preview, but watch it: it's just looking at the embedded JPG."
Feel free to supply your own references otherwise.
In fact, Leica uses DNG based on ISO 12234-2, of which a standard component is the embedded thumbnail and optional preview JPGs.
In general what you're saying makes no sense if you think about it. Raw data is NOT an image format. It is a dump of sensor data in mosaic bayer format which has no color model applied to it. It's not in a format that can be displayed nor shown on an RGB histogram. The dynamic range is wider that the gamut of an LCD display. So a conversion has to be done to view in, but at what parameters? So of course there's no accuracy, because there's no image yet! It's like dividing by zero -- a meaningless statement.
So in order for you to *see* the image the camera needs to make assemble a JPG with a white balance and color model. Read up on Demosaicing algorithms if you want to learn the gory details. It's a fair bit of processing and why cameras use very fast, specially designed image processing chips. After the camera has done this once so that you can view the histogram and preview image, it would be utterly stupid to throw that information away. Therefore it needs to be cached, and so it is stored in the RAW image data. Where else would they put it? And of course that plays nicely into image viewing and cataloging programs which need to render thumbnails quickly. Camera manufactures have no incentive to cripple the user's software experience. Quite the contrary.
Furthermore, consider what happens when you spin the image preview dial on your camera. With no preview, the camera would have to develop the raw image on every frame. First of all it might not keep up for the same reason that burst buffers fill up fast when continuous shooting. Secondly, it would drain your battery post-haste from the processor load. Nobody is going to design a camera like that.
I claim this is wrong. Here's a quote with reference:
"These are some snaps I've made with a LEICA M9. [LEFT]I've also provided real, original DNGs. If you want to see them, you'll need to download them and open them in Lightroom, Photoshop Adobe Camera Raw, Aperture, or whatever in order to see them. Your Internet browser can't see them, although Apple Mac OS 10.5 (Leopard) and newer opens DNGs in Preview, but watch it: it's just looking at the embedded JPG."
Feel free to supply your own references otherwise.
In fact, Leica uses DNG based on ISO 12234-2, of which a standard component is the embedded thumbnail and optional preview JPGs.
In general what you're saying makes no sense if you think about it. Raw data is NOT an image format. It is a dump of sensor data in mosaic bayer format which has no color model applied to it. It's not in a format that can be displayed nor shown on an RGB histogram. The dynamic range is wider that the gamut of an LCD display. So a conversion has to be done to view in, but at what parameters? So of course there's no accuracy, because there's no image yet! It's like dividing by zero -- a meaningless statement.
So in order for you to *see* the image the camera needs to make assemble a JPG with a white balance and color model. Read up on Demosaicing algorithms if you want to learn the gory details. It's a fair bit of processing and why cameras use very fast, specially designed image processing chips. After the camera has done this once so that you can view the histogram and preview image, it would be utterly stupid to throw that information away. Therefore it needs to be cached, and so it is stored in the RAW image data. Where else would they put it? And of course that plays nicely into image viewing and cataloging programs which need to render thumbnails quickly. Camera manufactures have no incentive to cripple the user's software experience. Quite the contrary.
Furthermore, consider what happens when you spin the image preview dial on your camera. With no preview, the camera would have to develop the raw image on every frame. First of all it might not keep up for the same reason that burst buffers fill up fast when continuous shooting. Secondly, it would drain your battery post-haste from the processor load. Nobody is going to design a camera like that.
What do you see when you open a RAW file for conversion and adjustments? Is it the preview JPEG embedded in the RAW file?
That is a grossly inaccurate assessment! Nikon has a very different engineering approach than Leica... which is exactly the reason that Nikon sells multitudes more cameras to professionals than Leica (and never mind the consumer market!)...
It doesn't matter given the subject at hand.
Quote:
Originally Posted by kdog
In fact, Leica uses DNG based on ISO 12234-2, of which a standard component is the embedded thumbnail and optional preview JPGs.
Optional. Of course, there has to be a way to convert bits and bytes to an image. JPEG is one way to do it.
Quote:
Originally Posted by mathjak107
depends on the software. lightroom is a preview which later takes the edit steps and transfers them over to the larger file.
So, when you open a RAW file in Lightroom, do you see the relatively small JPEG created/embedded for preview and work with it?
the beauty of lightroom is there is the main file which is nef,dng or even psd.
and then there are much smaller previews stored seperatly broken out in a different folder.
you dont need to have the main raw file present to edit. you can store the main body of the raw file on a portable hard drive.
you can keep the small preview folder on your lap top and edit the small previews.
later on when the preview folder has access to the main files again it will up date them with side car files of the edits.....
you can keep the side car files seperate or write them right into the file , its your choice.
i may not be 100% correct on everything but basically your main raw file can be edited through the light fast nimble previews.
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