![]() However, if you are smart about your camera settings, the space savings offered by the DNG format are more or less insignificant. So you could potentially save a lot of space by using the DNG format, provided you fully understand the implications of such things as lossy compression and down-sampling. And if you do not need full-resolution DNG files, there is even an option for lossy compression, with the ability to limit the total megapixel count. In addition, there is an option to generate smaller JPEG previews, which results in additional space savings. This alone can result in 50% or more in space savings. When dealing with uncompressed RAW files, DNG certainly does save a lot of space by converting huge uncompressed RAW files to losslessly-compressed RAW files. The DNG format is a lot more versatile than a RAW file, because it allows you to tightly control the RAW file conversion process and specify conversion options. 2) Disk Space Concerns – Does DNG Really Save Space? Depending on the size of the file and its resolution, this could take a long time, especially if you are dealing with thousands of images. Keep in mind that DNG conversion is not a simple process – the DNG converter must not only copy and generate EXIF data, but it also must generate a JPEG preview to save into the DNG file, if you choose to do so (and it is always a good idea, since images can be previewed quickly). Add the option of generating 1:1 previews on top of that process and I could be sitting and waiting for a while in front of my computer before I can finally start post-processing images. While converting small RAW files from low resolution cameras is barely noticeable, converting anything over 24 MP does take quite a bit of time. Whether I choose to convert my RAW files to DNG upon import or at a later point of time, the conversion process puts a significant burden on my import time and only complaints my workflow. Disk Space Concerns – Does DNG Really Save Space?ġ) DNG Conversion Increases Workflow Time. ![]() ![]() Have you used the MATLAB Tiff class to do advanced maneuvers with TIFF files? Let us know what you've done by posting a comment here. So if you were going to do calculations based on this raw data, you'd probably want to linearize it back to the original 12-bit The linearization curve can be found in the DNG file as follows:Ĭurve = Quantization off the original 12-bit values. After some investigation, we found that Nikon appears to be storing a nonlinear We wondered why the maximum sensor value was 768. You can clearly see the Bayer array pattern. Here's a screen shot of imtool showing the resulting color filter array at 400% magnification. Warning off MATLAB:tifflib:TIFFReadDirectory:libraryWarning To give the steps without explanation and refer you to the documentation for the Tiff class for more information. That's the good stuff! It's a 16-bit-per-sample 4310-by-2868 color filter array (CFA). We want is hiding in something called a "SubIFD." But as I mentioned above, that's just a thumbnail image. You can see that imfinfo thinks that this file is a 256-by-170 truecolor image. To use it successfully, it helps to have some familiarityīut first let's poke at a sample DNG file using imfinfo.įilename: '\\mathworks\home\eddins\files\I\ipblog_material\2011\books.dng' This class offers low-level access to the "guts" of a TIFF file. Instead, we have to make use of the MATLAB Tiff class. If you call imread on the DNG file, it will just give you back the thumbnail image. However, we can't read the raw sensor data using imread. Under the covers, a DNG file is a very specialized kind of TIFF file. To tell DNG Converter to do the conversion "uncompressed." Here are some screenshots of the relevant dialogs. After some trial-and-error we found that it's necessary I should caution you, though, that there are multiple steps involved, some of which are "advanced maneuvers."įirst, I suggested that we try using the free Adobe DNG Converter program to convert the NEF file to a DNG (Digital Negative) file. An academic colleague asked me recently how to read the sensor data (in Bayer or color filter array form) from a Nikon raw camera file (an NEF file) into MATLAB.
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