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Thread: digital files

  1. #1

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    digital files

    Im always reading how tiff and png are used to make high quality prints. TIFF is the preferred one from what i see, but mpix only taks jpeg or png.. and i hate jpeg.

    BUt can you explain as to why a png conversion can triple the size on disk for a file?

  2. #2
    darr's Avatar
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    Re: digital files

    Converting to PNG can lead to larger file sizes due to its lossless nature, support for high color depth, and bitmap storage, particularly for images that originally used lossy compression or had lower color depth.

  3. #3

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    Re: digital files

    but maxed out Nikon NEF raw... is already lossless..

    sure cropping an 11x14" image down to 8x10 can reduce the file by 30 MB but i had an old scan of a 35mm negative. the on disk file size of the 5100x3500 pixel image was 18 MB as a jpeg.. but i did an 8x10 crop, and exported as PNG... it went up to 58 MB the numbers are nuts.

    sure im using MPIX to do my printing, but god these files..

  4. #4
    darr's Avatar
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    Re: digital files

    Converting an NEF RAW file to a PNG file can result in a larger PNG file size than the original NEF file for several reasons:

    1. Compression Differences: NEF files are typically lossless compressed RAW files. They contain the original sensor data with minimal processing but use compression algorithms that preserve all the image information while reducing file size. PNG files, on the other hand, are typically lossless but use different compression algorithms. These algorithms may not be as efficient as those used in NEF compression, resulting in larger file sizes.

    2. Image Format: NEF files are in a format optimized for capturing and preserving raw sensor data. They store pixel values directly from the camera's sensor, which can be more compact than the format used in PNG files. PNG, on the other hand, is a format designed for the storage and display of images and supports additional features like transparency, which may add to the file size.

    3. Color Space: NEF files often use a standard color space like Adobe RGB or sRGB. When you convert an NEF file to a PNG, the color information may be stored in a different color space, like RGB or RGBA, which can result in slightly larger file sizes due to the expanded color information.

    4. Additional Metadata: PNG files can store additional metadata and text information (such as image title, author, and copyright) as text chunks within the file. This metadata can contribute to a slightly larger file size compared to NEF files, which may have less embedded metadata.

    5. File Structure: The internal structure and headers of NEF and PNG files are different. The file headers, metadata, and other file-specific information in each format can vary, contributing to differences in file size.

    While NEF files are optimized for raw sensor data storage and use efficient compression algorithms, PNG files are designed for broader image usage and may have larger file sizes due to differences in format, compression, and additional features. The conversion process itself can also introduce subtle changes in the file size, but the primary reason for the increase is the inherent differences between the two file formats.

    Hope this helps!

  5. #5
    Alan Klein's Avatar
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    Re: digital files

    I've noticed with jpeg, if you pick very high number, the final file will be larger in bytes than the original tiff.

    Is the process eliminating compression? Why is that happening?

  6. #6

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    Re: digital files

    TIFF is famously jokingly called "thousands of image file formats". It's basically a container image format more than a specific format. It can be any bit rate have multiple compression schemes or none (etc). Many programs only support certain incantations of TIFFs and not others. A long time ago I gave up on GIMP because it couldn't support compressed 16-bit gray TIFFs for instance, but Photoshop could. As far as why a PNG would be bigger than a TIFF though- are you sure the TIFF wasn't actually storing things "lossy" in the first place? TIFFs can be lossy or lossless..

  7. #7

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    Re: digital files

    its somehwat retardd in ways..

    ill have to find some of my old 58MB nikon RAW photos and see how they export..

    but the digital world is interesting in some ways. And its nice to see some of my old photos and how good they were. And then remember that i was using a different white balance setting, and not using a CPL on everything.. and most of the time just using auto exposure , but switching to manual if i wasnt happy and then using the wheel to under expost by about .5

  8. #8
    Corran's Avatar
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    Re: digital files

    Many years ago I was auditing a photography course at the university I worked at, mainly as an excuse to use their very large and well-maintained Epson printer. At the same time, an advanced digital photography class was being taught, and the instructor had strict requirements about image files, color space, calibrated monitors, etc. So I used to come in to print and there would be several exasperated students struggling for hours, days, weeks trying to get some semblance of a good print with accurate colors. They would get really angry at me because I would just rock up and start printing from my bog-standard JPG/sRGB files I edited at home and with maybe one test print to dial in any slight color shift I was off to the races.

    If you have a very good chain of equipment, process, and etc., perhaps you can realize some advantage with png files or other exotic digital processes, but as I understand it png is more of a standard for raster images / graphics and not photographs. I use it for graphics with transparency. Good JPG images saved on the higher quality side of the compression scheme should be fine for most anything. I just recently printed a 36x24 image from a high-rez 35mm film frame scan and it looks essentially identical to the original tiff scan as far as resolution is concerned.
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  9. #9

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    Re: digital files

    TIFF is a strange beast. It is actually a framework for holding one or more versions of the same image in different formats. This was really useful in early desktop publishing where a raster image was used for rapid display, but printing used an embedded Postscript version. There were also optimizations in the format for different processors (big-endian versus little-endian). The trouble is that most applications that handle TIFF are not clear on what they can read from them, or how they write them. So you get TIFF files that are valid but cannot be handled by a different application.

    PNG is optimized to compress runs of identical pixels, and can reverse the compression exactly. JPEG is designed to compress photographic images where adjacent pixels are almost certainly different. It does this by working out a mathematical near-equivalent of a small area of the image. This process is not reversible.

    Using PNG on photographs often produces a larger file (compared to JPEG) because the compression process has to be reset almost every pixel, introducing overhead.

  10. #10

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    Re: digital files

    Excellent explanation of jpeg compression but it does get into the mathematical weeds a bit.

    .

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