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Image Quality

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joelroffman

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I typically shoot in RAW, and the resulting image is around 23mb in size. When I export the image to my desktop for emailing, transferring to a flash drive, etc, the image is now around 9mb. Does the reduced size of this then-uploaded image make it less amenable to as fine tuning editing process as the RAW image was?
 
I typically shoot in RAW, and the resulting image is around 23mb in size. When I export the image to my desktop for emailing, transferring to a flash drive, etc, the image is now around 9mb. Does the reduced size of this then-uploaded image make it less amenable to as fine tuning editing process as the RAW image was?

Quality has nothing to do with the size of an image . Presumably the 23mb RAW image is losslessly compressed and and when an uncompressed RGB image is produced with one pixel representing each of the pixels claimed by the camera. And there is no loss in data. Lightroom Processes Pixels. When you export, if you create a JPEG, the result is a Lossy compressed image compressed at one of 12 levels of compression that when opened and uncompressed to its full size has unrecoverably lost some of the original pixel data. If you export that same image in a lossless format like a TIFF, it will be larger and every pixel going into compression is recovered when uncompressed for viewing.
If you export an image using a quality setting of 60 -90 you won’t notice the lost data. However if you process that lossy image and resave and uncompressed, eventually you will begging to notice JPEG artifacts.

Some things compressed smaller than others too. A Photo with mostly blue sky will compress smaller than an image with the same number of pixels but mostly foliage of varying hues.


Sent from my iPad using Tapatalk
 
What export settings did you use? did you constrain the resolution? Did you leave the Quality setting at 100 or set it lower? The latter can be set to somewhere between 75-90 without much noticeable loss in IQ with good gains in size reduction. But remember, you have taken a raw file and created a jpeg file, and this typically means that you have now "baked in" a number of adjustments. And, a jpeg is an 8-bit file format, so it is not going to lend itself to a lot of editing. If you have to send a jpeg for additional editing, then I would recommend full resolution and a quality setting of 90 -100.

Good luck,

--Ken
 
There’s a lot more to the file size than the raw and JPEG sizes. Actually, the raw file and JPEG are both extremely compact, achieved through different serious compromises: You can’t view or edit the raw file as is because it’s not RGB, and too much of the original information was removed from the exported JPEG version.

The “natural” file size of an image is:
number of pixels * number of channels * number of bits per channel

A 23MB raw file is typical of a 20 megapixel image, such as cameras capturing around 5500 × 3,600 pixels.

The natural file size for that image in RGB (3 channels) would be around 60MB at 8 bits per channel, or around 120MB at 16 bits per channel. You would get those file sizes if the 23MB raw file was converted to Photoshop or TIFF format. It can be somewhat smaller if compressed, such as TIFF with LZW or ZIP compression.

There are two reasons the photo is only 23MB as a raw file:
  • It’s only one channel (the raw data hasn’t been interpreted into RGB yet).
  • The camera may apply compression to the raw file. Because if a camera saves raw at 14 bits per channel, an uncompressed 20MP raw image would be more like 35MB, not 23MB.
So it isn’t actually a case of the raw file being larger. It’s really the raw file being much more compact than a fully viewable and editable 3-channel Photoshop or TIFF file, and the JPEG being even smaller because so much editing flexibility has been removed from it.

Does the reduced size of this then-uploaded image make it less amenable to as fine tuning editing process as the RAW image was?
No. For the reasons given above, editing flexibility can’t be judged by file size alone. It has more to do with what format and compression were used.

What makes the JPEG less amenable to fine-tuned editing is:
  • It’s been processed to 3-channel RGB, so it lost the ability to be edited with the wider flexibility of the original raw data.
  • It’s been compressed using JPEG lossy compression, which is of much lower quality than, for example, the lossy or lossless compression applied to raw files by some cameras. So regardless of file size, JPEG by its nature retains less editing flexibility than raw, TIFF, or Photoshop formats.
 
I typically shoot in RAW, and the resulting image is around 23mb in size
Remember that a RAW image is not an image but the recording of the sensor data. It must be put through a converter to get to an image. This is something LrC does in the background.
 
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