Tuesday, April 16, 2013

File Size Question.

 A friend has gotten a pan stitching program and asked about the file size of stitched images. He says the software he got produces 6x17 files around 35MB and he wondered what my experience was with file size of stitched images. Below is my answer:

There's no simple answer on the file size question. The file size varies. The variables are the size/number of the individual frames and the file format. A series of three 18MP frames stitched will be bigger than three 10MP frames. Of course the three frame 18MP stitch also will print larger than a three frame 10MP image without loss of image quality. If you shoot RAW and save the resulting stitch to PSD or uncompressed TIFF you will end up with quite a large image. For example the original master file of this one...

is 1.39GB. No, that "G" is not a typo. Bear in mind this blog copy of the image is reduced from a working TIFF master file that was made from three horizontal 18MP frames, If I print the full size file at 240ppi it would be 53½x 14 inches. I don't crop to any specific aspect ratio until I print and I use layers to do my final adjustments. For master files I leave the layers intact and save to TIFF with LZW compression, a lossless format, in either Adobe RGB or RGB Pro color space. For printing I would make another copy which I might crop/downsize to specific dimensions, flatten and save to JPG or TIFF in the sRGB color space. Each of those changes can shrink the file size to one degree  or another. I have a copy in JPG format that is shrunk to print about 6½x24 inches. It is only 5.9MB. Add to that the fact that JPG files vary in size based on content. High detail images don't compress as much as low detail images even at the same compression setting, just because of the way JPG compression works. The short answer (if there is one) is that 35 MB files are somewhere in the ballpark for a 6:17 aspect ratio stitched image but we're talking about a very big ballpark with a lot of possibilities for being either much  larger or or much smaller depending on the choices you make. The 800x216 pixel copy (JPG compression at 10) above is under 2KB.

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