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Author Topic: Information Please on export Panel  (Read 865 times)
free2australian
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« on: February 20, 2013, 05:36:11 AM »
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I Have a  Mac  and camera is a D700 - this equals to 4256 x 2832  in raw original file

I need to export  photos  at the highest resolution with no compression.  I size I need is  5MB

Lightroom export panel limit size to only provides an option kb.  Not realizing this I have provided my photos  by entering checking limit Size to 500k.  I was advised that this  1/10th of 5MB - Therefore the size of the photos  were too small.


Be grateful if somebody could give me the exact number I should enter to have the output size at  5MB.

Thank you
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john beardsworth
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« Reply #1 on: February 20, 2013, 05:53:21 AM »
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5000
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Simon Garrett
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« Reply #2 on: February 20, 2013, 05:59:08 AM »
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I don't think you can make LR produce an exact file size.  I just tried with a 12M pixel image, and setting 5M byte (which is approximately 5.243 kbyte, so I set "Limit file size to" to 5243) and it created a file of 3.9Mbyte.  Well, that's within the limit I set!

Conversely, If I unchecked the "Limit file size" option and set quality to 100, I got a file size of 10.3Mbyte.  

I think you may have to experiment.  

Thing is, jpeg compression is a bit of a black art.  When software uses an algorithm to compress an image, you don't know the size of the compressed file until you've finished.  To get a particular size, you could try with initial compression parameters, then if the file is too small try again with slightly higher quality parameters, vice versa if the file is too large, and iterate until you get the right size.  The software would have to do this with each image (as the compression you get depends on the image content), and this would make the jpeg compression rather slow.  

I guess LR just takes a conservative estimate of compression parameters that are pretty much guaranteed to be within the file size limit you set, but it might be quite a bit smaller.  
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PhotoEcosse
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« Reply #3 on: February 20, 2013, 09:06:38 AM »
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You say "I need to export  photos  at the highest resolution with no compression. "

Then, from your export panel screenshot, you seem to be exporting as a Jpeg.

All Jpegs are compressed. If you need a non-compressed file, as you state, then export as a Tiff.

And, of course, when exporting as a Tiff, LR won't let you set a maximum file size as any limitation on file size can only be achieved by compression.
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Simon Garrett
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« Reply #4 on: February 20, 2013, 09:56:23 AM »
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You say "I need to export  photos  at the highest resolution with no compression. "

Then, from your export panel screenshot, you seem to be exporting as a Jpeg.

All Jpegs are compressed. If you need a non-compressed file, as you state, then export as a Tiff.

And, of course, when exporting as a Tiff, LR won't let you set a maximum file size as any limitation on file size can only be achieved by compression.
Good point, I'd overlooked that.

Even setting the quality factor to 100% (100 in LR, 12 in Photoshop) there is still lossy compression on conversion to jpeg because:
  • The data is reduced to 8 bit
  • The color information is normally reduced in resolution by a factor of 2.

With quality 100%, the file size of a 12Mpixel jpeg is likely to be over 10Mbyte.  To reduce it to 5Mbyte you can either reduce the resolution (in the "Image sizing" part of the export dialogue) or increse the compression (in the "File settings" part of the dialogue) either by reducing the quality from 100 or by reducing the "Limit File Size" number.

For full resolution, no compression: export as 16-bit TIF.  For a 12M pixel D700 image, that will be about 70Mbyte. 
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kaelaria
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« Reply #5 on: February 20, 2013, 09:49:27 PM »
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5120k = 5MB.

Your questions make no sense, you can not have your cake and eat it too.  You can specify limits or you can specify no limits.  Pick one.
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elied
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« Reply #6 on: February 21, 2013, 05:17:27 AM »
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And the maximum resolution for an 8 bit uncompressed image to be 5 MB is 1.75 MP or, assuming 2:3 aspect ratio, 1080x1620 pixels.
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Rand47
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« Reply #7 on: February 22, 2013, 08:42:35 AM »
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I Have a  Mac  and camera is a D700 - this equals to 4256 x 2832  in raw original file

I need to export  photos  at the highest resolution with no compression.  I size I need is  5MB

Lightroom export panel limit size to only provides an option kb.  Not realizing this I have provided my photos  by entering checking limit Size to 500k.  I was advised that this  1/10th of 5MB - Therefore the size of the photos  were too small.


Be grateful if somebody could give me the exact number I should enter to have the output size at  5MB.

Thank you

Round trip your file to CS6, resize appropriately.  Export as tiff.  Done.
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