Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: walter.sk on January 27, 2012, 11:26:31 am
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I received a picture file from a friend who complained that she could not reduce it from a 14 mb 16-bit Prophoto RGB file, 1298x1699 pixels,
to a Jpeg of about 500kb. I downsampled the file to782x1024 pixels, 8-bits and sRGB, saved it as a Tiff, and then converted it to a Jpeg. Even with the quality slider at 0, the size of the Jpeg was over 1.5mb!
I gave the file to several knowledgeable friends who found the same dificulty. I suspect there is something wrong with the original Tiff (It is one layer, labeled "Background." I even tried duplicating layers and reflattening them, as well as trying to export a duplicate layer to its own file, but the problem persists.
2 questions:
1) Would somebody here like to play with the file and figure out why this is happening? and,
2) How could I attach the 14mb file on a LuLa post so people could give it a try?
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Upload the file to a file hoster (one still in business, of course) and post the link here.
If you have troubles to share it with the whole world: Just send me a PN with the link. I'm quite sure there is a whole load of crap stored in the EXIF/IPTC-area inside the file causing the problem.
Ciao, Walter
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check to see if it has an alpha channel
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I would second that. When saving a Tiff you should discard the alpha channel. This has caused me grief in the past. If I flatten a TIFF and forget to discard and open the TIFF in Faststone image browser the image shows the outline of the mask and the file size is always a lot bigger than it should be.
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You might try applying the nifty little program "JPEGsnoop" to the large jpeg. It will show you whether or not there is a lot of metadata.
I didn't think jpeg could carry an alpha channel.
--Milt--
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You are probably correct that Jpeg can carry an alpha channel.
Quote
I received a picture file from a friend who complained that she could not reduce it from a 14 mb 16-bit Prophoto RGB file, 1298x1699 pixels,
Unquote
Nor do I think that a jpeg can be a 16 -bit Prophoto RGB file? So the logical conclusion is that it is a Tiff?
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The file I got was a tiff, in 16-bit and Prophoto RGB. I checked and there are no alpha channels or any besides the master and R, G, & B channels. The metadata does not look at all corrupted or overly detailed, either.
I have found a website that lets me email a large file, but I would prefer to find a website that lets me upload the large file and then link to that in this forum. Anybody have a link?
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www.rapidshare.com
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Thanks for the link. However, I found a site called Drop Share, and put the file, Lilybouquet1.tiff, into a Public Folder. The link is below, and anyone can link to it and download the file.
http://dl.dropbox.com/u/59877871/Lily%20Bouquetv1.tif
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There is a lot of metadata attached. I copied and pasted the Raw Data tab from File > File Info in Photoshop CS5 and the simpletext document was over 1.7mb.
To remove the Raw Data info, you can't do it in File Info and it doesn't show up in bridge. Go back to the original image that you posted, select all, copy. Once its in the clipboard, go to File > New and the dimensions of the document should be the size of the new document. Now paste. Make sure your color settings are the same.
This will create a layered file. Flatten.
Go to the Raw Data tab under File > File Info and you will see almost no info. If you convert this to sRGB and save as a jpg, you will see the file size you are looking for.
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Interesting, I resized and saved as a 0 quality jpeg and the size was 800 KB and change. But if resized, saved as a PNG, reopened and saved as a 0 quality jpeg, and the size is 57K.
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Interesting about the metadata. In Bridge, I found only a few entries added by the maker, and deleted them with no impact on the over all file size. I will try your method and report back what happens.
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There is a lot of metadata attached. I copied and pasted the Raw Data tab from File > File Info in Photoshop CS5 and the simpletext document was over 1.7mb.
To remove the Raw Data info, you can't do it in File Info and it doesn't show up in bridge. Go back to the original image that you posted, select all, copy. Once its in the clipboard, go to File > New and the dimensions of the document should be the size of the new document. Now paste. Make sure your color settings are the same.
This will create a layered file. Flatten.
Go to the Raw Data tab under File > File Info and you will see almost no info. If you convert this to sRGB and save as a jpg, you will see the file size you are looking for.
Did it, and of course, it worked. Thanks for the heads-up thinking!