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07/30/2008 03:54:16 PM · #1 |
| My external hard drive is full. Yes, I could go buy another, and I probably will this weekend. I am curious about something though. I store all my RAW files and large full size edits on the external drive, and the web sized stay on my computer. Can I compress the RAW files and/or the large full size edits without degrading them? If so, what is the best decompression software to use? I currently have WinZip, but would consider other software if it preserves the file better. |
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07/30/2008 04:04:38 PM · #2 |
Yes.
At least with Windows, the "Compress Old Files" in Disk cleanup is a lossless compression and will not degrade photos. I believe WinZip's okay too but more work. Don't know about Macs. |
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07/30/2008 04:09:35 PM · #3 |
Thanks for the info! I have always been so afraid to compress photos
Message edited by author 2008-07-30 16:12:46. |
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07/30/2008 04:25:46 PM · #4 |
Any software which uses the "ZIP" algorithm is lossless compression, and can usually be decompressed by any other compatible software, such as Stuffit Expander (available on Windows and Mac).
I suggest you experiment with compressing and recovering a few files and folders first.
Incidentally, if your disk is truly full, you probably CANNOT compress the files now, as the software needs temporary space on the disk to construct and then save the new file. Plus, you don't want to delete the original until you've verified the integrity of the archive.
You should have everything backed up to other media (CD/DVD/Hard Drive) before you undertake this ... |
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07/30/2008 04:53:41 PM · #5 |
Originally posted by GeneralE:
Any software which uses the "ZIP" algorithm is lossless compression, and can usually be decompressed by any other compatible software, such as Stuffit Expander (available on Windows and Mac).
I suggest you experiment with compressing and recovering a few files and folders first.
Incidentally, if your disk is truly full, you probably CANNOT compress the files now, as the software needs temporary space on the disk to construct and then save the new file. Plus, you don't want to delete the original until you've verified the integrity of the archive.
You should have everything backed up to other media (CD/DVD/Hard Drive) before you undertake this ... |
Agreed with everything said here. Only thoughts to add are...
With RAR compression you can make solid archives with recovery files. this means that it will compress your files then add maybe 3 files to give some slack. lets say you break down 100 MBs, rar will make it one file of say 60 MBs then 3 files at 3MB each. these extra files are incase anything in the original archinve is damged they can replace the data.
Point is, I would strongly recommend Movign from zip to a better compression method. Try winrar. |
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07/30/2008 05:01:39 PM · #6 |
Originally posted by onesaint:
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With RAR compression you can make solid archives with recovery files. this means that it will compress your files then add maybe 3 files to give some slack. lets say you break down 100 MBs, rar will make it one file of say 60 MBs then 3 files at 3MB each. these extra files are incase anything in the original archinve is damged they can replace the data.
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Can you please elaborate? My brain didn't quite get that - is it the 60MB or the three 3MB that are the 'backup' files? |
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07/30/2008 06:18:30 PM · #7 |
My laptop does have WinRar. Once I click "add to archive" and it coverts it to a rar file, can I then delete the other folder, the original?
Also, can I copy these rar files to a CD and then be able to reopen them on any computer that has RAR?
Message edited by author 2008-07-30 18:20:37. |
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07/30/2008 07:20:06 PM · #8 |
Originally posted by Wyrdling:
Originally posted by onesaint:
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With RAR compression you can make solid archives with recovery files. this means that it will compress your files then add maybe 3 files to give some slack. lets say you break down 100 MBs, rar will make it one file of say 60 MBs then 3 files at 3MB each. these extra files are incase anything in the original archinve is damged they can replace the data.
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Can you please elaborate? My brain didn't quite get that - is it the 60MB or the three 3MB that are the 'backup' files? |
sorry about that.
start with 100 MB file (say 10 NEF pics or something).
compress with RAR 100MB => 60MB
RAR adds recovery file 3 files @ 3MB each
you end up with total 69MB (60
if the data gets currupted the 3 files can recover the compressed file. Hope this helps. Also I am pretty sure its lossless as is zip. |
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07/30/2008 07:48:18 PM · #9 |
WINRar, WINZip, and all the other file compression utilities are lossless. If you think a picture looks bad from an overly lossy compression, try software or documents.
The WINRar feature is a lot like Smart Par, it creates extra files that allow you to repair damaged parts of an archive. The more repair parts there are, the more damage that can be corrected. However, it also means making smaller pieces of the original archive. Lets say you want to make an archive of data that will be the size of a DVD when you are done. If you make one large file, the recovery file or PAR file would have to be quite large. If you split that 4 gig into 50 meg bites, then you have 80 files to deal with, but the recovery files could be smaller. The recovery files apply to the entire archive, not just one piece. Smart Par does a great job of this and you can specify the amount of protection. 10% is plenty. The neat thing about these files is that they can fix darn near anything. Lets say you lose file number 56 out of 80 in the example above. No problem, it will be recreated when you do the repair. You could damage files 2 and 14 and the same files would do the repair and you would be back in business.
How does it work exactly, I have no idea. But work it does.
Personally I like WINRar a bit better than WINZip. It makes a little tighter archive, will handle many file formats both compress and decompress for compatability with co-workers who do not have WINRar.
Either route is good insurance. |
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07/30/2008 07:53:45 PM · #10 |
File compression (zip, rar etc.) is a different concept to image compression (jpg)
When you compress an image using jpg, some of the image data is discarded, which is why highly compressed jpgs look blocky. This is called 'lossy' compression, because you are actually losing pieces of data in the process.
File compression on the other hand uses techniques to ensure that none of the original data is lost. If you compress an image into a zip or a rar file for storage then when you uncompress it, it will be exactly the same image as you started with. Because none of the data is lost, it's called 'lossless'
Originally posted by ShutterPug:
My laptop does have WinRar. Once I click "add to archive" and it coverts it to a rar file, can I then delete the other folder, the original?
Also, can I copy these rar files to a CD and then be able to reopen them on any computer that has RAR? |
Yes to both questions. But please ensure you're happy that the compressed (rar) file is working and on safe media, preferably with a backup somewhere, before you delete any original folders. An issue with compressed file formats like zip or rar is that if the file gets damaged, you've potentially lost all the images you had stored in there. Versus losing just one image in a folder of uncompressed images. |
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