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Old Jun 16, 2004, 4:21 PM   #1
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I was batch converting a bunch of files from my D70 camera origianally injpg to tif format before editing them. When I open the original 2.5mb jpg and save as tif in Photoshop, the file size is about 6.5mb. However, if I use ACDSee or others to do the conversion, the tif file size jumps to over 11mb!! (Yes, I am applying "ZIP" or "LZW" compression in ALL applications.

What is going on here? Is Photoshop "stripping" important data from my picture before saving it? Which one should I really trust?

Also, ACDSee askes for vertical and horizontla resolution (default 96dpi). Should I change this? Is this the difference in file sizes?

Richard
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Old Jun 16, 2004, 5:12 PM   #2
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Something isn't right. Photoshop should decompress your JPGs to just over 17Mb when you open them – it will show at the bottom if you have it switched on. No way LZW or ZIP compression of TIFF will get it down to 6.5Mb. Photoshop shouldn't strip data. Open the 6.5Mb TIFF and see how many Mb it decompresses to. And check the file size under image>image size. If it isn't still 3008 X 2000 pixels you are doing something wrong before you save.

Resolution has nothing to do with file size unless you resample.
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Old Jun 16, 2004, 5:48 PM   #3
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Slipe,

Thanks for your input. Here is what I have done after reading your post:

1. Went back and opened my original 2.5mbjpg from D70 in Photoshop. It opened to 17.2 mb as you stated.

2. I hit Save As/Tif and selected LZW compression. Once saved, windows reads file size as 6.5mb.

3. I open the TIF in Photoshop, and the file size at the bottom reads as 17.2mb

4. Went back and opened my 2.5mb original jpg from D70 in ACDSee. No place to read the uncompressed file size.

5. I hit Save As/Tiff and selected LZW compression. (Also an option for H/V Resolution with default value of 96dpi on each which I did not touch). Once saved, windows reads file size as 15.4mb.

6. I then went to Photoshop and opened the tiff created with ACDSee. It opened it to 17.2mb at 3008X2000

7. Went back and opened my original 2.5mbjpg from D70 in Infranview.

8. I hit Save As/Tif and selected LZW compression. Once saved, windows reads file size as 15.2mb.

9. I then went to Photoshop and opened the tiff created with Infranview. It opened it to 17.2mb at 3008X2000

Obviously I tried 3 different editors. The end result appears to be the same, but the Photoshop CS version of the tiff comes out as 6.5mb. Could Phtoshop CS have something new that causes this? I don't know. I thought all TIF conversions were the same.

What is your take on all this?
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Old Jun 16, 2004, 6:28 PM   #4
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Different files will compress differently, but usually LZW reduces a file by about a third. So 11Mb and change sounds about right.

I had thought all LZW compression was the same. Evidently Photoshop is doing something different and I have no idea what is happening. I'll get back after I run some files through Photoshop.
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Old Jun 16, 2004, 6:45 PM   #5
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I downloaded this image from Steve's sample photos:
http://www.steves-digicams.com/2004_...s/dsc_1393.jpg

It opened in Photoshop at 17,2Mb. Saved as LZW TIFF it was 10.7 Mb and as ZIP TIFF it was 9.9 Mb.

I saved them from Irfanview and got 16.9 Mb for LZW and 13.4 Mb for ZIP. Evidently there is a difference and all LZW or ZIP compressions aren't the same. I'm assuming Photoshop has more efficient algorithms. I'm using Photoshop 7. Maybe you have CS and it is more efficient yet. But 10.7 is close to what I've read it should be, so it is Irfanview and I assume ACDSee that isn't doing the job right.




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Old Jun 16, 2004, 8:35 PM   #6
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slipe,

I got the same results you did. Apparently Photoshop is the way to go. I was just simply amazed at the difference in file sizes.

I am still wondering whether or not it is a matter of more efficient algorithims in Adobe PS, or if something is being lost (although I doubt it..no one would use it if that were the case).

Bottom Line...I guess its better to use Photoshop for the conversions.

Also, something I noticed: if you use PS to convert, EXIF data is retained in the TIFF. If you use other converters, it gets stripped. A defenite plus here, since I was gettting upset that my exif data was dissappearing with conversions in ACDSee.

Also tried the test with PNG format, some folks have recommended it. File sizes in all programs were about even. PNG, I beleive,has more strictly controlled algorithm.
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Old Jul 2, 2004, 3:01 PM   #7
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I saved the Steves Digicams picture in several different formats.

When I opened them up in Photoshop, Photoshop displayed the file size of every one of them as 17.2M.

But when I looked at the file details in Windows Explorer they were all different. The ACDSee version TIFF with no compression was very close to the Photoshop TIFF size.

I don't know what conclusion to draw from this!!!
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Old Jul 2, 2004, 3:31 PM   #8
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Herb,

Are you saying the the non-compressed tiff in Photoshop and non-compressed tiff in ACDSEE were about the same size? That is proabably true. In the end they are all standard TIFF. It looks that the compression algorithms used by each product is different.

Iam more concerned with space, so I have decided to use Photoshop CS exclusively to convert from my original jpg to TIFF. With my D70, my original 2.5mb jpgs get saved at 6.5mb by Photoshop CS as opposed to 14.5mb my ACDSee 6.

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Old Jul 2, 2004, 4:34 PM   #9
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rblancojr -

Yes, that's what I'm saying. Windows Explorer displays the file sizes of the non-compressed TIFFs as -

When converted by ACDSee - 17,626
When converted by Irfan - 17,641
When converted by Photoshop - 17,649

When I had Photoshop save them in PNG format, Windows Explorer displayed the file sizes as -

Ordinary PNG - 9,490
Interlaced PNG - 10,984

For my purposes though, I don't see much point in using anything other than non-compressed TIFF. I just treat the TIFF files as temporary ones and use them to do any needed manipulation of the image. Then I turn the manipulated result back into a JPEG file. But if I especially value the picture, I usually preserve the original JPEG file too so that if I decide to have another go at it, I have the original data to work on.
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