Drum Scan File Size of 4X5 Color Slide

[Chen-Wah Lee]

I have sent my 4x5 color slide to a professional photofinishing lab to have it d rum scanned at 100MB in RGB. The technician recommended a 30MB file should be su fficient for a 20x24 final print size but I still ordered a 100MB file scan anyw ay (and paid accordingly). When I tried to open the CD file at home with Photosh op, I found the words "file size :21MB " under the preview image before I clicke d open the file. After I clicked open the file the Photoshop read the file in EP S format and then a screen stating Embedded Profile Mismatch appeared. I clicke d "Convert Document's Colors to the Working Space" to open the file. In the lowe r left corner of the screen I observed "Scr: 159.9M/224.5M". I wonder what the a ctual size of my file is and if I had paid 5 times more for what I have got back from the lab. Thanks in advance for your explanation. C.W. Lee

[Howard Slavitt]

In your operating system software (Windows or MAC) before any programs are opened using the "File Info" command (or whatever it's claled)to look at the file size. That's the actual file size. It's possible that the lab scanned the image to 100MB and then saved it in JPEG or another compressed format to decrease the file size, but that would be pretty stupid based on your request.

[Mateo_2867]

"Scr: 159.9M/224.5M" is displaying your scratch disk information. To see the file size, click on the arrow to the right of that field and pull up to "Document Sizes". This will display the actual size of the file with no interference from compression formats.

[Ellis Vener]

You a re kidding right? the lab you use charges you by the size ofthe file you wish to create, on the order of 5 times if you order a 100MB file as opposed to a 20MB file? i am about to bust a gut from laughing.

Find out what format the file was created in (probably PSD). Open the file in that format (do not convert). Go to the "Image" menu on the PS toolbar and go down that menu to the option for "Image size.' This will give you the overall file size (AKA "Pixel Dimensions); the width and height in pixels; and the document size in percent,inches, cm, points, picas, or columns; and the resolution of the file you have open. this is all in PS 6.0.

Now find out what the resolution is ofthe output device.

As a comparison, I am currently working on a 4000ppi (pixel per inch)scan from a 35mm slide that produced (in 16bit/channel mode) a 112MB scan. When rescaled to 300 ppi (pixel per inch) the file size remained the same but the Documet Size changed from something like .93 x 1.34 inches to 17.94 x 12.15 inches. The resolution of the original image has not changed.

Do yourself a favor and buy a copy of Adobe Photoshop 6.0 for Photographers(Focal Press, 2001) by Martin Evening.

[Noshir Patel]

It sounds like you were cheated. Lossless compression usually won't compress a file 4:1 (I don't know anything about the EPS format, so I can't say what might have been done).

In the future, get your files saved as a tif file by the technician. That way it is easy to know what you got. Load the file in photoshop and see how many pixels tall and wide it is. Multiply the width times height and then multiply by either 3 or 6 depending on bit depth (8 or 16 bits per channel). Divide by 1,000,000. Now you have megabytes. You can't necessarily trust the actual file size since it could be a compressed tif (they charge by the uncompressed size).

www.westcoastimaging.com and www.calypsoinc.com are very reputable and reasonably priced places you might consider using for drum scans in the future. They spell out on their websites exactly what they do and Calypso in particular does work for several big name pros.

The profile mismatch has nothing to do with resolution or file size, by the way (although color space is important for other reasons as the websites I mentioned explain).

[Ellis Vener]

That is partly right; you want the file as a PSD not TIFF (TIFF is a compression scheme, but a very good one. You also want to make sure the file was recorded in Adobe RGB (1998) not sRGB. sRGB is good for the compressed color range on the internet. The idea is to hold on to as much information as possible for as long as possible in the digital process.

[Mateo_2867]

Save the same file that has not been worked at all (no saved selections etc.) as a PSD file and as a TIFF. For the TIFF do not choose to compress it. Do a file info on both. The TIFF is larger, by only a few bytes. ???????? Doesn't a TIFF only use compression if you choose to?

mateo

[Glenn Kroeger]

TIFF is a generic image file format (Tagged Image File Format), not a compression scheme, in which LOSSLESS compression is an option that is usually not used. Photoshop automatically uses LOSSLESS compression on PSD files if they meet certain criteria (ie that the compression is worthwhile). If the file was scanned to 100MB and then compressed with a LOSSLESS scheme, you weren't cheated... but if the file is something like JPEG using a LOSSY compression, you lost something (although if it was saved at a very high quality, you didn't loose much)

[Ellis Vener]

Thanks Glenn, for setting me straight aboutthe TIFF format. I was under the impressed that the TIFF format was a compressed file format.

[tim atherton]

Putting it simply - PSD (PhotoShop Document I think) and EPS (Encapsulated PostScript - used for graphics and layouts) are propriotary formats.

JPEG is a lossy compression format - i.e. you lose data each time you close it and it compresses the file. TIFF uses a lossless form of compression (and only compresses by a smaller amount compared to JPEG) but you can also chose uncompressed TIFF when saving.

tim a