Drum Scan File Size of 4X5 Color Slide

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I have sent my 4x5 color slide to a professional photofinishing lab to have it drum scanned at 100MB in RGB. The technician recommended a 30MB file should be sufficient for a 20x24 final print size but I still ordered a 100MB file scan anyway (and paid accordingly). When I tried to open the CD file at home with Photoshop, I found the words "file size :21MB " under the preview image before I clicked open the file. After I clicked open the file the Photoshop read the file in EPS format and then a screen stating Embedded Profile Mismatch appeared. I clicked "Convert Document's Colors to the Working Space" to open the file. In the lower left corner of the screen I observed "Scr: 159.9M/224.5M". I wonder what the actual 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

-- Lee Chen Wah (leechenwah@hotmail.com), March 05, 2002


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.

-- Howard Slavitt (info@enaturephoto.com), March 05, 2002.

"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.

-- Mateo (mateoleyba@yahoo.com), March 05, 2002.

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.

-- Ellis Vener Photography (ellis@ellisvener.com), March 05, 2002.

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).

-- Noshir Patel (noshirpatel@yahoo.com), March 05, 2002.

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.

-- Ellis Vener Photography (ellis@ellisvener.com), March 05, 2002.

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 (mateoleyba@yahoo.com), March 05, 2002.

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)

-- Glenn C. Kroeger (gkroeger@trinity.edu), March 05, 2002.

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

-- Ellis Vener Photography (ellis@ellisvener.com), March 05, 2002.

It is a computer... what else would you expect?

-- Dan Smith (shooter@brigham.net), March 05, 2002.

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.

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-- Tim Atherton (tim@kairosphoto.com), March 05, 2002.

LZW Compression in the TIFF format is lossless.

-- David Goldfarb (dgoldfarb@barnard.edu), March 05, 2002.

Lee, talk to your print shop first - they will tell you what scan resolution and file type are required based on the print size and quality you want.

There is no way to get a quality 20 X 24 from a 30MB file.

-- Michael Mahoney (mike.mahoney@nf.sympatico.ca), March 06, 2002.

I tried the various recommendations given above and here are the results: 1) Howard's recommendation: 21.3M. 2) Mateo's recommendation: Doc:105.6M/105.6M. 3)Ellis' recommendation: under IMAGE SIZE : Pixel Dimension 105.6M- Width/Height:6832/5400 pixels; under DOCUMENT SIZE : Width/Height:25.1/20inches, Resolution 270 pixels/inch. I tend to believe the file size is 105.6M but I will take the CD back to the lab and kindly ask for their verification. I used to do conventional enlargement and am interested in digital manipulation recently - a long way to learn for me. In Hong Kong, most professional digital labs charge HK$50 (US$6) for a 20M (20M is the minimum size) drum scanned file and the charge goes up directionally proportional to the increased image size (HK$250/US$30 for a 100M image).

-- C.W. Lee (leechenwah@hotmail.com), March 06, 2002.

Kee: you have to do more than ask about file sizes, formats etc. You have to look at the histograms to see how well the slides were scanned and evaluate the lab's work. Not all 100 MB files are created equal and you can't simply arrive at conclusions on quality by the kind of specs. Drum scanners require expert technicians for best results. The results from good drum scanners, expertly used can be fantastic but that is not always necessarily the case. If you intend to get on seriously with Digital, two books I recommend are Photoshop 6 Artistry by Haynes & Cumpler and for color management, Real World Photoshop by Bruce Fraser. The Evening book is excellent but it does not cover as comprehensively important aspects of Photoshop and digital photography. The Fraser book covers very well the workspace conversions and you should be aware when you load up the files what and why you are doing. As for the comment, 'what can you expect, it is a computer' that gentleman probably has an ice-box not a refrigerator, after all, you can not trust 'artificial ice'.

-- Julio Fernandez (gluemax@sympatico.ca), March 06, 2002.

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