Alley in Pisa, Italy

by Lars Kotthoff

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I'm looking to use my CanoScan 8600F to digitally archive the photos I've shot on film.

The issue I've stumbled on is deciding on a file format. Ideally I'd like something that is lossless but with some reasonable compression.

So far I've tried (over the last few years):

TIFF - File sizes seem to be pretty big

JPEG2000 - Photoshop elements 4 supported it, but doesn't seem to have a lot of support else where

DNG - Not sure if this is an option for scanning

I'm also looking for some guidance on resolutions to scan at... this was asked in another question "What to consider when scanning 35mm film (and scanning in general)" but wasn't directly answered, other than to say that scanners were only optically capable of 1500dpi.

With some exceptions I don't expect to make prints other than maybe 4x6s.

I currently use Adobe Lightroom with my DSLR and my new laptop included Photoshop Elements 9, but I haven't used PE9 yet.

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I think the major concern is "colour depth" , TIFF as far as I know offer much wider "colour depth", while JPEG, even JPEG200 offers only 8bit colour depth. Raw for example is 14bit in colour depth. I will do some researches to confirm this later. –  Gapton Nov 17 '11 at 7:38

4 Answers 4

up vote 12 down vote accepted

I would say TIFF is probably the best format. JPEG 2000, like JPEG, is still a lossy compressed format when you really try to save space (the lossless version can compress a bit, but not nearly as much as the lossy form, and some forms of the "lossless" wavelet compression still can't fully reproduce the exact original image.)

When scanning in an original or master image, it's really best to maintain as much image detail and color depth as you can, and TIFF is an ideal format for this. It is guaranteed to be lossless, supports a wide variety of color depths including high color depths, has very broad support across many applications on multiple platforms, and even supports layers and other advanced objects that can be created with applications like Photoshop. TIFF also supports the storage of metadata, like JPEG.

I am not sure if DNG is an option for directly scanning film, and even if it was, I am not sure what the benefit of using DNG over TIFF for a film scan is. DNG has more merit in the digital RAW workflow, as it supports storing native camera RAW data and metadata, which really wouldn't be of much use for a film scan (which is always going to result in RGB pixels anyway.)

Regarding resolution, I guess it might depend on the nature of the film. If you are scanning very grainy film, you might not need to scan at an extremely high resolution, however scanning at too low of a resolution will likely even interfere with grain detail (which does have an aesthetic appeal to many, and that aesthetic might be diminished at too low of a resolution... and I would consider 1500dpi to be fairly low these days.) I'm a digital photographer, however I have researched film quite a bit as I have a strong interest in large format. To my understanding, a low-speed, fine-grain film like Velvia 50 is easily capable of over 3000dpi, which is double the dpi mentioned in the article you have linked. I have done some 35mm negative scans of old film just for kicks, and scanning up to 4800dpi (the maximum optical native of my scanner) produces an astonishing amount of fine detail. I would say scan at the highest resolution you can so long as you don't see negative returns, and I wouldn't be surprised if 4800dpi or even as much as 6000dpi was necessary to extract all the detail from your film.

If the initial file size worries you, you can always downscale your master file a bit from a high resolution scan, which should help improve sharpness a bit while also saving a little disk space. High-ISO black and white film will generally require less DPI, however keep in mind that film grain is not ubiquitous in size and distribution, and the full quality and shape of a single grain may require many pixels to render fully.

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DNG is an extended variant of TIFF. It is known as a space-saving format, but mainly in comparison to completely uncompressed formats, as many camera raw formats are. It has only one real space saving advantage over TIFF, due to leverage stemming from specific knowledge of the camera's sensor technical characteristics. For instance, a DNG for a frame from a 12 bit per pixel sensor would be smaller than a 16 bit per pixel TIFF file of the same image. (TIFF doesn't do 12 bpp.) To get that DNG benefit in a scan, you'd have to use a scanning program that knew such details about the scanner. –  Warren Young Nov 17 '11 at 9:56
1  
No, TIFF is not guaranteed to be lossless; however, baseline TIFF seems to be guaranteed to be lossless if compressed. Wikipedia: TIFF Compression Tag That said, my vote is for TIFF as well, so +1. –  Michael Kjörling Nov 17 '11 at 10:23
    
@WarrenYoung: Sure, "a" DNG file "can" be smaller than a TIFF file, assuming lower bit depth pixel data. But from the standpoint of using it for a film scan from a scanner, there would be no benefit. Knowing the details about the scanner wouldn't matter, since they output RGB pixel data anyway...thats their purpose. (Some can do literal B&W output too, but for scanning film, you'd probably expect RGB color. I guess a grayscale scan might result in 16bit per pixel values, which would be fairly compact.) –  jrista Nov 17 '11 at 23:18
    
@MichaelKjörling: I'm not sure how the primary image data in a TIFF image would ever be lossy-compressed. I know compression is possible, but I have never known it to store lossy image data outside of previews (which tend to be JPEG compressed, which is what I think the wikipedia page is referring to...all other commonly supported compression is lossless). Do you have more information about that? –  jrista Nov 17 '11 at 23:20
    
@jrista: What does it matter that scanners are RGB devices? If I have a 12 bpp film scanner and save it as a 16 bpp TIFF, I will probably get less efficient compression than if I save the data in its native 12 bpp format. That's what DNG and native camera raw formats do, which TIFF cannot, without using nonstandard tag IDs. In a sense DNG is a set of TIFF tags that extend the format to give it such features. –  Warren Young Nov 17 '11 at 23:59

For the file format choose either TIFF or JPEG with an high quality settings.

JPEG is lossy, but you are scanning and archiving not editing and resaving - so if you find the quality settings that gives you acceptable results on JPEG they will stay acceptable for ever - there is no data loss while the files are on-disk only if you edit and re-save them.

Also, from an archiving point of view, TIFF and JPEG are the only image formats I'm personally willing to bet will still be around in 10-20 years (TIFF in pro software and JPEG everywhere).

JPEG2000 is not even widely supported today, DNG even if it was relevant for scanning (and I'm not sure it is) doesn't have "critical mass" (yet?) and all the other image formats I know of are either not relevant for scanning or are "legacy" formats that are practically dead (or in most cases, both).

Now, for the resolution - there is one sure way to find out - test it yourself, on your specific scanner.

Choose one picture with the most details and color you can find, now start at your scanner's max optical dpi and look at the image on screen - look at it full screen and zoom in a little, then scan at each lower resolution setting (starting from the high resolutions and going down) until the results are no longer acceptable.

Now take the lowest resolution acceptable image and make a test print (tip, print one size larger then you need, just to be sure you can if you have to).

If the print is not acceptable take the next resolution up and repeat.

This will let you find the minimum acceptable resolution for you with only a small number of test prints - and give you the confidence you can actually print if you want to.

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TIFF or TGA. No lossy compression, so no data loss. And they're well standardised formats so you'll have no trouble getting it read by software (both your own and others').

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Hmmm... If your scanner can save some kind of RAW format, instead of TIFF (and absolutely no way no how JPG!) I'd go with that. Simply because of my experience this summer; I brought a Nikon Coolscan V ED scanner along for the holiday, scanning a lot of film as I shot it. By mistake, the Nikon Scan software was set up to save as TIFF instead of NEF (the Nikon RAW format) and this resulted in Lightroom not saving XMP sidecar files. XMP files only get made for RAW files. XMP files are a Good Thing. Not having them is a Bad Thing. Ergo - scan in RAW if you use Lightroom.

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It probably put metadata in the TIFF, though, and you could use a batch program to extract that and write to XMP files. –  mattdm Nov 17 '11 at 11:27

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