Technicalities... or Magic?

16 July 2013
Comments: 0
16 July 2013, Comments: 0

For those of you who prefer to imagine that your slides and photos are transferred and restored with a wee bit of elfin magic, you can skip this post! For those hardy souls who are willing to review the technical aspects of high-end photo and slide scanning technologies, I hope you find the answers to some of those age-old questions about hardware, software, and Kodachrome… (And, how great for me, I can momentarily combine my love of music with my passion for multimedia engineering!)

Paul Simon immortalized Kodachrome film and the Nikon camera with this song in 1973:

kodachrome-gloveKodachrome
You give us those nice bright colors
You give us the greens of summers
Makes you think all the world’s a sunny day, oh yeah!
I got a Nikon camera
I love to take a photograph
So Mama, don’t take my Kodachrome away…

Fact: Slides and negatives will always have dust, particles, and fine scratches on them, despite the most white-gloved treatment you employ.

Fact: You don’t want to capture those scratches and fibers in your 100-year archival media transfer! At least we assume you don’t!

Fact: Kodachrome and old black and white images require specialized software instead of infrared scanning technology to remove dust and scratches.

Fact: Both hardware and software play a significant role in output quality.

There are many proprietary hardware and software technologies available today to support removal of these anomalies in slides. Some brands are: Digital ICE, Magic Touch (Proprietary to Pacific Image), SilverFast, “Image Intelligence” by Fujifilms, and others. The difference between a software clean-up and a hardware clean-up is, in short, that software converter technology requires you to use photo-editing software to clean up photos after they have been converted to a digital image. Several software-based technologies remove defects more or less by considering the surrounding image information. As you might imagine, this software analysis could be less reliable than the infrared scan method (more on that below). But Kodachrome and many old black and white photos cannot be automatically cleaned with traditional infrared technologies (more on that below as well). Here is an image that was cleaned up by the software application only, and one with Photoshop touch-up after that:

Photo-correction-software-comparison

Let’s compare two specialized “surface defect removal” programs that we use at Meadia Productions: Digital ICE, developed by Kodak’s Austin Development Center; and SilverFast, made by the German company, LaserSoft Imaging. These are the two top-rated and most widely distributed programs for automatically and manually cleaning and correcting photos and slides. There are reasons to use one or the other. In addition, we use the best-reviewed scanner for slides and film on the market: The Epson Perfection V700 Photo Scanner. Its resolution of 6,400 pixels per inch is significantly higher than the 2,400- or 3,600-ppi maximum of many dedicated film scanners. PC Magazine reviewed this model and says, “Scan quality is the important measure, and that’s among the best we’ve seen.” “The Epson Perfection V700 Photo represents a breakthrough in flatbed scanning by offering the highest optical scan resolution (6400 dpi) available for photo studio applications.” I would also like to point out that with a 4.0 Dmax, it offers exceptional image quality, excellent detail in shadow areas and remarkable tonal range.

Here’s where we get a little technical.

An inexpensive flatbed may have an optical resolution as low as 1200-dpi (although the trend is upward). If you scan a 35mm film frame at that resolution, your maximum enlargement for a 300-dpi dye sub printer is 4×6. To get an 8×10, you have to be able to scan 2400 dpi. So the low number of the scanner’s optical resolution should be a least 2400 for film.  Ours is 6400 dpi containing enough resolving power to produce photo-quality prints well beyond the threshold of 8 x 10-inch prints. And this wonder-machine supports 48–bit color and 16–bit grayscale!

Next, to capture as much detail as possible from film, you need a very high Dmax, the maximum density at which shadow detail can be distinguished. Density range is calculated by subtracting the Dmin, or minimum density at which detail can be distinguished, from the Dmax. Dmax numbers are often inflated by cranking up the exposure so high that highlight detail is burned out (which would be represented by a much higher than normal Dmin). The independent testing organization NSTL noted, “Epson Perfection V700 Photo was tested at both 6400 dpi and 4800 dpi resolutions. This scanner yielded consistent OD (maximum optical density) values for each scan at both the resolutions. The SNR (signal to noise) values for all the scanned images for Epson Perfection V700 Photo scanner were found to be greater than one. NSTL observes from these measurements that the average maximum OD value for this scanner is greater than 4.0.” Yay for us!

Now, onto algorithms and that clean up on slides! With the Epson Perfection V700, the Digital ICE technology is integrated so fingerprints, scratches and dust can be removed easily (but, again, not for all slides or photos!). In addition, this scanner supports the innovative Epson Dual Lens System which also helps it achieve outstanding results. We also have integrated the professional scan software SilverFast Ai Studio 8.  (By the way, when I refer to SilverFast, I am referring to this top of the line version).

Digital ICE uses an automated combination of hardware- and software-sided correction. Digital ICE Technology can remove dust or scratch marks from color photos, film, or slides, using infrared technologies.

In SilverFast these components are divided in hardware sided iSRD and software sided SRD. SilverFast will use infrared scanning in the iSRD mode, and will support iSRD clean-up for those Kodachrome slides and silver-based black and white photos. The latest version creates a high density file from two samples (one exposed for the highlights and another for shadow detail) that is faster and more effective than most multi-pass approaches. This is their patented and award-winning Multi-Exposure which increases the scanner’s Dynamic Range, removes natural image noise and provides more details.

So a bit of explanation of the magic of infrared scanning and dust removal is in order here. And a photo or two 😉  The “infrared process” uses an infrared sensor to detect dust and scratches on the surface of the film. In a multi–pass process, the dust/scratch is mapped out and carefully removed from the scanned image, leaving the composition and quality intact. See this image:

Digital_Ice_Before_After

So that is cool. But what happens when you try this with certain Kodachrome and certain black and white images? First, the “technicalities” or science of the scan:  While chromogenic black-and-white films are supported by Digital ICE, other black-and-white films containing metallic silver, which form from silver halides during the development process of the film, are not. This is because the long wave infrared light passes through the slide but not through dust particles. The silver particles reflect the infrared light in a similar manner to dust particles, thus respond equally in visible light and infrared. A similar phenomenon also prevents Kodak Kodachrome slides from being scanned with Digital ICE. Kodachrome’s cyan layer absorbs infrared! LaserSoft Imaging released an infrared dust and scratch removal tool (iSRD – infrared Smart Removal of Defects) in 2008 which is able to remove dust and anomalies from the silver-based black and white images, and Kodachrome images. This technology works from within the iSRD supported scanner, so unlike software-only solutions it does not alter any underlying details of the image. Fujifilms system for dust and scratch removal, called “Image Intelligence”, works on a similar principle as Digital ICE and will also work on Kodachrome film.

What does a Kodachrome image look like using SilverFast Ai Studio 8? Glad you asked– An image is worth a thousand words. The scan on the left is of a Kodachrome image without using SilverFast Ai Studio 8 and the image on the right used SilverFast Ai with iSDR. Big difference!

Before and After Kodachrome with SilverFast

 

How about good ol’ manual clean-up of those slides, if the technology is making your head hurt. Sure – Even if your scanner has a dust-reduction system in place, cleaning your slides and negatives should be standard protocol. Most dust particles can be removed easily using a camel-hair brush or a baster style air blaster. More stubborn particles and smudges can be removed using film cleaner (or denatured alcohol) and a cotton swab (cotton only!!!).

The final question on everyone’s mind (in techno-photo-perfectionist world) is, 1) Is it better to adjust the image after scan, or okay to tweak the Output Histogram before the scan?  2) Use the inbuilt photo tools to sharpen or use Photoshop CS’s sharpening? Let’s just say, we generally retouch after, but that requires much more user input, an understanding or RGB and CMYK color corrections and patience to work with curves in individual color channels.

That will be another post for another day! 😉

 

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