Wednesday, December 5, 2012

Film Scanning Basics

Taken With Rollei Automat, Fuji Pro 160, Scanned with Epson v500

It seems like it's been a long time since I've written anything of a technical nature, and with good reason. I have an intention for this blog to emphasize the art of photography over the technical aspects, and for the sake of art, I've deliberately veered into film photography for the past few months. Photography is one of those pursuits, however, in which the distance between the art and the technology is pretty thin, whether you're pursuing it with analogue (film) or digital techniques. In actual fact, as I've never set foot in a darkroom, I'm using both, even with my playing at film. Somebody has coined the term "figital photography" to describe this mixing of analogue and digital - I guess that applies to me fully.

Photography is very technical, as opposed to the art of painting an image. It is all about "formulas" right from the start to finish. Whether you even realize it of not, the "art" of photography is primarily getting intuitively good at applying a series of various analogue and digital formulas related to the optics of your lenses, the speed and aperture capabilities of your camera and film (or sensor), the behavior of your flash versus existing light, color temperature, and then on to the processing tank and it's mix of chemicals, the temperature and timing involved, or if digital, you "process" your images through many strangely named manipulations of your RAW data files into an actual image.

If you're doing "figital" - the hybridization of using a film camera, and digital scans of your film, then at some point, your film slides or negatives must be converted to digital files. In the very beginning, you may want to fully entrust this process to the photo lab who processes your film - they can scan it and create a Photo CD of JPEG files for you to take home and stick in your computer. I don't recommend that you stay with this for very long. Simply do it long enough to decide whether using a film camera is for you or against you. Once you've decided that film is going to be a significant part of your life, then you must take the plunge and buy yourself a film scanner. Why not let the folks at the lab keep n doing it for you? Simple - because they don't know what you want, and once you get a JPEG file on a disk, you are very limited in what you can actually do with it. Having your own scanner, on the other hand, opens up another realm of technical  and artistic possibilities for you, and you can once again creatively shoot film without ever having to use a darkroom, or fiddle with messy chemicals, unless that's your thing. It also keeps your film processing cost very low - when you go to a One hour Photo and ask for "uncut negatives only - no prints, no scans", they typically charge only $5.00 for 35mm and $7.50 for 120 Roll-film.

So - on to the film scanner. I'm not going to be brand specific here, although as you already know, I own an Epson v500 which I bought on sale for $140.00. I cannot comment on other models, whether cheaper or pricier - some scanners cost as much as a high end DSLR, others are less than $50. I am going to assume the following features MUST be available at a bare minimum with the scanner you choose:

  • Some kind of effective dust control
  • ability to produce TIFF files, as well as JPEGS
  • some control over basic picture parameters in the device software (the ability to change Levels, Curves, White Balance, Brightness, Contrast, etc. during the scan - just like you do with digital camera software).
What then is the difference between a film scanner and an ordinary flatbed scanner like the one built onto your 3-in-1 Printer / Copier / Scanner? One word - "precision". A film scanner must be able to faithfully scan a very small image surface that is precise enough to be printable at much larger sizes - even beyond 8X11. Part of this precision comes from the scanner being able to hold your negatives or slides in a very precise position while scanning. The Epson v500 (a flatbed) uses plastic frames and locating tabs to do this. The first thing I want to clear up is how thee scanners specify the measure of this precision. It tends to be rather confusing. Epson advertises it this way - 

"6400 x 9600 dpi optical resolution for extraordinary enlargements from film up to 17" x 22"

Sounds impressive doesn't it? The fact is, if you use this kind of resolution in practice  you'll soon be returning your scanner back to where the sun never shines! This is very misleading, and in actual fact, the biggest resolution you should use for images, even up to 17X22 is only 600 dpi (dots per inch). The reason for this is found here, and here is a summery statement from this same article - 

" if you don’t resample, changing the PPI setting will increase or decrease the print size (it will increase if you drop the PPI, it will decrease if you increase the PPI)"

It sounds counter-intuitive I know, but if you read this article over enough times, it begins to make sense. If you own a digital camera, take a look at the "Properties" (EXIF Data) of one of your images - you'll find most of them are 300 dpi! So why do these scanners boast about these insanely high resolutions? Because numbers sell, and the first thing you'll want to do is scan a photo with the resolution set at this highest possible value - that's what I did, anyway, but it only happened once! I discovered first off that scanning at 9600 took over an hour for one image, and created an insanely large file of several hundred megabits for an 8X11 output. Reducing the scan size to 300 dpi brought the scan time down to a reasonable 3 minutes, and created a typical JPEG file size of around 4.5 MB - very similar to a digital camera.

This insanely large pixel density is built into the scanner for a reason. If you're scanning a slide, and want the output to be the original size (same size as the slide being scanned), then it will only look right when scanned at a higher density, like 4800 or more. With very small sized output, the scan time and file sizes become more reasonable at the high densities.

But the thing is, why would you ever scan a slide to output it's very small original size? I can't think of a reason, maybe you can. At least, be assured your scanner is capable of doing this if you ever need to.

So, the rule of thumb is - for an 8X11, or even an A4 printed output, set the Resolution at 300 dpi for a great looking print, or if you're greedy, use 600 dpi for "extraordinary". Anything beyond that is diminishing returns - unless you have a contract to put one of your pictures on a highway bill-board.

As for the rest of it - if it's a picture you really care about and want to work with, set the scan output to "TIFF" instead of "JPEG". The file size will end up being 8 times bigger, but the scan time will be the same (actually a little less because there is no time being used by the scanner for the JPEG digital compression). TIFF files have many advantages. Most printers will accept them directly, and being uncompressed, they are very close to behaving like a RAW file - they are far more tolerant to changing such things as Exposure Value, Dynamic Range, Gamma, Curves, Levels, Local Contrast and Colour Balance. They can also be used with most of the great Post Processing software like Photoshop, Lightroom, or my personal favorite - Photivo. Once you've worked the picture in 16-bit TIFF format, save that file for printing later, and then use your favorite software to down-convert it to a compressed 8-bit JPEG file for sharing it over a network. On your typical monitor, the TIFF and JPEG will look almost the same, but for printing, TIFF looks far better and also still retains the headroom of a large 16-bit file for further tweaking the print results if reuired.

My Epson software allows you to make most picture adjustments during the scan. I'm only just beginning to experiment with this. Basically, it means setting up your picture using "pre-processsing" instead of "post-processing". I'm still not sure about this - I can see some advantage in that you might stand a greater chance of getting it right, or at least closer to right, in pre-processing, but the disadvantage is that the image preview offered by the software is nowhere near as good as what Photoshop (and the others) gives you to work with on-screen. 

It can be frustrating and time consuming to learn all the ins and outs of scanning, unless you're really into this sort of thing, which I readily confess, I am. Your life-partner might object that you're spending too much time at the computer, especially if he/she cannot see the benefit of film over digital. It's all part of striving for a balanced life I guess.

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