Davey's DIY DSLR Diapositive to Digital Data Density Doubler (aka 4-D to 4-D (aka 4D24D (pronounced Forty-Two Forty)))

The purpose of the 4D24D toolset is to allow users to easily get high-res scans of their film negatives using a DSLR (Digital Single Lens Reflector) even if it has a low resolution sensor. This is achieved by taking multiple photographs of overlapping, partial segments of the negative, and then combining them into one "super-resolution" mosaic image. 4D24D makes this easier by automatically detecting groups of images which belong to the same film photo, correcting for slight camera misalignments and lighting inconistencies, and stiching the image together into a perfectly aligned and cropped output without any user input. You can take as many photos as you want, of film of any aspect ratio, and put them in any order, and 4D24D will figure the rest out for you!

The purpose of this project is to make high resolution film photography scans available at low cost to amateur photographers. Anybody who's ever shot on film knows that it's not cheap! Getting high resolution scans is no small part of that cost. At home scanning alternatives exist but are also very expensive. Even if you ditch a dedicated film scanner in favor of the more accessible DSLR film scanning method, stands to attach your DSLR to and gaurantee perfect alignment are incredibly pricy. Not to mention the cost of a nice, high resolution DSLR and macro lens. I built 4D24D so that even photographers without an expensive DLSR, macro lens, scanner or whatever else can still get quality scans of the film photos they've shot.

As previously mentioned, 4D24D is purpose built to get you great scans with a cheap DSLR, and no macro lens. While highly recommended, you don't even strictly need a stand or tripod to mount your DSLR to. If you've got steady enough hands, 4D24D can auto correct for any slight misalignments between the film and your camera sensor (you'll need VERY steady hands). With that said, here's what I recommend you have at a minimum before using 4D24D:

• Any DSLR + lens
• Camera lens reversing ring - this lets you mount your lens to your camera backwards to simulate the effects of a macro lens. It won't be quite as good, but it'll let you take in-focus shots of your film from very close up, which is a must to get the benefits of 4D24D.
• Backlight for film

[A note for stanky little degenerates: you can technically use any camera and lens for taking partial segment photos. I've even tested it out with an iPhone. Just don't expect immaculate outcomes.]

• A tripod/camera stand and mount. Helps you take consistent, level shots. The higher your target resolution, the more necessary this becomes.
• A film holder. Keeps your film flat, and allows you to slide shots across the backlight more easily.

• A focusing rail to dial in your camera's alignment and focus with precision.
• A mirror to use as orientation reference when aligning camera.
• A true macro lens.

I built 4D24D to be as easy as possible on the user, so you shouldn't have to worry too much about getting perfect shots for your film scan. However, there are some things you can do to give yourself a better chance of good results.

1. All shots MUST be in focus. 4D24D can correct for a lot, but if the film is not in focus, you will not get a good scan. Additionally, you may find that while the center of your shot is in focus, the edges are out of focus. Macro lenses are intended to compensate for this, and with a reversing ring you should be able to avoid the worst of it, but if you notice focus fall off, be sure you get at least one in-focus shot of every part of your film.
2. Do try to keep the camera as level as possible when shooting. This helps maintain focus, and saves 4D24D from having to warp the image too much. Shooting significantly off level could potentially introduce distortion to your image, lessen the final scan quality or cause imperfect blending of image segments.
3. Keep your background clean. 4D24D should be able to pick out your image even without a strong backlight or film holder, but the more uniform the background is for your scans, the easier it will be for the algorithm to piece it all together.

4D24D has the ability to automatically distinguish distinct film scans and estimate the true aspect ratio of your film. However, if you want to save 4D24D some thinking and speed things up, you can give it a hint in the following ways:

1. Take partial film segment photos in order. i.e. don't include a segment from film photo A among segments from film photo B.
2. In between distinct film photos, cover your lens and take a blank, black photo. 4D24D treats this as an indicator that a new film photo has begun, ignores the shot, and skips the film segment clustering process.
3. Tell 4D24D what aspect ratio your film is. 4D24D can figure it out on its own, but it just requires that much more number crunching.
4. An excessive amount of partial segments comes with diminishing returns and exponentially increasing computational load. You're probably not going to see nearly as much improvement between 10 and 20 segments as you will between 2 and 4, but you will be spending a lot more time waiting for results. This is something you'll probably want to play around with and find your preferred balance.

Check out the technical background primer for more details on the math behind this process.