A good drum scanner has greater dynamic range than a ccd scanner, but it doesn't have greater range than an HDR style multi-exposure ccd system, since the latter can have as big a dynamic range as you need. All you need to do is to take more exposures at different levels. A variable light source would also be good, but you'd have to be careful of spectral shifts. Perhaps neutral density filters would work.
The big problem is alignment, and the precise movement of the film. (I think it's better to move the film holder than the sensor.) The level of alignment is what it would take to make a huge print under an enlarger. The film must stay perfectly flat and parallel to the ccd sensor and lens.
Some type of x-y position system would be needed for the negative carrier, perhaps with two calibrated lead-screws.
So, get, build or modify a light box with a very even source, one that's quite a bit better than the industry standard type boxes. (I don't know how repeatable flash equipment is, but if it is repeatable enough, it might make a good light source, as you can use a very short duration of flash, which should help with vibration. You'd still need a constant source for focusing.) Make a tray that goes on top, it doesn't have to touch the light box, which will hold a film holder that can be moved in a repeatable, grid-like fashion. A clam shell holder with p95 acrylic would be ideal. You'd then need a mount for the camera. Since it wouldn't have to move much, it should be a multi-column mount for stability.
A macro bellows, such as a Nikon PB-4, along with a high quality enlarging lens would be a good choice, probably a 50mm, as they're capable of the highest resolution.
The carrier stage would have to be masked very well, and the light would half to be blocked from the front of the lens to the negative.
Operate the camera remotely through live view, although focus would be manual.
The whole system would have to be very sturdy and well-isolated from vibration.
Looks like the GigaMacro is already available. One would only need a backlight to scan transparent film media. In the $15 K range that's not too bad. But at the advertised resolution there are a bunch of very precision mechanical parts especially for X and Y motion that are costly. Essentially this is a step and repeat camera where the resolution and contrast will be limited by the macro lens. Scan time will be limited by the field of view of the macro lens and stitching time can be added to the physical scan time.
A higher magnification lens heading toward a microscope objective will provide resolution down to a few um but a small FOV, so many more images are required. But higher magnification requires tighter focus control, or auto focus, so more precision. Mechanical precision is expensive.
What's less expensive is signal processing. Thus it may be possible to trade the mechanical precision in X and Y motion for pattern recognition and image reconstruction algorithms; meaning the scan can be sloppy if the images overlap.
Lots of possibilities beyond the GigaMacro but using a high quality CMOS sensor with a magnifying macro lens would make sense and ultimately provide a less expensive machine than using a drum.
Nate Potter, Austin TX.
Problem here is(IMO):
We're not looking to design a line of cars, with a cheapo/intro model, a medium($40k/year) model, and a heart surgeon's model w/ all the bells and whistles .
The high-end scanners like the Azteks, Heidelbergs, Creo/Kodak's were designed for PROFESSIONAL use. That means MORE MONEY SPENT. The latest generations of drum scanners from Aztek, Heidelberg, Screen, and the latest hi-end flatbeds like the Kodak Eversmart Supreme II's, no expense was spared to put the BEST tech into them, and for them to perform flawlessly(well, when used properly). Just like the top-tier Ferrari's, they need a servicing every now and then. Just part of doing business. Bulbs and belts need to be changed, lead screws need to be lubed, and sometimes, a full goings-through needs to be performed to make sure no bugs pop out when not wanted. Of course many people neglect their "normal maintenance cycle", thinking "That won't happen to me". Well, it happens.
If you want the best tech possible, and I'm assuming 16bit TIFF file output, then you'll need to pay for it. PMT's aren't cheap, and small companies like Aztek(I was there yesterday actually, dropped in since I was in the neighborhood, they're 3 people total I saw in the office, YES... 3 people). They need to be paid, and keep enough to keep the lights on.
The problem I see here is two-fold: You have your lab owners/scanner operators(Lenny for instance), and you have your "amateurs"(some who might know just as much as the "pros", if not more, but might only be scanning for themselves, not as a service for profit). That's the KEY word: PROFIT. Its called keeping the lights on. The Aztek Premier will clock in around $50k after the scanner, mounting station, a drum or two, Pro software($1500), computer to drive the scanner, a shipping crate to hold it during transit, and $1k to ship it to you across the country/world, etc... Yes, its expensive. But you can buy an 80mp digital kit, outfit it with 3-5 "top tier" lenses, and still be around the same amount of dough in the end. If you're scanning/shooting for yourself, then its your call. But in the end, if you want to deliver the goods to paying clients who are willing to spend $100+ on a scan, then you'll probably want the best machine w/ the best support possible. In the USA, IMO, that's Aztek. They've been sooooo helpful in aiding me in my acquisition of my drum scanner, and answering technical emails/phone calls w/o asking for $$$ in return. They know I'm serious about my craft, and don't have money to burn, but I don't bullshit with their time either. They're professionals(IMO), and professionals SHOULD be paid.
If I was going to introduce a drum scanner, I'd want to make sure you can mount up to 11x14 film on it. And I WOULD NOT be doing it for less than $40k. If I hadn't already gone with a drum scanner, I'd be going with a Kodak Eversmart Supreme II flatbed(and still fluid mounting almost everything on it). IMO, its more flexible, and the minor difference in file quality(IMO) isn't worth the headache and risk of damaging someone's film on a fast-spinning drum scanner(even though I know how to properly mount film).
Oh, what about overhead on these "1000" scanners, there's gotta be tech support on these, someone to talk to when something goes wrong. That costs money, its called overhead.
I think that drum scanner manufacturers INTENTIONALLY priced themselves high, just so the "small fish" photographers w/ the "I need the best" mentality REALLY think twice before ordering something like these machines. There's more involved than most people really think...At least I know there is, I'm learning a buttload, and I'm not technical(but I'm learning I need to be )
just my $.02
This is a neat challenge. When my Cezanne dies, I'll probably pursue it.
Sure, we have many disadvantages compared to a big company, but we also have many advantages. The software available now for raw processing is much better than any scanner software I've used. We can replace our sensor, i.e. the camera, for a modest amount, and they have improved dramatically. Lots of the macro bellows and so on are available for little money, and enlarger lenses are close to free. In addition, we don't have to use materials that are compact or easy to move. For instance, we can use a 1/2 inch (or thicker) piece of glass as a base to slide the negative holder on, and many of us already have glass negative carriers for our enlargers. It's automating the whole thing that would be the really big challenge, but it doesn't really have to be that automated. If it must be, there are DIY CNC machines that have to be accurate down to a 1/1000 of an inch, and a technically inclined person could probably modify such a device.
In addition, commercial scanners have to be so precise because they only read a couple lines at a time, and the sampling has to be incredibly precise so that all of the sampled lines can be put together. With a dslr, though, you take reading of a much wider area, and as long as each sample area is overlapped enough, it's no problem for software to put the pieces together.
This is something I've been looking into for some time hence the reference to the GigaMacro. There is an experiment that can be performed to validate the approach which is to construct a pin grid system that allows systematic movement of a stage holding a target below a macro lens. No stepper motors involved, just shoot and manually move to next position.
Re focus, there is a technique used in photomacrography that might be of use called stacking, where the stage is moved along the lens axis to bring various points in focus. Not sure the utility in this context, but just brainstorming.
Re lenses, if you need to get down below 1:1 it might be worthwhile looking at microscope objectives. I've been seeing some pretty nice looking stuff from those. There are a couple of configurations, such as objective on bellows and infinity objective on a lens.
When is it more advantageous to move the imager vs. moving the stage?
That would certainly be worth looking into, especially for smaller than LF film. For LF, something on the order of 1:1, i.e. image size of one sampled area equals image size of sensor, should give pretty high quality. With my digital camera, an older model, that should allow a 10x enlargement or so, assuming the negative is sharp enough. That's bigger than I'd ever want to print. 1:1 would be well within the capabilities of an enlarging lens on a bellows.Re lenses, if you need to get down below 1:1 it might be worthwhile looking at microscope objectives. I've been seeing some pretty nice looking stuff from those. There are a couple of configurations, such as objective on bellows and infinity objective on a lens.
Well, a camera/bellows/lens combo is quite heavy, and it would be non-trivial to be able to move it precisely, perfectly parallel to the negative, and without inducing vibration. With the negative stage, on the other hand, you could use some thick textured acrylic (P95) to make a clam shell holder. You could put a small foot in each corner of teflon (or similar) tape, and you could slide it on a very heavy sheet of glass.When is it more advantageous to move the imager vs. moving the stage?
Here's picture of coraline algae growing on the glass of our aquarium. The colony was about 1/4th" in diameter. I used my d200, a Pb-4 macro bellows, and an enlarging lens. I simply eye-balled the alignment, and my D200 doesn't have live view.
If we just make a mechanical product that accepts a wide range of digital cameras it would allow you to choose your price/quality point by using a $500 camera or an $8000 camera. And as digital camera technology continues to scale so would the system, the mechanical part we build would not obsolesce.
Precision adjustment would be needed to set the height and level the plane of the camera. X Y placement needn't be precise as long as there's overlap because the stitching software can easily deal with the slop.
Yes! You guys have the idea both mechanically and optically. This can already be demonstrated using a light table and digital camera with a good macro lens of low distortion. Use conventional stitching software to reconstruct the image. The key here is that this is not live image capture - the subject is stationary.
The next task is to build a prototype that more or less automatically does the same thing, faster and more precisely. The trick in all this is to use low cost OEM parts on a solid chassis in order to keep the ultimate cost down. The engineering is relatively easy - the market analysis not quite so.
Nate Potter, Austin TX.
The usage problem I see with a stitching scanner is that there is no way to preview to set exposure/levels without actually doing the scan. If it had a high speed mode, it could do a quicky scan for setting exposure. Remember DSLRs are pretty sensitive to exposure accuracy.
It's a constructive comment because I like the idea.
I would agree that presently available stitching software can take care of alignment imprecision, except for focus of course. I would think a cnc router table would be a good start. Moving the film instead of the camera would provide an easier to build light source, as a smaller even diffuse light is easier to build that a very large (11x14+) diffuse source.
Putting the whole thing in a cabinet that is dust proof and light proof is a good idea. Not everyone has a clean pristine lab to set such a system in. To dampen vibration, electromagnets could temporarily attach the movable stage to it's frame during exposure, and release it's grip during positioning.
The stage itself could be a filmholder made of white diffuse plastic, or at least the center part of the it. If the film moves a little during positioning, the stitching software can take care of it.