DSLR Scanner: Camera Supports and Positioning

[Peter De Smidt]

This is a cheap and small opensource project that leaves the bottom open. http://www.shapeoko.com/

Thanks for posting this, Ludvig. I hadn't seen it, although Daniel and I have investigated Makerslide a bit. Last time we checked they were sold out. The open bottom would make it much easier to adapt a light source to the plan. The issues I'd like more info on is how precise the Z-axis is, and how vibration resistant the unit is. My guess is that the Microcarve would be better in that regard. Being able to see these machines in person would be really helpful!

[ludvig friberg]

The issue with vibration is not so big if flash is used I guess? Also if one leave some time for settling after a move there is nothing that would vibrate. I see what you mean about having a really nice precise Z-axis, that would be a huge help even just for normal focusing just add a encoder to drive the stepper on the Z-axis. No need to fiddle with the camera or bellows. Just a Live View on high magnification on a laptop it would be very easy to set focus like that.

Since the travel of Z is typically very small I would suggest that you motorize your velmex, that would make it a lot cheaper.

I will not have time for this project until after summer but I am leaning towards motorizing a milling table. I can use the table with my manual mill to get some cnc capability when needed. I have some steppers and other hardware around and i will probably not motorize the z-axis at all. I got pretty good results with my canon ef 100mm macro at f22. So I´ll start with that also since the focus motor inside that lens is controllable through software it makes things a bit simpler.

[Peter De Smidt]

That sounds like a good plan, Ludvig. Working on scanning is more of a winter activity for me, and I doubt I'll make much progress over the summer. Diffraction will be setting in at a set aperture of F22.

[ludvig friberg]

Yes I can see that, what I read about it it seems up to F16 is pretty good. http://www.photozone.de/canon-eos/48...28_50d?start=1
Thanks for the heads up!

[jb7]

$1000 Peter? That's too much, my first prototype cost me €16, in addition to the junk I already had lying around.

I don't feel comfortable with some of your strategies. I think it would be reasonable to assume that anyone contemplating a DSLR Scanner might be expected to already own a DSLR, and perhaps some sort of tripod head, or macro rail. Maybe even an iPad, which could be the shallow light source you mentioned earlier, that might be needed to go under a ready-made positioning stage. All of these things are easily removable, and are serving an additional role, and could be seen as a given, for many people.

However, the positioning stage is at the centre of this machine, and trying to justify the purchase of a dedicated device, as something that could be re-purposed elsewhere, just seems like a non-starter to me. Especially those simply wanting to scan film, and not get further involved in CNC, or machining.

Those stages look like precision instruments, though as you mentioned, it would be good to see one, to test it first. They look like they would need some real power to drive them, perhaps requiring some bigger and more expensive motors- bigger than a motor that only has to drive a sheet of glass across a flat surface. They're also distinctly non-diy, if that part of the strategy is an important factor...

And another thing- Focus stacking- again, I think the correct strategy will be to ensure the film is stretched as flat as possible, and not make multiple exposures to process later. Thereby removing the need to drive the z axis, and the need to add more processing to the backend.

I've also moved on to other projects, and don't expect to do much more on this over the summer- though I've still got some lens tests to show. Speaking of which, I think the maximum aperture to set has got to be f/11 or larger, assuming 1:1 reproduction...

[Peter De Smidt]

Regarding aperture, I wouldn't use a smaller one than F8 due to diffraction. Doing so will lead to a significant loss of sharpness, according to my tests. But it's easy enough to run your own tests once you have a system built. As always, your own experience is more valuable than the opinions and results of others.

As has been said ad nauseum, there is a wide range of approaches that would work. Some people will want the cheapest solution. Well, we have three manual designs already, and no doubt there's many more approaches that would work. Some people might be in it more for the DIY aspect. They can build as many of the parts themselves as they'd like. (FYI, John from Microcarve has posted tons of info for people who want to build the machine on their own, including completely from scratch. He'll also sell components, if needed. To do this right, you'll need a mill and a lathe.) Others might just want a very capable scanner that's straightforward to build. Given what Coolscan 9000s go for these days, spending $1000-$1500 on a more capable scanner doesn't seem unrealistic.

Regarding having a cnc machine...I've done a bit of investigating possible positioning systems. I've probably spent over 100 hours doing this. What I've found is that using parts to come up with a system that is high enough quality for our use quickly gets us to near the cost of a Microcarve. And with the parts, you still have a lot of precise alignment and construction to do. John has made over a thousand Microcarves, and he's been continuously improving them. That's a level of refinement that going to be very hard for people to match. In addition, an earlier design of his is being used for a commercial product very similar to what we're trying to do, the Giga Macro. I can only speak for myself, but I'd like a cnc machine. I expect that others interesting in building an automated scanner might share that desire.

I agree about keeping film flat. I've stressed that from day one. And by flat I mean with less than 0.008" variance, but this may not be easily achievable, especially with curly film. Wet-mounting won't necessarily solve this, as anyone with experience wet-mounting on a flatbed will know. With a drum scanner, when you pull the mylar tight, you're also pulling the negative against the curved drum surface. When wet-mounting on a flat sheet of glass, when you pull one side of the mylar, you're not pulling the negative down, at least you're not to the same extent as you would be on the drum scanner. If focus stacking in some situations leads to higher quality scans, then I would want to use it. Some other people might as well. Others will be happy shooting at a smaller aperture, and that's fine by me.

[Peter De Smidt]

An inexpensive way to determine position: http://www.micromark.com/Remote-Digi...city,9899.html

[ludvig friberg]

Yes these are quite good, I have a similar solution on my manual milling machine. But they have their readouts on the slider.
http://www.arceurotrade.co.uk/Catalo...gital-Readouts
Maybe easier with fewer cables?

They are a bit more sensitive to swarf and cutting oil than the expensive ones and they eat batteries much faster than my Mitutoyo caliper, which has lasted 4 years without a change!

[ludvig friberg]

I have worked out my plans for most of the aspects of this but one part is very unresolved in my mind. The issue of mounting the film. Since I am only interested in 120 film I have looked at some different solutions. The Nikon holder is not very good I think, it doesnt hold the negative very flat. The FH-869G to nikon I havent tried but sandwiching the neg between glass is obviously going to make it very flat. Newton rings might be problem though. The Hasselblad flextight solution seems pretty smart. Ideally I would like to have only one piece of glass and be able to mount a strip with three exposures, then I will manually slide the holder to the next exposure. To me the mounting and dustbusting is the most timconsuming part. The simplest is perhaps taping the neg to a piece of glass but its such a hassle to use tape. I have started drawing on some solutions and any ideas are welcome!

[Peter De Smidt]

Please keep in mind that I'm drinking my morning coffee as I type this.

For really curly film, a glass sandwich carrier would keep the film flat. You could use anti-Newton glass or acrylic for the bottom. Place the film base side down on the AN surface, and then place a sheet of clear water white (.i.e. low iron) optical glass over the top. Hopefully since the emulsion side is usually less glossy than the base side, you won't get any Newton's ring. For the top glass, you could also use anti-reflection coated glass which would minimize any interference patterns. The downside is that glass is expensive and delicate.

Another option is wet-mounting with drum scanner fluid, e.g. Kami, to a glass plate, covering the negative with a Mylar sheet. With some systems this leads to a big jump in quality. Wet-mounting made a big difference when scanning on my first scanner, a Canon flatbed, but it doesn't on my Cezanne. That said, I'd like to avoid it. It's expensive, messy, time consuming, and it can lead to film damage. It's not that hard to do, though, and so it is a viable option. If you do this, you'll need a glass surface quite a bit bigger than the negative, as you're using the surface tension of the fluid to help hold the negative and mylar down.

For film that's not so curly, though, I'm hoping to use an open-topped carrier. The bottom will be 1/4" thick P99 acrylic. This is very similar to what Screen uses for the bed of a Cezanne. This will be on the bottom, just as with the glass sandwich carrier. The top plate will be a piece of 1/4" thick black ABS with a hole cut out in the middle just a little bigger than the image. There'll be a top plate for each sized film I'll scan. To mount the film, lay the abs sheet top down on a light table. Position the frame of film over the opening. Use two small pieces of masking tape to hold the negative in place. Place the top sheet onto the AN sheet. (I'll probably have guide posts to aid alignment, and possibly some type of system to hold the sheets tightly together.)