1. robhooley167

    robhooley167 Sir, my fingers are stuck together

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    This is a follow on from the discussion in the Scanning film with a DSLR thread https://www.talkphotography.co.uk/threads/scanning-film-with-dslr.673380/, to avoid clogging that thread up.

    An idea was concocted to use a 5x4 camera to scan it's own film using a DSLR mounted to the lens-board and a light-box on the back of the camera

    Version one is being prototyped using an old MPP wooden double darkslide as a chassis. It certainly isn't going to win any design awards right now, but I'm constraining myself to make it fit in the footprint of a DDS, to avoid having to dismantle the camera to use it with a Graflok back.

    [​IMG]

    It uses two sheets of picture framing glass to sandwich the film, the fine texture on the glass should be sufficient to avoid the presence of Newton rings, glass is on both sides to enhance flatness.

    The next challenge is fitting an illumination source behind the glass sandwich, I don't think LED panels can provide even illumination without a fairly thick diffuser, so I'm looking into a few alternatives.

    For version two, the chassis will be custom made to fit slightly larger glass without increasing the external size of the unit, so that the sandwich can be slid in once the film has been added.

    Unlike @stevelmx5 I'm not so good at CAD, but I'll try to add a few drawings over the next week or so.
     
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  2. stevelmx5

    stevelmx5

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    Looks likes a good starting point Rob. Whilst I’ve had to draw up my components in Sketchup so I can export them for the laser cutter, I always prefer actually building something and working around issues/requirements on the fly.

    I’ve used 80% opaque 5mm acrylic as a diffuser panel and it’s showing good light spread without any major hotspots, so long as the light source is either at least 10cm back (eg an iPhone torch), or there is enough led illumination to blur the edges between light points so it looks like a bright even spread. I’d suggest using 5v/12v cool white led strips, depending on the power source you’re using.

    Good luck mate.
     
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  3. robhooley167

    robhooley167 Sir, my fingers are stuck together

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    Thanks for the tips Steve, I'm looking into using some electro-luminescent panel as the light source as I can cut it to size and it's only ~1mm thick. LED panel is my second choice with some heavy diffusers, admittedly brightness is not essential for this task as you'd be able to change the DSLR exposure time to deal with a weak light source, uniformity of the light is the key thing for this.

    I've been upgrading my CNC router over the last few weeks, when it's back up and running I'll make some new frames for this project!
     
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  4. stevelmx5

    stevelmx5

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    EL panel may be a good option but, like you say, you’ll require longer shutter speeds as they’re not that bright when you’re trying to illuminate the blacks in a Velvia slide (I’ve tried!). They are much easier to utilise though as they’re completely self-contained. I’m looking forward to seeing the results you get from them.
     
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  5. Woodsy

    Woodsy POTY Winner 2009

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    Have you considered yet what lens you'll use on the DSLR? I'm guessing something like a 60mm-ish macro lens for both the working distance and the depth of field correction?
     
  6. robhooley167

    robhooley167 Sir, my fingers are stuck together

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    I haven't thought too much about that yet, I was thinking of using my 40mm pancake lens as a first attempt, then going from there!
     
  7. ChrisR

    ChrisR

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    Interesting to see how this turns out. Is an iPad (or other tablet) a possible (temporary) light source?
     
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  8. robhooley167

    robhooley167 Sir, my fingers are stuck together

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    It would be an option yes! It would need to be diffused to avoid pixels appearing in the "scanned" image, but it could be an option!
     
  9. Woodsy

    Woodsy POTY Winner 2009

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    Surely if the DoF is shallow enough, that would provide the diffusion for you (pixel size, position and DoF depending)? Also, I'm not saying it's necessarily true for an ipad, but one should be careful using backlit LCD displays as a light source in this context, as the apparent brightness can vary as a function of position on the hemisphere into which the display emits.
     
  10. stevelmx5

    stevelmx5

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  11. steveo_mcg

    steveo_mcg

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    Couldn't you leave the GG in place and light that?
     
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  12. robhooley167

    robhooley167 Sir, my fingers are stuck together

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    I've considered it, but my GG is a bit grubby and has cut out corners, so will have a fair bit of light bleed around them.
     
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  13. steveo_mcg

    steveo_mcg

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    Ah, forgot about the cut corners.
     
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  14. joxby

    joxby

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    Led panels are pretty evenly lit, I can only assume the source needs to be a custom size and so will require a build, thus making it tricky to get an even output across it.
    Most of the small ones I've taken to bits are edge lit, shielded from direct exposure to the diffuser, its all reflected from a white box background, pretty even all the same..:)
     

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