GFX100s scanning - lens choice and image stitching

Hi everyone !

I need help with choosing the right lens/lenses for GFX100s for scanning 120 and 4x5 film. My colleague already has Flextight X5 but would like another more portable setup and also futureproof.

What I have in mind so far : Negative supply Pro line carriers+stand+light source - purely out of convinience as the budget is quite unlimited
But the lens is biggie for me - I was suggested to Pentax/Mamiya 645 macros with extension tubes, is that a good option ? What would be the best, never mind the budget, choice ?

And second question regarding this - for 120 film can i get away with single exposure or do i have to stitch from multiple ? Same goes for 4x5 - would one capture be enough ? 2 or 4 captures and stitch ? Im asking this because Im not familiar with image stitching and i cant imagine the consistency. If someone has a sample image i can pixel peep at would be amazing !

Thanks a lot for your input.
David

What is "enough" depends on how much resolution you need in the scans. There's no single answer to fit every use case.
Personally, given the 100mpix resolution of the GFX100s I would be fine with a single capture for all film formats and not bother with stitching.

The gfx100s can also do pixel shift which can yield up to a 400mp image on paper. I can get (brief) access to a gfx100s ii through a family member who has one at work, and I've been meaning to try it out. They've got the 120mm macro on it which permits 0.5x magnification, so a 6x7 frame should just about cover the frame. If/when I get around to it I'll see about posting some samples.

David Mackovic said:

But the lens is biggie for me - I was suggested to Pentax/Mamiya 645 macros with extension tubes, is that a good option ? What would be the best, never mind the budget, choice ?

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If digitizing 6x4.5 frames, you'll want a lens that is optimized for macro around 1:1. If you ever need more magnification than that, reversing the lens may be a good option.

For a really good 4x5 that you want to print huge, I'd consider stitching 2 frames. Otherwise I wouldn't stitch with such a powerful camera.

Neither of the native Fuji macros do 1:1 without tubes so they probably aren't optimized for that magnification.

The Pentax, Mamiya, and Hasselblad 120mm f/4 macros are all well-regarded. Some of the Hasselblad ones need extension for 1:1, I'd avoid those.

Though I haven't tested any of these lenses, I'd probably go with the Pentax SMC FA 645 120mm f/4 Macro, personally. I use a Pentax SMC D FA 50mm f/2.8 macro for film digitization (mostly 35mm) and have been very pleased with field flatness, low flare, and sharpness.

David Mackovic said:

If someone has a sample image i can pixel peep at would be amazing !

Click to expand...

Warning, large 118 MP file - made with 6 hand stitched full frame 35mm images on a 6x6 (because my auto stitching software failed). I could have made it better by making sure the planes were a little more parallel - my copy stand sags a little bit, pitching the camera down slightly, which I should have adjusted for using the rubber feet on my negative holder. It's a CZJ Sonnar 180mm f/2.8 @ f/5.6 on Kentmere 400, with an orange filter.

You'll want to use carriers that have glass to hold the film flat if you do image stitching. Although with 4x5 the greater DoF may allow you to get away with it.

I do digicam scanning with a Fuji xt5. I've done the pixel shift thing for giggles and it really just creates super bloated files that you don't need unless you know you're planning to print billboard sized. As to lenses to do camera scanning with on the GFX, I've been advised that one of the best is the Pentax 120mm Macro for the Pentax 645. You'll still want to get one with the life-size module, and a set of extension tubes.

David Mackovic said:

But the lens is biggie for me - I was suggested to Pentax/Mamiya 645 macros with extension tubes, is that a good option ?

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I agree, the lens is a biggie. If you are determined to use a GFX100s, then I would start by finding out what adapters are available. No point in deciding you want to use lens "x" if there is no adapter available to mount it on your GFX100s. Is there an adapter available which allows you to mount a Pentax 645 lens on a GFX100s?

Actually, the first place I would start would be with a Fuji brand macro lens made to mount on your GFX100s. Fuji makes excellent lenses, so I would be looking at third party lenses only if Fuji does not make a lens suitable for your purpose. And for your purpose, you want something that will focus close, has a flat field, and good sharpness, including the corners.

Given the abundance of pixels provided by the GFX100s, I would be happy with a single shot, but for 120 film (if 6x6cm), I might consider two overlapping shots rather than "waste" the pixels that are not used when shooting a square subject with a rectangular sensor.

The sensor on the Fuji GFX100s is 43.8mm wide × 32.9mm tall. The image area of a square 120 negative is 56mm x 56 mm, so to fill the height of the Fuji sensor with a 120 negative requires a magnification of 32.9/56 = 0.59x. If you want to fill the width of your sensor (two shots, stitched), then you'll need a magnification of 43.8/56=0.78x. In either case, the lens should be able to focus greater than 0.5x (1:2), but will not need to focus as close as 1x (1:1).

It looks like the most suitable lens in the Fuji line would be the FUJINON GF120mm F4 R LM OIS WR Macro. That lens focuses to 0.5x, so it would need an extension tube to provide enough magnification to fill the sensor of a GFX100s with an image of a 120 negative.

One other possible benefit of using a Fuji lens compared to a third party lens might be software lens correction? When a Fuji lens is used on a Fuji camera, I believe a certain amount of correction for things like vignetting, barrel/pincusion, etc. are applied by software? I expect some lenses need more corrections than others, but I don't know anything specific about the FUJINON GF120mm F4. Nor do I know if that lens has a flat field. But if I was interested in digitizing film with a medium format Fuji camera, these are questions I would be looking for answers to.

What about an enlarger lens on a bellows or helicoid set-up?

Ardpatrick said:

What about an enlarger lens on a bellows or helicoid set-up?

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I think that could be a good solution. We know most enlarger lenses are optimized for a flat field of focus and good sharpness at certain magnifications.

I started out using an enlarger lens on a bellows when digitizing 135 and 120 film with my Fuji XT-1, and I thought the results were pretty good.

I don't know if Fuji makes a bellows or helicoid in the G-mount. If not, then we are back to the question of what adapters are available.