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Nikon 18-55mm kit lens + extension tubes for scanning film

Started Jan 14, 2021 | Questions thread
D Cox Forum Pro • Posts: 32,979
Re: Nikon 18-55mm kit lens + extension tubes for scanning film

ken_in_nh wrote:

BBbuilder467 wrote:

ken_in_nh wrote:

BBbuilder467 wrote:

ken_in_nh wrote:

BBbuilder467 wrote:

ken_in_nh wrote:

BBbuilder467 wrote:

ken_in_nh wrote:

BBbuilder467 wrote:

ken_in_nh wrote:

And what about focus? Is there any reason to expect that manual focus would be better than autofocus? I for one can't think of why.

With manual focus using the extension tubes, the OP can adjust the image size relative to the focal length and find his working distance based on the tube length. Autofocus will be erratic, especially with the zoom lenses.

Why would autofocus be erratic? That statement makes no sense, as long as there's enough light. The autofocus sensors, after all, don't know the magnification, do they? To sensors, an image is an image, no matter its size, what lens made it, etc.

Try to get precisely 35mm across the frame on demand with autofocus using extension tubes. It needs to repeat the image size at that working distance every time.

Excuse me? This makes no sense.

How do you get precisely the same image size repeatedly?

Not by manual focus. You fix lens to subject distance, in this case a slide, and don't mess with the zoom. Pretty easy. Others use focus rails and make jigs to bolt everything down - minimizes vibration problems.

You do it handheld perhaps?

When I manually set 1:2, it's 1:2. It doesn't matter if it's hand-held or using focus rails. It can only be 1:2.

So what's your problem with focusing then?

I can't explain to the OP how to produce precisely 1:1.5 using extension tubes with autofocus. If you want to do it, go ahead.

The OP doesn't need "precisely" anything. You may have forgotten that one can always crop in post. So shoot a bit smaller, and crop to what you want.

Even using my professional slide scanner, I get a bit of edge when scanning slides. It's not a problem.

I agree. A bit of a margin is fine.

Don Cox

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