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When using extension tubes…

Started 10 months ago | Questions thread
BBbuilder467 Veteran Member • Posts: 7,057
Re: When using extension tubes…

SteveY80 wrote:

Atho wrote:

BBbuilder467 wrote:

Atho wrote:

DanRN wrote:

Atho wrote:

Is there an easy way to calculate the distance to which a lens will focus after adding a 10 or 16mm extension tube or both? (I know I will lose infinity focus, whatever the h€|l that means)

Hint. It must be really easy because I’m really stupid. No point in offering any complicated equations because I will just lose the will to live.

See if this page is of any use:

http://extreme-macro.co.uk/extension-tubes/#calculator

Thanks for the contribution. According the the calculation my minimum focus distance increases to 78.4 from 70cm…

That doesn't sound right. The minimum focus distance wouldn't "increase" when adding extension tubes.

With a 45mm lens and 26mm tubes, it's showing 183mm and 0.76x magnification, which sounds about right. That's from subject to sensor.

That's weird. I wonder if the "minimum focusing distance" on that form actually means the furthest the lens can still focus with the extension tubes attached?

It really doesn't make sense otherwise.

If you're using something like a 40-150mm zoom, rather than a shorter prime lens, I'd personally recommend looking at close-up lenses (e.g. a Raynox DCR-150) rather than extension tubes.

I think it's misleading combining the long focal length with the advertised magnification. My 45-200 came up at 1100mm. I think it does come out if I set it to 200mm and manually set minimum focus. It would be accurate with a prime, but varies throughout the zoom range.

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