Helicon FB Tube Questions

Shooting in macro mode, techniques, tips & tricks
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Joined: 10.09.2018 09:23

Helicon FB Tube Questions

Post by matt42 » 10.09.2018 17:11

As the new owner of an FB tube, I have a few questions for the cracks.
Is it correct that the tube doesn't detect a lens change, i.e. there is no change of the set number of steps?
If the aperture is changed, the preset number of steps will not be changed either?

In the manual for "setting the step" you will find part 7:

"...For example, you found the step 100 to be optimal at f4. When you choose f8, the program will show you that the recommended step is 200..."

Shouldn't the number of steps be calculated to 50, because the depth of field doubles when fading down from f4 to f8, so I only need half of the steps for the same range of depth of field?

Thank you for answering my stupid questions.



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Stas Yatsenko
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Joined: 06.05.2009 14:05

Re: Helicon FB Tube Questions

Post by Stas Yatsenko » 13.09.2018 09:47

Yes, that’s correct, the tube does not receive any data from the camera, so the aperture value has to be input in the app when you reconfigure the tube. The tube also does not receive the data about the current lens until you enter this data via the app.
The tube gives a command to the lens motor to shift focus by a certain step, i.e. to rotate the ring by a certain angle. The tube receives all the data about the required size of the step between shots from the user via configuration utility.
As for your question about DoF and steps, seems like you’re talking about the number of shots, while we meant the size of the step. Recommended step is not the number of frames to be taken, but the size of the step between consecutive shots. We say ‘Recommended’, because for some lenses we’ve determined the optimal step, i.e. the one that will allow consecutive shots to overlap and not to leave areas out of focus between shots, and on the other hand, for them not to overlap too much causing excessive shots.
Focusing steps of the tube is the value proportional to rotation of the focus ring of the lens, and not to the linear movement of focus in mm, it’s in arbitrary units. The step size will be different for different lenses and apertures, as well as distance to the object. Step sizes for some lenses and different apertures are preset in the utility. As for the other ones, the step size should be determined experimentally, for instance, this way: http://www.heliconsoft.com/helicon-fb-tube-setting-step/
So the wider DoF, the larger step should be set.

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