Focusing steps with FB Tube and Nikkor AF-S 55-300mm 4.5-5.6GED

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cybervet
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Joined: 23.02.2020 22:36

Focusing steps with FB Tube and Nikkor AF-S 55-300mm 4.5-5.6GED

Post by cybervet » 25.02.2020 03:55

I have just received my Helicon FB Tube and have been experimenting with a Nikon D3300 camera back and a Nikkor AF-S 55-300mm 4.5-5.6GED lens. Changing the recommended steps in the Configuration Utility doesn't seems to change the number of focusing steps that are useful in the stack. At 80mm this is limited to 3-4 useful steps and at 200mm it increases to 7-8 useful steps. This does not seem to change with the recommended steps varying from 5 to 200 and the change in focusing distance appears to be the same. Is this likely a limitation of the focusing step capability of the lens itself? This is not a terribly high quality lens or camera back, but it is what I have right now. Considering upgrading camera and/or lens, but am wondering if I am missing some technical steps with the configuration of the FB Tube?

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Catherine
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Re: Focusing steps with FB Tube and Nikkor AF-S 55-300mm 4.5-5.6GED

Post by Catherine » 27.02.2020 18:22

Just let me make sure there’s no confusion with the step size and the number of steps.

Recommended step is not the number of frames to be taken, but the size of the step between two consecutive shots. We say ‘Recommended’, because for some lenses we’ve determined the correct step, i.e. the one that will allow consecutive shots to overlap and not 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, in this way: http://www.heliconsoft.com/helicon-fb-t ... ting-step/

cybervet
Posts: 4
Joined: 23.02.2020 22:36

Re: Focusing steps with FB Tube and Nikkor AF-S 55-300mm 4.5-5.6GED

Post by cybervet » 28.02.2020 04:18

Thanks Catherine,

I think I am getting it figured out with a little experimenting. Will continue to determine the optimum "recommended steps" for this lens. Right now it seems to be somewhere between 50-80 at f/8, but I need to refine this some more.

The lens is obviously advancing with each shot either in a "burst mode" or in a single shot mode using a remote to reduce camera movement set on a tripod and multiple shots to create the stack. I have been very pleased with Helicon Focus especially its ability to compensate for the slight movement inevitable (at least in my hands) created during a hand-held burst mode.

I would totally agree that the focusing steps appear to be proportional and not finite units that change with the f-stop, focusing distance and lens length as with a telephoto zoom.

Thanks for the help.

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