Author Topic: tips on technique for bellows swing on PB-4 for macro use?  (Read 158 times)

keithostertag

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tips on technique for bellows swing on PB-4 for macro use?
« on: February 13, 2020, 17:29:08 »
Hello all-

New to the forum, hope this is an appropriate question:

I'm having difficulty learning to use the swing on my recently purchased PB-4 bellows unit. I have used bellows swing on 4x5 in the past, but not much and perhaps at this macro distance adjustments are a little different?

As a test, I've setup the bellows (using a Full Frame 105mm macro lens on my D810) facing a slide rule, the rule plane positioned at about a 45 degree angle from the lens plane. I focus on the center spot. So far so good.

My goal is to learn to swing the front standard in order to align the two planes so more of the slide rule markings will be in focus.

As I swing the front and compensate coverage by shifting slightly, I am not finding any point where the plane of focus obviously matches the plane of the rule. I swing just a little then increase it a little at time, but then of course I eventually run out of coverage and start getting vignetting.

Is it commonly necessary to refocus? I do that by moving the camera and leaving the subject-lens distance the same. Still, no joy.

I've also tried reducing the rule plane angle to something like only 20 degrees, but still I am not seeing an obvious alignment of the two planes.

Any tips on how I might approach this better?

Thanks,
Keith Ostertag


Birna Rørslett

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Re: tips on technique for bellows swing on PB-4 for macro use?
« Reply #1 on: February 13, 2020, 18:01:06 »
As you stated having used a view camera earlier, I take it you are familiar with the Scheimpflug principle?

It looks to me you have pretty high magnification and that implies massive movements are required in order to displace the plane of focus. In fact, far greater amounts than with ordinary photography. No wonder you run out of image coverage in the sensor plane.

I always found it better to do the movements at the rear instead of the front. That way the optical axis of the entire system stays more or less in the same position, so even a lens with modest covering circle can be used. However, now the requirements of accepting movements are on the camera/sensor instead and with a DSLR, the mirror box interferes and rapidly cut off peripheral rays. A mirrorless system such as Z would be better to this end.

The "cost" of rear movements is that illumination across the frame (sensor) will be more uneven and that sets the limit for the amount of swing/tilt possible. At least it was so in the film era where you had to stop when one part of the frame got -1EV or less compared to the other. With a digital system and some post-processing wizardry, one could probably use bigger rear movements.

Perhaps it is possible to attach the camera to a modified view camera bellows? That would allow more degrees of freedom, if the interference from the non-optimal shape factor of the modern camera can be circumvented.

keithostertag

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Re: tips on technique for bellows swing on PB-4 for macro use?
« Reply #2 on: February 13, 2020, 18:50:54 »
Thank you for replying Birna.

Indeed, your suggestion that the magnification was "pretty high" and would require "massive movements" prompted me to try with much less magnification, and now I can easily see the planes aligning. So that was the tip I needed! Now I am in the ball park and can experiment further.

Yes, I had read about the Scheimpflug principle in the past, but had not really studied it to any depth.

I am surprised your mention of using rear movements, since the PB-4 isn't designed that way. And with the view camera, rear movements are generally used for perspective control, while it is the front movements which are used for focus control, at least from my past experience. As my past experience with the view camera was at totally different magnifications, I can see now that my understanding of the optical properties needs enhancing :-)

You have helped me with your suggestion and I appreciate it.

Keith

Bill De Jager

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Re: tips on technique for bellows swing on PB-4 for macro use?
« Reply #3 on: February 13, 2020, 19:16:59 »
Perhaps it is possible to attach the camera to a modified view camera bellows? That would allow more degrees of freedom, if the interference from the non-optimal shape factor of the modern camera can be circumvented.

Another possibility is the Cambo Actus.  Michael Erlewine on this site uses this device for closeups with great results and has started several threads on the subject over the years.  I'm not sure how well it will work for high-magnification macro, however.  Also, the bellows plus lens plates would add up to considerable expense.