Pls recommend some focussing rail for use with helicon focus

Shooting in macro mode, techniques, tips & tricks

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Bob J

Focussing rail, and infinite depth of field

Post by Bob J » 11.10.2007 07:02

First, with respect to the focussing rail issue, I recently purchased two of the Novoflex Castle Q focusing rails, despite the fact that I already had one of the Really Right Stuff rails, and had ordered another. I was impressed by the overall smoothness of the device.

Unfortunately, I wanted to use this with the Canon MP-E 65mm macro lens, which for 5X magnification has a depth of field of about 0.095mm at f/8, and 0.048mm at f/2.8. The Novoflex advances approximately 7mm per rotation, so it would be necessary to guess at 1/70th of a rotation. That's essentially impossible, without a very high quality vernier adjustment.

The Really Right Stuff (and apparently the Manfrotto) advances by 1.25 mm per rotation, or 0.1mm per "hour" on a clock face, and that I can manage, especially with large dial as someone else suggested. The only issue is that there is a significant amount of backlash, so you have to advance the screw in only a single direction. You may also have to tighten the locking screw just enough to prevent wobble, without preventing adjustments.

I wish that there were long-length screw-thread rails that had vernier dials or controls, and maybe such are available for microscopes, but I haven't found any.

The Really Right Stuff rails may not be as available as the Manfrotto, because they don't use or support a dealer network, but you can find them on the net, and they are quite reliable.

Having said all that, my first attempt last weekend ended up with a truly ugly image. I was trying to take a picture of a rosemary flower about centimeter in size, at 3.3X. Despite using a very sturdy tripod and two Wimberley plamps to hold the branch, the wind blew the individual petals too much. The result was a number of sharp in-focus images that were displaced horizontally, with disasterous results. Maybe if I had been able to edit individual frames in Photoshop, this could have been avoided. As it was, I wasted several hours taking the pictures and post-processing them, only to keep the first picture with sharp pistols or stamens (I can't remember the difference) and pleasantly blurred petals.

Second issue:

I would like to take some pictures that really highlight the essentially infinite depth of field that Helicon Focus will permit. For example, a field of flowers that stretches out to the distant mountains.

Now, my Canon 90mm T/S tilt and shift lens (or my long gone but sorely missed Sinar P view camera) would handle that chore easily, with a simple tilt adjustment, although it might not focus as close as I would like without an extension tube.

However, suppose I'd like to show a dandelion or flower in the foreground that fills the frame vertically, and at the same time show the infinite depth of field with a mountain or cityscape in the distance, behind the flower.

George Lepp, the nature photographer who first introduced me to Helicon Focus at a seminar, showed an image of an arch of an ancient bristlecone pine tree, with the mountains framed in the center of the "hole" in the tree. There is no way that a Scheimpflug tilt will cope with that. However, he had nothing but sky between the tree and the distant mountain that needed to be in focus, so careful Photoshop work would have been sufficient.

But what if the intervening details were also important -- what then?

So the question is this. Suppose I use the Canon 180mm macro and focus on the flower in the foreground, at close to 1:1 or whatever it takes -- maybe 1:2 or 1:5.

What strategy should be followed to get the distant mountain in focus and anything in between as well?

If I change the focal point of the lens, is the perspective going to change so much that the various frames won't match up? I clearly can't change the focal distance enough to make a difference, so changing the focal point of the lens is going to be a necessity sooner or later.

Should I consider making up one composite image of the relatively near field subjects, and then using panorama techniques to blend more conventional images of the intermediate and long range viewpoints?

For short differences in working distance, the normal recommendation would be to change the focus distance via a rail, while leaving the lens's focal distance alone, but clearly that won't work for an object at infinity.

Has anyone experimented with using a combination of Helicon Focus and panoramic photography to extend the coverage in multiple dimensions, X, Y, and Z?

Any help would be appreciated. I'm sure that I can figure this out eventually, but it might take multiple weekends of experimentation plus post-processing, with attendent frustration along the way.

Bob J.

snickgrr
Posts: 8
Joined: 02.01.2008 00:43
Location: San Francisco, Ca

Post by snickgrr » 03.01.2008 23:51

I did a quick and not too rigorous test of moving the rail vs moving only the back and keeping the lens in the same spot.
I shoot commercially with a medium format back mostly on a large format type camera, that is a non focusing lens with bellows and front and rear standards.
So for the first I focused the camera and moved the entire set up forward via the rail for each slice, for the second I kept the lens where it was and moved the rear standard forward for each slice.
Very similar results for both from an overall performance standpoint, there isn't any difference in overall sharpness.
Halos appeared in the same spots on both although the fixed lens series might be a teensy bit better.
It appears you need fewer slices with the fixed lens series and the focus shifts back through the scene quicker as well. It also appears you can do a deeper depth of focus with this method as the scene itself doesn't get bigger and thus go out of frame as it does when you do the advance the rail type setup. This can seen readily in the BackMove jpg.
There hasn't been any sharpening applied except for a small amount in Iridient Raw Developer.
Attachments
BackMove.jpg
BackMove.jpg (190.06 KiB) Viewed 3268 times
RailMove.jpg
RailMove.jpg (152.79 KiB) Viewed 3268 times

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