Focus Stacking > Focusing Rail or Focusing Ring?

[l2oBiN]

Hello. I am interested in finding out whether a focusing rail would increase the quality of focus stacking captures. Currently I am tacking different planes of focus obtained through slight lens focusing variations. Obviously, att very high magnifications (>4-5X) this would become impracticle. What are your experiences and opinions on focus stacking in the field? Should I invest in a rail or not?

[elf]

The spreadsheet listed here will tell you how much DOF to expect at different magnifications: http://www.photomacrography.net/forum/v ... php?t=8054
The main purpose of the spreadsheet is to calculate focus steps when using the bellows draw, but it will also give you the DOF at any magnification.

And, yes, you need a focusing rail or bellows to do focus stacking. That is unless your name is Brian, aka LordV

[l2oBiN]

The spreadsheet listed here will tell you how much DOF to expect at different magnifications: http://www.photomacrography.net/forum/v ... php?t=8054
The main purpose of the spreadsheet is to calculate focus steps when using the bellows draw, but it will also give you the DOF at any magnification.

And, yes, you need a focusing rail or bellows to do focus stacking. That is unless your name is Brian, aka LordV

thank you for your advice. However, I am more after the differences and practicalities of using a focusing rail instead of simply the lens focusing ring/helicoid.

[elf]

It's far easier to use a focus rail than to manually focus the lens. LordV's technique of manually sliding the camera is an even better technique if you can master it. For shots from 1:1 to 1:4 it is possible to focus reliably using the lens. I used some red nail polish to divide my 35mm macro lens focus ring into 8 segments. At 1:1 24 images per revolution of the focus ring would give me a good DOF overlap. As the magnification decreases, the focus ring increment also has to decrease. By the time it reaches 1:4 on the 35mm lens, I can't reliably move it in small enough increments. I haven't used this technique after I adapted my spherical pano head to function as a focus rail.

You need to balance usablility vs reliability and repeatability. There are several posters here that are extraordinarily good at handholding and focus stacking field shots. And there are others, like myself, that can't handhold a shot at all

For field work I'd rate LordV's technique #1, focus rail #2, manually focusing lens #3, and using a bellows #4.

[PaulFurman]

Some lenses will change magnification significantly when using the focus ring. The focal length shortens like a zoom lens. When I use a lens like that hand held, I just rock my body to create a stack. Getting good shots that way needs full sun and high ISO. On a tripod, such a lens is maddening without a focus rail because the magnification changes so much. Tripods are frustrating anyways and I'm about ready to try a simple focus rail. Bellows are great but bulky in the field. The bottom part gets in the way of the subject.

It would be real nice to have a long focus rail on a tripod that had a counter-weight on the back so it had a lot of reach and was stable. Some telescopes have this kind of counter-weight.

[LordV]

I think fixed focus move camera is best at highish mags in the field. After quite a lot of practice I find this fairly easy on a solid surface but you can also do it using the leaf holding technique and resting the lens on the same hand. Mechanically a tripod/macro slider would be easier but you still have the potential problems of setup and subject movement if it's on plant. I often am able to cut off a leaf with a subject on (even with flying subjects) and place that on a solid surface for photographing before returning it to the same plant after.

Brian V.

[l2oBiN]

Ok.. let me rephrase my question.

Does focus stacking via rail yield better stacks than by focusing ring assuming identical number of focus planes were taken.

[AndrewC]

Ok.. let me rephrase my question.

Does focus stacking via rail yield better stacks than by focusing ring assuming identical number of focus planes were taken.

In my experience, yes, but it is not black and white and depends on magnification.

People focus stack landscapes - in that case you refocus !

In macro I alter distance - either by a rail or manually by "rocking", sliding or whatever. Once you get to 10x you have to use a mechanical slide, IMHO.

Andrew

[PaulFurman]

After writing some more, I remembered there's an FAQ for this question with some simple recommendations and complex explanations: http://www.photomacrography.net/forum/v ... light=rail My points below mostly relate to comfort/convenience, which isn't really your question but maybe still relevant.

For table top work it's more comfortable to turn a little knob on the side than reach up front between shots if you are doing cable release, mirror lockup, long-ish exposures, etc.

It depends on the lens being used, some might have quite fine focus control, some not even close to usable.

With a tripod in the field, a rail makes setting up a *lot* easier to get in position and compose the shot.

If the lens changes magnification when focusing, turning the ring is not going to work well for stacking. If the software has to scale a lot, one end will be enlarged or the edges will have to be cropped if you reverse order. This might not matter much depending on magnification.[/url]

[rjlittlefield]

Does focus stacking via rail yield better stacks than by focusing ring assuming identical number of focus planes were taken.

Study carefully the FAQ: What's the best way to focus when stacking?

If the same number of images are shot in the same focus planes, then the results will be essentially identical.

The advantage of a rail is that it may be easier to get even spacing, depending on the helicoid in the lens versus the gearing in the rail.

The rail will also give less change in magnification throughout the stack, but don't be misled into thinking that the change will be zero and that therefore the software would have to do "less manipulation" of the rail-shot images. With ordinary lenses (non-telecentric), there are always scale changes that need to be corrected.

--Rik