4

I am interested in doing focus stacking for macro shots and from what I understand there are two techniques for doing this.

One is to use a macro rail that adjusts the length to the subject (e.g StackShot)

The other is adjust focus in the lens either directly via the lens ring or through remote live view by picking the focus point (e.g Canon's EOS Utility lets you pick focus points remotely).

The second approach to me seems a lot easier and faster so I am wondering why anyone would use the rail approach. Is there any advantage of the rail approach? Has software which lets you remotely pick focus points (which essentially drive the lens motor) basically made the rails technique obsolete?

4

A macro lens' maximum magnification can only be achieved at minimum focus. So to get maximum magnification you must move the camera towards or away from the subject to focus a specific area of it. That is the main advantage of using a focus rail.

In the case of stacking images, though, maximum magnification in every frame is probably of secondary consideration to maintaining a consistent field of view and perspective in each frame.

So the best practice would seem to be to use a frame rail to focus on the nearest part of the subject you want to be in focus with the lens set to the MFD, and then use the focus adjustment of the lens to take subsequent shots at longer focus distances. This assumes you are using a lens that does not exhibit focus breathing.

2

A lot would depend on whether you need continuous focus through the scene or have more discrete points of interest. A micrometer (geared) rail can make it very fast and easy to make sure that you have complete coverage of the depth of a scene with greater precision than manual focus simply because the adjusting mechanism is finer and the scale is linear. Like creating a good HDR sequence, not missing an exposure along the way makes the software's job a lot easier. Live view and AF can be quicker and easier if you have, say, overlapping elements that need to be sharp but large (relatively speaking) gaps in the image field where nothing in particular needs to be captured, but it can be difficult to pick appropriate points of focus if you need continuous depth.

That said, if your lens is a true internal focus lens, the field of view will remain constant as the focus changes. If you use lens focus with such a lens, the relative positions of everything in the frame will be consistent from exposure to exposure, and you will get more accurate alignment/stitching, less distortion to deal with and less detail loss (no interpolation or scaling will need to happen). The macro rail, or a unit-focus or hybrid-focus lens will always change both the magnification and the relative position of things in the image, making the construction of the final image more destructive. It would then be worth using the lens focus (manual or AF) even if it's slightly more difficult to do so if ultimate image quality and resolution is the goal (and let's face it, our cameras are often capable of giving us much more than we actually need, so throwing away a few pixels isn't necessarily an unforgivable sin). You would need to test your lens to see whether or not it actually keeps things in place and in perspective as you focus.

0

A macro rail will let you perform fine compositional adjustments, rather than either moving the subject or camera and support - both of which are rather clumsy methods of adjusting composition when considering macro photography...

  • This is not what I am asking per se. Lens focus selection can be done without moving the subject or the camera... – numan Mar 29 '15 at 19:33
  • Yes, the focus selection can be done, as you say, without moving the subject or the camera. However, if you want to adjust the composition of the image a macro rail will help and avoid the need to perform clumsy adjustments of camera or subject. Other than for compositional adjustments, a focus rail will be of little interest to you but this is one of the reasons why macro rails are still made. – Darkhausen Mar 29 '15 at 19:51
0

Rail Pro: Easy to make fine adjustments without deranging your composition or moving the tripod once set up Good method for focus stacking, moving through the planes is always linear

Rail Con: Can move your camera away from the tripod's center of force downwards, increasing risk of low speed oscillation or settling of a light tripod

Lens Focus Pro: No extra gear to carry around Faster set up

Lens Focus Con: Composition changes mean moving the tripod Many lenses have focus breathing Usually have to manipulate the camera off-axis, increased risk of disturbing the composition

( as a side note: if you're never used a geared tripod head in combination with a rail you're really missing out on a great way to fine tune macro compositions. You're also missing out on a lot of extra weight =P )

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.