How to use Focus Rail?

[HaseebM]

Got myself a cheap focus rail to start with through eBay. Built is all steel but the movement is coarse. Anyway, I have a 100mm f/2.8L Macro and was wondering what are the steps? This is what I assumed should be correct:-

1. Place focus rail on tripod head.
2. Place camera with lens on focus rail.
3. Compose object and start either from bottom or top.
4. Move the camera by turning knob either forward or backward.

Now my question being, do I also change focus or leave the focus once set and then just turn the knob.

I assume I can do 1:1 or 1:2 or use other prime lenses on any object?

Thanks in advance.

[Inkanyezi]

Focusing for stacking can be done in several ways, and the stacking program takes care of aligning later.

The rail lets you move the camera once you have set focus, effectively letting you make focused "slices" of the object, which you intend the stacking program to merge into an image with greater depth of focus.

So you lock focus on the lens and move the camera with help of the rail.

You can also do it without the rail, by changing focus with the lens, which is easiest accomplished with a program that makes micro-adjustments of focus, as can be done with Magic Lantern and some Canon models, but it can also be done with a fully manual lens. In my opinion, doing it with manual focusing on a lens that is controlled with electric motors is not optimal.

Both these methods will create some mismatch between images, due to changes in viewing angle on the subject.

My preferred method for very small objects is using a bellows unit, with the subject and the lens locked in position and moving the rear standard with the camera body for focusing. This only creates a size mismatch (which is corrected by the program), but no perspective mismatch, as the lens and subject are fixed during the whole operation.

The rail can also be used for moving the subject instead of the camera.

[DanK]

Haseeb,

Start with the portion that is closest to you. The reason is that this is the largest view, and if you compose using the back of the image, you may lose material on the edges that you want. If you have composed using the closest material, then it makes no difference whether you start at the front or the back.

Re alignment: the software may compensate for small differences in alignment, but large ones are likely to be a problem. You should try to keep everything still.

For images in the range of 1:2 to 2:1, you don't need the rail at all. You can simply change the focus manually a small bit at a time. If you look at my site, you will see a large number of macro images in that range. Most of the flowers are stacked. I have never used a rail, or any electronic control of the lens.

Remember that regardless of how you do this, it is better to change focus too little between shots than too much.

If you find the rail easier to use, then by all means, use it. However, inexpensive rails are often more trouble than they are worth. For example, if the movement is coarse, you may find it hard to make small enough adjustments.

Dan

[rpcrowe]

Obviously when using any rail, you need a tripod solid enough to support both the camera/lens AND the extra weight of the rail.

I use an old Minolta rail which I found, used on eBay, for a rather low price several years ago.



This rail is exceptionally smooth. I credit most of the smoothness to the fact that the rail is not geared rather it rides on the three smooth rails.

I have never used a rail with coarse movement but, I can relate to the problems inherent when making minute adjustments working with a coarse unit. When I was a young Navy photographer, the standard Navy view camera was the 4x5 inch Graphic View and I hated it. The rail was geared which produced coarse, choppy adjustments. This camera dove me crazy, The Navy did not purchase these cameras because they were the best but because they were made in the USA. We had a drive in the Navy to "purchase American". While I agree with this philosophy, it really impacted the gear we had at our disposal.

As an example, rather than having Leica or Nikon professional 35mm camera gear. We were issued the Graphic 35 and the Kodak 35 which were not really even decent hobby cameras. Instead of using the Rolleiflex twin lens reflex, we were issued the Graphic 22 which, again, was not even a decent hobby camera. It was not until 1963 when I first used a Navy issued Leica M-2 35mm camera. What a terrific jump from the hobby cameras we were using. The Leica kits (M-2 rangefinder camera with 35mm. 50mm and 90mm lenses) put the 35mm format in a competitive place in Naval photography.

I thought that coarse adjustments were part and parcel of view camera work; until I had the opportunity to work with a Linhof 4x5 inch format view camera. What a great difference in ease of use and enjoyment of large format photography...

I don't know what to suggest regarding the coarse adjustments of your rail except that it just may be more trouble using than it is worth...

[HaseebM]

So I take it that I can the focus rail and yet change focus by a bit? Also am I limited to small macro objects or will this work on larger objects like a bunch of flowers for example. I have requested Manfrotto India to check availability on their 454 micro model which may be smooth. I am using a Manfrotto 055XPROB and 498RC2 head.

[Inkanyezi]

It certainly will work, within the range you can move the camera. That is if your rail has a 12 cm movement, that is also the limit of the DOF you can create by moving the camera upon it. It will certainly work for flowers, as long as you don't need greater depth than the length of the rail. However, using lens focusing may be a better alternative in that case, as there will probably be less misalignment due to the distance between your entrance pupil and the subject changing between shots.