I recently bought a new macro lens (paid for with an excellent month of sales in July!), and my research identified the real need for a macro focusing rail if I was going to do this properly. The Velbon Super Mag slider was the result. I bought the Canon 100mm f2.8 for two reasons – it seems to be the lens of choice for some great images on DP Challenge, and its review on The Digital Picture was very good as well. There is no way I can do a better review of a lens than they can! Incidentally, I bought my lens from a “used” seller on Amazon – about $100 less than the new price and a filter thrown in as well. The lens was in perfect condition – but that is another story!
Why do you need a macro focusing rail? Well, the main problem with macro photography is the extremely small depth of field. You can try to stop down the aperture to get more of the subject in focus, but that then requires more light (or a higher ISO), and after you pass F16 or F22, the quality tends to diminish a little as the diffraction of light around the aperture increases. As a result, many studio shots with a great depth of focus are as a result of focus stacking, where you take several images of the subject with a each one having clear focus on a part of the object. You then combine these in Photoshop, which blends the sharpest parts of each image into one composite photograph. You can do this by changing the focus ring on the lens to get the different parts of the image in focus, but I understand that this changes the perspective, and so the best way of getting focus stacking to work smoothly is to move the whole lens/camera towards the subject and change the areas of focus that way. Hence a macro focusing rail, which lets you move the camera in very small controllable ways to get focus exactly where you want it. Of course, the same approach lets you focus on a small part of the subject for single macro shots without having to move the tripod and risk disturbing the insect, say.
I looked around for various reviews of macro focusing rails. I wanted one that was sturdy, not too heavy, not too expensive, and had movements in both directions – towards the subject and from side to side to get the right position for the shot. After reading the reviews, I ended up with the Velbon Super Mag slider.
The unit has two main sections – a three rail unit with a long screw mechanism that moves the camera backwards and forwards about 2.25 inches (6 cm). It has a detachable sideways mechanism with three rails again that can move the camera 1.25 inches (3 cm). In the field, you would normally have both fastened together to allow the full range of movement, but for studio shots I preferred just having the actual focusing rail on the tripod. Why? It removed one potential piece of instability, and I just didn’t ever use it!
How stable is it – the main focusing rail is very solid. You move it forward with a knurled knob, and once in position, it stays there very securely. I found the horizontal slider to be slightly less secure. At each end of its travel, it is locked in place, but in the center, with the focus rail and a heavy camera on top, there is a little wobble. Of course, if you are using flash, this doesn’t really matter, and with a remote release outdoors, it would not cause problems, but this was the other reason I removed it for normal use. It is quick and easy to remove with an allen key (provided.)
I use Arca-swiss tripod mounting plates on my camera/tripod and always have one screwed into the bottom of the camera, and so I decided to buy an Arca-swiss mounting plate and connector combination. This makes it very easy to put the focusing rails on the tripod and add the camera with just a few twists of a knob. Not really essential, but it makes for a smoother workflow and makes it less likely that you would damage the camera by carrying the whole tripod/rail/camera combination around in one package.
I’ve used this a lot over the past couple of weeks, and I’ve got nothing but praise for its capabilities. I’ve really enjoyed my first steps in Macro, and the focusing rails have made this a lot more successful that it otherwise would have been.
One bonus – the rail can also be used to put the camera/lens on a tripod with the rotation point being under the nodal point of the lens. This means that the perspective of near and far objects does not change as you take the various shots for the panorama. Of course it needs to be in your camera bag, but if you plan to go out to take some panoramas, this will increase your chance of success!