In the previous article we took a look at the focus stacking technique. We had to take a large number of photos and move our setup a little step forward each time we focus, in order to complete the clarity in areas where there is no sharpness.
If we’re shooting handheld, we hope to get sharpness in every region by relying on our luck and taking plenty of shots. But if we don’t want to leave the job to chance, we need a more controlled work. So we use a basic tool: the macro focusing rail.
Macro focusing rail
If you search for images on Google and write “macro focusing rail”, you will encounter numerous different products. It is really hard to choose a suitable one among them.
In order to use the focusing rail, our camera must first be fixed. It must be firmly fixed and not move back and forth as we touch it, or we cannot speak of precision. Our lens must be focused at a fixed distance. If we are using an autofocus lens, we need to set it to manual mode. Otherwise it will focus different points preventing sequential shooting for focus stacking.
In the focus stacking, we will step forward a small amount with the focus rail after taking a photo, paying attention to maintaining the camera’s position. In this way, we take a new picture and continue to shoot until the object is beyond the point of view. It’s better to use a cable or a remote control instead of pressing the shutter button manually. Or our framing may shift as the shooting continues.
How to set stepping distance using the focus rail
Let’s say we’re working on an insect. When we take our first picture, we focus on the closest region of the insect. We adjust the rail to focus on maybe the antenna, or the closest part of the eye and take the first photo. In the next photos we need to move forward by sliding the rail. The amount of scrolling depends on both the magnification and the aperture value.
I have a table that I share in some articles. It shows the depth of field (in millimeters) for different magnification and aperture values.
When selecting a step size, we must select a value smaller than the depth of field shown by this table. For example, when shooting in f11 at 1X magnification, the depth of field is 1.5mm. We can handle the work using 1.1-1.2mm stepping on the rail. But if we work at 5X magnification and f4, we need to choose a step size of 0.05mm. As you can see, there’s a 22-times difference between the two. In other words, if we shoot the same object, we need to take 22 times more photos in the second case.
Fortunately most of the time it is not so difficult in practice. Let’s think we’re taking a picture of a bee. Let’s do focus stack at 1X magnification for the whole body of the bee. At 5X, we can’t fit the entire body of the bee in the frame, so we’ll just focus (for example) on the eye and make the focus stacking as much as the depth of the eye. Since the object becomes smaller, the depth will be smaller and hundreds of photographs will not be required.
But the difficulty continues. How do we step a 0.05mm?
Which focus rail?
Forward only (two-way) rails are sufficient.
In some macro-rail models, there is also a right-left movement along with the forward and backward movement (4 ways), and some also has an up-down movement mechanism. These rails often can’t support the load as they move or cause vibration and ruin our framing. Actually we need these extra movements. Suitable tripod heads (like Manfrotto Junior 410) help us.
Our only need is a rail with a 0.05mm accuracy that can only move forward and back. We should prefer simplicity and precision instead of extra features.
Chinese focus rails
As with many devices, I made a mistake in choosing the focus rail when I started this work and tried Chinese products first. Unfortunately, even the term “rough rail” is too kind for these products. Since the diameter of the rotation screw is kept small, precise rotation is not possible. Since the screw pitch of the rail is coarse, you move like a horse-drawn carriage on a dirt road rather than a continuous sliding motion. Although it has a chance to work at magnifications such as 1X, it is far from being a product I would recommend.
If you have a good bellows, you probably already have a rail. Because most of the bellows, apart from the mechanism that determines the bellows length, also have a rail at the bottom that can carry the whole system back and forth.
The Asahi Pentax bellows I used here is a very high quality product. The movement on the rail is very consistent compared to Chinese devices. Thanks to this rail, I was able to work up to 8X magnifications with enlarger lenses by slightly closing down the aperture and sacrificing quality.
But when I started to use microfilm lenses and microscope lenses with much lower depth of field without aperture, my bellows rail became completely useless.
Microscope lenses and magnifications such as 10X are so sensitive that if I lean a little on my chair, it bends the floorboards in a way that I can’t normally feel. This movement, which is reflected on the tripod and camera on the same floor, moves the sharpness in the ant’s compound eye an ommatidia (one unit of a compound eye) length away! As a result of focus stacking, this gap is clearly visible. When I shared this situation with my friend, he laughed at first, then he was amazed when he experienced the same situation in his own home.
In such cases where micron-level precision is required, the bellows rail is unfortunately insufficient. Let’s leave the bellows there for now and come to the solution that is the subject of this article.
Newport Linear Stage
The Newport family of equipment is not really about photography. They offer sliding solutions for precision lab or CNC work. Newport is not the only brand. There are also brands like Thorlabs, Oriel, Sigma Koki, etc. that you will come across frequently when you follow them. But somehow almost all macro photographers I follow use Newport. I also got this product and as soon as I got it in my hands, it made me say “this is exactly what I wanted”.
Two solid planes sliding on top of each other and a micrometer to adjust the sliding are the components of this device. Above the planes, on both the top and bottom, there are numerous screw bearings for connection to other devices. As you rotate the micrometer, the two planes slide over each other in a surprisingly precise and smooth motion. So that you can rotate the micrometer one turn and not feel the movement.
Newport’s models suitable for this job are 423, 426 and 433.
The 423 and 433 are cousins. They have a ball bearing sliding device. The model I have is 423. This model offers about 25mm of sliding and has a carrying capacity of 15.8kg. The 433, which has a slightly wider surface of the same model, can slide 46mm. Its carrying capacity is 19.5 kg.
The 426 is a bit different technologically. It has a different sliding mechanism designed to carry heavier loads. It’s called a crossed roller. It is a bit more durable. It has a 25mm mobility and 33.1 kg carrying capacity. But this increase also increases the price by 2 times.
There are two different micrometers in these products. SM-25 and SM-50. As the name suggests, they offer 25mm and 50mm scrolling possibilities. The sensitivity is the same in both of them, 1 micrometer, that is, they allow movement with one hundredth of a millimeter precision. There is also an SM-13 that I sometimes come across, which is insufficient for photography with a 13mm opening margin.
Newport Linear Stage – Camera and tripod connection
I have already mentioned that these products are not made for photography. In fact, there is an important difference between the models. All these models are produced in two different types, metric (meters) and imperial (inches). The difference is in the screw holes. Metric models have an M at the beginning. Like M-423.
The screws in tripod systems are directly compatible with imperial Newport devices without the M in the beginning. They both use the inch measurement. The screws we call thin tripod screws (1/4-20) fit perfectly into these holes. The first Newport I had was the metric M-423 model. In metric models, it is only necessary to change the screws. It is necessary to use M6 coded metric screws instead of 1/4-20. You can find these screws in hardware stores. Since the metric system is used in Turkey, finding them is not a problem.
423 model should be preferred over M-423
If you can find it, go for the non-metric model. After a while, I also acquired the normal 423 model with inch system to back up this important part. I am using it now because the connections are much easier. The M-423 is waiting in reserve.
We will connect the camera or the bellows to the Newport stage. For this, an arca-swiss clamp needs to be installed on the device. Sunwayfoto is a brand known for its quality products. I will connect aSunwayfoto clamp to the Newport. There are also cheap solutions, but since it is a part that we will leave the whole system standing on it, it is necessary to choose the best one.
We put the clamp on the Newport and tighten the M6 or 1/4-20″ screws according to the type of device and that’s it.
Then we can fix the arca-swiss compatible plate that we attach to the bellows or under the camera on this clamp. If you have a tripod, you already have an arca-swiss plate. When the whole system comes together, a spectacular image emerges.
Not one but two rails
After explaining so much about which rail to choose, I will tell you that you actually need two rails, not one! Don’t get angry right away, here is the explanation.
You set up and stabilize the camera and place the thing to be photographed roughly in front of it. You surrounded it with a desk lamp for lighting, a flash, a series of diffusers, reflectors, background objects, etc. Occasionally your hand bumped here and there, shook it. Something changed position. You look through the viewfinder, an empty bokeh field. Or the insect itself moved and took a step, came forward or backward.
Or never mind all that, you just wanted to change the magnification. You changed the bellows length. The frame changed completely, the lens focused somewhere else.
You can’t move back and forth with the micron by micron using Newport to refocus. It already has a maximum of 25mm of movement. We want to save that for focus stacking.
That’s why we have to have a rough rail in our system. Preferably we do this with a bellows rail. If we don’t want to use bellows, we need to find another rough rail. Even the bad Chinese products I mentioned at the beginning of the article will do. As long as it is mounted firmly.
After finding a rough place to start with the rough rail, we fine tune the focus with Newport and bring the focus to the front point where the focus stacking will start. Then the serial shooting process starts.
So, how does this affect the results? Let’s look at the two photos below. It would be better if you click and open them larger.
These are two photographs of the same species of red ant taken at different times. The first one was taken by stepping with the Pentax bellows. I had to work really hard to get precise panning. I shot twice from the beginning to the end, giving the smallest possible movement. I thought I would have a chance to catch the areas I didn’t get the first time in the second shot. Then I had to look at all the photos from both shots again to sort them in order of focus, to determine which one was in front and which one was behind, and to file name them accordingly. If I took exactly the same area again, I deleted them. No matter how many tiny movements I tried to make and no matter how many times I took two shots, I couldn’t make the step interval small enough, so I ended up with a total of 17 images of the ant’s face.
When I posted the first photo on Flickr, I commented under the caption “a desperate effort”. I didn’t get what I wanted the first time, so I took this ant photo again after I got a Newport. This time I got 170 photos very easily and with comfortable rotational movements, not tiny touches, since the Newport allows more precision than necessary. The number of photos is so high because I included not only the face but also the body of the ant. But what I want to say is that this is possible easily and without error.
To perceive the difference more clearly, let’s zoom in on a part of the ant’s face in the two images. In the areas I have marked, we can see areas that are missing sharpness due to uncontrolled shifts of the bellows.
I think the difference is easily perceived. So where can we find these Newports? We three friends bought a total of 5 on eBay. We had to follow and wait for about 3 months for this. They are not very easy to find. And when they are found, different prices are seen each time. I would say around $200 on average. Since it exceeds the customs limit, when you order it, it will most likely be stuck in customs and you will have to go and pay the tax.
We couldn’t find Newport as a brand new product. We wrote to abroad, but there was no reply. There is already no sale in Turkey. I don’t know if there are any in Turkey at the moment except the ones we have. After this article was published, there were many friends who were interested. Probably some of them have acquired it.
Finally, I would like to emphasize again that this product is not the only solution. Similarly, you can use any solution that allows micron precision movement. There are many designs in the “Homemade” section on the site. Talented friends have produced their own solutions and shared them with us.