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Macro photography

 

Macro photography is the branch of photography where really small things are photographed at large magnifications. As a rule of thumb, magnifications of 1 and up are seen as true macro photography, meaning subjects have to be projected life size or bigger on the sensor. The choice of subjects at these large magnifications is nearly endless, and some are below. Depicted are: a lichen, a fly, a close-up of a butterfly wing, and a snow flake.

 

Higher magnification

 

Working at larger magnifications has three consequences:

 

• First of all, when working with distance rings or a bellow, the increased distance between sensor and lens means that part of the light is lost, which needs to be compensated for with regard to the exposure. In the scheme on the right, the sensor is represented as the gray bar on the right, and for a normal magnification, the image (the blue bar) is more or less fully captured by the sensor. But if we go to a higher magnification (by increasing the distance between lens and sensor), then we see that a large part of the image is projected outside of the sensor, causing loss of light hitting the sensor.

If you're using an SLR than this is not an issue, since an SLR measures the light that reaches the sensor, so it compensates automatically for the loss of light. As far as the viewfinder goes, it will get darker and darker as magnification increases, which can be a bit of a problem when working with high magnifications since it is more difficult to accurately see your subject through the viewfinder.

 

• The second consequence with increased magnifications is that diffraction also increases, which is why the diffraction calculator (which can be found here) can be adjusted with the effective aperture factor that the calculators below give (the effective aperture factor=magnification+1). The effective aperture can be calculated by multiplying the aperture number with this factor. E.g. a lens set at f/8 will have an effective aperture of f/16 when the effective aperture factor is 2 (8×2=16).

Below on the left is an example of this effect, where all pictures where taken at magnification 1, which means the effective aperture factor is 2. So where you'd think you're using f/16 and still be relatively safe with regard to diffraction, you are in reality using an effective aperture of f/32, which is already causing softening of your image.

 

• Third, the field of view captured by the sensor changes significantly when working at higher magnifications (so, like diffraction, this is only something to worry about when doing macro photography). Below on the right, focus is on the front part of the lichen. When looking at the second picture, where the focus is on the rear part of the lichen, we see that the picture has a slightly wider field of view.

 

There are several ways to achieve higher magnifications, and some of them are described below.

 

Higher magnification - extension tubes/bellows

 

Extension tubes are hollow tubes that you can put between the camera and the lens. By increasing the distance of the lens to the sensor, you can get bigger magnifications. Extension tubes only come at several specific lengths, so there is not so much room for adjusting the magnification. At the left side of the picture to the left you can see three extension tubes.

 

Bellows do the exact same thing as extension tubes, but with bellows you can alter the distance between camera and sensor back and forth as much as you want, which gives a lot more freedom. A bellow system can be seen in the right half of the picture to the left.

 

 

 

 

 

 

 

If you use extension tubes or a bellow system, then you can calculate your new magnification with this calculator.

Focal length (mm):

Original maximum magnification of the lens:

Extension tubes/bellow extension (mm):

New magnification:

Effective aperture factor:

New closest focus distance (mm)*:

* Focus distance is the distance between sensor and subject.

 

Higher magnification - reversed lenses

 

By mounting a lens reversed on your camera (there are special adapters to do this), you also increase the distance of the lens to the sensor, which gives bigger magnification. But it starts getting really interesting when combining a reversed lens with extension tubes or a bellow system, to increase its distance to the sensor even more. Below you can see a reversed 50 mm lens (left) and a reversed 50 mm enlarger lens (right), both mounted on a bellow.

Calculating what magnification you will get by just reversing a lens is difficult, this will simply have to be tested to find out. But, once you know the magnification of your reversed lens, it is possible to calculate the magnification of a setup of this reversed lens in combination with extension tubes or a bellow system. You can in that case use the same calculator above, and at "Original maximum magnification of the lens" you fill in the magnification of your reversed lens that you measured by testing.

 

A thing to keep in mind when using lenses reversed is that the backside of the lens is not designed to be used as the front element. This means that it is not designed to minimize flaring and such, and using a reversed lens can indeed be very sensitive to flare. Look at the pictures below, where there is a massive amount of flare in the first example. The photo on the right was taken right after the first one, and by aiming the camera in a different direction the flaring was gone. For some reason, blocking this kind of flaring by using your hand to block the light is not as easy as might be expected. This was with the nifty fifty reversed on my bellow system, and I got quite some flaring with this lens. After a while I switched to the old enlarger lens which does not have this problem.

Also, if you have used a lens reversed for a while and want to use it the normal way again, clean it thoroughly. It has most certainly collected dust which will end up inside your camera giving rise to nasty dust bunnies.

 

Higher magnification - combining lenses

 

By combing two lenses in a specific way you can achieve quite high magnifications. There has to be a main lens attached to the camera, and on that lens you will mount a second lens reversed (there are special adapters for doing this as well). If you, for example, mount a 200 mm lens on your camera and combine that with a reversed 50 mm, you will get a magnification of 4 times (200/50=4). In my hands, this technique is fun for trying, but not too practical in the field.

Focal length of the main lens mounted on the camera (mm):

Focal length of the second lens mounted reversed on the first lens (mm):

Magnification:

 

Higher magnification - microscope lenses

 

Lastly, you can of course equip your camera with a microscope lens. In this case, there is an important difference between infinite and finite lenses.

Finite lenses project their image at a finite distance, and all they need is a distance tube (or distance rings/bellows) of the right length to use them on a camera.

Inifinite lenses project their image at infinity, and they need to be combined with a lens of an apropriate focal length (and with that lens focussed at infinity!) to obtain an image. In principle, having an infinite microscope lens on top of another lens works according to the same principle as the aforementioned method of combining two lenses, where one lens was reversed. Therefore, the focal length of the microscope lens can be calculated by using the same equation backwards. So an infinite microscope lens giving a magnification of 10 and specified to use on a 200 mm lens has a focal length of 20 mm (200/10=20). This calculation is what the calculator below does.

When you know which focal length your infinite microscope lens has, you can even go back to the previous calculator and calculate what magnification you will get by mounting it on lenses with different focal lengths. However, microscope lenses are not designed to be used in a broad range of magnifications, so you might get some increased aberrations or vignetting as a result.

Focal length of the main lens mounted on the camera (mm):

Magnification of the microscope lens:

Focal length of the microscope lens (mm):

Microscope lenses do not come with an aperture number like photography lenses do, but in stead they have a value for the numerical aperture (NA). The bigger the numerical aperture, the smaller the depth of field and the higher the resolving power of the lens.

If you know the numerical aperture of your lens and its magnification you can calculate its aperture number (f/#). However, at such large magnifications, the effective aperture is what is important and should be worked with. The calculator below calculates the effective aperture for your microscope lens.

Numerical aperture:

Magnification of the microscope lens:

Effective aperture (f/):

Another thing to keep in mind with infinite microscope objectives is wether the lens is corrected for chromatic aberration or not. Some are not because they are designed to be used in combination with specific microscope eye pieces that cancel out the aberrations. So uncorrected lenses are pretty useless for combining with a camera.

 

Lighting

 

As with conventional photography, using direct light or diffuse light makes a lot of difference. Direct light gives harsh light and strong contrasts, which does not look too good most of the time. The solution is to use a diffuser, giving a lot softer light. Below are two examples of this principle.

 

There is another reason for using diffuse light with macro photography; since magnification is so big, direct light can give rise to very noticable iridescence in your photos, which are patches of very colorful reflections. Below are two examples, and in the case of the lichen you can see how the iridescence disappears when using diffuse light.

 

Lighting - flash

 

A flash is a very covenient way of lighting a macro subject, but, just as with natural light, diffused light is the way to go in order to prevent unwanted artifacts as described above.

 

To the right are some examples of how a flash can change the lighting. The first picture is only flash light, and in this case the background looks a bit too dark. By using only natural light, the background becomes lighter, but now the subject becomes too dark. The solution is to use the flash at a lower power and to use it as a fill flash in stead. The result of that can be seen in the third picture, which is the most balanced of the three.

 

This way, the background in macro shots can either be lit by the flash or lit by natural light, or it can be dark or even completely black, depending on your setup and if you use a flash or not. Examples of both are shown below. I think both effects have their strengths and weaknesses and I actually like them both, but some people have a strong preference for one or the other.

 

When using a flash, there will inevitably be a reflection of its light on shiny parts of your subject. This is something to keep in mind, since the shape of your flash/diffuser will be visible in some cases, which might not be what you want. A large diffuser minimizes this effect, but getting rid of it completely is difficult. In the case of the beetle below it is not that prominent, but still noticeable on its shield. In the case of the spider the reflections are very clear in the eyes. In fact, when zoomed in to 100%, you can see my lens, the diffuser on top of it, and even three of my fingers holding the camera. The reflection is that clear!

 

normal - 100%

 

Focus and perspective

 

A common rule of thumb in animal photography is to have the focus on the eyes of the animal, and macro photography is no exception to this rule. Below are two pictures of flies where I did not have the eyes in focus, and the result is not very pleasing to look at, even though large parts of their bodies are in focus. We humans are naturally focussed on the eyes, and therefore having them in focus is often quite crucial.

 

Since macro subjects are so small, they are often most easily photographed from above. However, by photographing them at eye level, the bugs come more or less alive and they get a lot more personality. At least that's what I think. Below are two examples where this difference is pretty clear.

 

Field of view

 

If you know the magnification of your macro set-up, then the field of view can be calculated using the calculator below.

Sensor dimensions (mm):

×

Magnification:

Field of view (mm):

×

 

Depth of field

 

Working with an extremely shallow depth of field is probably the biggest challenge in macro photography. By keeping the whole subject in the plane of focus, you can circumvent this to a certain extent, as in the examples below. But, especially at really high magnifications, the depth of field might not even be sufficient for that. On the other hand, the shallow depth of field does a very good job at removing disturbing objects in the background by blurring them. Also maybe good to know is that the depth of field at these large magnifications is distributed 50/50 in front and behind the plane of focus (more on that here).

 

This calculator gives the depth of field for your particular set-up.

Circle of confusion (mm):

Magnification:

Aperture (f/):

Aperture given above is effective aperture:

Depth of field (µm):

Nominal aperture (f/):

Effective aperture (f/):

 

Focus stacking

 

A very effective way to deal with the shallow depth of field is by simply combing lots of photos with different focus points to give one photo where all the sharp bits from each individual photo is combined. This is a process called focus stacking, and more information about it can be found at editing/focus stacking. This process can be done both with a tripod, or handheld. The handheld process can be quite a challenge though, but it does work once you get the hang of it. Below are two examples where I combined a bunch of photos to yield a focus stack. The moth photo was a controlled setup in my living room with the camera on a tripod, the NSFW beetle photo a handheld focus stack out in the field.

 

Focus stacking - step size for focus stacking

 

When doing focus stacks, a safe step size that will give sharp focus stacks can be calculated. This is not exact science, but more of a guideline. Using a smaller step size is no problem, but will simply give more photos to process. However, using a step size that is too large might result in blurry bands in the end product.

 

On the right are some examples with different step sizes (all photos are at 100 %). For this set-up, a safe step size of about 9-10 µm was calculated, and the first example with a step size of 8 µm clearly gives a stack that is sharp throughout the whole picture. Using a step size of 17 µm is still acceptable, but already starts showing some parts with reduced sharpness. Using even larger step sizes such as 33 and 67 µm gives unacceptable results.

 

The calculator below gives the step size to be used for focus stacking, as well as the depth of field for your particular set-up.

 

 

Circle of confusion (mm):

Magnification:

Aperture (f/):

Aperture given above is effective aperture:

Depth of field (µm):

Maximum step size for focus stacking (µm):

Nominal aperture (f/):

Effective aperture (f/):

 

Focus stacking - stacking artifacts

 

Whenever there is dust on your sensor, this will probably show up quite clearly on your focus stack. If you have made the stack with the camera on a tripod, it will most likely look like a stripe, as in the first example where there is a stripe made of seven spots at the bottom, which is the result of combining seven photos for this focus stack. On the other hand, if the focus stack was made handheld, as in the example below on the right, then the dust spots will show up randomly on your stack. In this example there are five spots randomly scattered around in the upper right quadrant as a result of combining five photos for this focus stack.

 

Another effect is when a small creature enters the scene during your focus stack without you noticing it. That has happened many times I must say, and often I did not notice this before opening the pictures home on the computer. Below on the left is an example of that, where a little creature wandered into my frame from the left, leaving a spotted trail in the focus stack.

And then there is of course the possibility of the subject itself moving around, which is the rule rather than the exception in my case. If that happens during the focus stack, than you can end up with strange artifacts as in the example below to the right, where the antennae miraculously got cloned.

 

Wide-angle macro photography

 

After finding this article and seeing the amazing photos taken with that set-up, I simply had to try wide-angle macro photography myself, which was easier said than done.

 

Wide-angle macro photography - peephole lens

 

I first tried to use an old-fashioned peephole lens connected to a macro lens (see below to the left), which was quite easy to handle (no upside down image, more light reaching the sensor), but gave very low quality images, as can be seen below to the right.

 

Wide-angle macro photography - GoPro lens

 

After finding out the peephole lens set-up did not look too promising, I ordered a replacement lens for a GoPro, and connected that in a similar way as is described in the aforementioned article. In my case I used a bellow fitted with a reversed 28mm lens, which works ok, but a wider lens would have been nice to prevent vignetting upon stopping down the 28mm lens.

This system gives an upside down image, making framing quite a challenge sometimes, although I got used to it after a while. Also, very little light reaches the sensor because of the manual aperture, so the viewfinder is pretty useless in this case, and LiveView is the way to go. So this set-up is not too easy to handle and image quality is a far cry from the usual quality with a DSLR. But the set-up is a lot of fun to use nevertheless.

 

Some examples taken with this system (more examples taken with this set-up can be found here):

 

You can get really close to your subject with the set-up, even close enough to allow them to climb onto your lens! The picture to the right is the shield bug from the left photo taking a walk on my lens.

 

Finally, some photos of animals taken at approximately the same magnification, both with a wide-angle set-up and with a conventional set-up. A lot more of the surroundings ends up in the photos with the wide-angle system, which can be both bad or good, depending on what you're after with the photo.