In photography, a close-up filter (also called close-up lens or macro filter) is similar to a secondary lens attached to your primary lens, to provide a macro effect without requiring a macro lens at all. In other words: A macro filter will allow you to focus from a shorter distance to the subject and thus, create a macro effect on your pictures.
Now, as many of you might already know, buying new professional photography equipment is quite expensive. There is a quick rule you can generally apply when buying lenses: The better the lens, the more you will pay for. If you are not crazy about macro photography but you would like to take macro shots from time to time, I would not recommend investing your money in a lens which is specially designed for macro shots. Instead, you could invest your money in a set of close-up filters. Close-up filters are generally cheaper than purchasing a new lens and give beautiful results.
This article will show you how to work with close-up filters and will provide further details about them and what results you might expect by using them.
Working with Close-Up Filters
As already mentioned, a close-up filter or macro filter is nothing more than an additional lens that can be attached to an already mounted lens to your camera, by attaching it as a filter. The only cons of using such a filter is that you may experience severe aberrations (purple fringing) and loss of sharpness in your pictures. But that’s not a big deal, as your camera might have loads of pixels and you probably will end up adding your resulting image on Instagram.
Depending on the mounted filter a stronger macro effect will be visible. Take a look at the pictures below showing my tiny big bobby car – All images have the same amount of Megapixels and were taken with a EF 85mm f/1.2L II USM lens.
A macro filter has so-called optical powers, mainly marked as ‘+1’, ‘+2’, ‘+4’ and more. A higher power indicator will allow you to focus from a shorter distance than without the filter. You can put one filter on top of the other to reach further powers levels, such as ‘+3’, ‘+5’ and so on. For example to reach ‘+3’, you can mount the ‘+1’ and ‘+2’ filter on top of your lens. With an increase in the optical power level you may want to decrease the aperture of your lens. If you do not do so, you will have an insane bokeh effect on your pictures. Look at the following images, showing you the bokeh effect with different aperture settings.
Alright. Now that you know that adding a macro filter will help you achieve macro photos (what a surprise!), we will take a look at some maths to be able to work with them accordingly.
Calculating the required distances
In order to correctly focus with the filter mounted, you will need to adjust the distance to your subject, as with any additional power added, the closer you will have to get towards your subject. Whenever you are using a close-up filter, move your camera to the nearest possible focus distance to your subject, as this will make the maths possible later on. The minimum possible distance of your lens is marked on the focus indicator of your lens. It can also be found online by googling the name of your lens and typing ‘closest focusing distance’ and searching for your lens’ specifications. In the following image you will see that the mininum distance of my focus indicator is 0.95 metres / ~ 3 feet.
Now back to business. To determine the minimum distance required to focus with your filters mounted, you may refer to the following quick formula. For this example, we’ll use a power of ‘+4’ and an original fictional minimum distance of 2 metres. If you are working with feet instead of metres, make sure to change the amount of metres with the amount of feet.
Therefore, for a lens focusing at minimum 2 metres and a power of ‘+4’, you would need to move you camera to a distance of 0.22 metres. Now if your lens was only focusing at a maximum distance of 1 metre, with a ‘+1’-power you would be able to focus at … exactly – 0.5 metres. Easy maths. This is the main formula you will need to know to work faster and in an efficient way with close-up filters.
There is also a formula to calculate the maximum possible focusing distance. However, I would strongly advise to stick to the minimum distance formula – better work with defined numbers than with infinity. If you do it my way, you will not need to know that extra formula. I simply calculate the required minimum distance and adjust the distance from there by slightly moving – if even required – the camera to the back. With the same data as in the example above, with a power of ‘+4’ you would need to calculate the following:
You do not need to be a genious to calculate the distance required, but you should definitely invest some time in understanding how this is calculated, as it will make you work faster with your macro filters. Now that no more maths will be required, it is up to your creativity if you will reach great results with these filters or not.
Working with close-up filters can be fun. It may some time until you master to work with them, but it will deliver great macro pictures, without having to spend a lot of your budget on new equipment. Remember that you may experience some loss in sharpness as well as purple fringing when using close-up filters. You will find many different close-up filters at different price levels on the web. There are even sets of macro filters that you can get for less than 10$. The cheaper the filter, the more loss in quality can be expected.
Before you purchase close-up filters, you may double check the diameter of your lens’ filters, so you purchase compatible filters. The filter diameter can be seen on your lens as on the internet. For example, for my 85mm lens I had to buy a 72mm filter set.
One more tip: To achieve even better results with the close-up filters mounted, you may want to turn the automatic focus off and work with your live view with manual focus. When you are working with the live view, zoom in to check if the picture is sharp. And you may also want to use a tripod to not get shaky results.
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