What Is a Centre Spot Filter?

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What Is a Centre Spot Filter?

A centre spot filter is similar to a diffusion filter and can be used on a camera to create special effects on an image. The middle of the centre spot filter is usually made of clear, flat glass or may even be a simple hole in the filter. The outer part of the filter is diffused and may even be a different colour. Using a centre spot filter to shoot an image means that the centre of the image that is produced will be clear and sharp, while the outside of the image will be blurred. This effect will help to add emphasis to the centre of the image and is often used for portrait shots. It is particularly popular for wedding portraits when the soft focus surround is commonly used to add a romantic feel to a shot.

Types of Centre Spot Filters

There are several different types of centre spot filters, and although they all operate on the same principle of blurring the outside of an image, not all types of centre spot filters may be suitable for every camera, so it is worth considering each type before purchasing.


Diopter filter


This is a filter where the centre is a hole and the outside is made of diffused glass. This means that the centre of the image is recorded sharply and the outside is blurred. The degree of blurring in the outside of the image can be altered by changing the focal length of the lens and making the size of the aperture opening of the camera bigger or smaller. The only major issue with using a diopter filter is that although the blurring effect will be present, it is possible that the ring around the hole in the centre may also be apparent in the image. This can be alleviated by taking great care over how the camera is positioned but that can take time and effort. The use of an amount of lens shading can also help to remove the ring from the image.
 

Soft Spot Filter


This is a centre spot filter where the middle of the lens is made of clear glass and the outside of the lens contains small diffusion filters which help to give the blurred effect in the image.
 

Cokin's Radical Zoom


This is a particular model of a centre spot filter and is a variation on the soft spot filter type. It has the clear glass centre, but the outside of the lens contains many tiny concentric circles which are very close together. The dense circles have the effect of spreading the light that enters the filter which then creates the blurred effect on the outside of the image.
 

Points to Consider

Although a centre spot filter can add an interesting effect to certain shots, there are several issues which need to be considered in order to guarantee that a successful image will be produced.

Size

The majority of centre spot filters produced are at least 46mm in size, and many may be even larger. The size of the centre spot filter could have an effect on the image which is produced as the clear centre will be bigger on a centre spot filter that is larger in size. A problem could arise if the size of the clear centre of the filter is the same size as the opening of the lens of the camera. This will completely remove the centre spot effect, and the filter may actually reduce the quality of the image that is produced as it becomes just an additional piece of glass which is placed over the lens. The other potential problem to be aware of is that using the zoom on the camera may end up making the clear centre too big and may even result in the clear centre covering the entire image. A centre point filter can produce interesting images, but it is vital to check the size of the filter against the size of the camera lens before deciding on a model to purchase. The general rule is to try and use a soft centre filter with a camera that has a long focal length and that has a lens with a large aperture. That should stop any major issues occurring.

Impact of Light and Background

It is worth considering what type of shots the soft centre filter will be used for before choosing which model of filter to buy. If the filter will be used for shots which are generally well lit and where there is a uniform background, then a radical zoom type of soft centre filter will generally produce good results. However, using a radical zoom filter for an outdoor shot where the shot is lit by sunlight can result in the circles on the filter becoming visible with a flare effect on the image. A diopter filter may produce good results in situations which may not be evenly lit if lens shading is used to equalise the lighting. Lens shading will also reduce any harsh light which could cause a flare effect on the centre spot filter.

To Find a Centre Spot Filter on eBay

When searching for a centre spot filter on eBay, it is necessary to open the eBay homepage and then to click on the All Categories link at the top left side of the homepage. Every category on eBay will then be displayed, including one for Cameras & Photography. Clicking on this link will pull up a list of subcategories, and it is then necessary to click on the link for Lenses & Filters. The next set of sub categories will be displayed, including one for Filters. Clicking on this finds a list of types of filter, including a link for Special Effect . The last list of sub categories includes a link for Centre Spot , and the final step is to click on this link. A complete list of the centre spot filters that are for sale on eBay will then be listed. The search can be refined further if required as there are also links to main brands such as Hoya and Cokin . There is the facility to perform a direct search for a centre spot filter by making use of the search bar which can be found at the top of every eBay page. Entering specific keywords such as ''centre spot filter round'' will pull up a list of all of the types of filter that are available to buy.

Conclusion

The use of a centre spot filter can help to produce an interesting effect on an image, particularly if the aim is to concentrate on the centre of the image and ensure that it is the focal point of the shot. It is vital to consider the specifications of the camera that the filter would be used with before deciding which filter to purchase. Soft centre filters will really only produce good results when they are used with a camera that has a very long focal length and a larger aperture. It is worth being aware that shooting an image using a centre spot filter could take more time as the camera may require careful positioning, and it may be necessary to use additional tools such as lens shading. All of the different types of centre point filters can produce good and interesting results if they are used with a camera which has the necessary specifications and if sufficient care is taken with details such as lighting and the background. A centre spot filter can be a useful piece of camera equipment and will enable the user to experiment with images and effects.

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