Article

Graduated Filters

Graduated filters can be neutral or coloured. Neutral grads, or ND Grads for short are used for controlling the dynamic range of images, stopping the sky and highlights being over exposed and burnt out. We have a specific article on ND Grads. ND filters that are not graduated are usually used to allow the exposure time to be increased, and are explained in another article.

In this article we are looking at coloured graduated filters.

All filters have an effect on exposure, and being graduated, these filters will affect one part of the image more than another so while not primarily being used to control dynamic range or exposure they will have an affect. In many cases an ND grad will be used in combination with coloured grads either to balance the exposure effect back to neutral or to change the dynamic range.

The options for coloured graduated filters is the colour, strength, and if a single colour or more than one colour. The colour can fade gently or faster over half of the filter or be a shorter colour section providing more of a coloured streak. These grads come singularly and in sets.

In colour photography the effects achieved alter the colours as we see the image, while when used in Black and White photography we can use coloured filters to affect the tones represented by different colours.

Unlike the ND grads, the effect achieved can be mostly created in editing, however some photographers like to create these effects in the camera at the point the images are taken. Some may view images taken to be 'original' while editing in the effects to not. Others may see the artistic ability in creating at the point the image is captured, while editing afterwards may be more to do with editing skills. We look at other ways to achieve effects in the article  Filters - Other solutions .

So what can we do with coloured grads.

• Make the sea or sky bluer.

• Add or enhance colour to sand or rocks.

• Enhance autumn colours, or even create them.

• Enhance sunsets or create them.

• Produce silhouettes against coloured sky's.

• Add colour to a lifeless sky or scene.

• Add warm up effects selectively.

• Possibly cancel colour casts from mixed lighting.

• Change tones represented by colours in B&W photography.

• Artistic creativity.

Coloured grads are as much a part of many professional landscape photographers kit as the ND grads, and often allow the striking images they create to be generated. In part their ability is in being able to look at an average scene, and imagine the effect they could create with one or several filters.

Lets take a few examples:-

• Perhaps its a 'normal' evening, you can see a fair view and its a nice enough scene. So how do you improve, well you could add an orange grad to colour the sky, perhaps a coloured streak across the image over the sun providing a sunset effect, perhaps you could use an ND grad to hold back the sky area, allowing the land to be lighter and more colour saturated.
• Perhaps, when on the beach, the sun is high and the sand is near white, near to us its lifeless and will mostly appear over exposed or near to this, the sea is 'average' and sky is bright with no clouds, So we add a yellow or orange grad from the bottom to colour the sand, perhaps also a light grad to darken the foreground a little more, and a strong blue grad from the top that gives us a striking blue sky and adds more blue to the sea.
• Perhaps we have a woodland scene in autumn, leaves are falling and its a nice location, but with little sunlight the colours are not going to show up that well. We can use coral, tobacco or chocolate coloured grads, and enhance the colouring, perhaps a darker one from the bottom and lighter one from the top, so that nearer items appear a brighter colour but the eye is pulled through the scene to the lighter areas.

The effects can be a single coloured grad or a composite arrangement using a number, and combining them with ND grads and a polarizer.

You have some suggestions by looking at the sets available, you can for example get several sunset sets, several landscape sets, autumn tint sets, and other arrangements but as all are relatively expensive you will probably want to start with a few and progress. You will find some duplication between sets. You will find the cost of smaller sizes appealing and perhaps opening up the possibility of greater experimentation. Unfortunately you will find the information available from filter producers of little help.

Using coloured graduated filters

White balance

You have to be out of auto white balance to get the full effects, if you operate with white balance in auto you are likely to find most of the effect is cancelled out. As you will appreciate selecting a different white balance setting, by using the setting of colour temperature, tricking the camera while setting PRE, using a different standard choice than the light conditions, will result in an overall colour tint to the whole image. For example setting the white balance at sun when taking sunsets improves the colour rendering of the sunset, and using a blue/grey card to set the PRE, will have a similar effect to using a warm up filter.  You could use a pack of postcard sized coloured cards, perhaps cut from mountboard to produce a range of overall effect. In each case the bias you are introducing is the opposite of the coloured card. Alternatively you could just have a table of K values, and have an idea of how much to add or take away to shift the colour, but as the scale is not linear this is slightly more tricky than it appears. In your camera white balance settings you are likely to have a setting, to allow the image to be warmed or cooled, with most Nikon cameras this is done when setting white balance on the camera body rather than menus, with the sub command dial. From the menus you will have the same but may have more options. The D300 for example has a screen that allows you to introduce a colour adjustment in any direction of the colour wheel and at different strengths.

Black and White camera settings

Some cameras have B&W settings, these either convert the image to B&W only or may have other choices to allow you to select electronic colour effect filters. The Nikon D80 for example allows the photographer to add electronic filters similar to those used by photographers using black and white and adding external filters The D300 does the same but also allows the image to be tinted producing a wide range of different image options. All of these selections, like the colour balance ones, are effective over the whole area.

Exposure

The affect on exposure of using a graduated filter of any type will affect the exposure of a part of the image. Usually you can use matrix metering and the camera will take care of the changes you have introduced. Most manufacturers show the filter factor of each filter so if you want you can calculate the effect, see ND grads to see how to work out filter effects. You may find information represented in different ways but the easiest way to use this is in stops of light, 1 stop is the same as 1EV. If you have an EV table the effect can be easily seen. Camera Images and Photography Skills clients can obtain a laminated 3 fold EV table, see the Camera Images customer support page in their main training website for details. If you have done some of their more advanced courses or an Exposure Masterclass you are likely to have been given one.

Effect of filter sizes

In the article Filter holders, we look at the options, the holder and size options available and the effects on the image. Many use a filter that is suitable for their largest lens. With this lens the filter may filter from nothing to full strength well within half of the image area, while with a smaller lens, only around two thirds of the effect is achieved over the lens area.

Affect of aperture chosen

The aperture chosen will have an affect on keeping the graduation or softening the graduated effect, as well perhaps in some cases of limiting the overall area effect of the graduation.

Representation on the camera rear panel

You will find the colour representation of the effects you are achieving is not fantastic on the rear panel. If using Raw, and you should be, then the image that you see on the rear panel is a small JPG image.  In the studio when using gold brollies, these give the models more suntan, the effects are not very noticeable on the camera, but often too strong when looked at in editing. Ideally therefore you need a laptop with you and a tent (or hide) to allow you to see the image clearly. If using a tent be aware that the colour of the tent material can produce the same effect as viewing the image under the wrong artificial lighting conditions. Many find this too much to take out except on very special landscape photography days, and therefore will perhaps try a variety of settings and then over time get to know which settings they liked and did not like.

Concluding

These graduated colour effect filters can be a useful addition to your armoury, but have to be carried. Perhaps for most of us its a special project application rather than carrying a wide array all the time.

I don't carry my full grad kits and coloured grads every time I go out. When I do its often in my back up bag in the car rather than connected to my main camera bag. In my large sized set I have in addition to 4 ND grads, 2x ND2, ND4, and ND8's, I have a three filter grad set for sunsets (yellow, orange and red), a light blue and light tobacco. Only if I have thought before about something special, or its a special photo day of some type, will I add other filters. I tend instead to carry my smaller sized grad kit most of the time and this doesn't have any coloured grads in it at present, but having looked again at this I can see some experiments and some additional filters I would like to play with, so this may change.

I would say that generally an ND grad or set is essential but a coloured grad set is not, as you have the option to create very similar effects in editing.  Its therefore perhaps something for those who have already mastered most other areas and looking for a new challenge, or perhaps those who are specialising completely in landscape photography, that may find these attractive.

See also: Filter Section for more articles.