DIY Filter Project

In true Blue Peter style, Peter Bargh, makes a simple colour spot filter for use with your Pentax camera.

20/04/2012 - 00:00

Special effects filters have been popular since the 80s when the Cokin filter system exploded onto the market, furnishing photographers with all manner of crazy options.

Today most filters can be emulated using image editing software, but it's still fun to shoot through a filter when taking photos.

One type that was popular with wedding and portrait photographers was the colour spot or soft spot - a filter that has colour or diffusing material with a hole in the middle allowing the unfiltered part of the subject to appear in the center.

These filters are still available new from Cokin and Cromatek or you can pick up second hand options with brands such as Ambico, Pro-4 and Hoyarex.

Or you can make your own, with Pete's help.

What you need

• Coloured plastic
• Pen
• Scissors
• Craft knife or special purpose hole cutter
• Ruler
• Gelatine filter holder and adaptor

Step 1 Making your mark

First mark out squares on your plastic. I've used a Polyfile document folder. You could use large sweet wrappers, food cartons, large flat sided storage containers etc.



The square should be the same size as the gelatine filter that would normally go in the gelatine holder. You can hold the filter over the lens if you don't have a holder, or buy one here for the Hoyarex system Hoyarex Gelatine Holder  or Cokin A series A194 Gelatine Holder.

Measure and mark 72mm square for Hoyarex or 59mm square to fit the Cokin A-series holder

Step 2 Cutting the square filter

When the plastic's marked, use a pair of sharp scissors to cut out the squares. Using the Polyfile I had enough area to make dozens of filters. This particular material has a diagonal strip in the pattern so not only is it coloured and soft, but also has a slight streaking effect.

Step 3 Make the center hole

Now measure from one corner to the opposite diagonal corner and make a mark half way. This is the center for your circle. Unless you want to place the spot in a specific area - higher may be better for portraits. place a small coin or circular object and draw around it and use a sharp knife to cut the hole. I used a special hole cutter design for crafts which was just a few pounds off eBay. A Hole of around 10mm is fine for use with a standard zoom.

Step 4 Mount into the holder

Place the home made filter into your gelatine holder and slide it into the filter system holder.

Step 5 Attach to the lens and shoot

Screw the holder onto your chosen lens. In my tests I used a Pentax 16-45mm zoom which has a 67mm thread. Cokin make a 67mm adaptor for their A-series holder which was fine for this exercise.

The results

I took a few initial shots to determine which aperture and zoom setting to use. As you can the first photo below clearly shows the edge of the hole which is not a good idea. The lens was set at f/22 for this one. The middle photo is at f/4 and takes things to the other extreme where the center clear area is now not noticeable. Both photos were at 45mm. A slightly wider focal length of 31mm was set on the third photo and the f/4 aperture is now more useful. I used a similar setting for the second row of photos and show three photos to illustrate the scene without a filter and with yellow and blue spots attached.

Yellow filter small aperture		Yellow filter large aperture		Yellow filter wider angle
No filter		Yellow DIY filter		Blue DIY filter

Have a go at making a DIY filter and post your results in the Pentax User gallery. Also you don't have to make circle holes. Hoyarex and Cokin made other shapes including keyholes, hearts, stars, ovals and diamonds.

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