RONCHI

The Ronchi test is a very usefull tool to utilize and should be used at al cost. The problem is the expense and the trouble of aquiring a Ronchi screen can be discouraging. Lets face it if you can't borrow one , $14 US is a lot to pay for a 1" square piece of transparent film with a few lines on it , particularly if your only going to make one mirror. But alas I have a simple solution for you.

I have come by one simple method of making your own Ronchi screen using monofilament line as well as another which happens to be a little bit more involved but definitely worth the effort. The first method involvesusing a monofilament line , and with my personal method I use my Practica MTL5 35 mm camera, Black and white film and a home made grid.

METHOD #1

I can't take any credit for this method as I came by it some time ago while surfing the web but I found it to be logically sound .

1) Get yourself some monofilament fishing line ,the lighter the test strength the better. Cut 2 pieces of stiff thin plastic or metal 1" Square . Get some 5 min epoxy , a razor knife and a 3/8" drill bit.

2) Square up the two 1" pieces of plastic or metal ,clamp them together and drill a 3/8" hole through the centre of both of them .

3) Wrap two strands of monofilament line around the two 1" pieces over their full length, be cafefull not to overlap them.

4) Remove one of the strands of monofilament line without disturbing the second .

5) Glue the remaining monofilament line to the face of the 1" square on both pieces.

6) When the glue has set ,cut the monofilament line between the two 1" squares.

7) You now have two matching Ronchi screens.

If you feel daring prior to wrapping you can dye the monofilament line with black fabric dye so long as it is nylon.

METHOD#2

This is my favourite way to make a Ronchi screen and it may well be easier depending on your perspective and the skills and equipment you have at your disposal.

1)Lay out a grid of verticle or horizontal lines ,tape it square and flush to the wall .The larger the grid and the wider the lines the more accurate your end product will be .A frame of 35mm film is approximately 1" high by 1.4" wide ,so remember if you are going to fill your veiw finder with the grid of a 100 line per inch ronchi you need a grid with 140 lines on it . I have one below for your convenience some cutting and pasting may be required.

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2) Purchase a roll of black and white film. C43 can be developed using the same chemicals as colour and can be developed at any 1 hour photo shop. Propper black and white film is superior, as it doesn't have a nasty purple tint to it but costs much more to develop these days.

3) Set your camera up on a tripod using a standard 50 mm lens and a flash. You must use a remote cable when shooting, any movement is too much movement. I shot with 400 iso at F16.

4) Square you camera up with the screen and shoot away . Remember to remove any reflective objects from the vicinity as the may cause lens flare.

5) Experiment with different grids for best possible results. Your negatives will be your ronchi screen.

From one 24 exposure roll of film you could quite possibly make 36 square inches of Ronchi screen , that's $504 US or $775 Canadian. Big savings if you ask me for an investment of $12 for film and development.

If you still insist on purchasing one , here are the guys you want to talk to. http://www.edmundoptics.com/IOD/DisplayProduct.cfm?productid=1731

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