Making the Most of Medium Format: Make your own Rangefinder for Zone Focus Cameras 34

When I ordered a new Belair X6-12 I was worried that the shallower depth of field on the 90mm lens would lead to lots of out of focus shot and waste my precious 120 film. Not any more, with this amazingly simple rangefinder that can be customized for any zone focus camera.

Medium format photography is great. You get huge negatives with an amazing level of detail. The release of the new Lomography Belair X6-12 immediately had me drooling over its expansive 6×12 format but medium format can also have its drawbacks. With the longer focal length lenses you tend to get on medium format cameras you get a shallower depth of field. This can be used creatively but with a zone focus camera you can end up with lots of out of focus shots.





Shallow depth of field from medium format film

Before we dive in to this tipster it might be useful to have a quick recap. A rangefinder is a device which allows you to accurately measure the distance between yourself and a fixed object. They have been used for many years in photography to allow accurate focus on cameras which don’t let you see the actual projected image. This includes all of Lomography’s cameras which are either fixed focus or zone focus.

Fixed focus lenses are designed to work at their hyper-focal distance, the distance at which the maximum amount of the scene in front of you is in focus. Fixed focus lenses are often helped by being: A) fairly wide angle to increase the depth of field; B) having a smaller aperture, again to increase depth of field; C) often having a closest focus distance of around 1m away. With this type of camera, focusing is taken care of for you and as long as you don’t try to get too close, everything will be in focus.

Zone focus cameras require you to actually focus them to achieve sharp results. Some of us are better at this than others but I’ve found that I often end up with slightly out of focus shots. With the 90mm lens on the new Belair X6-12, the depth of field at f8 can be as little as 15cm. This is great for portraits with bokeh filled backgrounds, but not so great if you don’t focus correctly and leave your friend looking like a mushy blur.

To overcome this problem, this nifty rangefinder uses your eyes and outstretched arms to triangulate the distance to an object. It isn’t as accurate as a proper rangefinder but it will get you very close indeed and take a lot of the guess work out of focusing.

To make the rangefinder you will need the following:

A tape measure

A friend to help to help you

A computer with a printer and PDF software

software Paper or card to print on

Colouring pens to make your rangefinder easier to read

Step 1

Measure the distance from your left eye to a piece of paper in your outstretched left arm. This may be easier if you have a friend help.

Step 2

Measure the distance between the centre of youR two eyes (you will really need a friend to help here). Try to be as accurate as possible with this measurement. A small error hear will multiply up to be a much bigger error in distance to the object.

Step 3

Simply plug these numbers in two this amazing website and hey presto! It takes care of all the math for you. You will need to include the focus markings on the lens which for instance might be 1m, 2m, 3m and infinity. You can also include extra focus points not included on the lens to allow extra accuracy in focus. More on this in a minute.

Step 4

Print the card following the instructions on the website. You need to print at 100% magnification to ensure the card matches your measurements. I am lucky enough to have access to a plastic card printer so I used that to make one that fits nicely in my wallet.

Step 5

Colour the card in with permanent marker pens to make it easy to spot the change in distances.

Using the rangefinder

To use the rangefinder hold the card at arm’s length in your left hand and look through your left eye. Line up the left edge with the object you want to measure, then close your left eye and look through your right eye. The object should have shifted relative to the card. Look where it is now along the scale of the card and this will be the distance to your object. It can be useful to flick back a forwards a couple of times to make sure you aren’t moving your arm.



The hanging ornaments are 2m away

If you really are right in the middle of two markings, it is probably safer to go with the distance on the nearer marking, firstly the scale is not linear and halfway between two markings on the card is not half way in distance to the object. Also lenses give greater depth of field behind the point of focus than in front so you’ve a better chance of getting it in focus if you go for the closer marker.

The website above also gives the option to include a hyper-focal chart on the card which is great if you don’t want to worry about focusing your camera. Unfortunately for any new Belair owners the formats supported only go up to 6×9 so if you are using it at 6×12 you are out of luck.

As a bonus tipster, I mentioned previously that you could include extra lens markings to improve the accuracy of your focus. The instructions for this are below:

Step 1

Start by measuring on the card, the distance from the closest focus the camera can be set to (for instance 1m), to the infinity marker. In this case it is 4.7cm. Note, don’t measure all the way from the left edge!

Step 2

Using a tape measure, work out the total distance that the lens has to move to go from 1m to infinity. In this example it is 2.7cm.

Step 3

Dividing 2.7/4.7 gives us a figure of 0.57. This is the factor by which we multiply to work out the new lens markings.

Step 4

If I wanted to add a new lens marking for 1.5m I would measure the distance from the 1m mark on the card, to the 1.5m mark on the card; this is 1.5cm. Then I would multiply this by 0.57 giving 0.86cm. For the purpose of practicality I’m going to round this up to 0.9cm

Step 5

Using a tape measure, measure 0.9 cm from the 1m mark on the lens and make a new mark for 1.5m. Repeat for other intermediate markings. On my Diana I now know that 1.5m lines up with the first head of the small group of people on the 2-4m mark.

It is both easier and more important to do this for close focus distance rather than far distances as the difference between lens markings is larger at close distances and depth of field is shallower.

I hope you find these tips useful!