{"id":521,"date":"2019-05-22T12:10:11","date_gmt":"2019-05-22T12:10:11","guid":{"rendered":"https:\/\/lensnotes.com\/?p=521"},"modified":"2020-05-24T10:53:11","modified_gmt":"2020-05-24T10:53:11","slug":"focus-finder","status":"publish","type":"post","link":"https:\/\/lensnotes.com\/darkroom\/focus-finder\/","title":{"rendered":"Focus Finder"},"content":{"rendered":"\n
\"Paterson<\/a>
Paterson Micro Focus Finder<\/figcaption><\/figure><\/div>\n\n\n\n

<\/span>What is a focus finder?<\/span><\/h2>\n\n\n\n

A focus finder, also called a grain focus finder, grain focuser or an enlarging focuser, is a darkroom printing tool. It is used to verify the correct focus of the image projected on the printing easel<\/a> by the enlarger. The focus finder is a simple optical device comprised of a front surface mirror and magnifying eyepiece. It reflects the projected image up from the easel and provides a highly magnified view through the eyepiece. This allows precise focusing of the grain structure of the negative at the exposure plane of the printing easel<\/a>. <\/p>\n\n\n\n

The device simplifies and streamlines the darkroom printing process, eliminating guesswork when focusing the enlarger. A darkroom grain focus finder is especially useful when printing very thin (underexposed) or thick (overexposed) negatives, or ones that lack fine detail to be focused by eye. This might be especially tricky if you have no easy way of turning off your safelight<\/a> for focusing. The grain focuser <\/a>helps in isolating the projected image from the safelight ambiance. As the magnified image allows you to see and focus on the grain of the film itself, it works just as well with images of all subject matters. <\/p>\n\n\n\n

Focus finders come in a lot of different shapes and sizes, but they all operate using the same principle. The Paterson Micro Focus Finder <\/a>pictured above is by far the most popular model out there. <\/p>\n\n\n\n

<\/span>A useful tool even when not printing<\/span><\/h3>\n\n\n\n

In addition to helping you focus the image while printing, this device can be a very useful processing tool. Negatives placed in the enlarger set at at a large magnification can be inspected with a grain focus finder, even if you do not plan to print them at the time. This way you can view and compare the grain size and structure of different films or development techniques at microscopic level. In some ways, the focus finder can replace a high-magnification film loupe<\/a>.<\/p>\n\n\n\n

The enlarger focuser also provides an easy, albeit rudimentary, way to observe the performance of your enlarging lenses at different apertures. Just monitor a section of a densely detailed (or prominently grained) negative while gradually stopping down the lens. If there is a dramatic improvement in sharpness you will be able to spot it this way.<\/p>\n\n\n\n

Do keep in mind that film type, development and printing magnification might make grain all but non-existent in some situations. Even so, with enough practice you will be hard pressed to find a negative you will not be able to focus with a grain focuser<\/a>. The device works just as well with black and white and colour negatives or transparencies and with all kinds of enlargers.<\/p>\n\n\n\n

\"Peak
Peak Enlarging Focuser type 2000<\/figcaption><\/figure><\/div>\n\n\n\n

<\/span>How to use a grain focuser?<\/span><\/h2>\n\n\n\n

Once you’ve grasped the principles of operation, using a grain focus finder is a simple and intuitive process. Learning how to use a grain focuser is one of the most important steps of mastering darkroom printing. If you are to use this device for the first time, follow the steps below. <\/p>\n\n\n\n

<\/span>Focus finder maintenance<\/span><\/h3>\n\n\n\n

A few things to keep in mind before you start using your darkroom focus finder. It is a delicate optical device that relies on precise alignment of the mirror and eyepiece in the housing. A drop, knock or any external force applied to the enlarging focuser might affect its operation. <\/p>\n\n\n\n

The front surface mirror these devices use is extremely sensitive. It should not be touched or cleaned except in extreme circumstances. For this reason many models like the Peak focus finder are equipped with covers that protect the mirror when not in use. The Micro Focus Finder<\/a> by Paterson has a shield that slides over the mirror when not in use. If dust ends up on the surface of the mirror it is best to gently blow it off with a blower or canned air. <\/p>\n\n\n\n

\"Paterson
Paterson focus finder with the eyepiece removed to show the calibration bar<\/figcaption><\/figure>\n\n\n\n

<\/span>Adjusting the finder<\/span><\/h3>\n\n\n\n

Some higher magnification grain focus finder models like the Paterson<\/a> and the Peak pictured above have adjustable eyepieces. To use one of these devices, you first need to adjust the eyepiece to your individual eyesight. This is best done in bright daylight. If your focus finder has a mirror protection shutter or a lens cap you need to remove both before adjusting the eyepiece. Most focus finders have a solid black bar in the centre of the viewing area that is visible at all times. Have a look at the image above that shows a Paterson focus finder with the eyepiece removed showing the calibration bar. You need to adjust the eyepiece correction mechanism until the black bar is perfectly in focus.<\/p>\n\n\n\n

There might be a locking screw holding the adjuster in place, loosen it to adjust and do not forget to tighten it back once you are done. Make sure the adjustment has not drifted out of when locking it. Other designs, like the Peak focus finder, use a lens ring style adjustment – a knurled ring around the eyepiece that you turn to adjust. Once adjusted, you will generally not need to touch it again unless your eyesight changes or another user needs to use the focus finder. <\/p>\n\n\n\n

Some focus finder models are designed to be viewed from a distance, and do not require viewfinder adjusment. One such model is the Kaiser Focuscop pictured below.<\/p>\n\n\n\n

\"Kaiser
Kaiser Focuscop Grain Focus Finder<\/figcaption><\/figure><\/div>\n\n\n\n

<\/span>Setting up for a print<\/span><\/h3>\n\n\n\n

Focusing is one of the last steps when setting up an enlarger for a print. It is best done either in darkness or with just a dim safelight<\/a> on. Before you star the focusing process you need to have:<\/p>\n\n\n\n