The QuickDisc is a simple and useful tool for the determination of exposure compensation when photographing small objects with large format cameras. The use of the QuickDisc involves no calculation, it is lightweight, easy to replace and free for personal use. It consists of two pieces of cardboard, the disc, and the measuring strip. The measuring strip is marked in tenth of an f-stop, giving more accuracy than you will probably need. To determine the exposure compensation, you place the disc next to the photographic object and then measure its apparent diameter on the ground glass of the large format camera.
Similar devices are not unknown among large format photographers. The new idea of the QuickDisc is the round shape. With a rectangular device, you have to care that it is perpendicular to the optical axis, or it will be foreshortened and therefore give an incorrect reading. With the circular Quick Disc you do not have to worry about the orientation, you just have to measure the largest diameter to get an accurate reading. A detailed description of the Use of QuickDisc is available in the manual
You can print a copy of the QuickDisc on you own printer after downloading the QuickDisc file.
When photographing small objects the increased lens to film decreases the effective f-stop. This is not a problem with modern 35mm and most medium format cameras, because they meter the exposure through the lens (TTL). But only few large format cameras are equipped with such sophisticated metering systems.
In studio work exposure is often determined by trial and error with instant image film. If budget or weight is a concern, you have to correct the reading of a hand held exposure meter with a compensation value. To get a correct exposure, the photographer has to increase either the exposure time or open the aperture accordingly. The amount of the exposure compensation can be calculated by measuring the lens to film distance, and calculating the exposure compensation by using the following formula:
I think I am not the only one having other things than mathematics on my mind when photographing, so I designed the QuickDisc as an improved way of determining the exposure compensation by measuring the image scale.