Technique tip: close up magnification and
The magnification, or scale of an object in a close up image is:
Image size/object size.
1. To determine magnification, you can measure the size of the image
directly on the processed slide or negative.
2. To determine magnification before actually taking a picture, place a
ruler beside the object and note how much you can see across the narrow
dimension of the frame in the viewfinder.
3. Exposure compensation is required if you use extension tubes or
bellows between the camera lens and body, and if the magnification is
0.25x or larer (exposure compensation is not required if you achieve a
close up by putting a supplementary lens in front of a normally mounted
4. A through the lens meter will automatically indicate correct close up
exposure. If your camera does not have a through the lens meter, use
magnification to figure the required exposure compensation this way:
Exposure increase factor = (magnification + 1)pwr2
5. In order to use a small f-stop (for good depth of field), change
exposure time to make the compensation. To find the correct close up
exposure time, multiply the shutter speed for normal exposure by the
exposreu increase factor.
Example: Magnification = 0.4 x, normal exposure is 1/60 at f/16.
Exposure factor = (0.4 + 1)pwr2 = 2x.
corrected exposure = 1/60 x 2 = 2/60 = 1/30 at f/16.
More about close up lenses
Supplementary close up lenses
hints for close up photography