Using Hasselblad Digital Camera (MFDSLR) and Extension Tubes
With reference to manufacturers (Hasselblad) data sheet you can see that subject to 'film' plane, lens to subject, magnification and exposure compensation data is given for each lens tube combination.
In this case I will only use the section of the table dealing with the HC 3.5-4.5/50-110mm Lens
NB Hasselblad users can download these and other equipment Data Sheets from the Hasselblad download page on the Hasselblad web site
In the setup below I am using a 52mm extension tube between the camera and lens the subject a 2000 peseta note is attached to a convenient
vertical surface for the purposes of this exercise.
Section of note to be photographed I selected the left eye
The sensor area is 37mmx49mm containing 39Million CCD sensors, using the 52mm extension with the lens set at the 50mm end focused on ∞ gives a magnification of 1.01 x i.e. fractionally over life size. At the close focus position the magnification increases to 1.22x i.e. 10mm on the subject will be reproduced as 12.2mm on the sensor / film
One advantage of this technique is extension tubes cost only a fraction of the cost of a dedicated macro lens, so if you only occasionally shoot Close up and Macro having an extension tube set in your camera bag is a sensible alternative.
Also when using telephoto lenses you sometimes need to be able to focus much closer than the lenses closest focus position to get the framing required in sharp focus, using a short extension tube makes this possible.
to be continued ...