Hyperfocal distance (H) is a way to dertemine the distance to focus the lens for a given aperture and focal length to ensure maksimum DOF, when you want sharpness to infinity (e.i. landscape photograph):
H = FxF/fc F being Focal length f being f-number (aperture) c being the diameter of Circle of Confusion (CoC could be 0.021mm for 35mm negs enlarged to a 8x10 print). At 70mm lens f8 "H" would be (35mm neg): 70x70/8x0.021 = 29167 mm = 29.2 meter This means, that if you set the distance to 29.2m, you will get sharpness (on a 8x10 inch print) from infinity to as close as you can get at f 1:8 If you are a landcape photographer, you should have a table in your camera bag giving "H" for the most used focal lengths at let's say f22 or 32. At f22 the math should be: "H" = 70x70/22x0.021mm = 10.6 meter The near limit of sharp focus is: Fu(F+cf)/FxF+ufc (u being the used distance in mm) 70X10606(70+22x0.021)/70x70+10606x70x0.021)= 5338mm = 5.3m. The image (8x10) will appear sharp from 5.3m to infinity at f22 when focus distance is set to 10.6m Source: Andrew Hawkins & Dennis Avon; "Photography", UK 1979. all the best Jens Bladt mailto:[EMAIL PROTECTED] http://hjem.get2net.dk/bladt -----Oprindelig meddelelse----- Fra: Doug Franklin [mailto:[EMAIL PROTECTED] Sendt: 9. april 2004 06:33 Til: [EMAIL PROTECTED] Emne: Re: Zone Focus - what is it? On Fri, 9 Apr 2004 07:25:27 +0200, Boris Liberman wrote: > Please enlighten the ignorant, as usual... Using the hyperfocal distance of the lens, possibly modified, to make sure that everything you're likely to shoot is in focus. For example, take your lens and figure out what f-stop you want to use. The turn the focus ring until the infinity mark lines up with the "tic mark" for the f-stop you're using. The "tic mark" on the other side of center will tell you what's going to be in focus. So, just to pull some numbers out of thin air, you pick f/5.6. When you line up the infinity mark on the focus ring with the "5.6" tic on the barrel you might find that the opposite tic indicates 10m. That means everything from 10m to infinity will be in focus. So you don't worry about focusing unless the target is closer than 10m. You can shift it closer if you're not worried about things at "infinity" distance. TTYL, DougF KG4LMZ
