Archived posting to the Leica Users Group, 2003/07/24
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I’ve been using my 75 1.4 and it is a challenge to focus. After reading several posts, I ran a test roll and took a look at a depth of field table. In terms of shallowest depth of field, the 90 f2 APO Summicron and 75 f1.4 Summilux are just about tied. But at close focus, the Summilux takes the honors. At .75 m you get a whopping 7.5mm in focus. That’s 29.5 inches with just over 1/4 inch dof. The 90 f2 wide is a tiny bit less forgiving, but doesn’t focus as close. At one meter you’ve got 13.5 mm (1/2" ) The Nocti at one meter, wide open has a huge depth of field of 23mm – or about 7/8 inch. At 1 meter and 5 meters (16.4 feet --measurements are rounded ) Depth of field in centimeters (inches) hope the formatting is okay . . . 1 meter (39.4"') - --- f1 ---------------- f1.4 ---------------- f2 50 2.3cm (.9") -- 3.2cm (1.3") -- 4.6cm (1.8") 75---------------- 1.4 cm (.5") --- 2.3 (.9") 90--------------------------------- 1.35cm (.5") 5 meters (16.4') - --- f1 ---------------- f1.4 ---------------- f2 50 59.6cm (23.5") -- 83.7cm (33.0") -- 120.5cm (47.4") 75-------------------- 36.8cm (14.5") -- 60.6cm (23.9) 90----------------------------------------- 36.4cm (14.3") Hyperfocal: Wide open, the Noctilux hyperfocal is 273’ – not a useful concept. Focused at infinity, the nearest subject in focus: 50 f1.0 -- 77m (215ft) 75 f1.4 -- 118m (305 ft) 90 f2.0 -- 119m (307 ft) Counterpoint for the Noctilux! If you are using each lens to capture an equivilant subject size, the nocti is the thinist. Shoot a ˝ body shot – The subject is approximately 1 meter top to bottom: Distance from subject --- Depth 50 2.347m ---- 13.77cm (5.4”) at f 1.419.2cm (7.6") 75 3.512m ---- 19.0 (7.5”) 90 3.897m ---- 23.3 (9.2”) But the nocti you could probably stop down to 1.4 and shoot at a slower shutter speed with equivalent dof as the Summilux. For such thin focus depths, obviously rangefinder accuracy is critical. I just ran a roll through the Hexar RF – it consistently is in focus behind what is indicated (about 3/8 inch at 3 feet, measured from the film plane and 'in-focus' RF). And wide open, sharp infinity focus occurs before the lens stops turning. And of course if you shrink the circle of confusion, everything gets worse . . . I am pretty consistant on my close focusing – however I was surprised to learn ‘infinity’ is a football field and beyond. I actually have a bigger problem with 'less than infinity' focusing wide open than close objects. Shooting with my SLR I'm reminded by looking through the viewfinder that my 85 f1.4 is extremely shallow wide open (and I consider 2.0 the working 'wide open). I guess I need to burn more film with the rangefinder -- and close the Summilux a stop unless the light requires more. I'm also going to test my cameras regularly -- and I've also learned the M7 doesn't have a film plane mark! Kev. - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html