RoySmith Posted February 26, 2012 Share #21 Posted February 26, 2012 Advertisement (gone after registration) Welcome to the forum David I did the math for a 35 mm summicron lens, with the camera in landscape orientation. Say you focus on a subject 3 meters away in the centre of the viewfinder. You then rotate to reframe the subject to the one third line of the finder. This means you will have rotated 9° (1/6th of the 54° horizontal field of view of the lens). In the subject's direction, the plane of focus is now 3.0374 m from the camera which is 3.74 cm behind the subject. (3.000 / tan 9° = 3.0374). To correct for this you must step or lean back 3.74 cm when you take the picture (or lean forward that amount when focusing). On the other hand, with a 35mm lens, an aperture of f/2, and focused at 3 m, the depth of field is from 2.8 m to 3.23m (44 cm) assuming a 0.015 mm Circle of Confusion. With a 90mm lens, an aperture of f/2, and focused at 3 m, the depth of field is from 2.97 m to 3.03 m (6.5 cm) assuming a 0.015 mm Circle of Confusion. In this case the focal plane shift is 0.67 cm However, some people argue that there is only one plane in focus and that depth of field is irrelevant. Its interesting to at least understand the concept and see the numbers. Link to post Share on other sites More sharing options...
Advertisement Posted February 26, 2012 Posted February 26, 2012 Hi RoySmith, Take a look here Tips for focusing on faces. I'm sure you'll find what you were looking for!
steed Posted February 26, 2012 Share #22 Posted February 26, 2012 tilt the camera so you can focus upon an eyebrow. Works every time. Sometimes I use an eyeglass frame as well. Link to post Share on other sites More sharing options...
Paul J Posted February 26, 2012 Share #23 Posted February 26, 2012 Focus with the lens and then fine adjust by rocking your body back and forth. Link to post Share on other sites More sharing options...
thighslapper Posted February 26, 2012 Share #24 Posted February 26, 2012 At F2 and 2m on the 35/2 DOF should be about 40cm Halve that to keep within the vagaries of lens calibration and the fact it is unlikely to be 50:50 behind and in front still leaves you 20cm leeway. Jumping to f4 more than doubles this.... Having chased my puppy/dog around with an M9 for the last 8 months it becomes obvious fairly quickly that focussing rapidly and accurately with a rangefinder is no mean feat ..... so some other options need exploiting....... - stick it on C and just keep shooting and some will no doubt be ok.... - pick a focus setting and move yourself and the camera into the plane of focus as it changes.... - pick a focus setting and let the subject move into the plane of focus..... - pick and mix from the above..... Whilst shallow DOF and moving targets may give you some great photos I think the strike rate of in focus shots will be depressingly low.... and there is nothing so heart-breaking as missing the 'one' because you chose to make life difficult for yourself...... You can always add OOF with post processing ..... but not the other way round Link to post Share on other sites More sharing options...
Michael Geschlecht Posted February 27, 2012 Share #25 Posted February 27, 2012 Hello again david, It looks to me like you now have instructions for how to hunt w/ a rifle, a shotgun &/or a machine gun. I guess you can take your choice. Or you can take a little from each. It's your decision. I'm sure whatever or whichever you choose there will be any # of people to help you. If you change your mind while trying various ways there will still be plenty of people to help you. Best Regards, Michael Link to post Share on other sites More sharing options...
rramesh Posted February 27, 2012 Share #26 Posted February 27, 2012 The 'Snake Charmer' tip. Move your body to keep a constant distance with your subject. The good news is that kids don't bite. But do watch out for the rattle throw on your expensive camera. Link to post Share on other sites More sharing options...
DKbRS Posted March 1, 2012 Author Share #27 Posted March 1, 2012 Advertisement (gone after registration) Thanks all. And Michael, I have been practicing as per your first suggestion. One issue I've encountered (and I'm sure I'm not alone as a newbie), is that because I can shoot with the M9 at much slower shutter speeds that with my 5DII, I have been forgetting that it is not only me and the camera that needs to be still. My subjects' moving slightly had led to quite a few OOF shots. Link to post Share on other sites More sharing options...
jaapv Posted March 1, 2012 Share #28 Posted March 1, 2012 That is why old Daguerrotype portraits often had a prop like a Greek column or table with a plant. The subject could lean against it and hold still during exposure. Link to post Share on other sites More sharing options...
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