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 p.1 #15 · p.1 #15 · Missing US Spy Ship since 2015 spotted above the sky of Singapore | |
Focusing on moving subjects with a manual focus lens
Recently we have lots of talks about cameras not able to focus on moving subjects even for some of the latest and most advance systems ever made, or one brand is better than the other, or pro versions vs non-pro versions, or one must have bird’s eye and face detection in order to do it
Ever wondered how photographers before AF was invented did it? I think not! Because too many are over dependent on automation and don’t really care. But if they did, they would have come out with some kinds of solution or understand why at certain time even the best of the best was not able to get focus and hunt
I am sure there are many ways to focus on moving targets with manual focus lenses and the two methods I used most are Zone focusing and Hyperfocal focusing, both apply the DOF with respect to aperture openings to get the targets within the pre-determined range to be in focus
Zone focusing normally works best with shorter focal length or wide-angle lenses with shorter MFD and wider DOF
While Hyperfocal focusing works best with longer lenses like telephotos and telescopes with MFD normally in the hundreds of meters to km range and shallower DOF, and are not so easily figure out if one does not know how to do it or have the apps to assist them. But once understood and have the apps to assist them, they can easily apply
Hyperfocal Distance = [(focal length) ²] / [(f-number) (acceptable circle of confusion)] + (focal length)
Will not go into Hyperfocal Distance in detail since those who are interested can always look it up because it will occupy multiple pages, but will explain how I apply it to get focus on moving subjects
A few things one will need to get started are:
1) The camera or sensor size used (M4/3 (17.3, 13.0)
2) The focal length of the lens (700mm)
3) The aperture opening of the lens (f/13)
4) The nearest expected distant of your subject as a starting point (3.5km)
If the calculated result did not meet your initial expectation, one will have to sacrifice the longer end to give maximum coverage
For example, I knew that my target will never come any closer than 3.500km and my camera is M4/3 with 17.3, 13.0 sensor size (for calculating COC), and focal length of 700mm with aperture f/13
Punching in these data into my app will give me a result of 3.769km for Hyperfocal Distant, now if I set my lens focal distant to 3.769km it will now cover from 1.884km to 21.444km, which is more than what I will need to shoot this aircraft
To track and frame my target I used the above range to calibrate my SVBONY Red Dot Laser Viewfinder with the camera viewfinder mid-point, and just use the SVBONY Red Dot Laser Viewfinder from there on without any time lag
There are times that even the best AF system will hunt and images using manual focus look distorted even though they are in focus, this is because shooting long lenses over long distant will likely encounter heat waves/mirages/shimmers or thermal effects that will distort images making contrast or phase detections difficult
Below is an example of a Puma in focus but with shimmers and distortion, not only that there is also a wavy halo around the subject
https://www.fredmiranda.com/forum/utopfiles/49/8749.jpg
DMC-GH1 with BLUESKY ST-60700 Refractor Telescope
f/13 (estimated), 1/500s, ISO 400
Image cropped from 4128 x 2752 to 1920 x 1280
So, you see we can focus on moving subjects with manual focus lens, and once focusing is taken care of without having to worry about focus hunting or waiting to get focus, we can concentrate our efforts on framing to get our shots.
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