MarcusY
newbie
Reged: 05/07/2008
Posts: 14
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Hi,
I've been starting using my DSLR in manual mode for he first time, for the first module. I have an Olumpus E400 with ED 13-42 and 40-150 lenses.
I'm finding manual focussing really difficult, compared with my old SLR (a Yashica FX-3). There seems to be a lot of movement in the focussing ring that makes no noticeable change to the focus and when I do see the image focus changing, without a split prism screen it's not easy to tell when the subjet is in sharp focus. I'm also struggling with depth of field because these lenses aren't marked with depth of field info, unlike my old SLR lenses. So I have no idea what my DOF is. Are these issues common to DSLRs in general? If so how do people deal with them?
Marcus
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LargeFormat
old hand
Reged: 24/10/2006
Posts: 1179
Loc: Buckinghamshire and Cumbria
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The shorter the focal length of the lens the greater the depth of field. With your Olympus the lens will have a focal length half of that for your film SLR for the same field of view. If you set your 40-150 lens to 100mm it will have the depth of field similar to a standard 50mm on your Yashica. Whilst this may provide a comparison you are still likely to find it significantly more difficult to manually focus with the Olympus than with a film SLR with the latters larger viewfinder and split image/microprism.
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Garry McNamara
Snr Tutor/Bongo Banjo
Reged: 16/08/2006
Posts: 2079
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Well observed points.
Short focal length lenses were always harder to focus – 18mm and 24mm were a particular challenge - and that was when focussing screens were designed for manual focussing which modern ones are not well suited. Oh course the apparent increase in depth of field made critical focus well... less critical.
That allied to the extremely modest maximum apertures (f/2 used to be a regular feature - now f4 is as commonplace) and it's quite a task.
Live view or tethered capture (where he camera is operated via a computer and the image viewed on the computer’s screen) can help as you can zoom in on the image to fine tune focus.
Cameras with a full frame sensor use longer focal lengths for the same angle of view (with correspondingly less depth of field) and some allow you to change the focussing screen for a model more suited to manual focus.
Different focal length lenses also have varying depth of focus - where the lens can be moved a greater distance to and thro at the 'film' plane and still give the appearance of a sharply focussed image.
So a full frame camera with a manual focus friendly screen and a fast (f/1.2 – f/2.8) lens will be very nearly as easy to focus manually as your Yashica – except that even then the travel of the focus collar can be very small and not nearly as viscous as makes for pleasant focusing – that feel you are no doubt familiar with would put more strain on the motors that drive your autofocus.
Of course there’s nothing to stop you using your Yashica for the course!
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