Also, there comes a point where you run out of easily distinguished colors. The Nikon method of using colored lines makes this somewhat less of a problem, but it can still get cramped. The 105mm f/4 Micro I have is close to this point. It’s useful from the point of that when you don’t use it, you get shown the depth of field you’ll get with the lens wide open.Ĭlick to expand.On normal to long lenses, the DOF markings can get too close to be easily readable. This is probably why, as others have pointed out, it’s a feature that nearly all high end cameras have, but few people use very often. There is a downside of course, in that the view gets dimmer and dimmer as you close down the aperture. The depth of preview lever gives you a chance to ‘preview’ the scene before you take the picture, to help you assess what will be in ‘acceptable’ focus. However, from a few feet away, that poster shot would probably be acceptably sharp, and what you would ordinarily call, ‘in focus’. If you blew up your shot to poster sized and looked at it from 4 inches away, you’d see that it wasn’t actually pin sharp in front of, or behind the plane of focus. The scale on your lens give you an idea of the ‘acceptable’ level of depth-of-field for ‘normal’ prints viewed at a 'normal' distance. It’s not really IN focus, it’s just less out of focus than with the wider, more open aperture you started with. If you look through your camera and start at a wide aperture, so you have a bright view, and focus on something that is receding (a wall running away from you etc.), hold down the DOF preview lever, and progressively close down to smaller apertures (bigger f numbers) you will see that what appears to be in focus increases to both the front and the back of the point you focussed on. Now, smaller apertures give you increased depth of field (or depth of focus), but this focus is only really 'apparent' rather than actually in focus. You see this very easily when you shoot ‘wide open’ (at large apertures, or small f numbers, like f1.4 or f2). Beyond that to the front and back, everything will be out of focus, to some degree. When you focus your camera, let’s say at 5ft, it’s only those items that are 5ft away from the film plane that will be in correct focus. It’s probably just as well to remember that there is only one plane of focus.
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