I have an exam coming up and need some help please?with a single lens reflex camera, when is it recommended to use an assessory dioptric corrector lens?
I'm inclined not to answer homework questions, but I can help you on your way..
A camera's viewfinder displays a sharp picture for those with good eyesight. If you're a near- or far-sighted photographer however, the glasses may get in the way or the VF may scratch your glasses.
With that in mind, what do you think a dioptre does?
Additionally, why would a viewfinder with a focussing aid such as a split image somewhat render the use of a dioptre as a means to help focussing unnecessary?
Next to that, what could be a problem when a near-sighted photographer using a dioptre is not looking through his lens momentarily?
Far-slightness plagues most of us as we age. Reading glasses to the rescue. These corrective eyeglasses are commonly available in drugstores worldwide. Reading glasses are labeled as to their power. The unit of measure used is called “diopter” (Greek to see through). The diopter unit is just another way to express the focal length of a lens. 1 diopter = 1000mm --- 2d = 500mm – 3d = 333mm – 4d = 250mm etc.
SLR (single lens reflex) cameras feature an eye-level viewfinder. This is an optical presentation of the scene to be photographed. Such a scheme allows the photographer to pre-view an accurate projection of what the film or digital sensor will see during the actual exposure. Many digital cameras sport an electronic version of the eye-level viewfinder.
If your vison is less than optimal, some adjustment is possible and likely provided via a wheel adjacent to finder’s exit lens. This adjustment might be labeled in diopter units to correspond to the power of corrective reading eyeglasses. In other words, if you’re reading glasses are labeled +2d, then likely a +2 setting of the camera’s eyepiece corresponds.
If your camera’s eyepiece adjustment does not do the trick, a visit to an optometrist might result in a custom corrective lens to supplement the camera’s eyepiece.
Most of us “gray-hairs” remove our spectacles, adjust the eye-piece diopter corrector so we can clearly see the screen and the letters and numbers presented by the reticle (Latin for scale seen in optical instruments).