digital compact cameras since the first models use electronic viewfinders. These viewers are a very small version of TFT observable in the back of these cameras. Their main problem is that its resolution, in many cases is not sufficient for a perfectly sharp observation of the scene. Some models not even incorporated.
A new breed of cameras that are called interchangeable lens and electronic viewfinder (Viewfinder Interchangeable Lens Eletronic EVIL, in English) are different from traditional digital SLR models because they lack precisely optical viewfinder.
The first question we address is the explanation of what is an optical viewfinder. The answer is very simple. It is a transparent element through which channels the light from the scene and has gone through the target. Device is therefore a TTL (Through The Lens, in English) which means that the light has been used previously by the lens.
Its mission is also simple. Used to compose the picture.
The operation of the optical viewfinder can be seen clearly on the left side of the figure heading this article. Light passing through the lens is reflected by a semitransparent mirror. Some light is used by the mechanisms of AF and exposure metering (not reflected in the figure) and some is diverted to a pentaprism that offer the image to the viewer as if we looked at the scene with our naked eyes. When pressing the shutter
happens what can be seen on the right side of the same figure. The mirror rotates 45 degrees up taking as a turning its right end and light in all its intensity, is directed towards the sensor. From the point
of view of practical use optical viewfinder to take into account some considerations:
a) The scene viewed through this device is usually a high percentage (around 95%) of the scene recorded at the sensor end. The professional models raise the percentage to 100%.
In my work as a photographer I have seen this situation almost as an advantage. Because there are situations ended commitment that can be solved by the difference between what is seen through the viewfinder and what you just recorded in the sensor.
b) In the case of digital reflected not produce the parallax problem that occurred once in the chambers analog compact. In the latter, the display did not reflect the light from the target, but was, so to speak, as a separate window to the scene, with a slightly different angle, in some cases (eg, close-up photography) could cause problems.
c) Most camera bodies are associated with the control optical viewfinder diopter change for people with eye problems very mild. It's something that, frankly, I have not tried it on my camera.
d) The importance of optical viewfinder in an SLR camera is not negligible. In fact with the vision of the scene being offered through this device, we find some items. A scene image received from the target overlap or append a few more items:
d.1) points of focus.
accurately indicate where we are focusing on the scene to take the picture.
d.2) Focusing Screen.
This element, very common in the old analog SLR, governed by manual approach, it has become virtually obsolete from the moment the autofocus mechanisms have been done nearly ubiquitous. Its mission was to allow the photographer to make clear the area in which you want to focus.
d.3) Annex to the optical viewfinder (at the bottom, usually) is a small TFT screen that provides information on the parameters of the socket (Shutter Speed, Aperture, Diaphragm, etc).
Well, all these factors depend on the good visibility provided by the optical viewfinder. So that under certain conditions a poor (and small) optical viewfinder us greatly complicate the taking of certain pictures.
e) One last comment to refer to the plastic cover that surrounds the viewer and can cause problems for people with glasses, like myself. In fact, for example when using the Pentax * Ist Ds every 2 or 3 photographs should I clean the above glasses. This does not happen when I use the Nikon D200. And there are times You can lose a good picture for this simple and silly question.
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