AG Photo luxury
Video mode
Introduction
In September 2008, Nikon introduced for the first time a substantial change in the world of digital reflex cameras: the video function. This function first appeared on the Nikon D90 and from then on, it has always appeared on more models where now it is one of the areas where the large manufacturers are fighting it out.
Let’s assume for a moment that those who purchase a reflex digital camera want to take photos and not video, it is always useful to have at one’s disposal the possibility, using the same apparatus, of shooting video.
One of the advantages of being able to shoot video with a reflex camera is the fact that a person who has a digital camera with them intends to take pictures, and most likely does not have a video camera with him or her.
Digital video cameras were the first “to invade” digital photography by giving the possibility to take some photos. However, those who use a video camera shoot mainly video, and the photo is something that can be useful but it is not indispensable. Also, photographs shot by a video camera are not exactly comparable to those taken with a reflex camera whereas video shot with the latest reflex cameras can, in some instances, surpass the quality of video cameras. Further on, we will see why.
Another advantage of the video function is that it is possible to change the optics so you can shoot with various kinds of lenses in order to obtain a wide variety of possibilities in all kinds of situations.
Video
Digital video is nothing more than a sequence of photographs shown at high speed. To our eyes, it appears fluid because this speed is elevated beyond the threshold in which our eyes can distinguish individual frames. In order to make the video fluid, it is necessary (as it is for the resolution) to surpass this threshold by a large margin. At the moment, video has a frequency of 25-30 Hz or rather 25-30 frames per second (fps). With this standard the video is very fluid. In the past, some compact digital cameras were shooting video at 20 fps. Even at 20 fps our eyes do not see each frame, but the video also does not appear very fluid. At any rate, imagine for a moment a video camera as if it were a digital camera: the light arrives on the sensor, it is converted to an electronic signal and then the processor has to render it and save it. If we multiply this work by 25-30 fps, the effort undertaken by the processor is notable and requires a high calculation speed combined with a high write speed to the device’s memory. Therefore, increasing our frequency even just slightly is not an easy task from a technological point of view.
Video mode in reflex cameras
During the shooting of a photograph, the mirror that carries the light to the pentagrams of the optic viewfinder raises for a brief instant (the exposure time) and interrupts the flow of the light to the viewfinder in order to deliver it to the sensor. A video, however, is a continual sequence of images, and the reflex, during the shooting of the video (just as it is in live view) keeps the mirror constantly raised. Therefore, we can access the video function only in the live view mode. During the shooting phase, the optic viewfinder will remain obscured as seen in figure 01.
01 In live view mode or in video mode, the mirror is in this position.
Mirror up
Introduction
The camera
How it is made a Reflex camera
Photographic lenses
Equipment and accessories
Take a picture:
Buyer’s guide
Video cameras and reflex cameras: comparison of the sensors
The main difference between a video camera and a reflex camera is really in the sensor. The sensors of video cameras are CCD or CMOS, and they are much smaller than those in reflex cameras. This is because the video is nothing more than a series of frames in rapid sequence and, therefore, they have to have an elevated frequency as noted previously. Using a larger sensor with many megapixels would require powerful calculations and a calculation speed that is not currently technologically possible. For this reason, video camera sensors are typically smaller and, in high resolution video cameras, they generally come with a maximum of 4 Mp.
Reflex digital cameras with more pixels come to about 36mp (some with even more). In some reflex cameras there are 9 times more pixels present than in a video camera and the sensor is notably larger with a significant reduction in noise, even if the best reflex cameras have at best only 4 Mp for video.
Video cameras and reflex: fixed or interchangeable lens
Another substantial difference is the fact that a video camera has only one zoom lens with an ample focal extension, usually low luminosity and a small diameter. The reflex, instead, has a lens that is interchangeable and offers in this way an enormous variety of creative possibilities. Just as in photography, depending on the lens mounted, we can make use of macro, tele, wide-angle lens, with a depth of field and luminosity unthinkable for a commercial type of video camera.
Video cameras and reflex: focus
Up until a short time ago, a substantial difference between video cameras and reflex cameras was the continual focus. In fact, video cameras focus continually by following the subject as it gets closer and farther away. Some reflex cameras, in video mode, make exclusive use of a manual focus. In this case, the focus on various subjects becomes extremely difficult if the focus needs to be adjusted quickly. Now, in the new reflex models, they have a continual focus exactly like video cameras and allow us to zoom while always keeping our subject in focus. From this point forward, we can say that, in regards to the focus, that there are no more differences between the reflex and the video camera.
Video cameras and reflex: stabilizer
A characteristic of video that still differentiates a reflex from a video camera is the stabilizer. Currently, the video on a reflex digital camera is not stabilized while video cameras have the optic or software stabilizer. In both cases, it seeks to reduce the vibrations during shooting. In the first case, as with the stabilized photograph, the optic one is better since it does not cause a drop in the quality of the video while the second is done through processing that automatically reduces the quality even if often the reduction of quality is not that noticeable (see the chapter dedicated to the stabilizer for a more detail discussion). Currently, there is some software that allows for stabilization to be added in post-production. One of these is iMovie. This software reduces the distance between the video of a reflex camera and video cameras even if they do not close the gap completely with the optically stabilized video cameras.