Peter Epstein
Forum Enthusiast
I believe the 707 is effectively always in depth of field preview (to use the SLR terminology). In other words, the aperture doesn't change when the shutter is released. This is both good and bad.
It's good because it gives you a much better idea of what will be and what will not be in focus. You get to see just what the final image will look like. Unlike with an SLR, the camera can compensate to some degree for the smaller aperture and maintain the same brightness in the preview image. Maybe it's using a slower refresh rate to achieve this - I don't know.
It's bad because it makes manual focus difficult when the aperture is stopped down. You have to manually open up the aperture, focus, then stop it down again. It's also bad because the extra light you get with a wide open lens may be needed in order to provide an adequate preview image brightness. In other words, the camera can only compensate for the smaller aperture to some point. Beyond that, it simply can't get enough light quickly enough to produce a usable preview image.
Here's an interesting experiment. Go outside in daylight and set the camera to aperture priority. Get a wide range of distances in view. For example, you might sit down low to the ground. Adjust the aperture and watch the shutter speed change. As you do this, the image will show varying amounts of depth of field. The overall brightness of the preview won't change substantially, despite the fact that less light is hitting the CCD.
Now go inside in the evening and repeat the experiment. This time the image I expect the image to darken substantially as you stop down the lens.
I think what's going on here is that the exposure time for each frame of the animation is adjusted to produce the proper image brightness. When the exposure time gets long, the refresh rate goes down. Eventually, it reaches a threshold beyond which the designers chose not to go (for good reason).
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Peter Epstein
It's good because it gives you a much better idea of what will be and what will not be in focus. You get to see just what the final image will look like. Unlike with an SLR, the camera can compensate to some degree for the smaller aperture and maintain the same brightness in the preview image. Maybe it's using a slower refresh rate to achieve this - I don't know.
It's bad because it makes manual focus difficult when the aperture is stopped down. You have to manually open up the aperture, focus, then stop it down again. It's also bad because the extra light you get with a wide open lens may be needed in order to provide an adequate preview image brightness. In other words, the camera can only compensate for the smaller aperture to some point. Beyond that, it simply can't get enough light quickly enough to produce a usable preview image.
Here's an interesting experiment. Go outside in daylight and set the camera to aperture priority. Get a wide range of distances in view. For example, you might sit down low to the ground. Adjust the aperture and watch the shutter speed change. As you do this, the image will show varying amounts of depth of field. The overall brightness of the preview won't change substantially, despite the fact that less light is hitting the CCD.
Now go inside in the evening and repeat the experiment. This time the image I expect the image to darken substantially as you stop down the lens.
I think what's going on here is that the exposure time for each frame of the animation is adjusted to produce the proper image brightness. When the exposure time gets long, the refresh rate goes down. Eventually, it reaches a threshold beyond which the designers chose not to go (for good reason).
--
Peter Epstein
