09-01-2014 04:33 PM
I often shift the focal point using P shooting mode. Yet despite lots of research in the official manual and another manual, it's just not working. At most, it'll shift the aperature; not the focal point.
I've done this on every other Canon EOS I've owned, but can't seem to make the 70D do this. Any suggestions?
09-04-2014 06:43 AM
Thanks for posting.
To change the selected AF point, simply press the AF Point Selection button either in the upper-right corner of the back of the camera or next to the Shutter button, then use the Multicontroller pad to move the point in either direction.
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09-04-2014 10:35 AM
"I often shift the focal point using P shooting mode."
Focal point? What exactly are you trying to "shift"? Where the camera focus or perhaps the focal point in the view finder?
P mode sets the shutter and aperture to a predetermined set of rules. It is not designed to shift focus on any Canon DSLR, I know of.
09-04-2014 11:44 AM
Program mode provides a unique feature called "program shift" -- not be confused with moving or shifting the selected focus point (that's completely different.)
When you shoot in full auto (green box) mode, the camera attempts to be more-or-less "idiot proof" in that it not only starts by automatically evaluating the shot and picking all camera settings... it also locks you out of making changes to those settings. In full auto mode you cannot change focus points, nor exposure settings, etc. It's all locked in and automatic.
When you use "program" mode, the camera starts out by automatically evaluating the shot and selecting exposure settings... except you can override these using "program shift".
For any given exposure, to correctly expose an image on the sensor the camera will need some amount of light. You can deliver light slowly over an extended period of time, or quickly in a very short time. You control this by changing the size of the aperture opening in the lens and the duration that the shutter will remain open. Many combinations of aperture and shutter speed will result in a delivery of the same amount of light.
But it turns out that the effect you get in the resulting image will not be the same even though the camera collected the same amount of light. Fast shutter speeds are great for freezing action. Slow shutter speeds are great for providing deliberate blur which can be used to "imply motion" in a shot. Small aperture sizes are great for creating a broad depth of field (the range of distances at which subjects appear to be in acceptable focus) whereas a large aperture is great for creating a tack-sharp subject with a deliberately blurred out background (and/or foreground if desired.)
But since "program" mode is more-or-less starting out like "automatic" you don't initially get to tell teh camera what you want with respect to aperture or shutter speed. This is where "program shift" comes in to play... you can half-press the shutter button to cause the camera to meter the scene... THEN you can roll the front dial (you do not need to keep your finger on the shutter) and the camera will shift the exposure... as you roll the wheel to the left it will use smaller apertures but increase the shutter exposure time. Roll it to the right and it will use larger apertures and faster shutter times.
This is not the same as "exposure compensation" in which you use the rear dial (not the front dial) to tell the camera to increase or decrease the exposure relative to what the meter reading indicates (asking the camera to deliberately over-expose or under-expose the shot.)
Meanwhile back to your question about focus points... as you look at the back of your camera, the button in the upper-right corner shows an icon (in white... not blue) of a rectangle with some focus point in it (the icon displays 5 points arranged in what is more or less a "+" shape even though your camera really has 19 AF points and they are not arranged like the icon shows... Canon uses that same icon on every EOS digital camera.) This is the "AF Point Selection" button. When you press that button you may move the selected AF point.
This feature is available in all of the "creative" modes (Program, Av, Tv, and M). It is not available in the other modes.
See page 105 of your manual to understand how this works.
The 70D also allows you to change the AF area selection mode (different than just selecting a single AF point) and you may wish to review all of the AF options available on your camera... I believe this whole section starts on page 99.
Incidentally... if the camera is allowed to use all of it's AF points to select focus (or if you are in one of the basic modes that don't allow you to control the AF point selection or mode) then the camera is programed to lock focus on the AF point which is able to achieve focus at the NEAREST focusing distance to the camera. E.g. Suppose you want to photograph a person, but there is a plant in your shot which is a bit closer to the camera than the person you intend to photoraph. If both subjects (person and plant) are covered by AF points, then the camera will ALWAYS choose the point which can lock focus at the nearer distance... and if that's the plant, then you'll get a nice sharp plant and an out-of-focus person.