Aids for Stereo with twin cameras
SDM has a number of aids for taking images with twinned cameras.
Most photographers simply wish to press the button and rely on experience that the stereo-depth is acceptable.
For mid-range shots, this is probably acceptable but closer-up it is useful to know the far limit of the background.
One method is to use the on-screen deviation deviation indicators described in section 'Grids, Masks and Deviation Indicators'
Once you have verified that your intended area of interest has acceptable stereo-depth, you may simply 'snap away.'.
SDM also provides a 'rangefinder' mode that computes deviation from measured near and far subject distances.
Make sure that you have set the autofocus area to the middle of the screen and 'camera spacing' is the correct value in 'Stereo' menu.
In <ALT> mode, browse to the 'TWIN CAMS' OSD and then exit <ALT> mode.
Zoom to maximum telephoto, aim the camera at the nearest part of the subject and half-press the shutter until the 'Near' value is updated.
Repeat for farthest part of subject until 'Far' is updated.
In order to achieve focus in the time alloted by SDM, there needs to be a 'reasonable' amount of light.
Zoom-back to the desired focal-length.
The calculated deviation (in mm) for your camera-spacing will be displayed and a horizontal bargraph showing that as a percentage of your personal, maximum-allowable deviation.
If within limits, the bargraph is green, otherwise it is red.
Your maximum acceptable stereo-depth is defined by the maximum-acceptable deviation (defined as a fraction of image-width).
You set it as 'deviation factor' in the stereo menu.
If the near distance is coloured red, it means that you are too near to the subject for that camera-spacing.
This is based on the 'Near-subject factor' that you have entered in the Stereo menu.
It determines how much perspective distortion due to camera spacing you think is acceptable, even though deviation may be within limits.
It is instructive to see how the value changes at different zoom positions.
A more 'minimalist' version of the above OSD information is provided by the 'Advanced/OSD Parameters/Show misc values' option.
Focus on near and far as described above.
If deviation acceptable, 'far' distance will be coloured green.
If you are too near, 'near' distance will be coloured red.