26
the number of post trigger frames to a large number the trigger frame may not be in
memory, and this button will not do anything except display a warning.
Remember
:
Review Captured Video mode can not be stopped until all header information
is collected from the camera memory
.
If you have a camera with a large memory and
have selected a small frame size it may take some time to find all the image headers.
A 1GByte camera can hold about 508 full size images (1280x1024) in memory. The
smaller your image the more will fit in memory. (640x512 images give you 4 times the
number or 2028 image). Note: the images are always stored in the camera memory at full
precision of 10 bits per pixel.
S
PECIFIC
F
AST
C
AMERA
I
SSUES
Trade-off between Frame Size and Frame Rate
The FastCamera USB can read image lines from the sensor at a maximum rate of 500,000
per second (FV13) or 345,000 lines per second (FV40). These line rates are determined
by the
Clk/line
parameter that can not be smaller than the image sensor specified limit.
The height of the image you select will determine the
maximum frame rate
that you can
read from the sensor and write to memory. For example if you select 1280x128 line image
you can record at about 4,000 frames per second.
Note
: the width of the image does not affect the frame rate, though it does affect the
number of images that will fit in memory.
If you attempt to set the frame rate to a higher value than the frame readout time
(determined by the number of lines in the frame and the line reading speed, see discussion
above), you will still get only the maximum attainable frame rate and not what you asked
for. You can always review the timer ticks recorded in successive images or over the
whole sequence to verify the actual frame rate if you have any doubts.
Exposure
Exposure can not be longer than the frame period. (1,000,000 / frame rate given as FPS).
The shortest exposure is limited by the software to values the camera supports. You can
get down to 2 microseconds (FC13) or 2.5 microseconds (FC40). Just make sure your
object is bright enough to be visible with a short exposure.
Triggering Video Recording Externally
E
XTERNAL
T
RIGGER
C
ONNECTOR