Field of View (FOV)¶
Overview¶
The full Field of View for a particular device and lens combination is fixed. It depends on the optical magnification of the lens, the camera sensor size, video format, and the frame grabber digitisation.
Comparison of various CapiMetrics configurations is shown in the table below.
mag (um/pixel) |
pixels |
FOV L300 6.3x lens (um) |
FOV L100 3x lens (um) |
fps |
filesize |
||||||
L300 6.3x lens |
L100 3x lens x |
x |
y |
x |
y |
x |
y |
Mbyte/second |
|||
HVCS std |
0.925 |
1.93 |
752 |
480 |
696 |
444 |
1451 |
926 |
30 |
10.3 |
|
1⁄2 resolution |
1.85 |
3.86 |
376 |
240 |
696 |
444 |
1451 |
926 |
30 |
2.6 |
|
HVCS hires |
0.81 |
1.69 |
1280 |
1024 |
1037 |
829 |
2163 |
1731 |
25 |
31.3 |
|
1⁄2 resolution |
1.62 |
3.38 |
640 |
512 |
1037 |
829 |
2163 |
1731 |
25 |
7.8 |
|
CAM1/VCS PULSAR |
|||||||||||
CCIR (PAL) |
1.2 |
3.4 |
768 |
512 |
922 |
614 |
2608 |
1739 |
25 |
9.4 |
|
RS170 (NTSC) |
1.25 |
3.54 |
640 |
480 |
800 |
600 |
2264 |
1698 |
30 |
8.8 |
|
CAM1/VCS PX610 |
|||||||||||
CCIR (PAL) |
1.2 |
3.4 |
768 |
572 |
922 |
686 |
2608 |
1943 |
25 |
10.5 |
|
RS170 (NTSC) |
1.25 |
3.54 |
640 |
480 |
800 |
600 |
2264 |
1698 |
30 |
8.8 |
|
CAM1/VCS METEORII |
|||||||||||
CCIR (PAL) |
1.2 |
3.4 |
768 |
576 |
922 |
691 |
2608 |
1956 |
25 |
10.5 |
|
RS170 (NTSC) |
1.25 |
3.54 |
640 |
480 |
800 |
600 |
2264 |
1698 |
30 |
8.8 |
|
CAM1/VCS FALCON |
|||||||||||
CCIR (PAL) |
1.2 |
3.4 |
768 |
576 |
922 |
691 |
2608 |
1956 |
25 |
10.5 |
|
RS170 (NTSC) |
1.25 |
3.54 |
640 |
480 |
800 |
600 |
2264 |
1698 |
30 |
8.8 |
|
CAM1/VCS A602f |
1.44 |
4.08 |
640 |
480 |
922 |
691 |
2608 |
1956 |
30 |
8.8 |
|
CAM1/VCS PIXELINK |
|||||||||||
CCIR (PAL) |
1.44 |
4.08 |
768 |
576 |
1106 |
829 |
3130 |
2347 |
25 |
10.5 |
|
RS170 (NTSC) |
1.42 |
4.02 |
640 |
480 |
909 |
682 |
2572 |
1929 |
30 |
8.8 |
The FOV for capture display can be reduced changing the “grab image size” in the settings menu. Useful for producing recordings for comparing with another version of CapiMetrics or another manufacturers device.
The FOV for video recordings can be reduced further using the Region of Interest (ROI). Useful for the same reason above and also for reducing video file sizes and recording data rate, but still enabling the full FOV to be seen during recordings.
Video file sizes or recording data rate can also be reduced by using the “half resolution” option in the settings menu. Useful if you still want the full FOV.
Region of Interest (ROI) 
¶
The Region of Interest (ROI) is useful for performing image adjustments only only part of the image or for reducing the FOV used for video recordings and hence the video file size.
Click on the ROI toolbar button to draw the Region of Interest. Size is shown in the status box as you draw it.
The ROI rectangle can be dragged using the mouse.
A ROI drawn on the Live/Frozen Video window is saved between sessions.
Video recordings will only record the ROI. The whole image is recorded if there is no ROI. The ROI can be moved during video recordings if required.
When changing the resolution using “half resolution” in the settings menu, the ROI will keep the same pixel size. You’ll need to redraw the ROI if you want the same actual tissue area.
Use the ROI button and one mouse click to clear the ROI.
Grab Image Size¶
The size of image captured and displayed can be reduced using the “Grab Image Size” option in the settings menu.
Enter the new size in pixels or “calibrated” units. This reduces the FOV and size of images and video but keeps the same optical resolution and magnification (um/pixel).
The grab image will be centred in the full sensor area.
A value of zero will use the whole sensor area.
The setting is saved between sessions.
The grab image size is stored as pixels, so changing the resolution using the “half resolution” setting will keep the same grab image size in pixels, but not the actual image size in um.
Half Resolution¶
The half resolution option in the settings menu turns on “binning” in the camera sensor. This will halve the x resolution and the y resolution. Therefore the area will be 25% of the full resolution.
Each pixel will be the sum of four pixels so will have greater sensitivity and light level will need to be reduced.
Optical resolution will be reduced too and the magnification (um/pixel) setting will be automatically halved/doubled.
This is useful for reducing video file sizes and data bandwidth whilst maintaining the same FOV.
Zoom In 
/ Zoom Out 
¶
This changes the size of the image as displayed on the screen only. It doesn’t have any effect on images or video recorded, or any measurements, calculations, or processing functions.
High Resolution Frame Rate Problems¶
Slow computers or using other USB devices may cause problems with displaying and capturing video using the full High Resolution HVCS. Slow hard disc drives may also cause dropped frames when recording video in high resolution. Video file sizes will be very large too in high resolution mode.
These problems can be reduced using one or more of the following:
Remove other USB devices.
Use half resolution mode.
3. Use the Grab Image Size option to reduce the image size and USB data bandwidth.
4. Use a ROI to reduce recording to video file sizes and/or dropped frames.
5. Use frame skip in the image sequence settings dialog box to reduce recorded video frame rate and hence video file sizes and/or dropped frames.
