Re: [micro-manager-general] Questions on Hamamatsu Flash4

[Mark T. <ma...@op...>]

Hi Thomas,

On Sat, Dec 19, 2015 at 1:06 AM, Thomas Julou
<tho...@no...> wrote:
> - trying to acquire fast stacks I realised that I can’t even acquire fast time series… Compared to the live mode rate (very fast >10hz for full frames), running a MDA with 30ms exposure and 35ms delay results in longer illumination (almost 1/2 s by eyes) and hence longer delays. Where does this difference come from? is there a simple workaround?

The difference comes from the fact that with 35 ms interval (30 ms
exposure), µManager is (1) instructing the camera to take a single
snapshot for each time point, which incurs setup/teardown overhead in
the driver and camera, and (2) switching the shutter (illumination)
for each time point (if in autoshutter mode), which has at least some
overhead. Also, aside from the overhead, timing events by software is
generally not accurate enough for interval adjustment at millisecond
resolution.

Performing acquisitions at precise intervals that are not dictated by
the camera (based on exposure and other settings) requires either (a)
a camera that supports adjustable intervals when in streaming mode,
with µManager support for such functionality, or (b) external
triggering of the camera using an appropriate device. Unfortunately
(a) is not available for Hamamatsu cameras in µManager, and neither
(a) nor (b) is supported in the µManager GUI ((b) is on our eventual
roadmap) and therefore would require scripting.

The best workaround I can suggest (if the experiment allows it) is to
set the interval to 0 and use the exposure to adjust the actual
interval (which typically includes readout time, unless using a frame
transfer CCD). The hope is that you can adjust illumination intensity
to a level appropriate for the exposure.

Best,
Mark