Videomicroscopy using still cameras in movie-mode?

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Thomas Ashcraft
Posts: 25
Joined: Wed May 31, 2006 8:34 am

Videomicroscopy using still cameras in movie-mode?

Post by Thomas Ashcraft »

I am very impressed with Ralf's Hydra video which he made using a Canon powershot camera in movie-mode.

I haven't seen much written about using snapshot cameras in movie-mode to do videomicroscopy. For example, a Canon Powershot S3 IS 6MP Digital Camera can make a movie at 60 fps QVGA (320 x 240). That certainly seems adequate for capturing fast cilia movements and rotifer coronas and such.

Are snapshot cameras a good way to go for making short 10 and 20 second microscope movies? Are there drawbacks?

Thanks in advance for any info or references!

Thomas

rene
Posts: 125
Joined: Thu Mar 17, 2005 4:14 am

Post by rene »

I've found the brightness uneven between images, 'flickering' and was told that this was because of the 50Hz cycling of the lamp. Further then that, ok.

Rene.

Thomas Ashcraft
Posts: 25
Joined: Wed May 31, 2006 8:34 am

Post by Thomas Ashcraft »

Rene wrote: "I've found the brightness uneven between images, 'flickering' and was told that this was because of the 50Hz cycling of the lamp. Further then that, ok."

Rene,

What camera model have you used?

I can see that there could be a conflict with a frame per second rate and illuminator/rheostat flicker.

I am going to try and collect data on this subject as I have not seen much written so far.

Thanks.
Thomas

rjlittlefield
Posts: 727
Joined: Fri May 06, 2005 11:57 pm
Location: Richland, WA, USA
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Post by rjlittlefield »

Possibly relevant info...

I have encountered problems with line-frequency flicker. Especially with fluorescent lighting, there's a periodic cycling of brightness & color balance as the line power drifts in and out of sync with the video frames.

However, I recently purchased a midrange fiber optic illuminator (like eBay item 7631755942) and was pleasantly surprised to find that it's using some sort of high frequency switching power supply that delivers 36KHz AC to the halogen bulb. There's no significant ripple in the light at that frequency, due to thermal inertia of the filament.

I didn't quite trust the electrical meter, so I also ran a short series of exposures at 1/1000 second, and confirmed no difference in brightness between frames with random timing.

I don't know if this high frequency switching is common to other fiber illuminators, but if you're lucky enough to get it, you shouldn't have any flicker problems.

--Rik
Reworks and reposts of my images in this forum are always welcome, as are constructive critiques.

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