Download speeds & RBI flash

[nakbrooks]

I wanted to check the effect of different download speeds and RBI flash on bias and dark frames for my PL16803 camera.

 

See the attached data and graphs.

 

I would have expected RBI flash to increase counts somewhat but as the flash takes place before the exposure I wold have expected the effect to be the same for all exposure durations.  However that does not seem to be the case.

 

I'm probably not understanding the RBI flash process and its effect on the subsequent exposure. Can anyone explain this?

 

(Forum wouldn't allow me to upload as a spreadsheet so had to convert to pdf).

 

Nigel

 

Data.pdf

Charts.pdf

[MarkS]

Hi Nigel,

 

Have a look at the article on RBI in the articles section of the Moravian Camera website. It may help understanding of the phenomenon. There is a reference there to an article by Richard Crisp, who seems to have studied the issue in some depth.

 

I would expect the post flash effect to increase with increasing dark exposure time because the RBI has longer to shed electrons into the system - it behaves like an excess dark current.

 

Otherwise, I can't comment, but I am having to learn how to deal with RBI on my G4-9000, which exhibits strong RBI effects  - quite a bit worse than the 16803 because of the 12micron pixels....

 

Mark

Edited April 28, 2019 by MarkS

[nakbrooks]

Thanks Mark. I’ll check that link out.

[Lariliss]

From the data tables it is visible that mean counts are somewhat more with RBI for both 1Nhz and 8MHz compared to no-RBI with largest exposure.

Let’s look at the minimum values (without zeros): 8MHz RBI (274) is more than doubled compared to others (the same 103 and 127).

Maximum values: all of them about the same.

That tells the RBI functioning in general and your particular case.

Generally, RBI doesn’t affect the observations as the charge captured in traps slowly disappears and the shadow image fades. RBI causes ghost imaging.  However, the final banding comes from using a RBI clearing flash.

Actually, intensity of RBI on long exposures are only a few electrons or tens of electrons per pixel, which is typically below the influence of other disturbing effects (e.g. high clouds).

For certain cameras and setups RBI preflash might be turned on, but not in your case, I would say.