Need help: "correcting" exposures in time-lapse imagesets

["kinata" <forums@xxxxxxxxxxxxx>]

Saul, thank you, sir...replies follow.

>Is flash mode available in remote capture? If so, perhaps one could be  
>used to obtain a consistent exposure (no AE, and the "shutter speed"  
>effectively is determined by the flash).

Well, our brainstorm was to use a fluorescent dye,
without using a flash. The exposure times range
from 1 sec to 1/20 sec, ISO 200, f2.8. This
wouldn't represent a showstopper, as we're 
concentrating on the area of each image that 
contains pixels having that color of dye. So I 
just need to iterate through the pixels and count
those having a certain threshold of a defined RGB
value to get the area of the image containing the
dye.

>> Is there a way to compensate for exposure time in a relatively accurate way,
>> say, see each image as if it were shot in 1/20 sec? I wish I could use
>> the CHDK package, but the A40 doesn't seem to be supported.
>
>Perhaps you could include a test pattern in the frame (ie, place a  
>picture of a test pattern next to the plant) and be able to match  
>exposure settings by adjusting the levels of the images such that the  
>two test patterns match (if this works, it could likely be automated).

Now I reveal my true ignorance. I was thinking
that I could duplicate a layer containing a source
image, play with its opacity, and then merge
the layer back into the original source image to
arrive at a target "exposure". Might that work?

In a related issue posted elsewhere in this forum,
I'm wanting to isolate the dye part of the image:
-- convert the RGB triple for the dye color
    (approximately a cyan) to HSB (HSV?)
    colorspace,
-- rotate it to (say) green, and then
-- extract the green layer of the image.
This last is probably off-topic...just being
conversational.

Regards,
Kinata


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