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exposure compensation


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#1 vasanth edward

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Posted 24 April 2009 - 06:57 AM

wat is the stop diffrence between 0.1 fps to 1fps
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#2 Chris Millar

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Posted 24 April 2009 - 09:00 AM

wat is the stop diffrence between 0.1 fps to 1fps


3.321928 stops
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#3 Chris Millar

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Posted 04 May 2009 - 06:35 AM

PM from the OP:

hi chris ive compensated nearly four stops and still it is over exposed by 3to4 stops so pls could u help in finiding out the exact compensation value of it


The value I gave is the exact compensation for a speed difference factor of 10 (all other things being equal)

Not quite sure why you say 'still over exposed' either - you realize that going from 0.1 fps to 1fps and not changing anything will lead to underexposure, so to solve your issue, just leave it as is ...

Better yet, figure out what is going on - have you taken a reading with a light meter ?

more info please
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#4 Dominic Case

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Posted 05 May 2009 - 05:15 PM

Hold on - the first answer (3.32 stops) is correct ONLY IF the frame rate difference is an exact reflection of the exposure time change. But 0.1fps is very slow. I have no idea what sort of camera is being discussed here - film? digital? what sort? How does it vary exposure time at slow frame rates? If it changes nothing, then a 0.1fps exposure would be anywhere between 5 and 10 seconds (depending on effective shutter angle) which is unlikely.

My guess, in the absence of all relevant information, is that the camera gives the same exposure time on all fame rates slower than a certain amount - which would explain why the operator has compenasted four stops and finds it is four stops overexposed.
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#5 K Borowski

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Posted 05 May 2009 - 05:47 PM

3.321928 stops


Hi. Learn what significant figures and necessary precision are. That's like the idiotic sign I saw once that was selling 7 acres and change and they had three decimal points past the seven.

Assuming this is accurate, 3-1/3 stops is close enough.
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#6 Chris Millar

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Posted 05 May 2009 - 06:10 PM

I was aware of both of your considerations at the time ...

It was a rather blunt question with no qualification so I simply answered accordingly.

(At the time I wished that the calculator I had gave more decimal places).

:P
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#7 Chris Millar

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Posted 05 May 2009 - 06:22 PM

Hold on - the first answer (3.32 stops) is correct ONLY IF the frame rate difference is an exact reflection of the exposure time change. But 0.1fps is very slow. I have no idea what sort of camera is being discussed here - film? digital? what sort? How does it vary exposure time at slow frame rates? If it changes nothing, then a 0.1fps exposure would be anywhere between 5 and 10 seconds (depending on effective shutter angle) which is unlikely.

My guess, in the absence of all relevant information, is that the camera gives the same exposure time on all fame rates slower than a certain amount - which would explain why the operator has compenasted four stops and finds it is four stops overexposed.


This is why I say "all other things being equal" (which I guess in this case :rolleyes: is to effectively say a continuous rotating shutter and not some intermittent or electronic camera)

... and I ask the OP to explain why they used the word "still" with regard to the over exposure - due to the ambiguity of that statement it isn't clear yet.

looks like the beginning of a lot of discussion stemming from one little question - and notice the post count of the OP - hmmm
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#8 K Borowski

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Posted 05 May 2009 - 07:12 PM

I was aware of both of your considerations at the time ...

It was a rather blunt question with no qualification so I simply answered accordingly.

(At the time I wished that the calculator I had gave more decimal places).

:P


There is no problem with using as many decimal places as you want, just so long as you put in either percent error or error factors, or even better yet break down error with respect to shutter variance, film movement, reciprocity, and mirror/shutter spin.

;)
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#9 Chris Millar

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Posted 05 May 2009 - 08:00 PM

There is no problem with using as many decimal places as you want, just so long as you put in either percent error or error factors, or even better yet break down error with respect to shutter variance, film movement, reciprocity, and mirror/shutter spin.

;)


In this particular case I'll leave that to you Karl !
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#10 Satsuki Murashige

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Posted 06 May 2009 - 03:26 AM

Hey, don't forget about reciprocity failure! Useful information 19.576% of the time, +/- 15%. :rolleyes:
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#11 K Borowski

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Posted 06 May 2009 - 10:05 AM

Hey, don't forget about reciprocity failure! Useful information 19.576% of the time, +/- 15%. :rolleyes:


NICE!

Is that just with respect to reciprocity, or are you deriving for all factors combined as well?

I really like error factors, though, that are bigger than the number that is quoted, i.e. 19.765 Units +/- 25 Units :-D
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