Just a question, not so much a commentkevin_nordineMay 7 2007, 16:08:19 UTC
Hi Chris. I do like your journal very much. What sort of camera are you using? And now for the dreaded question (I hope this isn't too forward)... Do you have any time available outside of your work (for hire) to help me figure out a way to do something called a "Bright Field Correction" or "Gain Mask"? I'm trying to figure out a way to correct for the non-linearity in a 2K, 12-bit CCD camera. In other words, I'd like to smooth out the field as a post processing step. The cameras that are available to me don't do this automatically. There is an older CCD that I've used made by Leaf (DCB-1) which uses a file called a "Gain Mask" in this fashion. The mask is an average of 16 grayscale grabs of the off white field and is somehow rendered into a mathematically inverted array that looks something like a negative of the uneven field. It is then subtracted or divided (?) from the image file in order to produce a scan that results in a scan with a perfectly even field. I've been told that this is a fairly simple operation, but not one that is a standard sort of channel calculation in Photoshop or After Effects. So, I'm wondering if this is something that you may have dealt with and if there's a way that I might "coax" you into revealing what the steps are in the recipe or comment on the proceedure. Many thanks & apologies if need be for asking... Kevin. kevin.nordine@gmail.com
Re: Just a question, not so much a commentchriscoxadobeJuly 1 2007, 17:55:10 UTC
BTW - bright field correction or white field correction/calibration are pretty common in astronomy and microscopy.
Yes, division is the normal method of doing the correction - but you really need floating point numbers to handle that because many of your values will end up greater than 1.0.
Dark Field Correction/Subtraction is also common - but mostly for low light situations (LONG exposures).
In both corrections, the data needs to be applied to the linear (gamma 1.0) data before it gets processed in any other way.
Re: Just a question, not so much a commentkevin_nordineJuly 1 2007, 18:04:56 UTC
Hi Chris. Thanks for responding. This ends up being a custom "math filter" in AE, right? I may have someone to do this... I'll pass your comments along Thanks again, Kevin.
Re: Just a question, not so much a commentkevin_nordineJuly 1 2007, 20:47:12 UTC
Hi Chris. Thanks for your timely response. I think I have someone who can do this for me as an AE plug-in... I'll pass it along for them to read. Thanks again, Kevin.
I do like your journal very much. What sort of camera are you using?
And now for the dreaded question (I hope this isn't too forward)...
Do you have any time available outside of your work (for hire) to help me figure out a way to do something called a "Bright Field Correction" or "Gain Mask"? I'm trying to figure out a way to correct for the non-linearity in a 2K, 12-bit CCD camera. In other words, I'd like to smooth out the field as a post processing step. The cameras that are available to me don't do this automatically. There is an older CCD that I've used made by Leaf (DCB-1) which uses a file called a "Gain Mask" in this fashion. The mask is an average of 16 grayscale grabs of the off white field and is somehow rendered into a mathematically inverted array that looks something like a negative of the uneven field. It is then subtracted or divided (?) from the image file in order to produce a scan that results in a scan with a perfectly even field. I've been told that this is a fairly simple operation, but not one that is a standard sort of channel calculation in Photoshop or After Effects. So, I'm wondering if this is something that you may have dealt with and if there's a way that I might "coax" you into revealing what the steps are in the recipe or comment on the proceedure.
Many thanks & apologies if need be for asking...
Kevin.
kevin.nordine@gmail.com
Reply
No, I really don't have much time outside of work.
I'm having enough trouble maintaining a life outside of work...
Reply
Yes, division is the normal method of doing the correction - but you really need floating point numbers to handle that because many of your values will end up greater than 1.0.
Dark Field Correction/Subtraction is also common - but mostly for low light situations (LONG exposures).
In both corrections, the data needs to be applied to the linear (gamma 1.0) data before it gets processed in any other way.
Reply
Thanks for responding.
This ends up being a custom "math filter" in AE, right?
I may have someone to do this...
I'll pass your comments along
Thanks again,
Kevin.
Reply
Thanks for your timely response.
I think I have someone who can do this for me as an AE plug-in...
I'll pass it along for them to read.
Thanks again,
Kevin.
Reply
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