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The ICF Database - Not all ICF are created equally


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#1 Shane

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Posted 04 March 2009 - 17:25

Although the subject title is pretty obvious, the following two ICF (Internal Cut Filter) spectra illustrate the extreme variation that can occur between models.

I would like to create a database of ICF spectra for the various makes and models but this would require a collection of ICF which would obviously be a difficult and expensive undertaking. However, if anyone has an unwanted, damaged or broken ICF, that they would like to "donate" to the project I would be grateful. Please contact me via email if you can help.
Thanks.

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#2 kds315

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Posted 05 March 2009 - 12:56

Sigma SD14 ICF

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#3 kds315

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Posted 10 March 2009 - 14:01

© astrosurf.org given in Angstroms (divide by 10 to get nm)

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Posted Image
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#4 kds315

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Posted 18 March 2009 - 14:46

As measured today:
- Nikon D70 ICF (violet)
- Makario ext. ICF (turquiose)
- Schott BG40 (white)
Cut-on for the last two is about 320nm, Nikon is ca. 335nm

I prefer to use the BG40 since it damps NIR very well but allows UV to pass.
Also useful to be used with a normal UV transmissive, absorbing filter like
Schott UG1 for instance to suppress NIR leakage.

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#5 Shane

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Posted 18 March 2009 - 17:07

Thanks for posting these Klaus. I actually have a D70 ICF here (courtesy of Bob) but you beat me to the posting. I have often wondered if the D70 curve posted on astrosurf was correct as I would have expected more of a sharp cut-off at the red end, however your spectrum appears very similar. It would also appear that the Makario ICF is a pretty good match at both ends considering the cut-off for the modified D70 sensor appears to be around 320nm.
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#6 Andrew

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Posted 18 March 2009 - 17:14

I have ICF from D40X. Interested? Send me yours adress!

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#7 kds315

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Posted 18 March 2009 - 17:15

Most welcome Shane. I have made tests using the Makario filter and
indeed it works pretty well and allows to use a mod. camera as if it
were an "off the shelf" one. It is a bit on the cold side (as is the BG40)
but a simple WB adjustment makes it work perfectly.
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#8 Shane

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Posted 18 March 2009 - 17:48

Andrew
pm sent
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#9 Shane

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Posted 18 March 2009 - 18:07

It is a bit on the cold side (as is the BG40) but a simple WB adjustment makes it work perfectly

To be expected from the additional UV but it is good to know that it is easily compensated for with WB adjustment.
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#10 Shane

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Posted 30 March 2009 - 19:05

From the D200 ICF it is obvious why this must be modified for UV photography. I would really like to compare these ICF transmission spectra with the Nikon D40 if anyone has one.

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#11 kds315

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Posted 30 March 2009 - 19:14

Well that surely explains a lot. Thanks Shane.
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#12 Shane

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Posted 03 April 2009 - 22:15

Thanks to Andrea, Bob Friedman and Andrew (Poland) for contributing their ICFs for the project.
Shane
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#13 kds315

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Posted 04 April 2009 - 08:57

Since you have the ICF on Adrew, how does the one of his D40 look like?
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#14 Shane

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Posted 04 April 2009 - 14:53

Since you have the ICF on Adrew, how does the one of his D40 look like?


I just received the D40X ICF yesterday and will try to run it in the next week or so when time permits. It would be nice to be able to compare it to the D40 if anyone has one. Also looking for Fuji, Canon and Pentax ICF.

I would imagine there are a lot of ICFs from DSLR conversions that are sitting around "collecting dust". They will probably never go back into the camera unless it was self-converted.  After all, if it costs around $400 to get the camera converted, who is likely to spend that again to get it converted back, especially if the camera is showing signs of age.
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#15 Trainwreck

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Posted 05 April 2009 - 13:42

I have the ICF from a D100.

#16 Shane

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Posted 05 April 2009 - 16:09

Thanks Trainwreck - pm sent.
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#17 Shane

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Posted 10 April 2009 - 02:49

Nikon D70 Custom ICF for Full Spectrum UV through IR. This appears to be a Schott Borofloat glass which has a slightly higher UV cut-off than the Schott WG280.

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#18 kds315

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Posted 10 April 2009 - 03:03

The one I have usaed for my D70 has >90% at 270nm. I find that one shown cuts off a bitg too much of useful response.
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#19 Shane

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Posted 10 April 2009 - 03:09

The one I have usaed for my D70 has >90% at 270nm.


Assuming that the sensor can really be effective at that wavelength then I agree. I would at least go for the Schott WG280.
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#20 brianc1959

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Posted 11 April 2009 - 12:25

Assuming that the sensor can really be effective at that wavelength then I agree. I would at least go for the Schott WG280.


Personally, I can't understand why fused silica isn't the standard material for this purpose.  Surely the amount of money saved by using an inferior material is minimal.




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