# Filter Factor



## Mitica100 (Nov 3, 2022)

I haven't posted in a while here with technical data and I thought I'd get back with some info, useful or not. LOL

FILTER        Factor
UV (0)          1
Y (K2)           2
O (G)            3
R (25A)         8
G (XI)            4
SKY (IA)        1
A (85)           25
F (85C)          2
B (85B)          3
D (81A)         1.5
A (81C)         1.8
D (82A)         1.2
D (80B)          3
D (80C)          3.5
IR (89B/R72)  16
IR (70/092)     20-40


Filter factorProportion of light transmitted (1/FF)Number of stops195–100%01.375% (3/4)1⁄31.470%1⁄21.567% (2/3)2⁄3250% (1/2)12.540% (2/5)11⁄3333% (1/3)12⁄3425% (1/4)2812.5% (1/8)3166.25% (1/16)4
 

That's it...


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## AlanKlein (Nov 4, 2022)

You ought to use the filter manufacturer's recommendation.  They could be different than the above.


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## webestang64 (Nov 5, 2022)

Comparison chart from a filter book.........


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## AlanKlein (Nov 5, 2022)

AlanKlein said:


> You ought to use the filter manufacturer's recommendation.  They could be different than the above.


Many old filter factors were based on JKodak Wratten filters.  YOu ought to check with the current filters' manufacturer recommendations.  Also, check the specs brochure from the film manufacturers.


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## RAZKY (Nov 5, 2022)

AlanKlein said:


> Many old filter factors were based on JKodak Wratten filters.  YOu ought to check with the current filters' manufacturer recommendations.  Also, check the specs brochure from the film manufacturers.


Which filter factors for currently available  black and white, color conversion and light balancing filters are not based on Kodak Wratten filters?


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## AlanKlein (Nov 6, 2022)

RAZKY said:


> Which filter factors for currently available  black and white, color conversion and light balancing filters are not based on Kodak Wratten filters


I have no idea.  Why should I care about Wratten equivalents? If they're provided by the filter manufacturer, OK.  That might help some people who are familiar with Wratten filters.   But that doesn't help me determine the factor number?

I use the factor number provided by the filter manufacturer that came with the filter.  I then write the stops required on the filter case for easy reference so I can adjust the exposure at the time I use it.  I don't change the ISO setting in the meter but just add the number of stops to the shutter speed or aperture or combination.  If I remember too.


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## AlanKlein (Nov 6, 2022)

I just thought of a time knowing Wratten numbers for modern filters might be helpful. That's when you want to match filters from different manufacturers when buying new ones since they use different numbering systems for their filters.


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## RAZKY (Nov 6, 2022)

AlanKlein said:


> I have no idea.  Why should I care about Wratten equivalents? If they're provided by the filter manufacturer, OK.  That might help some people who are familiar with Wratten filters.   But that doesn't help me determine the factor number?
> 
> I use the factor number provided by the filter manufacturer that came with the filter.  I then write the stops required on the filter case for easy reference so I can adjust the exposure at the time I use it.  I don't change the ISO setting in the meter but just add the number of stops to the shutter speed or aperture or combination.  If I remember too.





AlanKlein said:


> I just thought of a time knowing Wratten numbers for modern filters might be helpful. That's when you want to match filters from different manufacturers when buying new ones since they use different numbering systems for their filters.


Contrary to what you assert, most currently available black and white, color conversion and light balancing filters are still designated by Wratten numbers.


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## AlanKlein (Nov 6, 2022)

RAZKY said:


> Contrary to what you assert, most currently available black and white, color conversion and light balancing filters are still designated by Wratten numbers.


We're talking past one another.  Please re read my post.  The point is I don't need to know about Wratten filters or factors.  I'm not buying Wratten filters.  I'm buying new filters and the manufacturer gives me the stops I need to adjust.  The only point of knowing the Wratten number is if you need to replace a filter and want the same level of filtration assuming the new filters match the Wrattens.  Then you buy a new filter with the same Wratten number.


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## RAZKY (Nov 7, 2022)

It is indeed a most complicated subject that not everyone has the capacity to understand.


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