What is the filter factor for.......

What is the filter factor for a No. 25 red filter, and a No 23 Orange filter, when used over the lens for b/w photography?

Try this:
http://www.kodak.com/US/plugins/acrobat/en/motion/support/h2/h2_filters.pdf
This does not list 23, only 23 A. My instinct would be to start with factors of 4 (23) and 8 (25).

Regards,

David

Filter factors are somewhat film dependent but, usually, the red filter has a filter factor of 8 and the orange is 4 or 6. Best to look at the film manufacturer's data sheet.

filter factor?

USE your meter. Factor CAN vary from manufacturer to manufacturer.
Better safe than wrong.

best

Robb Scharetg
www.scharetgpictures.com

PHOTOTONE said:

What is the filter factor for a No. 25 red filter, and a No 23 Orange filter, when used over the lens for b/w photography?

Click to expand...

Robb Scharetg said:

USE your meter. Factor CAN vary from manufacturer to manufacturer.
Better safe than wrong.

best

Robb Scharetg
www.scharetgpictures.com

Click to expand...

It would seem that you are stating that the meter's spectral response follows that of film. That is not true. Even the Zone VI modified meters, while better than some, are still not completely in accord with the film's spectral response.

Filter factors will be dependent upon the color of the filter and the object being exposed...for instance a Red filter will have a higher filter factor when exposing a green object than it will have when exposing a red object. I have went so far as measure my filters using a color transmission densitometer. I took readings of each of the channels and printed out the densities for each of the channels...this seems to work best for me.

When I meter through a #23 I invariably get a 2 stop filter factor, and when I meter through a #29 I invariably get a 4 stop filter factor. I don't own a #25.

As Donald says above, this obviously doesn't apply equally across your picture -- after all, you're using it specifically as a contrast filter, thereby exploiting different reflectivity in your subject.

Meter first (*), then bracketing...
Be aware that not all emulsions and light situations are alike, high noon light is far off the same as sunset light, but this you already know.
Just give it a try, it might work for you to.

Good luck,
Philippe

(*) Put the filter on (over) the light-meter and compare with the unfiltered metering, in the same light situation.

Don't meter through strongly colored filters. Meter cells are not matched to the spectral color sensitivity of film. For that matter, various films have different enough spectral response to merit individual filter factors. When using strongly colored filters - say B/W contrast filters or maybe an 85B, meter separately, and apply the factor. Factors vary under different light. Note that the 25 loses 3 stops in daylight and only two under tungsten.

List of filters and factors and stops change under daylight and tungsten follows. The list may get garbled up but you should be able to sort it out .

(Values in round parentheses are for other panchromatic films)

#3 (K1) Light Yellow day 1.5 or 2/3 stop
tung none none

#8 (K2) Yellow day 2x (1.5x) or 1(2/3) Stop
tung 1.5x(1.2x) or 0.5 Stop(1/3)

#9 Deep Yellow day 2x or 1 Stop
tung 1.5x or 2/3 Stop

#11 Lt Yellow Grn day 4x(3x) or 2 (1 2/3)Stops
tung 4x (3x)or 2(1 2/3)Stops

#12 Deep Yellow day 2x or 1 Stop
tung 1.5x(1.2x) or 0.5(1/3) Stop

#15 Deep Yellow day 2.5x(2x, 3x) or 0.7(1) Stop
tung 1.5x or 2/3 Stop

#21 Orange day 4x or 2 Stops
tung 2x or 1 Stop

#23A Light Red day 6x or 2.5 Stops
tung 3x or 1.5 Stops

#25 Red day 8x or 3 Stops
tung 5x(4) or 2.25(2) Stops

#29 Deep Red day 20x or 4.25 Stops
tung 10x or 3.25 Stops

#47 Blue day 6x(8x)or 2.5 (3)Stops
tung 12x(25x)or 3.5(4 2/3)Stops

#47B Deep Blue day 8x or 3 Stops
tung 16x or 4 Stops

#58 Green day 8x (6x)or 3 Stops
tung 8x(6x) or 3 Stops

#61 Deep Green day 12x or 3.5 Stops
tung 12x or 3.5 Stops
Best,

C