Meter through B&W Filters

[Xmas]

Hi

If you want to be picky you need the

filter spectral response
sensor (film) spectral response
film spectral response
colour of zone 1 shadow
or colour of zone that you want to control

convolute (and maybe integrate)

But depends what you are worried about, cine guy will want the leading ladies face spot on between cuts so incident with dome on her nose, Answell his zone 1 with some detail, HCB might not bother, he left things to his printer...

I use a dome on a Weston cause I shoot peoples faces (or hands) and I need to margin for non-Caucasians the shadows can look after themselves, no filters. If I'm doing hills and valleys, I bracket with or without filters, and meter on zone I if I can.

Noel

 

[fretlessdavis]

If you have a Kodak Grey Card it's easy to ascertain your personal filter factor for each of the filters you own by using your hand held meter at the grey card first, then through the filter .

Different tones respond to filters differently, as well as different films. This won't give results that are any better than just using published filter factors. Like my example before, tones that will give the same reading on a handheld meter can often vary widely in terms of actual tone on the film. If I used the same filter factor on red sandstone and blue water, the red sandstone would be very dense, where the blue water may have very little detail left.

Yes meters won't give perfect readings with a red filter, but try using a spotmeter with a red filter on it, and pointing it around a scene. It'll give you a good idea of the contrast range, of the scene, and a better idea of what your baseline exposure should be before adding the filter factor. Not perfect because of the sensitivity of film, but it'll give you a close idea. This is what I do for landscapes. After a while it's pretty easy, and you can guess based on experience, and be close enough. A universal filter factor has just never worked for me.

 

[BrianShaw]

Here is something I've always found quite useful on this topic. Talks about filters, factors, and light source. Now quite as strong as one would may like on how this all relates to specific films, other than ortho vs panchromatic.

http://www.ohio.edu/people/schneidw/vico222/222Handouts/295filtr.pdf

... and not at all useful for color work.

 

[RalphLambrecht]

I always have accurate exposures metering through color filters with my Pentax digital spot.

mine is thrown off by several stops when using a red or deep orange filter.I'm much better off with the filter factors

 

[Regular Rod]

There was a simple formula on a similar thread recently, now I can't remember... Bill, was it...

ASA / filter factor # = new EI?

Like 100 ASA with yellow filter (factor 2) is 100/2= EI 50?

So 100/red (5) = EI 20?

Is that right?

Yes

RR