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05-22-2012, 06:11 PM   #1
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TTL Metering with Coloured B&W Filters

Hey everyone, I've recently been shooting a lot of B&W, and I've pretty much replaced my UV filter with a K2 Yellow. I know that it has a filter factor of 2 and according to the Ilford site my camera meter should automatically adjust for it. However, when I slide it in-front of my lens nothing changes (except everything turns yellow of course). Even more frustrating is that the same thing happens with my red filter (although Ilford said that I should need to adjust 1-2 stops for this). Does anyone have any advice on this? What do you do with yellow? orange? red? 85C (well this is for colour but same deal no?)? Any help would be great.

Thanks

Elliot

-- If anyone cares I'm shooting using an MX and an LX

05-22-2012, 06:40 PM   #2
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You do not have to do anything, the meter will take care of the exposure factor.
Just be carefull of dark filters and slow film. You may need a tripod due to the slow shutter speeds.

Phil.
05-22-2012, 11:21 PM   #3
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QuoteOriginally posted by Simian Summit Quote
However, when I slide it in-front of my lens nothing changes (except everything turns yellow of course).
By this, do you mean the light reading with and without the filter are the same? What should happen: with the filter on, about 1 stop greater exposure.
05-23-2012, 07:06 AM   #4
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QuoteOriginally posted by Nesster Quote
Originally posted by Simian Summit Quote However, when I slide it in-front of my lens nothing changes (except everything turns yellow of course). By this, do you mean the light reading with and without the filter are the same? What should happen: with the filter on, about 1 stop greater exposure.
That's right. I meant that when I slid the filter in front of the lens I saw no change in the TTL metering. Which is what I was confused about since I was expected the meter to read 1 less EV.

05-23-2012, 07:48 AM   #5
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And this is consistently so with both mx and lx? I'll go check my filters and cameras and report back...


...and I'm back. Using a newly CLA'd KX and M 50/1.4 lens, observations:

even a 1a daylight filter changes the reading, by about the thickness of the shutter speed needle, a fraction of an EV
yellow Y2 reduces EV by a bit more, I'd say 1/2 EV at the most, a bit of a surprise
Red R2 reduces a full two stops
polarizer reduces ~1.5 EV

Last edited by Nesster; 05-23-2012 at 07:58 AM.
05-23-2012, 11:05 AM   #6
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A) The TTL meter should adjust for the filter in the sense of the extra light cut out by the filter will be compensated for.

B) The Hutchings Filter Factor suggests an extra adjustment of exposure to "protect the densities in shadow areas".

These are:
#12 - medium yellow (minus blue) FF 0
#13 - yellow green FF 1
#16 - medium orange FF 1
#21 - light red FF 1
#23A - medium red FF 1
#25 - red FF 2
#44A - cyan (used with panchromatic film to simulate the effect of ortho film) FF 1

FF1 means give an extra stop of exposure, FF2, two stops, etc.

Hope this helps.

Kris
05-23-2012, 07:04 PM   #7
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Thanks everyone. After seeing Nester's post I ran to put my MX (with A50/1.7) on a tripod to repeat his results. I found much the same thing...

Yellow K2 ... 0-0.5
Red 25A ... 1 (This is different than what Nester found)
Green X1 ...2 (this is what it should be)

Given this should this and Kris' suggestions on EV compensation (which more or less agrees with some other stuff I found from Filters in Black and White Photography), should I be dialing back the film sensitivity on my meter, or does no one bother to do this?

Elliot
05-23-2012, 09:10 PM   #8
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I usually do nothing and let the TTL meter take care of things. I might add a 1/2 to 1 stop if using a dark red filter.

Phil.

05-24-2012, 03:23 AM   #9
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QuoteOriginally posted by Simian Summit Quote
Given this should this and Kris' suggestions on EV compensation (which more or less agrees with some other stuff I found from Filters in Black and White Photography), should I be dialing back the film sensitivity on my meter, or does no one bother to do this?
Eliot, my red filter is a very dark, deep one - they come in different intensities. Your camera automatically compensates for the filter since it reads through it - and as Phil says, you do not have to do anything.

When shooting with a meterless camera and a hand meter, or a camera whose built in meter is not in the lens, the filter factors come into play. In those instances I often first use the meter with and without the filter in front of it, just to get an idea about the exposure adjustment I'd have to make... This is one reason why in the lens or behind the lens metering was such a goal for camera makers.
05-24-2012, 08:59 AM   #10
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QuoteOriginally posted by Nesster Quote
When shooting with a meterless camera and a hand meter, or a camera whose built in meter is not in the lens, the filter factors come into play. In those instances I often first use the meter with and without the filter in front of it, just to get an idea about the exposure adjustment I'd have to make... This is one reason why in the lens or behind the lens metering was such a goal for camera makers.
I can appreciate this, although why I asked the question is that I wasn't seeing the shift that I expected to see in the meter readings. So I was wondering that if the camera is metering using a standard of 18% grey and colour tone of the image changes will this fool the meter to inaccurately measure the light. If the general consensus that no one bothers to worry about it unless your using a deep red filter, then the answer may be no the light meter generally isn't fooled.

Thanks for all your input

Elliot
05-24-2012, 09:45 AM   #11
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Elliot, I was pondering just that on my way to work this morning.

While a generic "TTL will take care of it" approach works well enough for most of us, most of the time... I recall in the olden days film manufacturers would specify factors that took into account film spectral sensitivity and what sort of lighting you were shooting in, e.g. this Ilford sheet




Lucky for most of us, in this hobby we often can get by with approximations... while there is room for the precise and persnikety.

Here's a good discussion of the variables involved.
filter factors and metering through filters - zone system - Photo.net B&W Photo - Film & Processing Forum
05-24-2012, 02:54 PM   #12
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I'll admit to only worrying about the additional filter factors I quoted (which are in addition to the compensation needed for the filter given by the TTL system) when using my 5x4 large format camera. Every neg is so expensive I want to get the best out of it!

K.
05-28-2012, 11:24 PM   #13
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QuoteOriginally posted by Nesster Quote
Eliot, my red filter is a very dark, deep one - they come in different intensities. Your camera automatically compensates for the filter since it reads through it - and as Phil says, you do not have to do anything.
This is not necessarily true. The camera meter may, or may not, be colour blind. A good test of your meter's colour sensitivity is to aim the camera at a gray card (lens at infinity, card filling the screen) and take a picture of it with each of your various filters with the meter needle adjusted to give "correct" exposure (or just put the camera on automatic).
Set the lens to wide open to ensure that slight variations in aperture setting from exposure to exposure don't affect things (limit your variables as much as possible).
If your meter is colour blind, then each of the frames that you shot will look exactly the same. If your meter is not colour blind, then you will have an idea of how much to bias it with any given filter.
05-29-2012, 04:43 PM   #14
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IMO viewing and composing through a deeply colored filter is a PITA.
I do use them on my rangefinder cameras etc., but never on an SLR.
OTOH SLR cameras are much more amenable to the use of a polarizer.

Chris
05-29-2012, 10:04 PM   #15
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Hopefully the meter has a spectral response curve similar to that of the film. Unfortunately, that varies considerably depending on what film you favor! Both of which point to a central point. Filter factor is a "best" guess at how much correction to apply. Much depends on the spectral sensitivity of the film in question as well as the manufacturing standards applied to the filters themselves. (Ever notice how much variability there is between Y2 filters...all with a nominal filter factor of 2?)

Using TTL metering is probably at least as accurate as blindly accepting a single factor to fit all films.


Steve
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