Meter through B&W Filters

lhalcong · Feb 12, 2014

Metering with a sekonik through B&W red or orange filter does not work , I have to meter without the filter and then use the compensating factor. Correct ?

Tom1956 · Feb 12, 2014

That is the best idea, as the spectral sensitivity of the meter cell is an unknown and probably not at all linear. Translation: possible color blindness leading to erroneous readings. You're following the safest idea.

Jeff Kubach · Feb 12, 2014

That's what In do.

Jeff

RalphLambrecht · Feb 12, 2014

lhalcong said:
Metering with a sekonik through B&W red or orange filter does not work , I have to meter without the filter and then use the compensating factor. Correct ?

In my experience ,the safest way to go is meter withoutfilter and apply the filter fsctor afterwards.meters have a different spectral sensitivity to eyes and/or film
:confused:

brian steinberger · Feb 12, 2014

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

Poisson Du Jour · Feb 12, 2014

Look up the filter factor for both the red and the orange filters, individually.
With the Sekonic, adjust the ISO2 button to give +3.0 (e.g. 8EV) for the red filter. Meter the scene with the Sekonic with the filter in place. At the conclusion of metering (e.g. averaging), press ISO2 for the factored exposure. Transfer to the camera. Bracket up (but not down) from the reading/ISO2 setting, and take notes.
Same technique for using a polariser, though a couple of potential traps there. Another time.

Bill Burk · Feb 13, 2014

lhalcong said:
Metering with a sekonik through B&W red or orange filter does not work , I have to meter without the filter and then use the compensating factor. Correct ?

I think if you have a hand-held meter... Metering without the filter and then applying the manufacturer's filter factor is a good plan.

Likewise, it's obvious when you put a red filter on the lens and the meter on the camera only sees one or two stops difference.... There's something wrong about metering through the filter. I've ended up with thin negatives exposed by red filter because I didn't notice it (years ago when I shot lots of black and white landscapes in 35mm on auto).

So I was intrigued by the Gordon Hutchings filter factors, intended to be used after metering through the filter.

If you look in Google Books for Using the View Camera By Steve Simmons, the free preview includes the page which explains the Gordon Hutchings filter factors.

I haven't seen a lot of excitement regarding the Hutchings factors, and Doremus Scudder pointed out an apparent fallacy. The caption under the chart explains blue light in shadows are why you need additional exposure when metering through a deep red filter. Doremus pointed out that red light would curtail blue light to the meter, leading logically to the opposite conclusion, that a meter reading of blue shadows through a red filter will already recommend additional exposure.

I have to believe Gordon Hutchings tested his factors, and so looked again. The practice described is to take meter readings of bright, mid-tone and shadow through the filter to determine exposure and developent... THEN add the Hutchings factor... If you base your exposure on three meter readings, the shadow reading isn't playing as much a role (Hutchings-style) in the overall exposure calculation... While shadows play a significantly greater role in exposure calculation when you base your exposure from a shadow reading and your development from a highlight reading (Zone System-style). So maybe the Hutchings factor works if you do your metering his way.

One of my favorite thoughts about determining exposure, is that you can be eclectic and pick and choose pieces of technique that fits your way of working. But you should check that the pieces fit together well and do not correct for the same thing twice.

Bill Burk · Feb 13, 2014

Poisson Du Jour said:
With the Sekonic, adjust the ISO2 button to give +3.0 (e.g. 8EV) for the red filter. Meter the scene with the Sekonic with the filter in place. At the conclusion of metering (e.g. averaging), press ISO2 for the factored exposure.

I think you double-compensated here.

Dr Croubie · Feb 13, 2014

RalphLambrecht said:
In my experience ,the safest way to go is meter withoutfilter and apply the filter fsctor afterwards.meters have a different spectral sensitivity to eyes and/or film
:confused:

Actually, the real safest way to go is to hack the firmware/bayer filter of a digital camera to have exactly the same spectral response to your film in question, take test shots with the same lens and filter in place and look at the response curves. Or have a portable darkroom and develop your test-shots on site.

But given that it's Black and White film then you'll have enough latitude that +/- 1 stop out from 'perfect' can easily be fixed when enlarging/scanning, so just meter without and take off the filter factor as everyone else does, it'll be near enough.

R.Gould · Feb 13, 2014

I I am using 400 film and filters I would set iso 200 for a yellow filter, 100 for an orange and 50 for red, and meter using those settings, works fine for me

250swb · Feb 13, 2014

R.Gould said:
I I am using 400 film and filters I would set iso 200 for a yellow filter, 100 for an orange and 50 for red, and meter using those settings, works fine for me

It couldn't be any more difficult than doing exactly that, or so I thought until I read this thread.

Steve

StoneNYC · Feb 13, 2014

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?

David Allen · Feb 13, 2014

I seem to be in the minority camp here as I always metered through filters (when doing landscape work - I rarely ever use filters today). However, this is using a Weston V meter which responds to colours very much like film. I have always found filter factors to be unreliable as they do not account for dominant colour of light or colours within the scene. For example, when metering dark shadows to determine ZoneIII there is often a lot of blue light and the exposure compensation is often more than 3 stops.

I am aware that earlier in-camera meters had spectral sensitivity problems and do not know how your meter responds and how you meter.

I would be interested in what other photographers approach is.

Bests,

David
www.dsallen.de

Xmas · Feb 13, 2014

The problem is the spectral sensitivity of CdS cells and TTL metering - you need to know what you are doing.

Taking the battery out of the OM1 is easier I might needle follow rather then push the button.

The rest of us can work around non average sceanes any way we chose.

pdeeh · Feb 13, 2014

250swb said:
It couldn't be any more difficult than doing exactly that, or so I thought until I read this thread.

If you're finding photography straightforward then you're clearly doing it all wrong

gone · Feb 13, 2014

"If you're finding photography straightforward then you're clearly doing it all wrong"

I will assume this is satire, and funny satire at that. All you'll ever need to know on this subject is stated concisely and clearly by R. Gould (and thank you for that post). If you will just commit this to memory or jot it down somewhere, you can then adjust your in camera meter to agree w/ this, and extrapolate the different ISO films from the 400 base. But if you did that, then we couldn't argue about how many angels can dance on the head of a pin.

Xmas · Feb 13, 2014

momus said:
"If you're finding photography straightforward then you're clearly doing it all wrong"

I will assume this is satire, and funny satire at that. All you'll ever need to know on this subject is stated concisely and clearly by R. Gould (and thank you for that post). If you will just commit this to memory or jot it down somewhere, you can then adjust your in camera meter to agree w/ this, and extrapolate the different ISO films from the 400 base. But if you did that, then we couldn't argue about how many angels can dance on the head of a pin.

It probably was satire and quite risible, but true if you want shots 'like' Ansells, he employed a zone system and quaint developers...

But R Gould post wont (always) work with a CdS meter camera with a meter cell behind the filter e.g. lots of the early range finders and almost all early SLR, It is important not to 'set up' beginners with a new film camera and a yellow filter. It is ok with a silicon cell behind the filter, camera except you don't adjust the ISO at all!

If you don't understand that, please read momus' post again, If I use a filter I remove the battery from my 'post' cell metering cameras first... and use my Weston as RGould suggests, note YMMV

Lots of our kids are moving from lomos to metal cameras and need basic training that does not occur in a DSLR course in college...

Noel

benjiboy · Feb 13, 2014

lhalcong said:
Metering with a sekonik through B&W red or orange filter does not work , I have to meter without the filter and then use the compensating factor. Correct ?

That's O.K, as long as you don't forget to reset the compensation factor when you remove or change the filter, I find it a better method with my Sekonic L358 to apply the filter factor after taking the meter reading easy, and you can't forget to reset the meter.

pdeeh · Feb 13, 2014

momus said:
I will assume this is satire, and funny satire at that. .

well, I wouldn't dignify it with the epithet 'satire' but, yes, to be clear, it was intended to be humorous.

Sirius Glass · Feb 13, 2014

brian steinberger said:
I always have accurate exposures metering through color filters with my Pentax digital spot.

Same for me with Minolta and Nikon through the lens meters. According to others I must not have enough experience with this since I have been doing it this way since the 1970's.

Silly me

Too old to care · Feb 13, 2014

R.Gould said:
I I am using 400 film and filters I would set iso 200 for a yellow filter, 100 for an orange and 50 for red, and meter using those settings, works fine for me

This is what I do. My Leica M6 TTL cannot meter correctly through colored filters either, max correction with a red filter on the Leica is one f-stop, a yellow filter is less than 1/2 f-stop. So, set my ISO according to the settings above, meter w/o the filter, attach the filter and shoot away.

Wayne

Xmas · Feb 13, 2014

benjiboy said:
That's O.K, as long as you don't forget to reset the compensation factor when you remove or change the filter, I find it a better method with my Sekonic L358 to apply the filter factor after taking the meter reading easy, and you can't forget to reset the meter.

Hi Ben

Your meter has silicon cells it should be reasonable through a filter, the early CdS cells are woeful in lots of conditions? Have you tried it?

Noel

Mr Bill · Feb 13, 2014

I'm in the camp of metering the subject directly, then apply the filter factor.

An important point is where you get your filter factors from. I recently posted in a thread about filter factors for some sharp-cutting red filter (like Wratten 25). Someone was using factors supplied by the filter manufacturer, which I maintain is the wrong place to get them from - you should ideally get them from the film maker, and ideally for the light source you use.

Since I went to the trouble of writing an explanation, I'm also going to paste it in here:

Let me demonstrate why this matters. We now know that your B+W 090 (light red) is equivalent to Wratten 25, right? Looking at two Kodak film data sheets, T-max 100 and the obsolete Tech-pan, here are Kodak's filter factors:

Wratten 25 (red), Daylight: T-max factor = 8 (3 stops), Tech Pan factor = 3 (1.6 stops)
Wratten 25 (red), Tungsten light: T-max factor = 4 (2 stops), Tech Pan factor = 2 (1 stop)

So Kodak, who ought to be the most knowledgeable about their own films and filters, have the filter factor for this one specific filter anywhere from 2X to 8X. In other words, the exposure correction should be somewhere from 1 stop to 3 stops, DEPENDING on the film and light source. THIS IS WHY THE FILTER MAKER CANNOT PUT A (reliable) BLANKET FACTOR ON THIS FILTER. (If your only data is from the filter maker, intial exposure tests are probably worthwhile.)

Most of the time your exposure won't be so sensitive to filters - this is sort of a worst-case situation. The #25 red cuts sharply at about 600 nm (at 580 nm and lower virtually nothing comes through) so exposure only occurs from there on up. This means that there can be a big exposure difference between films with different amounts of red sensitivity, such as the two listed.

If anyone is inclined to meter THRU the filter, they ought to consider how the meter would handle the difference between these two films: Tmax 100 vs Tech Pan.

StoneNYC · Feb 13, 2014

Mr Bill said:
I'm in the camp of metering the subject directly, then apply the filter factor.

An important point is where you get your filter factors from. I recently posted in a thread about filter factors for some sharp-cutting red filter (like Wratten 25). Someone was using factors supplied by the filter manufacturer, which I maintain is the wrong place to get them from - you should ideally get them from the film maker, and ideally for the light source you use.

Since I went to the trouble of writing an explanation, I'm also going to paste it in here:

Most of the time your exposure won't be so sensitive to filters - this is sort of a worst-case situation. The #25 red cuts sharply at about 600 nm (at 580 nm and lower virtually nothing comes through) so exposure only occurs from there on up. This means that there can be a big exposure difference between films with different amounts of red sensitivity, such as the two listed.

If anyone is inclined to meter THRU the filter, they ought to consider how the meter would handle the difference between these two films: Tmax 100 vs Tech Pan.

Or Acros100

benjiboy · Feb 13, 2014

Xmas said:
Hi Ben

Your meter has silicon cells it should be reasonable through a filter, the early CdS cells are woeful in lots of conditions? Have you tried it?

Noel

I know the spectral sensitivity of Silicon Blue cells is better than Cadmium Sulphide ones Noel, your'e quite right, but they are still not perfect or as good as photo electric meter cells it's just the method I tend to use myself that works for me.

Meter through B&W Filters

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