Yellow, Orange, Red Filter Factors?

[jamgolf]

I have a simple (or perhaps not so simple) question. I've purchased Heliopan Yellow #8, Orange #22, and Red #25 filters. According to the specs, Yellow has a compensation factor of 1.5 stops, Orange 2-stops and Red 3-stops. However, when I take a spot meter reading in EV mode with a Sekonic 758, the difference in readings between a straight reading and one through the filter is 0.6 stops for Yellow and 1.1 stops for Orange filter.

I want to trust my own readings, but I am confused by the difference. I have taken readings from different subjects ... sky, stuff around the house, ground, etc. and the difference in EV readings is never 1.5 stops for Yellow or 2 stops for Orange.

This has me puzzled. What am I not getting? What is the correct compensation factor to use?

[paulbarden]

The filter factor given by the manufacturer can be trusted.

[jamgolf]

Thanks, Paul.
I usually trust whatever the manufacturer specs say, and will probably just use the compensation factors per specs, but I am definitely confused by the EV readings.
I mean I trust the light meter to provide a correct exposure value when not using a filter, it feels very strange to ignore the meter when using a filter.

[Mark Sawyer]

I want to trust my own readings, but I am confused by the difference. I have taken readings from different subjects ... sky, stuff around the house, ground, etc...

Use a grey card in daylight, not colored subjects in whatever light source is around the house. Also, meters wander. Paul is right, trust the manufacturers.

[jamgolf]

Thanks, Mark
I have actually taken readings in daylight and the difference in EV values is ~0.6 for Yellow and ~1.1 for Orange filter.
For instance, on a sunny day, I take a reading off a puffy cloud in the sky the reading might be 15.7 EV and if I put a Yellow filter in front of the spot meter the EV value is 15.1 - for a 1.5 stop compensation I would expect the reading to be 14.2.

While I do not have a Kodak 18% gray card, I do have something close to it.

[Sal Santamaura]

There are three variables involved. The spectral response of your light meter. The spectral response of each film. And the spectral composition of the scene, which is a product of both the subject and the light falling upon it.

Therefore, there's only one answer: test, test, test. :)

[Alan Klein]

Do you trust the film manufacturer's recommendation on their specification sheet or the filter manufacturer's recommendation?

[jamgolf]

Alan, I would like to trust both the film manufacturer's recommendations and the filter manufacturer's recommendations.

But as Sal said "test test test" and that's what I have been doing with films and developers etc. and same thing here - instead of blindly accepting the compensation factors, I thought let me check the differences in EV values with/without filters - but I am a bit surprised and confused by the EV readings - so I thought I should ask if I am misunderstanding something.

[Pieter]

Just shoot some film with the factor as specified and the metered-through-the-filter reading (not always accurate, by the way) and maybe bracket, too.

[Tobias Key]

I got a similar set of filters recently and I found the readings I got putting the filter over my spot meter did not correspond to the filter factors at all. I just used the manufacturer's recommendation and haven't had any problems.

[jamgolf]

Thanks for all the advice and input.
I'll probably run some tests by exposing sheets using the manufacturer's specified compensation factor vs the metered compensation factor, just for my peace of mind.
Otherwise, I know I will just keep thinking/wondering about it.

[tgtaylor]

The Heliopan filter factor for their #8 yellow filter has a spread of 1.3 to 1.5 stops. This spread is probably due to manufacturing variance between samples. I have a Tiffen Deep Yellow 15 glass filter with a filter factor (according to B&H) of 3.3 (1.3 stops). I just measured mine with a Sekonic 758DR and got a reading of f45.4 @ 1/4" without the filter and f45.4 @ 1/8" with the filter (1 stop instead of 1.3 stops). Nonetheless, unless measuring thru the lens with the filter attached to my f6 or Pentax MF cameras, I would go with the manufacturer's specification of 1.3 stop for LF photography. For the former I would go with the camera's meter setting.

Thomas

[Doremus Scudder]

You're finding that filter factors are not nearly as "simple" as you may have believed.

Manufacturers give you exposure factors that work under the controlled lighting, metering and exposure parameters they test with and err, if at all, on whatever they deem "the safe side" to be. They work well for most real-life situations.

When you read an exposure through the meter you introduce a whole lot of other variables: the color temperature of the light source you are using (sunlight, late-afternoon sunset light, indoor tungsten or led lighting, etc., etc.), the spectral response of your meter (which likely doesn't match what the manufacturer used to determine the filter factor), and the colors of whatever you are metering (note that even objects that appear "colorless" and grey to the eye are often not nearly "neutral" as far as what the manufacturer used to determine the filter factor).

So, to use the filter factor or to use the reading through the meter? With smaller cameras with TTL metering, using the meter with the filter in place seems most reasonable. Since there will likely be a discrepancy, it's a good idea to keep careful notes and err on the side of overexposure a bit until you can come up with a "factor" for using the filter over the meter.

The same applies to using your spot meter to read through the filter, but be aware that spot meters, with their small field of view will give you even more variation in readings than an averaging meter. If you meter something yellow with a yellow filter in place, you'll get identical readings; if you meter something blue through a yellow filter you'll get a reading that implies a much greater filter factor than "standard." You need to take that all into account if you decide to read scenes through your filter. However, that's what I do.

In lieu of that, use the manufacturer's recommendations, keep your light source in mind and adjust the factor if needed for that and keep notes. If you find your factor needs adjusting to give good results, don't hesitate to change it.

Best,

Doremus

[BrianShaw]

Thanks for all the advice and input.
I'll probably run some tests by exposing sheets using the manufacturer's specified compensation factor vs the metered compensation factor, just for my peace of mind.
Otherwise, I know I will just keep thinking/wondering about it.

Ironically, I did the same thing a couple of days ago with a set of Kodak Wratten series V filters... and got the same numbers. Daylight with a diffused white surface in background. Sekonic L-558 using the flat-field incident reading. Don’t bother with the measured number... it’s wrong. The manufacturer recommended is a lot closer. But at least we got nearly identical measurements!

[Drew Wiley]

Everything depends on the specific film in question. So yes, the manufacturer's tech sheet for that specific film is generally an excellent starting point. But then, filters vary a little between respective manufacturers, or sometimes have faded a bit; so there is no substitute for actual testing with your own filters. In reference to the filter set in question, my own set when used with TMax films, for all practical purposes, requires one EV exposure compensation for light no.8 yellow, 2 EV for 22 deep orange, and 3 EV for 25 medium red, all densitometer verified. Most common pan film are nearly the same in response to these three filters; but that consistent pattern diverges when green or blue filters are involved, or even a deep red no.29. Don't meter through the filter - that is often misleading; use filter factors instead. Meter spectral sensitivity might very well differ from your film itself, perhaps significantly.

[Two23]

I assume that since you're using colored filters that you're shooting b&w pan film? The variances most of you are talking about here don't seem to be enough to screw up your exposure calculation. Your shutter isn't exact either.



Kent in SD

[Bob Salomon]

I have a simple (or perhaps not so simple) question. I've purchased Heliopan Yellow #8, Orange #22, and Red #25 filters. According to the specs, Yellow has a compensation factor of 1.5 stops, Orange 2-stops and Red 3-stops. However, when I take a spot meter reading in EV mode with a Sekonic 758, the difference in readings between a straight reading and one through the filter is 0.6 stops for Yellow and 1.1 stops for Orange filter.

I want to trust my own readings, but I am confused by the difference. I have taken readings from different subjects ... sky, stuff around the house, ground, etc. and the difference in EV readings is never 1.5 stops for Yellow or 2 stops for Orange.

This has me puzzled. What am I not getting? What is the correct compensation factor to use?

Read up on hysteris failure which occurs when metering many fiyrts through the filter whit a CDS cell meter.
Try your first tests by using the filter manufactures filter factor.
And as many have stated film speed, filter factors, processing times, etc. are only guides. Test first.

[Alan Klein]

Everything depends on the specific film in question. So yes, the manufacturer's tech sheet for that specific film is generally an excellent starting point. But then, filters vary a little between respective manufacturers, or sometimes have faded a bit; so there is no substitute for actual testing with your own filters. In reference to the filter set in question, my own set when used with TMax films, for all practical purposes, requires one EV exposure compensation for light no.8 yellow, 2 EV for 22 deep orange, and 3 EV for 25 medium red, all densitometer verified. Most common pan film are nearly the same in response to these three filters; but that consistent pattern diverges when green or blue filters are involved, or even a deep red no.29. Don't meter through the filter - that is often misleading; use filter factors instead. Meter spectral sensitivity might very well differ from your film itself, perhaps significantly.

Glad to hear that because B+W recommends that for the yellow +1 , orange +2 and red +3 filters I use from them. The only difference is for my orange filter, they say its +2 stops however it's equal to a #16 Wratten not #22 as you have listed. https://www.bhphotovideo.com/c/product/7474-REG/B_W_66015530_77mm_040_Yellow_Orange_16.html

[jamgolf]

Doremus, Brian, Drew, Bob, Kent, Thomas, and Alan
Thank you again for your very helpful responses.
Much appreciated!

I should most probably use the manufacturer's recommendations but just as an interesting exercise, I might do an experiment comparing similar exposures using metered value vs manufacturer's EV factor.

[Alan Klein]

Doremus, Brian, Drew, Bob, Kent, Thomas, and Alan
Thank you again for your very helpful responses.
Much appreciated!

I should most probably use the manufacturer's recommendations but just as an interesting exercise, I might do an experiment comparing similar exposures using metered value vs manufacturer's EV factor.

Don't forget to post your results here so we can argue about it again. :)

[Heroique]

I should most probably use the manufacturer's recommendations but just as an interesting exercise, I might do an experiment comparing similar exposures using metered value vs manufacturer's EV factor.

I too will be interested in your findings.

I remember starting out with my Lee polyester b/w set, and being suspicious of their easy confidence in compensation stops. I decided not to overthink it, just go with their numbers, see the results, and make any judgment calls with more time in the woods and general field notes.

My overall experience? Their numbers have worked, I’d estimate, for 95% of my diverse landscape shots. I’m thankful my field notes haven’t led to a lot of over-thinking and distracting rationalizations. If I didn’t take notes, maybe that’s the situation I’d find myself in.

(For those who might be curious, here’s what Lee recommends for their set: )

Yellow # 8 (+1/3 stop)
Yellow-Green #11 (+1 2/3 stops)
Orange #21 (+1 stop)
Red #23a (+2 stops)

[Drew Wiley]

Lee polyester quality control is on the so-so side. But even if those figures do apply to one kind of film, they might not to another. Not all pan films have the same spectral response. It's a broad category. And any such adjustments also are relative to the kind of light source. That's why on film spec sheets you often encounter two separate sets of filter factors, one for daylight, the other for tungsten. You also often get a spectral response curve - but there you need to be especially careful making comparisons, because they don't all share the same light source either - some are based on warm color temp exposure instrumentation, some on nominal daylight balanced ones.