Filter factor adjustment in developing

pentaxuser · Oct 5, 2022

koraks said:
When using a red filter, I only photograph red objects. With a green filter, only green objects. Etc. I prefer to keep things nearly separated like that.

I can imagine that on occasions a specific colour, say, a red car might occupy a very large portion of the scene with a person standing close to the body of that car with a green tee shirt. In that sort of case it would appear that if you wanted to create a sharp difference between the 2 colours using a red filter then you may not need to alter the exposure

I cannot work out if in Drew's question of "do you shoot pictures of all red or all green objects etc? " he is agreeing that you and, I think, AgX are right in those situations. If he is then we have at least a third person who agrees with you

So in such a situation of a scene with nearly all one colour it becomes very worthwhile to know that no compensation for the filter is required

In practical terms what counts is where does compensation matter. Is it a 99% one colour scene or a 95% or an 85%, how does one decide?

Thanks

pentaxuser

koraks · Oct 5, 2022

pentaxuser said:
how does one decide?

Depending on the envisioned effect.
Depending on how much effort you want to put into figuring out what to do.
Depending on how much of a safety margin you want to use.
Depending on lots of things.
Personally I just either apply a filter factor or just meter through the filter. With small format gear, it's usually the latter. Works well enough in practice.

To be fair, I do the same as Drew and just apply a filter factor. I never suggested this wouldn't be necessary. We just had a somewhat theoretical discussion on what a filter does (and does not do). And evidently I didn't take Drew's initial comment seriously; if course it was a rather silly rhetorical question.

pentaxuser · Oct 5, 2022

koraks said:
Depending on the envisioned effect.
Depending on how much effort you want to put into figuring out what to do.
Depending on how much of a safety margin you want to use.
Depending on lots of things.
Personally I just either apply a filter factor or just meter through the filter. With small format gear, it's usually the latter. Works well enough in practice.

To be fair, I do the same as Drew and just apply a filter factor. I never suggested this wouldn't be necessary. We just had a somewhat theoretical discussion on what a filter does (and does not do). And evidently I didn't take Drew's initial comment seriously; if course it was a rather silly rhetorical question.

Thanks koraks. I got the impression that in cases of nearly all one colour you might be able to ignore compensation which might have been useful on occasions depending on shutter speed needed etc but it seems that we were in the largely theoretical sphere and for all practical purposes filter factors are needed in all cases There is no real-life situation in which exposure compensation is not required

pentaxuser

koraks · Oct 5, 2022

pentaxuser said:
There is no real-life situation in which exposure compensation is not required

I didn't say that. But it isn't common. As I said, it depends...

Juan Valdenebro · Oct 6, 2022

take11 said:
Hello everyone,

I hope I'm posting in the right section.

I'm going to use Ilford hp 5 plus 400 with a dark yellow filter with factor 3x (so 1.5x stop loss). I was thinking about shooting it at 800 with hand held light meter set at 400 and developing at box speed.

Shall I develop like I pushed the film or is box speed fine? Is my idea right or shall I reconsider everything?

Thanks in advance and for eventual suggestions

Hello,
HP5+ with a deep yellow filter looks great.
Most developers, well used, will give you with HP5+ an exposure index of 400 without filter. With or without filter, your development should be the same: the standard one for your enlarger: all you need is giving your film a stop and a half more light in camera for every photograph.
If you'll scan, everything will work: that's a different story.
Camera meters can be fooled easily by light, and sometimes filters fool them too. Your best bet would be handheld incident metering with the dome recessed, held vertically, aiming at camera, set at 125.
After that, all you have to do is nail development: it takes time, but it's a lot harder if you're not sure about development, and not sure about exposure either... You can totally trust this metering and exposure.
Good luck!

DREW WILEY · Oct 7, 2022

Heck, I used a deep blue tricolor 47 filter yesterday on a forest scene to do exactly the opposite of the standard advice - turn it into an almost 19th blue-sensitive plate look with blackened green foliage a blanked-out white sky, and lightened shadows. An abandoned bight white Victorian building was in the foreground. Then I duplicated the shot with a red filter to bring out the clouds in the blue sky and deepen the shadows. I'll probably print both versions, and they'll probably both be intriguing prints, but in quite different ways. In other words, learn the rules, then selectively break them to your own esthetic advantage.

Incidentally, I never meter through contrast filters; that can get you in trouble because meters have different sensitivities across the spectrum. It might be OK with mild filters; but anything like that 47 Blue, or 25 Red I just mentioned, or even mid-density contrast filters, and you might be in for a significant error. Recommended and ideally tested filter factors are a much more reliable route. Such testing involves bracketed roll film exposures of a neutral 18% gray target, plus an exposure without any filter in place as a reference to compare your results to. A transmission densitometer helps if you want to be really accurate; but just visual comparison on a light box is often sufficient. And results for one specific type of panchromatic film don't necessarily apply to another. You need to test for each filter & film combination.

Vaughn · Oct 7, 2022

Our brains are pretty efficient at auto color-correcting. A polarizing filter in the jungle can be used to reduce the reflection of the blue light from the sky off the leaves. This removes a blue cast on them that we may not notice standing there.

Photographing pictographs, etc on red rocks is an interesting time for filter use. An all-one-color situation. And trying to make one's way cross country in the Redwoods (especially in second growth) is sometimes called being lost in the green shit. But at least one has reddish trunks coming out of the green shit for color-contrast! But generally I only use a yellow filter occasionally (in the Fall) in the redwoods.

Personally, since I use a hand-held meter, I never change the ISO on my meter off the ISO I rate the film at. That'd be disaster waiting for me...bad enough when I have holders with two ISO types of film in them! I figure the exposure, then apply the filter factor.

M Carter · Oct 7, 2022

The only advice I can add is - take your filter and a meter and meter all kinds of stuff with it. If you don't have a spot meter, get very close to specific colors and also meter full scenes. Meter without the filter, then hold the filter over the meter's sensor and see the difference. You'll learn a fair amount, and you'll have a specific filter factor for your specific filter for general scene use. You can suss it all out in a few minutes.

When I do zone system work and use filters to change the skies, I always take a spot-sky reading through the filter, it's a big help.

My filter wallets have cards with the factors for every color filter I use. Very handy to know for sure!

Pieter12 · Oct 7, 2022

Why change the ISO and not the f-stop or shutter speed? You are just introducing another layer of complication to the process. You should have an ISO, developer and development time for that film that you are satisfied with--leave it alone.

Juan Valdenebro · Oct 7, 2022

Hello Pieter,
No ISO change recommended in my post: camera remains at 400, but scene reflectance fools most meters to some degree if we use reflected metering.
But when we meter for filter use, in case of handheld incident metering, that's an optimal place to adjust exposure using the manufacturer's filter factor because that's a stable amount of extra light every time, so it makes sense because that's the easiest and most precise way.

DREW WILEY · Oct 8, 2022

All kinds of arguments can be made over one's preferred metering style. I'm 100% within the reflected handheld spot meter camp myself. That allows precise measurement of small discrete areas and not just general illumination; and high versus low luminance values in the scene can be quickly compared, and all in between to. This has served me well for decades.

Juan Valdenebro · Oct 8, 2022

You're totally right about spot reflected metering, Drew: not only precise, but as you said, the only way to do it if we want to control low and high values. My Sekonic spot meter on well placed gray card meters identically or within a tenth of a stop, every time, from a vertical meter, recessed dome, incident metering.
Both options are equally valuable tools: each of them can't be used sometimes, because of spatial and luminic conditions of certain scenes.
For roll photography, film technology allows us to control highlights, even whites under direct sunlight, with development simply.
That's what I do in general when I photograph: but for my tests, inside the scene I include a strip of gray card and spot meter it, because in those cases I'm next to my scene.
For street and other fast types of photography without tripod and without time, the only option is using some years to learn how to judge light without meters: it's relatively easy for maybe the six or seven strongest levels of common outdoors light.

DREW WILEY · Oct 8, 2022

Yeah, for rapid shooting like with a Nikon and color film, TTL center-weighted metering can be helpful. I actually learned on an early externally coupled CDS 45 degree averaging meter on a Honeywell Pentax H1, and almost never botched an exposure, even with Kodachrome. But when I got into large format film for sake of printmaking per se, and then also into black and white LF printing, I switched over to Pentax digital spot meters.

The most important factor regardless is that one gets familiar enough with their own meter and film selection that it all becomes spontaneous and second nature. Same goes for filter use. I've seen photographers in the wilderness packing over twenty different gel filters and 7 lenses for their 4x5 camera. They were still fiddling around confused with all those choices when it turned dark, and was already too late to even get a shot. I was done an hour before. Keep it simple.

Juan Valdenebro · Oct 8, 2022

I didn't talk about it, but TTL metering, even when it's center weighted, leads to many wrongly exposed frames, no mater if color film is used.
Exposure will be correct only if the center of our composition reflects the same amount of light that a gray card reflects, so very few frames will be optimal.
How much deviation from precise exposure a person can take, is another story. But even color negative film suffers severely after underexposure, and that's the common case (not overexposure) both from white walls (1 to 2 stops underexposure) and from light sources (even more).
And color slide film is a lot less tolerant than color negative.
Of course if the center of the scene is close to middle gray in promedy, those few cases will show correct exposure, but not because of the center weighted system, but because of the central tones in our frame. Avoiding overcast skies -base of the center weighted design- is useless if the center of our scene is a white wall. Or worse, a lamp, or a window with light behind it.

Sirius Glass · Oct 9, 2022

DREW WILEY said:
All kinds of arguments can be made over one's preferred metering style. I'm 100% within the reflected handheld spot meter camp myself. That allows precise measurement of small discrete areas and not just general illumination; and high versus low luminance values in the scene can be quickly compared, and all in between to. This has served me well for decades.

I agree. The incident meter is used for white on white or black on black or gray on gray. The spot meter is only used for Zone System exposure adjustments.

Sirius Glass · Oct 9, 2022

Juan Valdenebro said:
I didn't talk about it, but TTL metering, even when it's center weighted, leads to many wrongly exposed frames, no mater if color film is used.
Exposure will be correct only if the center of our composition reflects the same amount of light that a gray card reflects, so very few frames will be optimal.
How much deviation from precise exposure a person can take, is another story. But even color negative film suffers severely after underexposure, and that's the common case (not overexposure) both from white walls (1 to 2 stops underexposure) and from light sources (even more).
And color slide film is a lot less tolerant than color negative.
Of course if the center of the scene is close to middle gray in promedy, those few cases will show correct exposure, but not because of the center weighted system, but because of the central tones in our frame. Avoiding overcast skies -base of the center weighted design- is useless if the center of our scene is a white wall. Or worse, a lamp, or a window with light behind it.

Use any meter including the TTL to read without the sky in view. The sky throws off the readings and gives center weighed reflectance meters bad name.

DREW WILEY · Oct 9, 2022

Huh ? Cinematographers aren't Zonies, but are addicted to Pentax spot meters. There is an IRE scale on those. I use em for everything even though I left behind the ZS long ago. The only incident meter I own was inherited, and lies in the bottom of a drawer somewhere - a Weston meter so ancient it was probably last used to measure the light falling on Gondwanaland.

Filter factor adjustment in developing

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