Light metering and lens filters

[Hardus Nameous]

@hooray4mo were you able to find the filter factor for your filters?

 

[AlanKlein]

I use big Mamiya polarizers on my MF cameras. +1.5 stops works just fine. Having a meter with two ISO settings makes it easy.

1.5 stops may work if the polarizer is set for maximum polarization. I often find that's too much and wrings out the life in foliage. So I back off and reduce the polarization which then means only 1 stop required.

 

[Stevedevil01]

This isn't a petting zoo.

No its a Photo Forum, where we need to be constructive and help others reach their goal, We can all slate each others work, but that gets us nowhere, you seem to offer such knowledge, it would be good to share this, as we all started somewhere

 

[hooray4mo]

@hooray4mo were you able to find the filter factor for your filters?

I haven't done too much research just yet.
I did take a picture of the lenses and their "information" though.
On top, from left to right I have a Hoya 80B (Blue), a Vivitar Yellow - No.8 (K2),
and a Fotomate Cross [I know this one doesn't exactly fit in with the rest of the filters, but it was included in the case with all the others].
And on the bottom there's a Tiffen 25 Red 1, Lyncrest x1 (Green), and a Hoya 85 (Orange-ish?).

I'm planning to test them all out on some BW film, and do some bracketing shots once I get my step up rings in the mail.

 

[Hardus Nameous]

The Tiffen and Hoyas should be easy to get from their websites; the others may take some digging or experimenting though.

 

[RAZKY]

I'm on the market to buy a light meter as I've been getting into portrait photography a lot more lately. I also have quite a few lens filters that came with the various cameras that I've acquired over the years. With that being said, I want to get ahead of the learning curve and learn to use a light meter properly with the lens filters.
How would I go about adjusting the settings on the light meter appropriately/accurately to compensate for when a lens filter is attached?
Obviously it will vary depending on each individual lens filter, as they have differing intensities.
(Before you ask, I HAVE tried googling and also YouTubing some answers but I have yet to come across anything that gives me an in-depth answer =/)

This may help:
The table below gives approximate filter factors for a variety of common photographic filters. It is important to note that filter factors are highly dependent on the spectral response curve of the film being used. Thus, filter factors provided by the film manufacturer should be preferred over the ones documented below. Furthermore, note well that these factors are for daylight color temperature (5600K); when shooting under a different color temperature of ambient light, these values will most likely be incorrect.

Filter purpose​	Wratten number​	Other designation​	Filter factor​
Contrast filters​
Colour conversion (blue)​
Warming filters​
Cooling filters​
Colour conversion (orange)​
Neutral density​
Polarizers​
Ultraviolet	UV(0)	1
Skylight	1A or 1B	KR1.5	1
Yellow	8	Y, K2, Y48, 022	2
Yellow-green	11	X0	2.5
Orange	21	3
Red	25	A, 090, R2	8
Deep Red	29	F, 091	20
Green	58	X1	4
Infra-Red	89B	R72	16
Infra-Red	70	092	20-40
3200 K to 5500 K	80A	KB15	4
3400 K to 5500 K	80B	KB12	3
3800 K to 5500 K	80C	KB6	2
3400 K to 3200 K	81A	A2	1.4
3500 K to 3200 K	81B	1.4
3600 K to 3200 K	81C	KR3	1.4
3700 K to 3200 K	81D	1.5
3850 K to 3200 K	81EF	KR6	1.5
3000 K to 3200 K	82A	B2, KB1.5	1.3
2900 K to 3200 K	82B	1.5
2800 K to 3200 K	82C	KB3	1.5
5500 K to 3400 K	85 / 85A	KR12	1.6
5500 K to 3200 K	85B	KR15	1.6
5500 K to 3800 K	85C	1.3
0.3	96	NDx2	2
0.6	96	NDx4	4
0.9	96	NDx8	8
3.0	96	NDx1000	1000
Linear polarizer	PL or LP	3 to 4
Circular polarizer	PL-Cir, C-PL, CP	3 to 4

The table below illustrates the relationship between filter factor, the amount of light that is allowed through the filter, and the number of stops this corresponds to.
Filter
Factor

Filter Factor	Proportion Of Light Transmitted (1/FF)	Number Of Stops
1	95–100%	0
1.3	75% (3/4)	1⁄3
1.4	70%	1⁄2
1.5	67% (2/3)	2⁄3
2	50% (1/2)	1
2.5	40% (2/5)	11⁄3
3	33% (1/3)	12⁄3
4	25% (1/4)	2
8	12.5% (1/8)	3
16	6.25% (1/16)	4