question about stacking square filters

[ericantonio]

Hola! Happy 1 millionth day of quarantine.
I used to have yellow/green filters on my 35mm lenses. So I have a bunch of 49/52mm filters. Kinda hard to find yellow/green somewhere. Instead of finding filters to use for my Pentax 67, I figure I get the square ones so I can use them with my LF lenses as well.

I'm assuming I can stack a yellow and a green filter to make a "yellow/green" filter yes? It seems kinda obvious but hey, all this alone time is making me lose arguments with myself.

Also, what would be the approximate filter factor for that? Same as a yellow/green or add the yellow and add the green square filter together?

See, I'm losing an argument with myself already!

[Alan Gales]

You would add the filter factor of the yellow filter to the filter factor of the green filter.

I used to stack Cokin filters together back when I shot 35mm. The Cokin filter holder was made so you could easily do this.

[Mark Woods]

Meter a gray card through the filters to get your compensation. If you have a meter on the 67, put the filters on and meter through the lens. When I was shooting cinema, I stacked as many as 9 filters with no problems -- that said, one had to be careful about reflections.

[ericantonio]

You would add the filter factor of the yellow filter to the filter factor of the green filter.

I used to stack Cokin filters together back when I shot 35mm. The Cokin filter holder was made so you could easily do this.

That's what I thought, like "use your common sense man" but all this alone time is making me nuts. And I start questioning reality!

[ericantonio]

Meter a gray card through the filters to get your compensation. If you have a meter on the 67, put the filters on and meter through the lens. When I was shooting cinema, I stacked as many as 9 filters with no problems -- that said, one had to be careful about reflections.

Wow, great tip thank you!!! 9 filters. Dang man.

[Alan Gales]

That's what I thought, like "use your common sense man" but all this alone time is making me nuts. And I start questioning reality!

No worries. We were designed to be sociable creatures. Too much alone time will make anyone nuts. That's why solitary confinement in prison is such a punishment.

[Doremus Scudder]

When you stack colored filters, you just get the effect of the strongest filter. E.g., when you stack red and yellow, the yellow filter passes red orange and green; the red filter cuts out the orange and green, so you just get red. The yellow filter is doing nothing but degrading the image.

The same with yellow and green. Yellow passes red, orange and green, but the green filter only lets the green through, so, again, the yellow filter is doing nothing.

If you stack complementary colors, say green and red, you just get neutral density. If the filters are sharp cut and good quality, you'll get black...

Rule of Thumb: Don't stack colored filters.

A "yellow-green" filter is somewhere in strength (i.e., how much of the blue end of the spectrum gets eliminated) between yellow and green. If that's the filter you need, you just have to get one. You can't make one by stacking the stronger green filter together with the yellow.

Go to the Wikipedia site on Wratten numbers and familiarize yourself with the progression of colored filters from weaker to stronger (yellow - red) and the variations in between. Take a look at the color wheel and the concept of complementary colors as well and it will all become clear.

Best,

Doremus

[ericantonio]

When you stack colored filters, you just get the effect of the strongest filter. E.g., when you stack red and yellow, the yellow filter passes red orange and green; the red filter cuts out the orange and green, so you just get red. The yellow filter is doing nothing but degrading the image.

The same with yellow and green. Yellow passes red, orange and green, but the green filter only lets the green through, so, again, the yellow filter is doing nothing.

If you stack complementary colors, say green and red, you just get neutral density. If the filters are sharp cut and good quality, you'll get black...

Rule of Thumb: Don't stack colored filters.

A "yellow-green" filter is somewhere in strength (i.e., how much of the blue end of the spectrum gets eliminated) between yellow and green. If that's the filter you need, you just have to get one. You can't make one by stacking the stronger green filter together with the yellow.

Go to the Wikipedia site on Wratten numbers and familiarize yourself with the progression of colored filters from weaker to stronger (yellow - red) and the variations in between. Take a look at the color wheel and the concept of complementary colors as well and it will all become clear.

Best,

Doremus

Looks like I need to get some reading in today!! Thanks for the information.

[Dugan]

We won't worry about you until you start telling yourself jokes you've never heard before.

[LabRat]

With relatively mild color film filters, transmission readings can work, but for denser B/W filters, this changes... The optical density is different than the spectral sensitivity of the film... Then meters have differing color sensitivity across the reading spectrum... You can observe this by putting a strong colored filter on TTL metered cameras and notice the difference in reading and the listed filter factor... Then try it on a different TTL metered camera and you might see another change in reading... Then the pan film has its own sensitivity curve, and the overall dominant colors of the scene lighting change this too... And different color filters behave different...

You should try to not combine filters too much as each increases the air to glass # of surfaces affecting overall contrast and even internal reflections can ghost around some combinations... Combining color filters for B/W is not recommended or needed as there are single existing filters for not too much $$$... Usually multi filters are used with the appropriate color filter and some effect filter like ND, polarizing, soft filters etc...

For yellow/green, either darker yellow or lighter green have a similar effect without complicating the combined filter factor...

Also note that published filter factors are a starting point to be combined with film tests and the entire system...

Choose a couple of filters, know why you will use them, test, and be aware of conditions that will throw the exposure off...

Steve K