Darken Green in B&W - What Colour Filter?

[Martin Aislabie]

Guys, I am trying to photograph some flowers in B&W

The trouble is they are not much different in tone from the background vegetation.

What colour of filter do I need to darken the green foliage, so I can lift the tone of my subject from its background :confused:


Also, is this the best location for such a thread?

Thanks

Martin

 

[Ian Grant]

A red filter darkens green.

Exposure discussion I suppose is a better place

Ian

 

[BradS]

Green foliage always gives me trouble. I think the problem is that, although it looks green to our eyes, it really emits or reflects a great deal of IR as well. Whatever the reason, I often find that filters do not give the expected results with green foliage....and in fact, actual results can be quite contrary to expectations.

I've had some success by avoiding the green issue altogether. For example, red roses against their green leaves....with no filter, the red does not stand out against the green. So, instead of trying to make the green darker or lighter...I've had better luck concentrating on the red...the obvious thing to do is use a red filter to make the red flowers lighter...which worked well. (and this jives well with Ian's advice too )

Ultimately, you will need to experiment and keep careful notes so that you can figure out what works and maybe, form a theory about why.....exposure makes a big difference too...

 

[Mike1234]

In nearly every case there is more yellow in "green" vegetation than green. The opposite of green is red, as Ian states, and the opposite of yellow is blue. Blue and red make magenta and this is the "most" effective filter to darken most foliage. Careful though... the darkest magenta or red filters can render foliage as nearly black. Of course, to make red flowers stand out, then red is the better choice. It's not just about darkening greens but also about lightening the flora, as Brad alludes to.

EDIT: Opposite of green is MAGENTA. Red is opposite of CYAN!! So a red or blue or magenta filter should do the trick depending on color of the flora.

 

[Q.G.]

Remember though that the only way you can "lighten" one colour is to darken a, or several, other(s).


So best bet is still to keep thinking simple, and just aim at darkening green.
If a flower is near that colour, the change in contrast will be small. If the colour of the flower moves away from green towards the 'opposite side' on the 'colour wheel' the contrast will increase.
But all you can do to make a flower stand out against something using filters, is to darken that something the flower should stand out against (hoping the filter will leave the flower untouched).


IR, by the way, will not be a problem.
If it were, we would not need expensive IR films.

 

[Nicholas Lindan]

The opposite of green is magenta - a magenta filter passes red and blue and blocks green. Cyan blocks red, passes green and blue. Yellow blocks blue, passes red and green. Cyan, magenta and yellow are the subtractive colors - they are the colors used in color prints to subtract from the white of the page.

However, leaves have quite a bit of deep red in them and at infrared they appear white. A red filter won't add much contrast. When a tree removes the chlorophyll from it's leaves the red and yellow colors of autumn reveal the other pigments in the leaf.

You might find a very deep blue filter - indigo - will give you the look you are after - though it may actually lighten some leaves.

Yellow flowers turn black with an indigo filter, so it wouldn't be a good choice for making them stand out. You might then try, as suggested, using a filter the same color as the flower, making the flower lighter than the leaves and not darkening the leaves per-se.

To judge the effect of the filter compare the 'value' of the leaf and flower with a grey card with and without the filter.

For lots of fun with this get the large Rosco color filter sampler book and a gel filter holder.

 

[keithwms]

Yellow, orange, red or dark red or even IR... depending on how much effect you want. N.b you can tune the effect finely, if your subject is stationary, by doing a double exposure- one exposure with and one exposure without the filter.

For a subtle effect you might just shoot with a pan or extended pan film. The added red sensitivity may be all you need.

 

[Q.G.]

I love this "making the flower lighter than the leaves and not darkening the leaves per-se"

As if putting a filter in front of a lens magically increases the light coming off the flowers, leaving the light coming off the leaves unaffected.

That of course is impossible.
All a filter can do to make the flower 'lighter' is indeed make the rest (the leaves) darker, block the light coming from everything else but the flowers.

So you will, by force, be "darkening the leaves per-se".

 

[Mike1234]

OG is, of course, right for the most part. The OP just wants to increase the tonal differential between foliage and flora. Choice of filter color and density is expansive. One could compensate with exposure to "effectively" not affect foliage density thereby only "affecting" flora. It's a matter of perspective to some degree.

 

[BradS]

OG is, of course, right for the most part. .

only in a sophistical sort of way....
We generally increase exposure when using contrast filters...so, of course, the red flowers do turn out lighter when photographed with a red filter.

 

[Mike1234]

Sorry, Brad... I added to my post as you were replying. FWIW, I agree with you.

 

[Nicholas Lindan]

As if putting a filter in front of a lens magically increases the light coming off the flowers

Yeah, that was badly phrased.

Filters can only darken, obviously.

But sometimes the effect is as if the object was lightened rather than the surround darkened. If you have more than two objects in the scene the distinction between lightening and darkening becomes real.

I judge filtration by comparing the results of the filter on the object against a grey card. Something that darkens the leaves would darken them in relation to a grey card - if the leaf and card have the same relative value and placing a filter in the light path doesn't alter the relationship of the filter to the card then in my book it didn't really darken the leaves. Conversely if the flower became brighter in relation to the grey card with the filter in place I think of the filter as lightening the flower rather than darkening the grey card or the leaves.

Lets say we have a scene of a flower, leaves and sky. In the prints the tonal value of the sky stays the same. If the relationship of the flower and the sky stays the same but the leaves go dark then I think of it as darkening the leaves because that's what it looks like in the final print. If the filter darkens the leaves and sky, passing the wavelength of the flower, then I think of it as lightening the flower - again, because that's what it looks like in the print as the exposure was increased to maintain the sky's (and in this case, the leave's) tone.

Science Vs art; reality Vs perception. Photography is the use of science and reality to make art and alter perception.

 

[Q.G.]

only in a sophistical sort of way....
We generally increase exposure when using contrast filters...so, of course, the red flowers do turn out lighter when photographed with a red filter.

Ah!
But "in a sophistical sort of way" i must argue that you only increase exposure to get the same density in the flower you would have gotten without the filter (compensate for unwanted absorbtion), while the disproportionate blocking of other colours by the filter would ensure that the foliage still has less density on the negative, despitre increased exposure.

The red flower actually appears as light in your photo as it would have done witout the filter (unless you want to overexpose it). The green foliage will appear darker.

Unless you add additional lights to pick out bits of your scene, and those alone, you really only darken things.
"Really", in a non-'sophistical' way.

It doesn't matter much, were it not that thinking in terms of lightening and darkening only makes the issue appear more complex than it actually is.
A filter selectively blocks light. It is as simple as that.
Though you of course can, there is no need to think about it in any other way.

But even then, it really doesn't matter much.

 

[Martin Aislabie]

Thanks guys for the advice

I used to know the colour wheel stuff but as I haven't done colour in decades it’s all gone

I have some colour photography books in the attic gathering dust - which I cannot get to

The suggestion of Nicholas to compare the colour though a filter against grey card is a really great idea

Martin