*%@!ing Red filters!

[Stuart B]

I've recently started back shooting B&W - Medium format, usually Delta 100 or FP4. I picked up some filters pretty cheap, and thought I'd try them out. I have a deep yellow and a dark red. Try as I might I cannot get those nearly black skies that are supposed to happen with red filters. I've shot test series of blue skies with no filter, then the yellow filter (compensate exp 2/3 stop) and then the red filter (compensate 3 stops). The negatives look virtually identical! The blue skies show almost no decrease in density, certainly nothing like the results I've seen elsewhere

Is there something I'm missing? Something obvious that I'm not doing?

Thanks.

 

[Jeremy]

Stack a polarizer with your red filter and burn in the sky in printing.

Also, what red filter do you have?

 

[Q.G.]

Do the other parts, besides the blue skies, show a difference in density?

 

[Anscojohn]

Perhaps your filters are faded and passing too much UV and blue light.

 

[Leighgion]

Huh, that is strange. Was the sky hazy at all? I found even a small amount of haze can significantly trip up attempts to darken skies.

Also, got any samples to show?

 

[railwayman3]

You may need to experiment further with the exposure compensation...if you are making a full compensation for the red filter, you may be bringing the sky back to the same density in the negative as the unfiltered shots, while the rest of the subject is less affected.

And, are you printing the negs yourself, or entrusting them to commercial D&P? Automated minilab printers (both B&W and color) are notorious for cancelling out the effects of camera filters.

(Also, some of the very deepest "black sky" effects are produced by using infra-red film rather than standard B&W films.)

 

[jeffreyg]

Remember also that the red filter will darken foliage and increase contrast especially if there are white clouds.

 

[DWThomas]

The optimum situation for sky and red filter is similar to that for a polarizer -- mid-morning or mid-afternoon with the sun behind your back; e.g., camera pointed away from the sun and into a crystal clear blue sky. There are a few flavors of red filter too, some probably have less effect. As others have commented, a bit of haze starts to interfere with the results noticeably.

 

[Stuart B]

I shot some more tests today down on the beach. Beautiful sunny day, not a cloud in sight. I was shooting at 180deg to the sun, into the darkest blue part of the sky. No filter, Yellow filter, Red filter. All three negs are virtually identical. I'm guessing it has to be the amount of exposure compensation. I've been allowing three stops for the red filter, because that's how it meters. Maybe less would help. The only other thing I can think of is maybe my scanning software (Vuescan) is trying to 'help', and is flattening the contrast too much.

Thanks for the responses.

 

[Nicholas Lindan]

Is there something I'm missing? Something obvious that I'm not doing?

As others have mentioned, the color of the sky is important.

For the most effect you need a very deep blue sky. If you are in a city you are going to be out of luck for 90% of the time as the pollution and haze are going to be in the way. You need clear fresh air: mountains, middle of the ocean with a good wind, the great plains and the desert will provide the most dramatic skies. In the great lakes region the best skies are with a stiff NE wind and high pressure bringing clear dry air down from Canada.

If the sky is a pale blue then don't expect much.

A polarizer stacked on a red filter will provide the most dramatic effect, but it will depend on the time of day and angle of the sun.

And, also previously mentioned, you need to be doing the printing yourself as automated printers will 'fix' your dark skies for you and return them to a blah state.

 

[Jesper]

Greg has a point. The further you are from the sun the less amount of red there will be.
You will get the darkest possible sky with the sun close to the horizon and directly behind you (look up Rayleigh scattering if you're interested in physics).
Different filters will have different effect, but the picture in relation to the sun is usually more important.

If you want an even darker sky you might consider IR-photography

 

[Vaughn]

Print the dang negatives already!

 

[Anscojohn]

I shot some more tests today down on the beach. Beautiful sunny day, not a cloud in sight. I was shooting at 180deg to the sun, into the darkest blue part of the sky. No filter, Yellow filter, Red filter. All three negs are virtually identical. I'm guessing it has to be the amount of exposure compensation. I've been allowing three stops for the red filter, because that's how it meters. Maybe less would help. The only other thing I can think of is maybe my scanning software (Vuescan) is trying to 'help', and is flattening the contrast too much.

Thanks for the responses.

******
Perhaps are you metering through the filter, then adding the filter factor's exposure to that reading?

 

[2F/2F]

Try again, doing either exposure compensation or metering through the filter, but not both, and see what happens.

P.S. Are you just shooting the blue sky, or are you making "actual" compositions? When you say "density", I assume negative density...however, it just struck me that you could mean print density. Have a look at the negs, first and foremost. If all you shot was a patch of sky, and they were automatically printed, then you should expect what you got.

 

[jd callow]

I believe Stuart B typed "The negatives look virtually identical!" so it is unlikely he was referring to machine prints or prints of any kind.

The filters could be old and faded, your compensation could be for stronger filters than you have, you could have been over exposing all of the frames and hence reached max density, it could be haze, it might be that there is a difference from frame to frame, but you are not seeing it in the negs (make a contact print) or it might be that you are using ttl metering and then compensating which would pretty much negate any filter effect, but then I am just repeating what most everyone else has already stated. Scanning is no way to measure density unless you turn all automated features off.

 

[Stuart B]

Thank you everyone for your responses. To answer your questions, the Red filter is not old and faded. I have metered it with the flat diffuser on my Autometer iV. It indicates a 3 stop compensation. I have not been shooting hazy blue skies, they have been deep blue. The negs look very similar, but maybe a contact print would show differences that are not visible to the eye. I will also experiment with less filter factor compensation.

Thanks again

 

[fschifano]

Are you looking for something like the attached picture? Absolutely clear, deep blue skies with a few high cumulus clouds, sun to my back. You need those conditions for the red filter to do its stuff. Metered normally and 3 stops added for a red 25 filter. Film is probably Arista.EDU Ultra 100, but that's not too important. Most any panchromatic B&W film will behave similarly. Kodak's Tmax films behave a bit more dramatically than most under those conditions.

 

[mopar_guy]

Filter factor, or no filter factor.

There are two ways to look at this:

1-Expose a scene with blue sky on panchromatic film with no filter. The sky may be a light color in the final print. Or you can use a yellow or orange or red filter to reduce blue in the scene. Filter manufacturers supply data for filter factors but here is the problem: for example a yellow filter will transmit yellow and absorb blue so a yellow filter will make the sky appear darker with less effect on yellows and reds, but if you compensate exposure by applying a filter factor the value of blue (the sky in this case) will be close to the original value. This leads us to--

2-Expose the scene with blue sky on panchromatic film with a yellow or orange or red filter and ignore the filter factor. This method WILL produce more of a change in the appearance of the sky. Different films will produce different results. The problem is if there is a lot of blue or green in the scene other than the sky, the scene may be generally under exposed.

 

[mopar_guy]

Here is a different example for contrast:

The classic picture on panchromatic film of red flowers in green foliage. Expose with no filter and the values for red and green (flower and foliage) will have a very similar brightness in the negative and the final print. Or use a red filter, and use the filter factor and the red flower will be lighter than the green foliage.

If you are thinking of using a filter, if it is yellow or red or any other color, you can look at the scene through the filter and get some idea of the effect it has on the brightness values in the scene.

 

[Vaughn]

There is only one thing to consider -- filters absorb (thus reducing the exposure) of their opposite colors more than they do their own colors.

When using a filter, the relationship between the colors rendered on the negative created by the filter remain the same no matter what exposure one uses. But because filters darken all colors to some extent, one must apply the filter factor to achieve the same over-all exposure as if one did not use a filter at all.

If the OP did not see any difference in the tonality of the sky in the his negatives and then assumed that the red filter created no change-- that can only mean that he did not reconize the change created by the filter in the other colors represented on the negative -- lighter reds and greens relative to the blues. Which is why I suggested he print them -- then he would see the shift in the tonality.

Vaughn

 

[mopar_guy]

Vaughn raises an important point. There is more than one exposure that will yield very similar prints.

 

[johnnywalker]

The optimum situation for sky and red filter is similar to that for a polarizer -- mid-morning or mid-afternoon with the sun behind your back; e.g., camera pointed away from the sun and into a crystal clear blue sky. There are a few flavors of red filter too, some probably have less effect. As others have commented, a bit of haze starts to interfere with the results noticeably.

I thought the optimum situation for a polarizer was at right angles to the sun, not having the sun directly behind you.

 

[DWThomas]

I thought the optimum situation for a polarizer was at right angles to the sun, not having the sun directly behind you.

Well, I may have mis-remembered. I believe the key is sunlight reflections off any water vapor toward the camera at about 53º off the sun hitting the vapor is polarized. So actually there would be an arc from off to one side and down to the other. But then maybe that's about rainbows, although I think the mechanism is related. But I may be hopelessly confused, as despite having about $300+ invested in polarizers, I have hardly used them in the last dozen years. (And then for getting rid of reflections.) At least on an SLR we can play around and see what happens -- that's a little easier than a red filter. :rolleyes:

 

[Q.G.]

Stuart,

You still haven't said anything about thow the other parts of the different negatives compare.

It has been suggested several times that the orientation relative to the sun makes a difference. Unless you are using a polarizer (which you are not) it doesn't.

 

[Vaughn]

...Unless you are using a polarizer (which you are not) it doesn't.

Correct - it has all to do with the color of the light. A more intense blue will be show more change than a pale blue (actually sky tends to be more of a cyan than blue, which is why an orange filter tends to darken sky the most). Our students always seem to want to use a red filter to "increase contrast" -- even with our overcast foggy skies!

My most commonly used filter is a yellow one in the Fall under the redwoods to lighten the yellow leaves.