*%@!ing Red filters!

mark · Dec 11, 2009

I've given this some thought and I think this is what is happening.
The OP may have over exposed his negatives and got the 18% grey he should have gotten if he metered the sky, then metered the sky through the filter and adjusted so the resulting exposure would have been the same. My question would be, is the contrast of the other aspects of the scene the same or different?

Since the OP is scanning his negs he must be able to post them so people can see them. I would like to see them.

Vonder · Dec 11, 2009

In my experience, there is only dramatic difference in outdoor scenes with red or green filters. Yellow and orange produce nearly identical images:

http://www.wolfeyephoto.com/BW_Filter_Effects/filters.htm

I let the camera do all the metering, keeping aperture the same.

Stuart B · Dec 11, 2009

Thanks to everyone who has responded. I took railwayman's advice and experimented with different amounts of compensation for the filters. I seem to get the best results if I don't compensate for the yellow filter at all, and if I only compensate 1 stop for the Red filter, leaving it 2 stops under.

Another mystery solved...

Thanks again.

pentaxuser · Dec 11, 2009

If it is any consolation I have never achieved black or near black skies except with IR film but a polariser over a 25 red will dramatically darken the sky further if you shoot at right angles to the sun. It's quite an experience rotating the polariser and watching the sky darken and the clouds stand out as you do it.

In B&W I am not sure that a cloudless blue sky is any better than a grey cloudy sky. Polarised deep inky blueness is fine if you can see the blueness. Inky greyness in B&W without white clouds is just not the same.

pentaxuser

RalphLambrecht · Dec 11, 2009

Stuart B said:
Thanks to everyone who has responded. I took railwayman's advice and experimented with different amounts of compensation for the filters. I seem to get the best results if I don't compensate for the yellow filter at all, and if I only compensate 1 stop for the Red filter, leaving it 2 stops under.

Another mystery solved...

Thanks again.

Look for a Macbeth color checker card and photograph it with each filter and that filter's compensation factor to get a feel for the effect of the different filters. Don't meter through the filter! Your meter has a different spectral sensitivity then your film. Trust the filter factor more than the meter. This is especially important with red filters!

glen · Dec 11, 2009

I've shot lots of IR, you've too much UV, shoot sunrise or sunset, sun at your back. R72 4 stops, deep red 3 stops.

Q.G. · Dec 11, 2009

With a red filter (or even orange or yellow) filter on the lens, you have no UV.

Ian David · Dec 11, 2009

Stuart B said:
Thanks to everyone who has responded. I took railwayman's advice and experimented with different amounts of compensation for the filters. I seem to get the best results if I don't compensate for the yellow filter at all, and if I only compensate 1 stop for the Red filter, leaving it 2 stops under.

Another mystery solved...

Thanks again.

1 stop is not much compensation for a red filter. Perhaps you should spend a bit more time trying to work out why you are not seeing much effect from your red filter. As QG says, you need to look at relative densities on your negs, rather than just the density of the blue sky alone. So, perhaps include some fluffy white clouds in your tests which should help make things clearer.
As for the advice in a couple of posts to just stack on a polariser, I would again recommend that you try to understand what is going on before you look for band-aids. Polarisers are useful tools, but you should generally be able to get a very noticeable effect from a red filter alone.

Ian

Denis R · Dec 11, 2009

read the book

kodad filters

use polarizer and split ND

mopar_guy · Dec 11, 2009

iandavid said:
1 stop is not much compensation for a red filter.

Ian

Why?

Vaughn · Dec 11, 2009

mopar_guy said:
Why?

Colored filters do not allow 100% of any wavelength through -- and of course, block certain wavelengths more than others. An orange filter blocks a little of the orange light, but a lot of the cyan is blocked (thus darkening the sky more than anything made up of orange light.)

Some filters block a higher proportion of all wavelengths than others -- thus have a higher "filter factor". A yellow filter lets a lot more light of all wavelengths through than a red filter.

Therefore if one does not apply a sufficient filter factor, the negative will be underexposed at all wavelengths -- not just the target color.

So to answer "why?" -- it is because one generally does not want to underexpose one's negatives. It would be like using a 3 stop neutral density filter and only increasing the exposure by one stop -- one's negative would be two stops underexposed.

Vaughn

Ian David · Dec 11, 2009

mopar_guy said:
Why?

Perhaps I should have said "1 stop is not much compensation for a red filter if adopted as a general rule".
Stuart says he has a deep red filter. The effect of the filter on a scene will depend on the nature of the scene. But if he adopts a general rule that he only gives one extra stop when shooting with this filter, I think he will likely end up with more underexposed negatives than he would like. That's just the way red filters work. This may not be a problem if Stuart only ever wants to point his camera at the sky with no other objects in the scene, but I was assuming from his original post that he is trying to come to grips with how a red filter works, and that he might want to use it on a scene with a fuller range of tones.

Ian

(Oops - only just now saw your post above, Vaughn - thanks!)

Vaughn · Dec 11, 2009

No problem, Ian. I have no idea why Stuart likes to underexpose his negatives by two stops. Perhaps his meter is off a bit, or perhaps if he scans all his negatives -- and he finds that thin underexposed negatives scan easier -- and then one can compensate for the lack of local contrast in the shadows by changing the curve in PhotoShop or something.

mopar_guy · Dec 11, 2009

Here's another example: I am trying to photograph a red barn on a partly cloudy day. I decide to use a red filter. The red filter will darken the blue in the sky (absorb blue and green) and the red filter will have a lesser effect on the red building (the red in the building is transmitted through the filter onto the film). If I wanted the sky to be very dark (dramatic), using the three stop filter factor will theoretically allow more of the light from the sky to hit the film and to lighten the appearance of the sky in the final print. Also using a three stop filter factor will give the building a lighter appearance in the final print.

I understand the theory of using colored filters to CHANGE the apparent contrast of a scene. I guess what I have been trying to express is that the person behind the camera has some choices to make. Maybe the choice to create contrast with a colored filter can mean different things to different people. It is often a complaint that "the sky is not dark/dramatic enough in my photo of...". Well, what I am hearing in this complaint is that the SKY is a compositional element in the photograph (perhaps the most important compositional element to the one pressing the shutter release) and that the photographer is dissatisfied with the result. This is exactly what the original post is concerned with.

The person making the original post has stated that he is more satisfied using a one stop filter factor for his purposes (it looks better to him). Why do we have a need to try and convince him to use a three stop compensation when he is obviously not happy with that choice. Are we violating some sacred "photo" law? Will somebody be calling the "photo" police. I think that such a crime should be punished by a lengthy term in "photo" prison. Why do we foist these silly "rules" off on everyone. If I wanted my photos to be exactly the same as every other photographer's photos, then we all need to use the same film, the same camera and work off of the same "cheat sheet".

Respectfully disagreeing with the rest of the flock,
Dave

Vaughn · Dec 12, 2009

If I wanted the sky to be very dark (dramatic), using the three stop filter factor will theoretically allow more of the light from the sky to hit the film and to lighten the appearance of the sky in the final print. Also using a three stop filter factor will give the building a lighter appearance in the final print.

Incorrect -- it will be the amount of exposure one gives the photo paper through the negative that will determine how light or dark the sky and barn will be represented in the print.

Once one puts on the red filter, changes in the exposure of the negative will not significantly change the tonal relationship between the sky and the barn.

Underexposing film is not a crime -- but if one wants shadow detail and some local contrast in the darker mid-tones, one might be a bit disappointed in not getting much. Generally, a well exposed negative is easier to work with -- it gives the photographer the creative opportunities to make the prints that he or she wants.

An underexposed negative, since it will lack information in the shadows that can not be regained by any printing method, limits the creative choices...the shadows will never have detail. Brett Weston made incredible prints using deep, detail-less blacks -- and he used those "negative spaces" as part of the composition. But I have a feeling (since I have not seen his negatives) that they were not underexposed.

If Stuart is happy with the prints he gets with underexposed negatives, that is great -- he should go for it (and at that point the negatives would not be considered "under-exposed" but exposed just as he wants them). But as it appears that he has not made any prints yet, how can he know? The proof will be in the looking at the prints -- which has not happened yet.

Vaughn

mopar_guy · Dec 12, 2009

Agreed. The under exposed look that will result would be somewhat like those old westerns that were shot in black and white with a dark red filter to simulate nighttime.

mopar_guy · Dec 12, 2009

The method to ignore the filter factor works rather poorly with a red filter buy may work very well with a yellow or orange filter.

Vaughn · Dec 12, 2009

Easily with the yellow filter -- the latitude of the film usually will handle one stop under-exposure (especially TMax) and still give one decent results. Orange is a two stop filter factor, I believe -- depends on which orange filter. One might still get away with a two stop underexposure...sort of depends on one's metering method. If one lets the meter read too much of the sky, one would probably end up with not enough exposure on the ground.

Personally, I don't like dark over-dramatic skies as a general rule...IMO, the sky should add to the image, not over-power it.

RalphLambrecht · Dec 12, 2009

Vaughn said:
Colored filters do not allow 100% of any wavelength through -- and of course, block certain wavelengths more than others. An orange filter blocks a little of the orange light, but a lot of the cyan is blocked (thus darkening the sky more than anything made up of orange light.)

Some filters block a higher proportion of all wavelengths than others -- thus have a higher "filter factor". A yellow filter lets a lot more light of all wavelengths through than a red filter.

Therefore if one does not apply a sufficient filter factor, the negative will be underexposed at all wavelengths -- not just the target color...

Vaughn

I wonder how the manufacturer's filter factor is determined? In other words, is it neutral gray that needs the filter factor to render identically with or without the filter?

RalphLambrecht · Dec 12, 2009

Vaughn said:
Easily with the yellow filter -- the latitude of the film usually will handle one stop under-exposure (especially TMax) and still give one decent results. Orange is a two stop filter factor, I believe -- depends on which orange filter. One might still get away with a two stop underexposure...sort of depends on one's metering method. If one lets the meter read too much of the sky, one would probably end up with not enough exposure on the ground.

Personally, I don't like dark over-dramatic skies as a general rule...IMO, the sky should add to the image, not over-power it.

Strictly speaking, once the minimum shadow density and the EI of a particular film/development method has been determined, there is NO latitude towards underexposure only towards overexposure, because minimum exposure was defined by the above. Some photographers (and film manufacturers) define latitude as what underexposure people are willing to accept in certain situations, which is fine, but it still is an 'underexposure'. That does not mean that one cannot get away with underexposing the film, or do it purposely to obtain a desired effect (sometimes any picture is better than none), but this has nothing to do with latitude. (see attached graph)

Also, why not expose the film properly, make sure it has all the shadow detail, and then print it down as desired? This way, you can have it both ways. It's easy to darken the shadows and hide detail, but it's impossible to get detail out of a blank negative.

Stuart B · Dec 12, 2009

Vaughn said:
I have no idea why Stuart likes to underexpose his negatives by two stops. Perhaps his meter is off a bit

Actually, I don't like to underexpose my negs. For the purposes of the effect I was trying to achieve, I found that only compensating 1 stop for the red filter worked. In other circumstances, it would lead to unusable negatives.

Vaughn · Dec 12, 2009

Stuart B said:
Actually, I don't like to underexpose my negs. For the purposes of the effect I was trying to achieve, I found that only compensating 1 stop for the red filter worked. In other circumstances, it would lead to unusable negatives.

I guess I am confused by what effect you are trying to get. Re-reading your posts, I have not been able to tell exactly. My best guess is that you are aiming for a particular density of your sky values on your negative (close to the base+fog value of the film?) One does not need filters for that -- just meter the sky and reduce your exposure by 3 stops or so.

If that is what you are attempting, then it is a purely academic exercise. I guess I am just hung up on the image and print making -- never been one for a bunch of testing.

I agree, Ralph. There is a considerable difference between decent results and good results. I tried to google some transmission curves for a 25 filter. Found some others and what I get from them was that color filters block all visible light frequencies to various degrees...thus reducing the overall exposure. So based on those curves, I assume the manufacturers can figure how much extra exposure is needed to bring all but the target wavelengths back up to what they would be without the filter. After all -- "neutral gray" is just a combination of all visible light wavelengths.

Vaughn

Chuck_P · Dec 12, 2009

RalphLambrecht said:
............ there is NO latitude towards underexposure only towards overexposure.................

Click to expand...

Ralph, my comments below are just my opinion so I'm not saying that it's wrong as I realize I may be missing something from your post, but this is my thinking as it relates to your graph. I have my own simple graphs to illustrate my point, right or wrong.

I believe the discussion of a film's exposure latitude ends when we have to resort to development modification to keep the highend luminance values of the subject to within printable densities on the negative. IMO, at that point, we have exceeded the latitude of the film, that is why we have to modify it's development to maintain printable densities. Your graph indicates that latitude extends to beyond Zone XII (Log E 3.6). IMO, a film's exposure latitude is strictly within the context of how much exposure variation can be given the film (in low contrast subjects) and still keep the high end values easily manageable given normal development.

High contrast scenes do not allow much, if any, exposure latitude. I can make use of my film's latitude with important densities that lie between Zone I and Zone V, because I know that I may also provide exposure from between II to VI; III to VII; IV to VIII, an V to IX for that same subject, provide normal development, and have printable densities through IX (IX being just like I in that it has tonality but no real texture). I may provide plus development in a low contrast scene which is a development modification, but that modification itself has its results still within easily printable high end densities.

As soon as I have to resort to modification in development just to be able to print Zone X densities or higher, latitude is a mute point it seems to me. There has to be a limit to latitude and to me, your graph does not indicate one. You obviously know what you're doing and you have some awesome photographs, perhaps my thinking on film's exposure latitude needs a make over.

Also, why not expose the film properly, make sure it has all the shadow detail, and then print it down as desired? This way, you can have it both ways. It's easy to darken the shadows and hide detail, but it's impossible to get detail out of a blank negative.

Click to expand...

Very much agree.

Chuck

el wacho · Dec 12, 2009

yes, don't judge negs from software scans as there might be some sort of compensation/compression kicking in. i've done similar to what you are doing using tiffen yellow and red 25 and it gave me the predictable red filter look - sky was dark grey.

Larry Bullis · Dec 12, 2009

RalphLambrecht said:
I wonder how the manufacturer's filter factor is determined? In other words, is it neutral gray that needs the filter factor to render identically with or without the filter?

Back in the dark ages when as a young photographer, I couldn't accept any result that wasn't over dramatized, I started using a red filter and was very disappointed that even with the three stop factor, I still lost detail drastically in the shadows.

I think your question is a very important one. I think that we can safely presume that the manufacturer uses a neutral gray, not just a mid value, but also one with no deviation in hue from neutral. Beyond that, I wouldn't guess.

It's more complicated than that, I think, which makes it harder to apply in individual circumstances. My loss of shadow detail puzzled me, but to compensate I began to give four stops filter factor, and alter the development accordingly. Worked much better.

Here's what I came up with:

Shadows are shadows because direct sunlight is blocked by a solid object. The filter darkens anything blue/cyan/green. The sky is blue (didn't you know?) or may tend somewhat toward cyan. Anything illuminated exclusively by skylight, then, is lit with blue/blue-cyan light. So, as the filter darkens the sky, it also darkens the shadows, which are lit with only the light coming from the sky. As landscape painters discovered long ago, shadows don't look right if they aren't a bit on the blue side.

*%@!ing Red filters!

mark

Vonder

Stuart B

pentaxuser

RalphLambrecht

glen

Q.G.

Ian David

Denis R

mopar_guy

Vaughn

Ian David

Vaughn

mopar_guy

Vaughn

mopar_guy

mopar_guy

Vaughn

RalphLambrecht

RalphLambrecht

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Stuart B

Vaughn

Chuck_P

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el wacho

Larry Bullis

*%@!ing Red filters!

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