Colour Negative Film and Filters

iranzi · Sep 4, 2011

Matt, with negative film the filter should affect highlights more than shadows, not the way you describe it. At least following the logic of the passage i quoted.
This phenomenon is well worth looking into. This is the first time i hear about it.
Does this mean that dichroic filters and all the rest of them behave in the same manner?
Are there any curves published for filters?

Also, why are people afraid of underexposing their yellow layers?
If you expose for the shadows (as is normal with neg film) you are likely to overexpose that layer in overcast/shadow/bluish conditions. What's getting underexposed and why?

iranzi · Sep 4, 2011

DREW WILEY said:
Iranzi - sometimes the old photo books contain some very useful information. But color neg films are
very different than when that book was written. That's why it's so important to keep testing as new products arrive. Everything is affected when a color neg film is not exposed at the correct color temp
it was engineered for; but how significant this will be for your personal work depends on a lot of variables and just how far off the lighting is. But if you want the optimum differentiation of subtle hues in these films, some filtration and exposure compensation is necessary in order to adequately
fill out all three dye curves. Recip failure for long exposures complicates all this, and you might have
to do some experimentation with cc filters as well.

In view of the issues discussed here, how different are the modern films from the ones 40 years ago?
Because the filters haven't changed. The same filters are still prescribed for the same conditions.

Athiril · Sep 4, 2011

iranzi said:
In view of the issues discussed here, how different are the modern films from the ones 40 years ago?
Because the filters haven't changed. The same filters are still prescribed for the same conditions.

Well the filters being talked about have a mired factor.

Here is some resource
http://www.leefilters.com/lighting/products/mired/
http://en.wikipedia.org/wiki/Mired

Athiril · Sep 4, 2011

iranzi said:
Just found this in "Colour Photography" by Eric de Marie (1968), p.110.

"Except for the polarising filter, the effects of a filter on a film are not those you would see if placed the same filter over the viewer. The filter would not modify the highlights on the film but would only begin to show results, and with increasing strength, as the tones darken. In a snow scene photographed with a pale yellow filter, for example, the highlights of the snow would remain white on the film, but the middle tones might look slightly yellow. A filter always has more effect, therefore, on an under-exposed shot than on a correctly exposed or over-exposed shot".

It's clear that he's talking about slide film, although it's not specified (later on p.115 he recommends filters for negative films to bring the color temp back to daylight and reduce amount of adjustment while printing)
So, on a negative film, the filter would have more effect on highlights and midtones, and virtually no effect on shadows, more effect on overexposed film and less on underexposed.

If that's correct, it's quite a big difference between the effects of filters on slide and negative films, and the difference in applications.
For example "correcting" bluish shadows with the same number warming filter will have more effect on slide film than on neg film.

Does this sound right to any of the filter users here?

Slide film is made as a final product with a high contrast for projection. Slide film also has very high colour separation. So any colour difference of course is bigger on slide film.

IE: Shoot outside of daylight.. say in the shade which is colder, you don't get the chance to balance slide after exposure unless printing specially or scanning.

Since the colour separation is bigger, any whites, greys, neutrals etc that are a blue instead of neutral are going to be affected by the high saturation, the effect is pronounced since there is no saturation in a full neutral grey etc.. so any neutrals or close to neutrals in a different temp light will be very noticeable. The difference between two light temps will also be increased.

Not to mention your eye is compensating and exhausts against both luminous and chroma intensity, so it is kind of self-masking in that way, where the film is not and will respond to full chroma intensity.

iranzi · Sep 4, 2011

It's like we're speaking different languages. I mean thanks for the input but how is it in reference to my questions i just don't know (nothing personal. most likely i'm just not thinking it through. will give it another go)

iranzi · Sep 4, 2011

For example, when i say "For example "correcting" bluish shadows with the same number warming filter will have more effect on slide film than on neg film"
The key word here is "shadow" not "slide". And the difference between filters affecting different luminance ranges on slide and neg films.

And of course filters have mireds. My point is that they have exactly the same numbers as 40 years ago, i.e. 81A was and still is 1.8 decamireds. So i'm wondering what's so different about modern film.

Athiril · Sep 4, 2011

If your filtration on slide film isn't spot on but simply close, neutrals wont be neutrals they'll be coloured.

Filtering filters the light. It attentuates some wavelengths. Look at the mired pages. The shadows are being exposed by light, if there is less light there is less exposure no matter where it is on the film, if there is less light of a specific colour there is less exposure of that colour.

iranzi · Sep 4, 2011

so why is this guy in the book talking shit? or is he not?

markbarendt · Sep 4, 2011

Athiril said:
If your filtration on slide film isn't spot on but simply close, neutrals wont be neutrals they'll be coloured.

Filtering filters the light. It attentuates some wavelengths. Look at the mired pages. The shadows are being exposed by light, if there is less light there is less exposure no matter where it is on the film, if there is less light of a specific colour there is less exposure of that colour.

Exactly.

The reason they have not changed in forty years is that the physics of light hasn't changed in that time.

iranzi · Sep 4, 2011

thanks for enlightening me. what else do you know?

MattKing · Sep 4, 2011

iranzi said:
Matt, with negative film the filter should affect highlights more than shadows, not the way you describe it. At least following the logic of the passage i quoted.
This phenomenon is well worth looking into. This is the first time i hear about it.
Does this mean that dichroic filters and all the rest of them behave in the same manner?
Are there any curves published for filters?

Also, why are people afraid of underexposing their yellow layers?
If you expose for the shadows (as is normal with neg film) you are likely to overexpose that layer in overcast/shadow/bluish conditions. What's getting underexposed and why?

One question at a time

First, dichroic filters are an entirely different subject because they don't pass image bearing light - they reflect non-image bearing light. You use them to illuminate something (like a negative).

Second, while filters may affect the light more in the highlights, they affect the response of properly exposed film more in the mid-tones and, indirectly, in the shadows. That is because it in the mid-tones the film is in the linear portion of its curve and is most responsive to changes in the quantity of light. In the shadows, you are more likely to end up in the toe of the curves, and therefore vulnerable to experiencing an unusable low density in one of the curves - not enough differentiation between tones.

If you are filtering the highlights, again you might be in the shoulder - outside the linear portion of the curves - again not enough differentiation between the tones.

What you have to remember though is that a filter has the effect of leaving the filter's colour relatively unadjusted while moving the complimentary colour down the curve - a yellow filter may have the effect of moving the blue down from the shoulder to the linear portion of the curve, and thus increasing the differentiation between blue tones. When you adjust for the filter factor, the relative place on the curves is shifted more for the complementary colour than for the colour of the filter itself.

So if you are filtering to remove an overall blue cast you use a yellow filter and you adjust the exposure (using the filter factor) so that the shadows retain detail.

Don't confuse this with the situation where the shadows are illuminated with one colour of light while the highlights are illuminated with another colour of light. Filtering for that situation is always a compromise, because there is no way to balance the entire scene correctly without changing the illuminating light itself. At best you can control the compromise (yellow highlights might appeal to you more than blue shadows) while making sure that there is enough illumination in all important parts of the scene to enable correction in "post" (either with different burns and dodges under the enlarger lens, or with different "burns" and "dodges" using digital tools).

iranzi · Sep 5, 2011

Thanks Matt. So what about that book passage then? According to it the slide's shoulder (shadows) is most affected by the filter, not the straight portion. Is this author just a lying sack of shit? Cheers

P.S. Dichroic filters are completely different, but the ones in my enlarger head also used in illuminating the photographic paper not just the negative.
Also, the viewing filters for colour prints have more effect on highlights of the viewed print, for instance. The same cc values used for a subsequent print using my dichro head will result in less effect on highlights, etc

P.P.S Photography in a very broad subject, too big for any one person. That's partly the reason why I often find it difficult to believe those who come here only to answer questions and never ask them. But that's my problem i guess. No disrespect to anyone. In fact i'm in awe of the amount of knowledge here and willingness to share it.

markbarendt · Sep 5, 2011

iranzi said:
Thanks Matt. So what about that book passage then? According to it the slide's shoulder (shadows) is most affected by the filter, not the straight portion. Is this author just a lying sack of shit? Cheers

I think the author is just reporting his experience.

Matt was right earlier when he indicated that the "effects" are more visible in the mid and low tones. More "important" may be a better description than "visible".

As I understand it, filters don't discriminate, they change the color balance fundamentally at all brightness levels.

The effect we actually perceive is a different matter, even a personal matter since we all see a bit differently.

For me the effects of filters are most important in the middle tones. When the tones get close to black or white, the effect is visible, but not necessarily important enough to matter. I.e. The clouds may show either a slightly warm or cool bias but if the skin tone is right a bias in the clouds may not be important.

iranzi said:
P.S. Dichroic filters are completely different, but the ones in my enlarger head also used in illuminating the photographic paper not just the negative.
Also, the viewing filters for colour prints have more effect on highlights of the viewed print, for instance. The same cc values used for a subsequent print using my dichro head will result in less effect on highlights, etc

We can normally see a wider range of brightness than the paper can represent.

If you have any doubt of that fact hold up a print next to a light bulb. The light bulb will be brighter than the paper. Even though the light bulb is brighter than the paper's white the light bulb may still have a visible color to it.

As much as we might like to believe otherwise, prints never display reality.

iranzi said:
P.P.S Photography in a very broad subject, too big for any one person. That's partly the reason why I often find it difficult to believe those who come here only to answer questions and never ask them. But that's my problem i guess. No disrespect to anyone. In fact i'm in awe of the amount of knowledge here and willingness to share it.

I have learned much in the years I've been participating here. sometimes by asking questions, sometimes by debating and defending a position, mostly though just by listening or hunting about in the archives. Many of the questions we all have, were answered well before our arrivals and searching is always a learning experience. Other questions get answered in reading the daily banter.

iranzi · Sep 5, 2011

Thank you Mark.

Hikari · Sep 5, 2011

Having run a color darkroom for many, many years, under normal lighting conditions that you mention there is no reason to filter--that can easily be done in the enlarger. When you shoot under a condition that is very biased to a color--shooting under dim tungsten where the dominant color is in the red--then filtering the exposure is going to be very important if you want to color balance that as there is very little blue information in the yellow layer as it is underexposed.

DREW WILEY · Sep 5, 2011

Hikari - some of these new color neg films are capable of a much better rendition of many hues than
the older films were; but you sacrifice some of that potential without proper filtering. There are significant ways in which these films are engineered differently. I'm hearing a lot of complaints about
Ektar, for instance, which are completely unnecessary. People can balance for this and that in the
darkroom, or putz around with it in Photoshop, but if the exposure is out of whack in the first place,
there are certain nuances that just can't be recovered because all three color layers are affected. I'm
getting prints that are quite unlike anything possible before with color neg films, with most the cross
contamination of layers we simply took for granted before, now all cleaned up - subtle shades of green and yellow clearly differentiated. Filtering does make a significant difference, even with just an overcast sky.

DREW WILEY · Sep 5, 2011

I should have added a practical example to my lost post. In the past we could pick a particular neg
film for portrait work based upon the complexions and background involved, and it wouldn't seem to
make much difference whether an 81A filter was in our kit or not. The film was engineered to accommodate a variety of common lighting conditions and still render pleasing skintones and a few
vibrant secondary colors, and we didn't worry too much about accuracy of the secondary chroma.
And some photographers capitalized on the idicsyncrasies of color neg film and did interesting creativework, though the overall results could hardly be called accurate. But fairly recently a category of color neg films has come along which for the first time can realistically compete with
chrome films for the rendition of a wide spectrum of hues. Ektar might be the foremost of these, but
is fussy with color temperature. It isn't engineered to dump or mix everything into mild skintones.
The chrom is better differentiated, but not unless you support each of the three separate layers with
equivalent exposure. And this often requires filtration.

Hikari · Sep 5, 2011

Drew, unless emulsions have radially changed since last year when I closed my color darkroom, I stand by my post. An 81A is not significant or even wanted filtration, especially since the final color print may not want color shifted in that direction.

markbarendt · Sep 5, 2011

Hikari said:
... since the final color print may not want color shifted in that direction.

That thought applies to any filter.

If one is going to filter, one should have a darn good idea of what they will be getting in return.

DREW WILEY · Sep 5, 2011

If you've adequately expose all three dye curves, you can always balance the color temp back in the dkrm. If you haven't, then you're stuck with less than ideal results. You can't post-correct either with
a colorhead or by futzing around with the curves in PS, because you've already cross-contaminated
the respective curves to a certain extent. I've done months of testing on this and the proof is in the pudding. With a highly saturated neg film like Ektar, the difference in hue purity and distinction is significant even with an 81A applied when appropriate. And back when I was shooting Portra 160VC,
I sure wish I had known this, because it would have made a real difference. Every time someone poo-poohs this principle, and brags about how good their prints look, what I see is that they've balanced for one thing at the expense of another, and really haven't hit the target at all. Their colors
look contaminated, because that's what they are.

iranzi · Sep 5, 2011

Drew, I know you print using additive method, which you claim is responsible for purer hues. Is it not possible that your whole workflow is responsible for the results in prints that you're describing, not just the filtering?

DREW WILEY · Sep 5, 2011

That's a good observation, Iranzi. Yes, the improvement is cumulative. An additive light source helps,
switching to the newest materials like Ektar and CA Type II paper also helps, and learning correct
filtration helps. But given a level playing field, if I take the first two advantages, but then try printing
an unfiltered neg taken on the same kind of film, the results are not equal. All these seemingly little things add up.

markbarendt · Sep 5, 2011

Iranzi,

I'd bet it's a given that Drew's whole process contributes.

If you take out all the slop out of the process and each step is done using the best practice everything comes out better.

brucemuir · Sep 5, 2011

markbarendt said:
Iranzi,

I'd bet it's a given that Drew's whole process contributes.

If you take out all the slop out of the process and each step is done using the best practice everything comes out better.

It does strike me abit how so many are against a little proper technique.
It makes sense to me at least that Ektar would benefit from tight parameters.

Ligament · Oct 3, 2011

DREW WILEY said:
That's a good observation, Iranzi. Yes, the improvement is cumulative. An additive light source helps,
switching to the newest materials like Ektar and CA Type II paper also helps, and learning correct
filtration helps. But given a level playing field, if I take the first two advantages, but then try printing
an unfiltered neg taken on the same kind of film, the results are not equal. All these seemingly little things add up.

Drew, I find your comments on filtration for color negative films to optimize exposure of the dyes makes sense to me. However, I'd like to read more about it. Can you recommend some links in which this topic is discussed?

Also, how do you choose your filters? Do you carry around a color meter? If not, would that not induce user error that may cause selection of an inappropriate filter that would make the image worse? Is there such a thing as an economical, yet accurate, color meter?

Colour Negative Film and Filters

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