Filter factors

Melvin J Bramley · Sep 30, 2024

I exposed a roll of Ilford Delta 100 behind a yellow filter just as I do with HP5.
The results showed no noticeable effect of sky darkening, minus blue, though I think I still had a light loss of X2.
Will an orange filter X2 suffer the same effect?
When all else fails how do you add contrast to clouds using Delta 100.
Other than that the D100 developed in ID11 blew me away enough to re evaluate my exploration of the 6x6 format!
I'll take that back.
If D100 can do what it does in 35mm , my enlarging 6x6 to 16 x 20 should be no issue?

RalphLambrecht · Sep 30, 2024

Melvin J Bramley said:
I exposed a roll of Ilford Delta 100 behind a yellow filter just as I do with HP5.
The results showed no noticeable effect of sky darkening, minus blue, though I think I still had a light loss of X2.
Will an orange filter X2 suffer the same effect?
When all else fails how do you add contrast to clouds using Delta 100.
Other than that the D100 developed in ID11 blew me away enough to re evaluate my exploration of the 6x6 format!
I'll take that back.
If D100 can do what it does in 35mm , my enlarging 6x6 to 16 x 20 should be no issue?

a gradient filter, blocking the sky more than the foreground, can be an option. That combined with a contrast filter does wonders and can overdo it.

Alex Benjamin · Sep 30, 2024

There are three yellow filters, #8, #12 and #15 (to use the Wratten numbers), each increasing in effect, before you reach orange #21 or red #25. Not sure which yellow filter you used. #8 has little effect on darkening the sky, at least in my experience. I go to #12 or #15 for that, as I don't like the overly dramatic effect of orange or red.

Alex Benjamin · Sep 30, 2024

Should have added that Yellow #12 is also called "minus blue". Filter factor is 1 1/3.

xkaes · Sep 30, 2024

Alex advice is "on the money". One other approach to darkening skies behind clouds is a polarizer filter -- but it depends on the angle of the sun and the sky. With a PL filter, you can control how dark the sky gets -- and you can use it with any other contrast filter at the same time. To REALLY makes clouds stand out, use a PL and a 25A (red)!!!

DREW WILEY · Sep 30, 2024

Depends how blue a sky really is. One can progress from light Y to med Y, to light orange to deep orange 22, to red-orange 24A, to red 25, to deep red 29. A deep green filter will also significantly deepen blue. For a gentler effect, light yellow-green 11 is also an option.

I'm not personally fond of polarizing filters - they can easily be overdone, and their effect depends on the angle in relation to the sun; but that is yet another potential tool in the kit.

Otherwise, if you are enlarging 6x6 to 16X20, you are really enlarging a 645 crop of 6X6. That's kinda on the upper end of what I'd personally regard as the sweet spot for D100 without grain beginning to show - certainly doable in a high quality manner; but I wouldn't want to crop it much more.

Paul Howell · Sep 30, 2024

There must a difference in Delta compared HP5 in terms of red sensitivity, I looked at the Delta 100 data sheet and comparing it to Tmax 100 don't understand why a yellow filter would not darken the sky some. A dark yellow or orange might work better with Delta, or even a green. Of course the problem with a orange or red is that green foliage will also darken.

MattKing · Sep 30, 2024

Perhaps it was the sky that day - it does vary a lot you know!

reddesert · Oct 1, 2024

Filters like yellow, orange, etc have a stronger effect on the sky if it is clear and low humidity, and especially at higher elevations. If there is haze or humidity, the sky contains a lot of white and blue-cutting filters will have less effect.

250swb · Oct 1, 2024

Melvin J Bramley said:
I exposed a roll of Ilford Delta 100 behind a yellow filter just as I do with HP5.
The results showed no noticeable effect of sky darkening, minus blue, though I think I still had a light loss of X2.
Will an orange filter X2 suffer the same effect?
When all else fails how do you add contrast to clouds using Delta 100.
Other than that the D100 developed in ID11 blew me away enough to re evaluate my exploration of the 6x6 format!
I'll take that back.
If D100 can do what it does in 35mm , my enlarging 6x6 to 16 x 20 should be no issue?

A yellow filter is pretty subtle and is best for adding a bit of contrast on a cloudy day or taking grass and leaves up half a zone. So what it did and what you wanted it to do may be down to the deepness of the blue in the sky which is more intense on a summer day that an autumn day allied with atmospheric haze. Perhaps a bit of burning-in would darken it enough, either in the darkroom or post processing on the PC?

loccdor · Oct 1, 2024

MattKing said:
Perhaps it was the sky that day - it does vary a lot you know!

Yes, there is no filter that can fix a completely featureless sky, there has to be some detail there to begin with.

You can try orange or red, but then in shots where there is already a lot of sky contrast you may find it dials it up too much. In the end it's a balancing act.

Alan Edward Klein · Oct 1, 2024

reddesert said:
Filters like yellow, orange, etc have a stronger effect on the sky if it is clear and low humidity, and especially at higher elevations. If there is haze or humidity, the sky contains a lot of white and blue-cutting filters will have less effect.

I;ve found the same problem. I think pollution adds to the problem. I shoot on the East coast in NJ and NY and yellow filter barely works. I'll use orange and even then not so hot. You got to wait for a cold fall day when everything clears up and the blue is blue and not some washed out hue of blue.

Melvin J Bramley · Oct 1, 2024

I will try a green filter next, see what happens.
Point taken on the orange filter and effects on foliage!
I do not wish to lose too much light.
A light yellow has given me the results I like on HP5 and TRI X.

pentaxuser · Oct 1, 2024

Melvin J Bramley said:
.
A light yellow has given me the results I like on HP5 and TRI X.

The skies being equal on both HP5+ and D100 I cannot think of any reason why a light yellow works on HP5+ and not on D100

I don't think the skies have to be identical. As long as both skies looked blue to the naked eye then a yellow should make a difference

In the two prints from the HP5+ and D100 was there a comparable yellow in both scenes and if so was that a lighter colour in both scenes?

pentaxuser

wiltw · Oct 1, 2024

Melvin J Bramley said:
I exposed a roll of Ilford Delta 100 behind a yellow filter just as I do with HP5.
The results showed no noticeable effect of sky darkening, minus blue, though I think I still had a light loss of X2.
Will an orange filter X2 suffer the same effect?
When all else fails how do you add contrast to clouds using Delta 100.
Other than that the D100 developed in ID11 blew me away enough to re evaluate my exploration of the 6x6 format!
I'll take that back.
If D100 can do what it does in 35mm , my enlarging 6x6 to 16 x 20 should be no issue?

Ilford states this about Delta 100 Pro, when using cameras with TTL metering...

"Follow the instructions given by the filter manufacturer. The exposure increase in daylight may vary with the angle of the sun and the time of day. In the late afternoon or the winter months, when daylight contains more red light, green and blue filters may need slightly more exposure than usual."

"With some automatic exposure cameras, the correction given for deep red and orange filters can produce negatives under exposed by as much as 1½ stops."

...useful insight although you might be simply metering handheld and applying filter factors.

Paul Howell · Oct 1, 2024

In OP case his sky was light, increasing exposure would add density making the sky lighter not darker?

wiltw · Oct 1, 2024

Paul Howell said:
In OP case his sky was light, increasing exposure would add density making the sky lighter not darker?

The 'underexposure' mentioned by Ilford applies only when using TTL metering...and the OP was apparently manually offsetting overall exposure by the stated filter factor.

DREW WILEY · Oct 1, 2024

When establishing my own filter factors for D100 using a gray card and roll film bracketing, then actual densitometer readings of the developed film, I was surprised just how much it differed in instances from certain other pan films I was accustomed to. Published filter factors on the specific spec sheets are a good starting point. But even the same nominal filters from different brands sometimes have different effective densities, or variations due to quality control issues.
There is simply no substitute for actual testing.

Then there is the matter of the atmosphere itself. Filters are good for a lot more than just bringing out clouds in blue sky. But the sky is a lot less blue many places than it once was. Even at high altitude, I've only experienced a deep blueness to the sky once in the last decade that resembled what I remember growing up in the mountains half a century before. Even color film sees the difference. Films have also changed.

But our own color vision makes even weak blue stand out even against clouds which are more light grey than white; hence we assume that our b&w film will see it the same way as we do by using a yellow filter, when there's really going to be a "merger" of tonality which is barely discernible. Recognizing the difference comes with experience. But most of today's films, under today's compromised skies, don't respond to an old number system K1 or K2 yellow filter like they once did. I rarely use anything weaker than a 22 deep orange.

_T_ · Oct 1, 2024

Are you comparing the different frames from each film in a way that is conducive to making such comparisons? I.e. both frames shot at the same time with the same framing from the same position with the same perspective and the same camera and lens with equivalent settings and equivalent processing?

Because I’ve found that changing any one of those things can sometimes have a greater effect than that of the filter.

xkaes · Oct 1, 2024

Paul Howell said:
In OP case his sky was light, increasing exposure would add density making the sky lighter not darker?

Depends on the sky and the filter. A light blue sky and a 25A (red) filter will darken the sky even though you open-up three f-stops. It won't let any of the blue in the sky hit the film, and the film is lens dense -- and darker in the print.

Melvin J Bramley · Oct 1, 2024

I found this old thread,

Filtration differences Delta 100, FP4

I've noticed a variation in how Delta 100 and FP4 filter using a yellow green filter(11). FP4 seems more normally responsive to this color than Delta 100. I'd not shot D100 with a yellow green (almost my standard on FP4. Recently, I made some pictures using D100 and an 11 - what I got on film see...

www.photo.net

At least I am not alone.

Paul Howell · Oct 1, 2024

xkaes said:
Depends on the sky and the filter. A light blue sky and a 25A (red) filter will darken the sky even though you open-up three f-stops. It won't let any of the blue in the sky hit the film, and the film is lens dense -- and darker in the print.

He was shooting with a yellow.l

RalphLambrecht · Oct 1, 2024

Alex Benjamin said:
There are three yellow filters, #8, #12 and #15 (to use the Wratten numbers), each increasing in effect, before you reach orange #21 or red #25. Not sure which yellow filter you used. #8 has little effect on darkening the sky, at least in my experience. I go to #12 or #15 for that, as I don't like the overly dramatic effect of orange or red.

It's said that #8 renders the contrast more like the human eye sees it.

DREW WILEY · Oct 1, 2024

D100 is a little more green depressed than certain other common pan films. For a light-yellow green filter like Hoya XO or Wratten 11, it needs a half stop more added to the general filter factor; same with med green like Hoya X1.

Similarity to human eye response is better obtained with a light yellow-green filter rather than a yellow one. Or you could shoot an orthopan film like Fuji Acros, which does essentially the same thing without any added filtration.

pentaxuser · Oct 1, 2024

Paul Howell said:
In OP case his sky was light, increasing exposure would add density making the sky lighter not darker?

Well nowhere does the OP say how his sky was and yes I agree that most skies are lighter than the rest of the scene but I had assumed that the sky was clearly blue and there were clouds in the clear blue sky In that case a yellow filter should produce a noticeable effect whether the film is HP5 or Delta 100 film

It always did when I have used both Delta and HP5+ films It is the no difference remark that has puzzled me and the OP. Perhaps he was simply expecting to see a greater darkening in the sky than he saw and as a result what he saw was perceived as being no discernible difference from a "no filter" negative

Perhaps he is asking 2 questions : Q1 what does he do to change things next time
A1 It would look to be to change to a deeper filter such as orange
Q2 What can he do with his current negative to improve the look of the sky
A2 Will lie in the print stage in the darkroom with D&B and or grade of paper or the use of the nearly ubiquitous scanner

pentaxuser

Filter factors

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