My filters consistently decrease my negative contrast - what am I doing wrong?

BHuij · Mar 4, 2018

I shoot FP4+ developed in Rodinal as well as HP5+ developed in HC-110 as my two go-to films. I have already calibrated them in both roll film and sheet film for N, N+1, N+2, and N-1, which covers about 99.9% of my shooting.

I am using Cokin series filters, and since I shoot such a wide variety of 35mm and medium format cameras, as well as a 4x5, I just hold the filter in front of the taking lens at time of exposure rather than trying to mount it.

The filters I use most are the P-001 (yellow), P-002 (orange), P-003 (red), and P-004 (green). Looking online, Cokin lists the following EV compensations for these filters:

Yellow: 2/3 stop
Orange: 2/3 stop
Red: 3 and 1/3 stops
Green: 2 and 2/3 stops

I have read elsewhere that the general rule of thumb for "standard" yellow, orange, red, & green filters is more like

Yellow: 1 stop
Orange: 2 stops
Red: 3 stops
Green: 2 stops

My problem is this. It seems like no matter what I try (I have tried both the Cokin recommendations and the more generalized exposure compensation numbers), I end up with a thin and flat negative any time I use a filter of any color. I will post some negatives and/or contact sheets when I have a chance to scan, as examples.

Just today, I went to the park to shoot the new snowfall on the trees. I shot one frame of FP4+ with no filter, intended for N development. That negative came out great, and exactly as anticipated. About 15 minutes after exposing that first frame, I shot another sheet of FP4+ (from the same box, loaded at the same time into a film holder, etc. etc.). This one had a lot of sky in it which I wanted to darken down quite a bit to emphasize the clouds, so I used the P-002 orange filter, with two stops of exposure compensation given. Specifically, I metered the area I wanted to expose at Zone IV, dialed in the proper exposure (1/60), and then backed the shutter speed off two stops to shoot (1/15) through the filter.

This sheet went into the exact same rotary drum as the first one, was processed by the same chemicals at the same time (also a "N" developed negative)... and came out thin and flat.

Those two negs are drying right now, but once I can show some pics I will.

I have a similar couple of negs from last summer. I was shooting in an aspen grove, so basically white trunks taking up a lot of the frame with mostly out-of-focus green foliage in the rest of the frame. I wanted to emphasize the whiteness against the foliage by darkening the leaves down a bit, so again I used the orange filter and gave 3 stops of exposure compensation. Luckily I was also finalizing some calibration tests at the time, so I took an exact copy of the photo with no filter and no exposure compensation, at the same time. Souped at the same time, etc. etc. Once again, the no filter shot came out looking pretty good, and the orange filter one came out looking thin and flat. Definitely less contrast than the no filter shot. Unfortunately this isn't a perfect comparison as the no filter frame was on FP4+ and the orange filter frame was on HP5+. However, both were developed in their respective developers at an already-established and stable N+1.

I could understand if I just wasn't giving it enough exposure compensation that my negs would be thinner, but I don't understand how they're also losing contrast when an orange filter should definitely be increasing contrast.

Any insights? I'm not comfortable with using contrast filters in my B&W work anymore, and that sucks, because there are lots of times when theoretically they would be great - just can't get them to work for me right now, for whatever reason.

Svenedin · Mar 4, 2018

I have to confess I don’t understand or use your zone system stuff. However, I do routinely use yellow (mostly) and occasionally orange and red contrast filters. My Olympus TTL cameras correct automatically for the filters but on my MF cameras I add exposure factors just like you do. It depends on the light (and the film) what a filter will actually achieve. In overcast conditions in high latitudes the effect of a filter is minimal. In latitudes closer to the equator (or at altitude) the effect is striking. It’s about the spectral composition of the light especially UV and it also varies according to the season of the year and the time of day.

shutterfinger · Mar 4, 2018

I'm not a regular filter user but one thing about your procedure stands out like a sore thumb, you're using nominal filter densities rather than metering through them in the real life lighting you are exposing the film in.
I always meter the scene then pick a middle tone and meter it through the filter to get the exposure compensation needed for that lighting condition. The exposure compensation can vary 1/2 to 2/3 stop. I don't know if extra development for the filtered exposures will be needed or not, testing will tell.
A RGB three exposure sandwich image of mine (tri color using Kodak T Max 400 TMY film).

Heirloom Tomato #2 by c99photo, on Flickr

Svenedin · Mar 4, 2018

It seems there are 2 things going on for the OP. First his photos with filters are “thin” (underexposed) but second they are not altering the contrast (clouds etc) as he would wish.

Svenedin · Mar 4, 2018

This is a yellow filter in Gibraltar (20 miles from the coast of North Africa). It was a blue sky in January. It would never conceivably have this effect in the mainland U.K. even in mid-Summer.

https://flic.kr/p/YKqbRa

neilt3 · Mar 4, 2018

Your holding the filter in front of the lens by hand ?
How far in front of the lens ?
If there's a gap light could be getting past and reflecting off the back of the filter , reducing contrast .

Regarding the thin negatives , if the way you work out your exposure and develop the film usually gives you good results without a filter , then the metering or working things out wrong for the filters and underexposing .
I found quite often just using the usual stated +1,+2 stops extra resulted in thin negatives .
I now use my spot meter and meter through the filter .

BHuij · Mar 4, 2018

neilt3 said:
Your holding the filter in front of the lens by hand ?
How far in front of the lens ?
If there's a gap light could be getting past and reflecting off the back of the filter , reducing contrast .

Regarding the thin negatives , if the way you work out your exposure and develop the film usually gives you good results without a filter , then the metering or working things out wrong for the filters and underexposing .
I found quite often just using the usual stated +1,+2 stops extra resulted in thin negatives .
I now use my spot meter and meter through the filter .

I'll have to give that a shot. I've heard metering through the filter is bad news because your meter doesn't respond to different light wavelengths the same way film does, so you're liable to get a false reading.

To answer your question, the filter is touching the lens barrel, there's zero space in between the front of the lens and the filter.

shutterfinger · Mar 4, 2018

Item #2: filter holders have Opaque edges, many filters do not. Holding a non opaque edge filter against the lens barrel allows light to enter from the edge of the filter affecting contrast.
There's a reason holders and lens barrels are opaque, its to prevent light piping from the edge of the elements.

John Koehrer · Mar 4, 2018

The compensation, like other things photographic are starting points suggested from the mfr. It's going to
take some testing to fine tune the actual value.

mshchem · Mar 4, 2018

shutterfinger said:
I'm not a regular filter user but one thing about your procedure stands out like a sore thumb, you're using nominal filter densities rather than metering through them in the real life lighting you are exposing the film in.
I always meter the scene then pick a middle tone and meter it through the filter to get the exposure compensation needed for that lighting condition. The exposure compensation can vary 1/2 to 2/3 stop. I don't know if extra development for the filtered exposures will be needed or not, testing will tell.
A RGB three exposure sandwich image of mine (tri color using Kodak T Max 400 TMY film).

Heirloom Tomato #2 by c99photo, on Flickr

That's pretty darn COOL! Now if you could figure out how to recreate Dye Transfer Love it.

shutterfinger · Mar 4, 2018

BHuij said:
I've heard metering through the filter is bad news because your meter doesn't respond to different light wavelengths the same way film does, so you're liable to get a false reading.

If so it varies with the type of sensor in the meter. I would not equate test conducted in 194X with sensors manufactured in 199X or later.

shutterfinger · Mar 4, 2018

mshchem said:
That's pretty darn COOL!

I used the same factor for each sheet of film to ensure correct color balance. The 3 images were mixed in PS and No color correction was applied. All three filters, Lee Polyester technical Separation, read within 1/3 stop of each other.
The color fringing in the shadow edge is from the the afternoon's sun movement. The second shot of the same subject has rainbow like color streaks while the tomato remains the same color from the later in the day sun movement.
www.flickr.com/photos/thirteenthumbs

DREW WILEY · Mar 4, 2018

Don't waste your time reading through a meter! They have their own spectral idiosyncrasies. I'm not familiar with the Cokin system, but strong filtration can indeed
affect not only base-line exposure but actual contrast or gamma. You have to test for it. I've done densitometer plots with FP4 regarding this very question; but
the results are related to my own filter set.

dasBlute · Mar 4, 2018

Meter through the filter. The change in the shadows will be different than in the clouds. I typically use red/orange
for a reduction in overall contrast. For example, the clouds will drop a couple of stops in brightness, whereas the
shadows may only lose one. That's a reduction in overall contast and very useful. For local contrast, I move the filter
in and out of my line-of-sight on the part of the scene I'm interested in changing the contrast of, that's more of a gut feel.

jim10219 · Mar 4, 2018

Try using the red filter instead of the orange filter for contrast. The orange won’t give much of a difference, especially if you’re trying to separate green from white tree trunks, or a lighter blue sky from gray clouds. Remember, a colored filter will darken a white object further than a like colored object. Combined with the changes in exposure, if not calculated properly, it’s possible to experience exactly what you did. Also, you could be getting some lens flare behind the filter from not holding it close enough to the lens, or from using a non coated filter and not shielding it from the sun. I use Cokin filters from time to time, but mainly just for graduated neutral density. For just about everything else, I use the screw on type to avoid flare issues (they also cover the ends which can pipe light through the filter if exposed) and keep my hands free to hold/operate the camera or shade the lens.

photog_ed · Mar 4, 2018

Have you tested your shutter for accuracy? Every large format shutter I own is slow at speeds faster than 1/30, with faster speeds being worse. If you are doing your film calibration at 1/60, you could be exposing by a stop or two more than you think you are. Then when you shoot at 1/15, which is probably accurate, you may be getting a lot less compensation than you think you are.

dasBlute · Mar 4, 2018

DREW WILEY said:
Don't waste your time reading through a meter!

<grin> Perhaps he should just lick his finger and see which way the light is blowing?

This is just poor advice, plain and simple. The light meter is your primary tool in-the-field. Filter factors and tables inform but can never compete with the veracity of the scene in front of you.

Huub · Mar 5, 2018

I would actually love to see a simple photo of the negatives you are talking about, which would make assessing the issue a bit easier.

When using filters myself, I think more in terms of shifting colour rendition in the negative then in increasing or decreasing contrast. For instance when using an orange filter I know that blue tones will get darker and contrast in the sky will increase, making clouds stand out. But what also happens is that the contrast in the greens and especially the darker greens will get compressed. So overall you do win contrast in the sky, but loose contrast in the greens and the shadows. Especially in late summer, when folliage is dark, this can lead to under exposed and flat shadows. This in turn can be compensated to some extend by adapting exposure and development, but that too will have influence on the skies again. So a lot of times I choose to expose for the shadows, not to overdo the filtering, and try to solve the problems in de darkroom, using burning and dodging techniques and split grade printing.

What I would do in your case is two things. First I would get some mat black paint and paint the edges of the filters black, elimenating possible stray light. The second thing is that I would do some testing, using 35mm or roll film camera's with the films you use. Take a scene that is more or less standard for your own photograpy and take a picture without a filter. Then put on the filter and shoot the same scene again a couple of times, each time varying the filter compensation. With yellow i would do +0.5, + 1, + 1.5 and + 2 stops, with orange I would shoot +1, + 1.5, + 2, + 2.5, +3 et cetera. Take notes of exposure and frame numbers. After development you can asses the negatives, to see what is happening and decide on the right compensation factor. The small 35mm negatives will probably be big enough to give the info you need and keep this test cost effective. Once you know the right filter factor you should also expose some large negatives side by side, both with and without filter until you get a better feel for what is happening in which kind of light.

Doremus Scudder · Mar 5, 2018

BHuij,

I can think of a couple of things that may lead to your results.

Shutter variances spring immediately to mind. Many shutters are slow at faster speeds and fast at slower speeds. If you've calibrated using a fairly fast, but significantly slower than marked, shutter speed, then that may be key to your problem. Check the shutter(s).

Applying filter factors is rather safe except when the light is of a different color than "neutral." Filter factors fail when the light is colored. Say you have lots of blue sky and the open shadows are lit by this blue light. Using a yellow filter and just applying the standard factor will result in underexposed shadows and less density in the sky, since yellow removes blue. This is intentional for the sky, but may be inadvertent for the shadows. If your situation has strong shadow lighting from the blue sky then maybe this is your issue. Orange and red filters operate similarly, but block progressively more green light, enhancing the effect on both sky and shadows. A similar but converse situation is using filters early in the morning or late in the day when the light may be predominantly orange/red. In this case, a yellow filter would overexpose a bit if you just applied the factor while green and blue would underexpose.

FWIW, I have never had the problem you describe except for thin (underexposed) negs when using yellow-red filters in situations with strong lighting from a very blue sky. I've learned to recognize this situation and deal with it. If you apply filter factors, you need to be aware that your factors for yellow-red filters will be considerably higher in this situation.

As for metering through your filters: I'm an advocate of metering through filters, but with appropriate compensations for spectral response and the effect of strong filters on emulsion contrast. A #8 yellow filter doesn't need much compensation; you can just read through it and shoot, but stronger filters run up against not only the difference in spectral response between meter and film, but film emulsions react differently when they are exposed to colored light than "neutral" light. Depending on the film, both exposure and contrast can be affected. Testing with the stronger filters when metering through them will give you some compensation factors (I test my #25 red, my #58 green, #44 cyan, etc. for both exposure and contrast "fudge factors"). Otherwise, err on the side of overexposure a bit.

Don't give up on filters! They are great tools and you'll get this problem worked out somehow. Pix of the negs would be nice...

Best,

Doremus

juan · Mar 5, 2018

I had similar trouble with the Conkin System on my 8x10 when I used the filters in front of the lens. When I moved the filter inside the bellows, the contrast problem went away. I think the filter system was allowing in stray light. I’d look in that direction.

Doremus Scudder · Mar 5, 2018

juan said:
I had similar trouble with the Cokin System on my 8x10 when I used the filters in front of the lens. When I moved the filter inside the bellows, the contrast problem went away. I think the filter system was allowing in stray light. I’d look in that direction.

Also a good possibility! Keep in mind that when using filters behind the lens, you'll need to focus with the filter in place to avoid a focus shift.

If this really is a possibility, the OP may be able to test quickly by using a good quality, coated glass filter from a reputable manufacturer that is the same as one of the resin filters. Shoot one shot with the yellow resin filter and then the same with the glass filter and see if there is a difference. If so, then maybe it's time for some new filters...

John51 · Mar 5, 2018

shutterfinger said:
Item #2: filter holders have Opaque edges, many filters do not. Holding a non opaque edge filter against the lens barrel allows light to enter from the edge of the filter affecting contrast.
There's a reason holders and lens barrels are opaque, its to prevent light piping from the edge of the elements.

OP could test this by covering the edges of a filter with black tape. If that does the trick, then the edges of all his filters can be painted matt black and still fit in their cases.

DREW WILEY · Mar 5, 2018

A process of elimination. I only use high quality coated glass screw-in filters and a good shade, so the alleged "bellows flare factor" is virtually nil.

RalphLambrecht · Mar 5, 2018

BHuij said:
I shoot FP4+ developed in Rodinal as well as HP5+ developed in HC-110 as my two go-to films. I have already calibrated them in both roll film and sheet film for N, N+1, N+2, and N-1, which covers about 99.9% of my shooting.

I am using Cokin series filters, and since I shoot such a wide variety of 35mm and medium format cameras, as well as a 4x5, I just hold the filter in front of the taking lens at time of exposure rather than trying to mount it.

The filters I use most are the P-001 (yellow), P-002 (orange), P-003 (red), and P-004 (green). Looking online, Cokin lists the following EV compensations for these filters:

Yellow: 2/3 stop
Orange: 2/3 stop
Red: 3 and 1/3 stops
Green: 2 and 2/3 stops

I have read elsewhere that the general rule of thumb for "standard" yellow, orange, red, & green filters is more like

Yellow: 1 stop
Orange: 2 stops
Red: 3 stops
Green: 2 stops

My problem is this. It seems like no matter what I try (I have tried both the Cokin recommendations and the more generalized exposure compensation numbers), I end up with a thin and flat negative any time I use a filter of any color. I will post some negatives and/or contact sheets when I have a chance to scan, as examples.

Just today, I went to the park to shoot the new snowfall on the trees. I shot one frame of FP4+ with no filter, intended for N development. That negative came out great, and exactly as anticipated. About 15 minutes after exposing that first frame, I shot another sheet of FP4+ (from the same box, loaded at the same time into a film holder, etc. etc.). This one had a lot of sky in it which I wanted to darken down quite a bit to emphasize the clouds, so I used the P-002 orange filter, with two stops of exposure compensation given. Specifically, I metered the area I wanted to expose at Zone IV, dialed in the proper exposure (1/60), and then backed the shutter speed off two stops to shoot (1/15) through the filter.

This sheet went into the exact same rotary drum as the first one, was processed by the same chemicals at the same time (also a "N" developed negative)... and came out thin and flat.

Those two negs are drying right now, but once I can show some pics I will.

I have a similar couple of negs from last summer. I was shooting in an aspen grove, so basically white trunks taking up a lot of the frame with mostly out-of-focus green foliage in the rest of the frame. I wanted to emphasize the whiteness against the foliage by darkening the leaves down a bit, so again I used the orange filter and gave 3 stops of exposure compensation. Luckily I was also finalizing some calibration tests at the time, so I took an exact copy of the photo with no filter and no exposure compensation, at the same time. Souped at the same time, etc. etc. Once again, the no filter shot came out looking pretty good, and the orange filter one came out looking thin and flat. Definitely less contrast than the no filter shot. Unfortunately this isn't a perfect comparison as the no filter frame was on FP4+ and the orange filter frame was on HP5+. However, both were developed in their respective developers at an already-established and stable N+1.

I could understand if I just wasn't giving it enough exposure compensation that my negs would be thinner, but I don't understand how they're also losing contrast when an orange filter should definitely be increasing contrast.

Any insights? I'm not comfortable with using contrast filters in my B&W work anymore, and that sucks, because there are lots of times when theoretically they would be great - just can't get them to work for me right now, for whatever reason.

Drew,Your films spectral sensitivity may be different from what Cokin or the general assumption are; these films are losing sensitivity towards red and you may just have to come up with your personal compensation factors. I experienced the same with TMax films and red filters, especially when measured through the filter with a Pentax digital spotter. Just increase exposure and/or lengthen development to get the contrast you desire.

mrosenlof · Mar 5, 2018

a couple of things. the filter factor for a specific filter is not just based on the color, but on the density of the filter. there are light greens, dark green, and similar in most other colors. You need to make sure which filter you're using. Meter through the filter or meter without the filter and add compensation, both work well enough.

holding the filter against the front mounting ring of the lens is most likely introducing flare into the image. Those filters are made to be fit into a filter holder. Might as well use them as intended.

But given enough extra exposure to compensate for the filter, I wouldn't expect B/W negs to be thin and flat if there's flare going on. Dense and flat yes, it's extra disorganized light, but not thin.

You are *adding more exposure* to compensate for the filter aren't you?

My filters consistently decrease my negative contrast - what am I doing wrong?

Privacy & Transparency

Privacy & Transparency