getting confused: zone placement with an orange 16 filter

[jbl]

I've been thinking about this in the back of my head for a couple of days and seem to have driven myself into confusion.

Take the following, basic landscape. An expanse of dark green foliage, a mountain with foliage on it, a blue sky with some clouds. Assume I compose so that the sky is 2/3 of the frame and the bottom 1/3 is the landscape with the mountain.

With Tri-X, I shoot with an EI of 320. Let's say I spotmeter the foliage on the mountain and place it on Zone IV. I then double check the metering in the sky with the open sky and the clouds to double check on the high end of exposure. Everything works out.

The thing I don't get—or seem to have confused myself thinking about—is how to handle this situation with an O16 filter on the lens. It's official filter factor is 4x, but Tri-X's data sheet lists an O15 (not an O16) as having a filter factor of 2.5x (1.3 stops). At this point, I'm confused as to what to do. If I place the foliage on Zone IV, do I just open up 1.5 stops and maybe bracket a half stop in each direction? My spot metering of the sky has got to be completely invalid because the O16 filter will bring down the brightness of the blue in the sky. I'm a bit at a loss of what to do.

Any help is appreciated. Thanks!

-jbl

 

[Vaughn]

Well, I should probably wait until someone else chimes in, but I would just bracket -- but I would do a base exposure at 2 stops open for the filter and then over and under expose by one stop. Or if you got film to burn, do 1/2 stop and 1 stop over and under (5 negs) and then check out the results. Print them to get a feel of what the filter will do.

Greens will darken a little with an orange filter. Green is a combo of cyan (sky blue) and yellow, and your open shadow areas will also darken as they are lit up with the cyan light from the sky and thus will darken when you filter out the cyan light.

You can also meter thru the filter to get an idea of what is happening, tho the meter probably does not act in a precise linear manner to different colors.

That is how I understand it, anyway.

Vaughn

 

[David Allen]

The effect of a filter will vary with time of day and angle of the sun.

What you need to do is meter exactly as you have described BUT do this through the filter (i.e. place the filter in front of your meter's cell or lens).

No need for uncertainty or bracketing.

By the way, when I used to do landscapes, I found both red and orange filters gave a too over powering result. I would strongly recommend a Minus Blue filter (a very specific type of yellow filter that has the Wratten number #12)

Best,

David
www.dsallen.de

 

[Doremus Scudder]

jbl,

There are a couple of schools of though on this. The first is to simply apply the filter factor ... intellegently. That means being aware of your light source (e.g., warmer sunlight at morning/evening or incandescent lighting as well as knowing what effect the filter will have on important areas of your scene, such as green foliage, shadows lit primarily by blue light, etc. One modifies the factor and/or brackets to compensate.

The second method is to simply meter through the filter and use the resulting exposure, thus allowing the meter to apply the filte factor. The problem here is that the meter's spectral response is not exactly like that of the film you are using (with the possible exception of the Zone VI modified meter). This is not a problem except with the strongest filters (red, dark green, maybe dark orange, etc.). With these latter, however, modification may be in order.

The third variable is the film's contrast response to light of different colors. This is most important when using strongly colored filters. The response varies from film to film. Note, just using the manufacturers' filter factor does not compensate for this, nor does metering through the filter.

Both of the above methods assume that you have made your exposure determination beforehand. With the first, you are guessing somewhat where e.g., sky values will end up. The metering method gives you more precision here.

I meter through the filters, but have done testing to determine what extra exposure modifications need to be made for the mismatch in spectral response of meter and film (e.g., + 2/3 stop and N-1 with a #25 filter for tri-x).

If I were you, I'd meter through the filter, give a bit more exposure as a safety factor and then keep careful records for a while, compiling data on the filters and films you use. You may find that one filter needs a bit more exposure, or more development, or both, or whatever. These data you can then compile into a table that you can memorize and/or use in the field.

Best,

Doremus

www.DoremusScudder.com

 

[RalphLambrecht]

meter and place zoneswithou th filter.once the exposure has been worked out this way ,add filter and filter factor.

 

[baachitraka]

If you place the foliage(autumn) on Zone IV and if your spot-meter reading shows f/8 and 1/60 without filter, then you can divide the shutter speed(e.g) with the corresponding filter factor. With factor 4, the values will be f/8 and 1/15.

 

[ROL]

I've been thinking about this in the back of my head for a couple of days and seem to have driven myself into confusion.

This is a good thing! You are thinking about the scene and exposure as a connected task (previsualization). You will work it out eventually and gain a real understanding of the ZS and placement (Yeah!).

Take the following, basic landscape. An expanse of dark green foliage, a mountain with foliage on it, a blue sky with some clouds. Assume I compose so that the sky is 2/3 of the frame and the bottom 1/3 is the landscape with the mountain.

My speciality. This can be difficult placement–wise, but will test and reinforce your understanding and implementation of the ZS.

With Tri-X, I shoot with an EI of 320. Let's say I spotmeter the foliage on the mountain and place it on Zone IV. I then double check the metering in the sky with the open sky and the clouds to double check on the high end of exposure. Everything works out.

Well, If the "dark green foliage" is important to your composition, I probably would place it on III, and let the sky and clouds go, contracting (reducing) development if (likely) necessary. Do you want it to be dark (with texture) or a lighter grey (IV) in the print? If rendition of the sky is more important (to your composition), then make certain the brightest clouds were no better than VIII, and let the darkest regions (the foliage?) go (this may also be helpful).

The thing I don't get—or seem to have confused myself thinking about—is how to handle this situation with an O16 filter on the lens. It's official filter factor is 4x, but Tri-X's data sheet lists an O15 (not an O16) as having a filter factor of 2.5x (1.3 stops). At this point, I'm confused as to what to do. If I place the foliage on Zone IV, do I just open up 1.5 stops and maybe bracket a half stop in each direction? My spot metering of the sky has got to be completely invalid because the O16 filter will bring down the brightness of the blue in the sky. I'm a bit at a loss of what to do.
-jbl

I think you have this right. Either apply the filter factor to your exposure directly – 4X: open up (or reduce shutter speed) 2 stops, or meter through the filter. The reasons for doing one or the other have already been given, and may ultimately amount to simple preference. I use filter factors in all film formats for natural settings. You could ensure results and investigate which works better for you by bracketing one stop, but I think you will find for most B/W films there is almost always enough latitude for a successful print, if you follow through exposing based on your placement decisions.

Be careful with strong filtration, unless you're after a specific effect. Many neophytes apply overly strong filtration in the hopes of getting an overly dramatic (contrasty) "ansel look", reds being the most common. These will wipe out intermediate tonalities, decidedly "un–ansel like". Orange will certainly help in darkening the sky and resolving clouds, but it will also likely muddy your landscape. I never use anything stronger than a deep yellow, sufficient to filter blue and thus darken skies, define delicate cloud structure, and maintain full tonality in the landscape itself, with panchromatic films.

 

[RalphLambrecht]

i thought,the zone system would eliminate the need to bracket

 

[RalphLambrecht]

ate cloud structure, and maintain full tonality in the landscape itself, with panchromatic films.

good point!