exposure of dark evergreen trees?

[Bill Glickman]

I am amazed how my ambient light meter does a perfect job exposing my Velvia chr omes when the light meter is saturated with the same light as the subject is. I t seems sensless to make spot meter readings and then interpret the refelctivity % and translate that back into stops to compensate the spot meter reading... ho wever, there is one area that this ambient reading consistently fails me, and I don't know why...

Under broad daylight, evergreen trees are saturated with bright sunlight, my ambient meter is reading the same bright sunlight, so I shoot at the reading on my abient meter.... focused at infinity of course, no issues of bellows compe nsation... the image is always to dark, by 1 stop to 1.5 stops, so I have to o pen up an additional 1 - 1.5 stops everytime, and then the evergreens are expose d properly. Does anyone know why this phenomina occurs? Where it really gets m e is when the evergreen trees are only a small portion of the scene, then the sc ene will get exposed properly, but the Evergreens are too dark? Any input would be greatly appreicated. Thank you..

[Ben Diss]

I don't know the answer to your question, but I would be interested to know how a spot meter would work in this situation. Is it possible that the shadows between the needles and branches are not being accounted for with the ambient meter?

[N Dhananjay]

I can think of two things that are happening - meter technique and subject range.

Metering technique: The best way to take an incident reading is probably to point the mater at the camera from the subject. If you point the meter at the light source, the trouble you run into is that the subject receives light at a different angle from how the dome on your meter receives it. By walking into the subject and pointing at the camera, the same light falls on the dome and in the same way as it is falling on the subject. Alternatively, the light you're measuring might be more than what actually falls on the scene. In this case, you're measuring the sunlight falling on the scene. However, the evergreen trees are probably in the shade i.e., in their own shade. So while the sunlight bathes the tops of these trees in the same uniform light your meter is measuring, the part right under the top is in the shade of the tree. That would give you the underexposure of a stop or so. If you can walk into the scene i.e., the trees are not far away, you could walk under them, point the meter at the camera and take the reading which should work appropriately. If you can't walk into the scene, you can try shading the meter and taking a reading or using the meter in your shadow.

Subject contrast range: Alternatively, maybe your contrast range is very extreme. So in order to hold detail in some of the highlights of the scene, the really dark stuff ends up on the toe of the film. The incident light meter really doesn't care about the reflectances of individual areas and it is upto you to see where different areas would fall. Your film can obviously handle only a short range of luminances before it starts throwing stuff away. So dark and VERY dark areas can't really be separated well because they are on the toe of the film or worse, beyond. Now normally, reeally dark stuff makes up small areas in your picture and you can lose that without too much grief. However, if your principal subject area is very dark (or very light), you might want to compensate your meter reading so that instead of this stuff ending up on the toe (or shoulder of the film) where tonal values are compressed or thrown away, you can move them just a little bit (reemember too much pulls them too far in towards middle gray - you don't want to lose the dark value, just separate the dark values out a little better) into the straight line part of the curve where a little more tonal separation can exist between the darks. Alternatively, if your subject contrast range is just so extreme (bright highlights to dark shadows), you can choose to lose detail in one end (let your shadows fade to black - probably the better option with transparency film). If you just have to maintain both ends of the scale you can try other esoteric techniques like rating your film slower and pulling development or preflashing your film.

Hope this ramble helps. DJ

[james mickelson]

Wonderful answer. Re-rate your film. But watch your highlights with possibly decreased development as the compensation. The evergreens are in too much shade. Only the tips are exposed to light. Shade your meter and the trees will be exposed properly. Also a yellow #11 or green #58 filter will alter your tonalities in the evergreens. James

[Alec Jones]

Nope, you're all wrong! It's the chlorophyll. Green foliage can reflect nearly 100 percent of infra-red light, even though it is pretty dark in the visible portion of the light spectrum. Remember all that white foliage you've seen in IR film shots? Unfortunately, the color sensitivity of most meter cells doesn't match the color sensitivity of film. Fred Picker and Dennis Purcell discovered this phenomena when Fred was developing his modified Spot Meter. He corrected his meter with different cells and IR filters. Otherwise, you have to make the adjustment you've described. At least now you know why!

[Carlos Co]

Alec, I'm not sure what you mean - your explanation seems to be contradictory to Bill's observations.

[Carlos Co]

Alec, perhaps you meant that the leaves absorbs ambient light energy? Please clarify.

[Lot Wouda]

It seems to me that Dananjay and james are on the right track and that Alec didn't read the question or doesn't know what ambient light metering is. And this is because Velvia simple is a very high contast film. Try Kodak VS100 which abridges more brightness and has by far the most latitude of all slide-films thus far and which is as sharp as Velvia with no irritating magenta-bias. Maybe even the magenta-bias of Velvia coincides with the green of evergreen in such a way that it just does not take that much dark-green.

[Lot Wouda]

BTW, at what altitude did you shoot these slides? I mean because of the amount of UV-light, especially in the shadows, which are turned more blue at higher altitiudes, which press away the original greens on slide too.

[Bill Glickman]

Thank you all for your input... this just goes to show what an excellent forum this is to bring good ideas and experiences together.

N Dhanajay, you raise some excellent meter technique issues, they were all well explained and I fully agree with them, however I already take them into consideration when metering, so they do not represent the problem here. The contrast range issues does not apply, because sometimes I shoot straight Evergreens with nothing else in the scene and even the trees that are in the front and not the least bit shaded also experience the darkening.

Lot, the altitude is insignificant, I have shot them at sea level and 10,000 ft, and the same result happens. I also check my Gossen 3 color meter beofre every shot, and have not had color temp as a variable yet. However, you raise an excellent point about the bias of Velvia film, and this may an odditity that has no fix, assuming there is other items in the scene you want exposed properly. I will try the Kodak film you suggested.

Alec, you may be on to something here... this is the kind of answer that may make sense, but is not widely known. However, as Carlos pointed out it seems you possibly misworded your answer, becuae remember the shots are darker than expected not brighter. Could you please elaborate on this?

Also, I have a call into Fuji Tech. support, I will advise of any answers they come up with. Thank you.