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Don,
I'm not sure what you expect from using a densitometer instead of a normal light meter for determining filter factors. Although a normal light meter might not exactly match the spectral sensitivity of your film, this is usually sufficient in practice. It is still photography and not rocket science!
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 Originally Posted by Lex Jenkins
Hey, Don, if it's not going off on a tangent too much, mind if I ask why you find yourself doing more incident than spotmetering these days?
This isn't a trick question and I don't have an axe to grind. I'm just often curious about the metering techniques we use.
Lex,
The reason that I am using incident metering more these days is that a lot of the work that Sandy, Clay and others have done regarding films and development times is based upon BTZS methods and procedures. BTZS utilizes incident metering. In order to save effort, time and to not "reinvent the wheel", I try to follow their shared experience. Hope that this answers your question.
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Originally Posted by Jorge
It has to do with the thickness of the material and being able to read it with the densitometer probe. If the material is too thick you will have extraneous light going into the probe, plus the aligment of the sensor will not be the same as if it was a thin material, for which these instruments are designed.
Suppose you turn off all the lights to read the glass or acrylic filters, then at the same time you have light from the densitometer bulb escaping due to thickness.
Jorge,
I can understand what you are saying. I am not sure that it is applicable and I am not sure that it is not applicable. The factor that I see is that the sensing unit in the head of the densitometer is still reading only the known light as presented on the light source side of the material. Extraneous light or the absence of it would seem to be of no effect since the sensing unit is flat against the material. I have tried to read densities of samples of the material that I want to use for filters and the readings seem to be reasonably accurate (at least at this juncture). I will try the readings in actual field conditions and see how they hold up. Thanks for your thoughts.
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Originally Posted by Thilo Schmid
Don,
I'm not sure what you expect from using a densitometer instead of a normal light meter for determining filter factors. Although a normal light meter might not exactly match the spectral sensitivity of your film, this is usually sufficient in practice. It is still photography and not rocket science!
Thilo,
If I were using a spot meter for my exposures, it would be a simple matter of metering through the filter. However when I am using incident metering I am not able to meter through the filter and must assign some exposure factor to the filter effects. I have long felt that filter factors are arbitrary in that the considerations involve not only the general density effect on light transmission but also the effect that a yellow, orange or red filter would have on the relative transmission of cyan in a sky for instance. I would like to know not only that a yellow filter has a 1 1/3 stop general density effect but also a 2 1/3 stop effect on a sky luminance for purposes of visualization at the time of exposure as an example. While the first effect (general density) is useful as far as a proper exposure, the knowledge of the 2 1/3 stop effect on a sky luminance is useful insofar as visualization is concerned.
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Originally Posted by dnmilikan
...development times is based upon BTZS methods and procedures. BTZS utilizes incident metering...
Fair enough. I've been curious about the BTZS method. So far I've only glanced over the material. Thanks, Don.
Three degrees of separation from Kevin Bacon.
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[quote="dnmilikan"]
Originally Posted by Thilo Schmid
If I were using a spot meter for my exposures, it would be a simple matter of metering through the filter. However when I am using incident metering I am not able to meter through the filter and must assign some exposure factor to the filter effects.
Don,
I did recognise that point. But what keeps you from using a spot- or normal reflective meter for determining filter factors "at home" as you would do with your densitometer? I can't belive that you do not even own one.
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Paleo = old, ancient, prehistoric.
Probably doesn't work as a political prefix, but I like it along with 'analog photography'.
Paleo-photography, anyone?
Murray
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Originally Posted by dnmilikan
000
About four of your posts have the text '000' in them, but nothing else.
What gives?
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