Incident metering of shadows? Sandy King says so

Trask · Oct 26, 2014

In a recent (and still active) thread regarding Barry Thornton's Two Bath developer, a poster linked to an article by Sandy King regarding two-bath development. In that article, Mr King writes:

"Kodak T-MAX 400 was used for this testing. Exposure was determined by a single incident meter reading, taken in the deepest shadows where open detail was desired, with the meter set to box speed of ASA 400. An incident meter reading in the shadows is one of the simplest and most reliable methods of determining exposure for most scenes. Other methods of metering are perfectly acceptable so long as the exposure is sufficient to give texture in the deepest shadows where detail is needed."

This is the first time I have seen it suggested that a photographer, when measuring different light levels in a scene, would use an incident meter to measure the shadows. As an incident meter is not pointed at the subject but rather back at the camera, it has no idea what it is being held in front of -- which, of course, is the point of using an incident meter. I cannot understand how one could measure shadows or highlights with an incident meter?

I suspect this was an error, one of those things where you know what the right word is and yet go ahead and write the opposite. If anyone can explain to me how to go about measuring shadows with an incident meter, I'd be interested to know as I use an incident meter for 99% of my exposures.

Old-N-Feeble · Oct 26, 2014

No, it's not an error. Many photographers are very successful at utilizing that method and Sandy King is one of several photographers whom I would never argue against their procedures. On the other hand, I don't feel comfortable with this method. I much prefer a spot meter and understanding how my films respond to differing light wavelengths.

Jim Noel · Oct 26, 2014

I use a spot meter for about 98% of my exposures. There are times when I want to be doubly certain that the film will recor shadow detail that I desire, for instance when a large percentage of the image is in shadow. At these times I use an incident meter by placing it in the shadow area aimed directly at the lens and placing the reading on Zone III to III 1/2.

Bill Burk · Oct 26, 2014

This is similar to the metering technique described in Beyond the Zone System (BTZS)

It's not a mistake to rate a 400 speed film at 400 and incident read shadows and take readings without adjustment to base your exposure.

But it encapsulates two common exposure decisions in one action:

1) Expose for the shadows
2) Rate film at "half box speed"

Taking an Incident Meter reading of the shadows and reading the calculator dial "as-is" would make the scene appear too "light".

You are supposed to deliberately underexpose one stop to make everything in the shade look "darker".

Many people rate their black and white negative film at "half box speed". Notice Sandy King doesn't do that here. He is effectively rating a 400 speed film at 200.

That's because effectively he is making that one stop shift by ignoring the fact you are supposed to underexpose the shadow reading.

palec · Oct 26, 2014

I see two possible explanation
1: that the meter is reading light reflected from deepest shadow through diffusion dome positioned towards the subject, giving some exposure latitude towards shadows
2: that part of the picture is in the shadow, so I take the reading, typical for incident meter, by pointing meter diffusion dome towards lens

baachitraka · Oct 26, 2014

Its very reliable method but it will work when speed fall below the box speed after development otherwise you would see shadow falling close to middle gray.

baachitraka · Oct 26, 2014

If no shadows are found it is possible to simulate shadow illumination with hand.

Fixcinater · Oct 26, 2014

Bill Burk said:
Taking an Incident Meter reading of the shadows and reading the calculator dial "as-is" would make the scene appear too "light".

You are supposed to deliberately underexpose one stop to make everything in the shade look "darker".

Many people rate their black and white negative film at "half box speed". Notice Sandy King doesn't do that here. He is effectively rating a 400 speed film at 200.

That's because effectively he is making that one stop shift by ignoring the fact you are supposed to underexpose the shadow reading.

What you've written seems overcomplicated, why not just state that he's placing those deep shadows at an appropriate exposure value? Any meter is going to give you results based on 18% gray, so adjusting for shadows/highlights isn't rating the film differently but just placing them appropriately on the tonal scale.

Or am I mis-interpreting what you've written?

Regular Rod · Oct 26, 2014

Exactly how is one supposed to make incident readings of "the shadows"?

Walk over to the shadow part of the subject and stick the incident meter out facing the light landing on the subject take your reading. Now go over to the brightest part of your subject and repeat the process. Assuming the light hasn't hanged between readings, you will get exactly the same values!

The light coming off the subject is surely what we are really interested in?

RR

Patrick Robert James · Oct 26, 2014

Generally, it is hard to overexpose film when you are using a two bath developer since the highlights are held back by it but underexposure can be an issue. Therefore you want to err on the side of too much exposure. Taking an incident reading in the shadows is an easy way to do it. Frankly, I always err on the side of too much exposure if I am not sure regardless of the developer.

grahamp · Oct 26, 2014

If you understand what you are doing, any exposure metering method should give you the same result. Bill seems to have this method encapsulated very well.

At the other end of the scale (so to speak), I have used a while card as a reflective target when light levels are too low for a reliable meter reading from the subject. I know the white card is 3 stops brighter than a grey card would be, and I can adjust accordingly, including a reciprocity correction in this case.

baachitraka · Oct 26, 2014

Incident meter do not know anything about the outside world. It just measures the illumination.

It is assumed the white dome mimics gray card with 18℅ reflectance. So when reading shadows we do not want to see them falling close to middle gray on prints.

On considering that, we need to adjust the shadow illumination by 1 stop at least.

Old-N-Feeble · Oct 26, 2014

This argument has been repeated countless times ever since BTZS started. Again, it works for some but it's not something I'm the least bit interested in. I like a good spot meter and I doubt anything anyone argues is a better system will ever convince me otherwise. If I spot-read a shadow and decide it belongs at Zone III that's exactly where I'll place the exposure.

Regular Rod · Oct 26, 2014

Old-N-Feeble said:
This argument has been repeated countless times ever since BTZS started. Again, it works for some but it's not something I'm the least bit interested in. I like a good spot meter and I doubt anything anyone argues is a better system will ever convince me otherwise. If I spot-read a shadow and decide it belongs at Zone III that's exactly where I'll place the exposure.

+1 here too...

RR

John Koehrer · Oct 26, 2014

Regular Rod said:
Exactly how is one supposed to make incident readings of "the shadows"?

Walk over to the shadow part of the subject and stick the incident meter out facing the light landing on the subject take your reading. Now go over to the brightest part of your subject and repeat the process. Assuming the light hasn't hanged between readings, you will get exactly the same values!

The light coming off the subject is surely what we are really interested in?

RR

I guess the UK doesn't have shadows?

You're reading light falling on the subject, not being reflected from it.. If you're in a shadow, that means the light falling in the shade is blocked.
Your meter may be in need of service.

Or just maybe operator error?

Bill Burk · Oct 26, 2014

Fixcinator,

I'd hoped my explanation wasn't overcomplicated so I must have messed up...

Yes, Sandy King placed those shadows appropriately on the tonal scale. He did it simply. He set the Exposure Index to 400.

To get similar readings with a reflected light meter (or an incident meter reading taken from the fully illuminated parts of the scene), you would set the Exposure Index at 200.

Fixcinater · Oct 26, 2014

Bill, thanks for that, your last statement clarified the difference you were speaking to.

I guess I would prefer to do the mental calculations as needed rather than constantly fiddling with the meter's adjustments to get a an appropriate direct reading. I can see the advantage of that method, though.

Sirius Glass · Oct 26, 2014

Sandy King's method will work. An other method which I use us to decide on the zone level for the shadow, set my Gosen Luna Pro SCB light meter for that zone and use the spot meter attachment set on the shadow.

Allen Friday · Oct 26, 2014

The incident system:

http://btzs.org/Articles/Sensitometry Part 5.pdf

Old-N-Feeble · Oct 26, 2014

What seems to escape many folks vision is that values within shadows vary just as much as values in sunlight. A lump of charcoal in shadow is darker than clean snow in shadow which is different than tree bark or rocks of varying values or foliage, etc. Find the important darkest shadow detail and meter off of that then place that value where it should be. Then meter the brightest important highlight detail to determine development time and adjust exposure as needed to compensate for the new E.I. as affected by adjusted development.

The fact is, BTZS is NOT as accurate as the Zone System. There is nothing as accurate as reflected metering, adjusted development for contrast control, and knowing how adjusted development affects E.I.

Oren Grad · Oct 26, 2014

Old-N-Feeble said:
The fact is, BTZS is NOT as accurate as the Zone System.

That's right. It's more accurate, because it takes into account the film and paper curves, both of which have a huge effect on tonal values, while the Zone System as usually presented ignores both.

BTZS does not require use of incident metering. It presents incident metering as a tool that can be useful in many circumstances - more circumstances than many people give it credit for - but it is considered not an exclusive or mandatory tool but rather as complementary to spot metering of reflected light.

Oren Grad · Oct 26, 2014

baachitraka said:
If no shadows are found it is possible to simulate shadow illumination with hand.

This.

In Phil Davis's words:

"As you work with the Incident System you'll soon discover that some types of subjects can't be metered directly. For example, if you're trying to photograph the Grand Canyon, it's clear that you can't very well walk into the actual subject space with your meter.... If you need to know the illuminance value of a distant tree or rock shadow, it's usually safe to take a substitute reading in the shadow of a similar tree or rock close by. Read your own body shadow as a substitute for open shade in the subject area, shade the meter cell to various degrees with your hand, the dark slide, or your focusing cloth to simulate more deeply shaded areas...."

To all who don't understand what BTZS actually says about incident metering, read the article that Allen linked just above.

Allen Friday · Oct 26, 2014

I use BTZS testing of film and paper and ZS metering--spot metering of the most important shadow and highlight. The BTZS testing gives me the same results that ZS testing does (and yes, I match my film to paper when using the ZS), it just does it much more quickly.

Regular Rod · Oct 26, 2014

Oren Grad said:
This.

In Phil Davis's words:

"As you work with the Incident System you'll soon discover that some types of subjects can't be metered directly. For example, if you're trying to photograph the Grand Canyon, it's clear that you can't very well walk into the actual subject space with your meter.... If you need to know the illuminance value of a distant tree or rock shadow, it's usually safe to take a substitute reading in the shadow of a similar tree or rock close by. Read your own body shadow as a substitute for open shade in the subject area, shade the meter cell to various degrees with your hand, the dark slide, or your focusing cloth to simulate more deeply shaded areas...."

To all who don't understand what BTZS actually says about incident metering, read the article that Allen linked just above.

The more I read this the more have to conclude that this use of the term "incident" is in error!

RR

gone · Oct 26, 2014

You can make incident readings of shadows even if you don't have a spot meter by looking around for something near you that has a similar value, then meter that.

Incident metering of shadows? Sandy King says so

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