Light meters with reflective, incident and spot metering

Bob S said:

Not with the finish on the Zebra. Go to the Novoflex site and learn about them

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They have an anti-reflection coating on their gray card which is good. Here's the link for those interested. $19.
https://novoflexus.com/novoflex-9x8-grey-white-card-for-manual-white-balance-exposure/

Alan Edward Klein said:

To simplify my question. Would a reading of an object be the same with a 1-degree spot meter if the sun's angles are different? Could that change the setting you choose?

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If the sun chages its position it illuminates differently the faces of our subject, so the same spot will recive more or less light and it will be differently relfected, so tell an extreme difference you may have a shinning glare on an spot or another.

But when spot metering we approach the calculation differently. We meter Spots and from the metering we'll know what will result in that spot.

If we make a an ISO standard processing those spots metered 0+/- will have a 0.62D density over the Base+Fog (not exposed film). For each stop more(less in an spot density will increase/decrease by 0.62/3.33 = 0.17D.

So if I'm metering an spot in the scene, if reading is +1 then after development that spot should have 0.62+0.17 = 0.79D more than Base + Fog.

If Base + Fog of your film/processing is (say) 0.15D then total density will be 0.79+0.15 = 0.94D. We also know that spots at -3.33 will have 0.1D over F+B.

If performing N+/- these values will change acordingly...

Of course it is not necessary to calculate the predicted density when spot metering, but if having to print in the darkroom challenging scenes then we may end thinking in similar terms: we know the quality loss for each local underexposure stop and how difficult highlights become to print for each local overexposure stop.

At the end, with challenging scenes, before shutter release we balance what shadows will be lost to make some highlights easier to print. If the scene is not contrasty then meter like you want, no problem. Also if scanning then no problem, 3.0D is no problem for the scanners and later you do what you want with photoshop.

...but if having to print a sound optic print from a challenging scene then better if one thinks it twice before releasing shutter, or a sound print will be more chanllenging than the scene itself.

So your answer to my questions are what?

1. Would a reading of an object be the same with a 1-degree spot meter if the sun's angles are different? ________?

2. Could that change the setting you choose? ____________________?

I wonder how Miroslav Tichy metered his pictures. He probably used a spot meter.

Alan Edward Klein said:

1. Would a reading of an object be the same with a 1-degree spot meter if the sun's angles are different? ________?

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Yes...

if rays come at 45º light received is 70% of the case light is perpendicular.



Also the reflectivity changes depending on direction...

Alan Edward Klein said:

2. Could that change the setting you choose? ____________________?

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Yes...

Suposedly you want a shading to depict volumes, in case of incident metering you don't change the reading. Incident metering would be the perfection if illumination was always uniform, but it isn't.

But in reflective spot metering you also correct the exposure depending on the relative brightness of the subject. If you meter on a perfectly white wall then you want that wall at +3, if you meter a very light caucasian cheek you want it at +2.. if you meter on concrete you want it at 0+/-

If subject is mate and illumination angle aganist the surface is 45º then you should correct exposure by 1/2 stop.

__________________________

Clearly incident metering and reflective metering are very different approaches to decide an exposure that is to deliver a good image.

Incident metering imposes a certain density level on each film spot depending on subject's spot relative reflectiveness in the camera direction. Prolem is that illumination may not be uniform.

Reflective metering imposes an exposure to get the scene recorded, not matering how illumination is.

138S said:

Yes...

if rays come at 45º light received is 70% of the case light is perpendicular.

View attachment 264125

Also the reflectivity changes depending on direction...




Yes...

Suposedly you want a shading to depict volumes, in case of incident metering you don't change the reading. Incident metering would be the perfection if illumination was always uniform, but it isn't.

But in reflective spot metering you also correct the exposure depending on the relative brightness of the subject. If you meter on a perfectly white wall then you want that wall at +3, if you meter a very light caucasian cheek you want it at +2.. if you meter on concrete you want it at 0+/-

If subject is mate and illumination angle aganist the surface is 45º then you should correct exposure by 1/2 stop.

__________________________

Clearly incident metering and reflective metering are very different approaches to decide an exposure that is to deliver a good image.

Incident metering imposes a certain density level on each film spot depending on subject's spot relative reflectiveness in the camera direction. Prolem is that illumination may not be uniform.

Reflective metering imposes an exposure to get the scene recorded, not matering how illumination is.

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OR you could just use the appropriate meter correctly and stop the whimsical pondering.

Sirius Glass said:

OR you could just use the appropriate meter correctly and stop the whimsical pondering.

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Sirius, IMO here "YMMV" is the right answer. We have many ways to decide the same or to take different decisions.

At the end what counts is undertanding what we are metering with the way we use, diferent meters/modes do meter different things, we get different information. Depending on what we value in the image a meter may be more or less suitable, this is beyond our personal preferences and our particular skills to interpret information from each kind of meter.

Alan Edward Klein said:

So your answer to my questions are what?

1. Would a reading of an object be the same with a 1-degree spot meter if the sun's angles are different? ________?

2. Could that change the setting you choose? ____________________?

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If your light source changes, your metering may change. This seems somewhat obvious to me.

Fortunately, the Sun tends to follow a relatively predictable path. On the other hand, if a giant white truck pulls up behind you, and you're photographing something relatively close by, you might want to double-check your metering. Or not.

The goal here is to capture light on a light-sensitive medium. Unless you're creating negatives for specific processes that have unusual demands, common sense is going to be the most... "common"... approach.

Alan Edward Klein said:

To simplify my question. Would a reading of an object be the same with a 1-degree spot meter if the sun's angles are different? Could that change the setting you choose?

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The instructions that come with the cards deal with surface sheen reflections, not the inherent reflectivity of the cards.
Speaking about metering generally, when the position of the light source changes, the amount of light reflecting off the subject toward the camera often changes. Which of course changes how dark or light that subject appears to be. If you use a reflective meter like a spot meter, that will change the reading, in accordance with how dark or light the subject appears to the camera.

Alan Edward Klein said:

So your answer to my questions are what?

1. Would a reading of an object be the same with a 1-degree spot meter if the sun's angles are different? ________?

2. Could that change the setting you choose? ____________________?

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1. No the readings would vary.

2. Yes, but you might perceive the difference and intentionally give greater exposure because you noticed the shine and decided to make it lighter on the print. In that case, the reading and your intentions may cancel each other out (you might select the same f/stop and shutter speed despite the meter saying you can stop down).

Alan Edward Klein said:

Thanks for providing that information I have that same card and instructions somewhere in one of my cases. Here's the instructions from that card regarding using it in daylight:

ln daylight, orient the gray card the same way as recommended for artificial light using the sun as the main light. in shade, under overcast skies, or in backlighted Situations, use the brightest area in front of the subject, usually the sky, as the main light. in daylight, you can make the meter reading of the card located at the subject or at another position, such as near the camera, as long as the card receives the same illumination as the subject and is oriented correctly, the same way as you would orient the card at the subject position.

So my original question is repeated. If we need to orient the angle of the gray card to get the "correct" reading, would the angle of the natural object we're-reading also have different readings based on the angle to the sun? Would that reading be more affected by a 1-degree spot since you're only measuring one object rather than let's say center metering (assuming you've selected the correct center)?

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The key information, however, was depicted in the graphic found in the PDF, whose essence is stated in text which I quoted from Wikipedia

Calcu Light X and XP meters will do this. You change the piece on the head of the meter. Can also get a piece so you can read exposure directly on the Ground Glass of the camera.
Many available on the used market for low prices.
The XP version is really good in very low light, think moonlit scenes - it is that sensitive.
Small, like a thinner pack of cigarettes and lightweight.
Mine have worked in 123 degrees in Death Valley to minus 64 in Canada and have not given me any problems.

Deleted. Wrong thread.