Light meters with reflective, incident and spot metering

[BradS]

A better comparison would be: The Spot meter is like a Jeep that can go both to highways and to challenging mountian tracks with rocks in the middle. Other meters may be more convenient for the highway but they cannot go through challenging tracks.

Here you have 3 examples of challenging situations where an incident meter won't be useful: .

You’re missing the point. The point is about need not about useful.

People starting out in large format photography do not need a spot meter. It’s not helpful to go on and on about how useful it is if it makes them feel overwhelmed or confused.

Useful? Maybe.

Necessary? Absolutely not!

 

[138S]

You’re missing the point. The point is about need not about useful.
People starting out in large format photography do not need a spot meter. It’s not helpful to go on and on about how useful it is if it makes them feel overwhelmed or confused.
Useful? Maybe.
Necessary? Absolutely not!

Brad, to start in LF one not even needs a meter. Also in LF also there is no need to use Zone System or a derivative... but let me point that for anyone starting it is an amazing teaching, of impressive value, learning the heritage treasured since Adams and Archer, and this involves exploring the scene spots to realize how the print will be, metering the different zones. Later do what you want, but first know the classics.

Now, please explain me how the hell would you meter that shot with an incident meter, if not owning an helicopter:



You and the camera are in the shadow, the snowy mountains are miles far... is it that difficult to realize that an spot metering can be critically useful ?

Look, spot metering is the easiest way to meter accurately, and the easiest way for a LF rookie get control on what he gets. You point to different areas and you know what under/over exposure you will have in each spot. What is difficult or confussing in that ????? One has to be a total dummie to not understand that.

 

[BradS]

Brad, to start in LF one not even needs a meter. Also in LF also there is no need to use Zone System or a derivative... but let me point that for anyone starting it is an amazing teaching, of impressive value, learning the heritage treasured since Adams and Archer, and this involves exploring the scene spots to realize how the print will be, metering the different zones. Later do what you want, but first know the classics.

Now, please explain me how the hell would you meter that shot with an incident meter, if not owning an helicopter:

View attachment 263901

You and the camera are in the shadow, the snowy mountains are miles far... is it that difficult to realize that an spot metering can be critically useful ?

Look, spot metering is the easiest way to meter accurately, and the easiest way for a LF rookie get control on what he gets. You point to different areas and you know what under/over exposure you will have in each spot. What is difficult or confussing in that ????? One has to be a total dummie to not understand that.

childish name calling.

 

[Lachlan Young]

What's far more amusing is that the image being cited as being impossible to make without a spot meter... was made in 1944, several years before commercially available spotmeters were on the market (the SEI etc seem to have arrived in the late 1940's). You can meter a scene like that just fine with any meter and a little judgement (and printing ability).

 

[138S]

childish name calling.

Not at all... I know you can use an spot meter, I was saying that someone starting in LF has to be a dummie if not being able to judge an spot evaluation. If he is not able to understand that in 5min then better he gets a DSLR, because this is the easiest thing he has to learn.

only tell me how you would meter the Owens Valley shot with an incident meter. Have you an answer or not ?

All we are able to meter that scene with Sunny 16. At f/16, ISO 100, 1/100s we have that snow at around +3 overexposure, perhaps a bit more.

This said if we want an accurate metering of that mountain:

> The Incident meter won't give any clue.

> An averaged meter won't tell what overexposure will the snow have

> The spot meter will tell the precise under/overexposure in any spot we want to know.

IMO, a Rookie has to use the spot meter to learn and to get precise feedback, when one is experienced then he can use other ways.

 

[Alan Edward Klein]

Not at all... I know you can use an spot meter, I was saying that someone starting in LF has to be a dummie if not being able to judge an spot evaluation. If he is not able to understand that in 5min then better he gets a DSLR, because this is the easiest thing he has to learn.

only tell me how you would meter the Owens Valley shot with an incident meter. Have you an answer or not ?

All we are able to meter that scene with Sunny 16. At f/16, ISO 100, 1/100s we have that snow at around +3 overexposure, perhaps a bit more.

This said if we want an accurate metering of that mountain:

> The Incident meter won't give any clue.

> An averaged meter won't tell what overexposure will the snow have

> The spot meter will tell the precise under/overexposure in any spot we want to know.

IMO, a Rookie has to use the spot meter to learn and to get precise feedback, when one is experienced then he can use other ways.

I believe the sunny 16 rule works on snow too. The rule doesn't know what subject your shooting.

 

[Sirius Glass]

You’re missing the point. The point is about need not about useful.

People starting out in large format photography do not need a spot meter. It’s not helpful to go on and on about how useful it is if it makes them feel overwhelmed or confused.

Useful? Maybe.

Necessary? Absolutely not!

+1

 

[Sirius Glass]

only tell me how you would meter the Owens Valley shot with an incident meter. Have you an answer or not ?

Easy. A softball question. Aim the incident meter in the direction that points towards the camera.

 

[Andrew O'Neill]

The only metre I'm aware of that can do both without adding an attachment is one of the Sekonic models. Too rich for my blood, though. I've always gotten by with either a Minolta IV, with reflective attachment, or a Minolta spot V.

 

[138S]

Easy. A softball question. Aim the incident meter in the direction that points towards the camera.

This won't work...

In the Owens Valley shot the camera is in the shadow so you are to measure the incident light in the shadow, while the far snowy mountain is illuminated by direct sun rays, having a very strong incident illumination around 3 stops higher.

If you metered that way then the snowy mountain would have been overexposed by around +6 or +7, as you have to add the extra snow brightness to the incident overpower in the sunny area.

 

[Lachlan Young]

I believe the sunny 16 rule works on snow too. The rule doesn't know what subject your shooting.

That's the truth. And the foreground looks like it has been burnt-in in the darkroom & possibly had a bit of help from a filter at negative exposure time. Adams was very familiar with the EV/ LV scale or equivalents. Highlights were likely EV 16, shadows EV 12. With those remarkably invariant values known, you will know the range of the subject relative to the range of the paper you wish to print on, the rest is a case of working out how much you might want to reduce processing by (allowing for system flare and enlarger light source etc - which quickly become familiar knowledge - and how much you can afford to flatten the film's gradient), where you want to place your exposure relative to shadow values (he could have taken a meter reading here and indexed that for where he wanted the detailed shadows to fall) and then making your exposure. That's about it. Then lots of burning-in when printing.

 

[Sirius Glass]

This won't work...

In the Owens Valley shot the camera is in the shadow so you are to measure the incident light in the shadow, while the far snowy mountain is illuminated by direct sun rays, having a very strong incident illumination around 3 stops higher.

If you metered that way then the snowy mountain would have been overexposed by around +6 or +7, as you have to add the extra snow brightness to the incident overpower in the sunny area.

Duh, then do not stand in the shade. One needs to be in the same light. This is not rocket science.

 

[Sirius Glass]

I believe the sunny 16 rule works on snow too. The rule doesn't know what subject your shooting.

Yes, I have done it many times.

 

[138S]

I believe the sunny 16 rule works on snow too. The rule doesn't know what subject your shooting.

Yes, a subject that's on the snow has to be exposed the half, as it is illuminated directly by the sun and by the reflexion of the sun in the snow.

Another thing is how and snowy area will be exposed, if we meter the incident light going to the snow then, as being it the very reflective, the snow zone will be al +3.

 

[grat]

So you believe a digital camera as a light meter should read the same whether you point it towards the light source or away from it?

So you believe there's no difference between a single CDS photocell and an array of photosites behind a lens?

 

[138S]

So you believe a digital camera as a light meter should read the same whether you point it towards the light source or away from it?
Imagine the extreme case of the meter being in a dim doorway. An incident meter with proper diffuser will read the ambient light, while an undiffused meter, whatever you call it, will meter the exposure that makes the outside area middle grey when pointed in that direction. Try an app with "incident metering" in this kind of situation, or a less extreme one, such as a room with a single window. With the brightness sensor, at least you have a chance; good luck if it uses the camera!

RECTIFICATION:

This App in particular:



Uses the light sensor and not the Front Camera.

I found that by casting shadow on the camera lens and on the camera sensor, and viewing how the reading moves.

I got confussed because I had installed this App that was new to me to make this test, sorry...

Also I found that this mobile in particular (Xiaomi Note 8 Pro) has a very good light sensor, mostly nailing the same than the Lux reading than the dedicated Lux Meter, not matering the direction. Other phones I had previously delivered a very directional reading, so I judged wrongly that this reading could come from the light sensor.

In this mobile (like in many other) the light sensor position cannot be seen by looking on the screen's top, it is hidden, it had to be located by casting a shadow in the screen's and whatching the reading.

It was a surprise to me that reading could be that consistent with the one the Lux meter delivers... Modern times

 

[grat]

By contrast (ugh), the light sensor on my phone is entirely directional, but the front camera isn't. My light meter doesn't have the flat lumi-disc for 2D readings, but I suspect that would be closer in nature to the light sensor.

 

[138S]

By contrast (ugh), the light sensor on my phone is entirely directional, but the front camera isn't. My light meter doesn't have the flat lumi-disc for 2D readings, but I suspect that would be closer in nature to the light sensor.

TEST PERFORMED

For incident metering, I've completed an extensive practical test, playing for some 60min in different illumination situations including direct sunlight, and pointing the meters to different directions.

Compared a Lux Meter to that App+Xiaomi Note 8 Pro.

Result: I got discrepances of about 15% nominal in the reading, this would be under 1/4 of stop perhaps 1/6. We may find that discrepance is common between commercial meters.

Disclaimer: Apps may allow to adjust corrections for the offset and gain, still some smartphones may sport a very directional senstivity that require a very different interpretation. IMO it can be recommended that anyone wanting to use the smartphone for incident metering he should check the consistence of the readings with an Lux meter or at least comparing with the spot metering on a grey card, checking different orientations to the light source.

(Since my Weston Master IV died I had no incident meter, personally I use Spot a lot, but I wanted to know if my particular phone could deliver a reliable reading if wanted, if I was always incident metering I would like a Sekonic or a charming Weston).

 

[macfred]

Is there anyone out here who practices photography ?

 

[grain elevator]

So you believe there's no difference between a single CDS photocell and an array of photosites behind a lens?

What you quoted was a response to 138S talking about "incident" metering apps that use the front camera, stating they'd work more or less the same (perhaps more "directional" as a diffused actual incident meter. If that was the case, then any camera that meters off the sensor would read the same exposure whether pointed toward the light source or toward the subject, as it's designed to. That's obvious humbug.
As to others getting hung up on dome vs. disk diffuser, I think that's beside the point. The phone camera has no diffuser at all and as such direct light will strike the sensor, making the reading too high in these situations. So as far as these apps do work in such situations, it must be by computational power (identifying a light source in the picture to adjust the reading), I think error prone.

 

[Lachlan Young]

Is there anyone out here who practices photography ?

I really have no idea why people want to make metering as difficult as possible - they should be able to get a more than sufficiently accurate exposure with one meter reading, two if they really need to know the contrast range.

 

[macfred]

I really have no idea why people want to make metering as difficult as possible - they should be able to get a more than sufficiently accurate exposure with one meter reading, two if they really need to know the contrast range.

That's it.
Moreover, it is inconceivable to me that photographers like H.C.B, E. Adget, R. Doisnau, S.Leitner and countless others have been so intensively involved with their light meter. Experience, intuition, imagination and other factors come into play here.

 

[138S]

stating they'd work more or less the same (perhaps more "directional" as a diffused actual incident meter. If that was the case, then any camera that meters off the sensor would read the same exposure whether pointed toward the light source or toward the subject

I don't think... an average subject reflects a (say) 18% of the sourced illumination, so reading on subject has to be 2 or 3 stops lower than the reading on the light source. (It would be a similar reading if your subject is snow, a particular case).

Still, after checking it, today most Apps use the light sensor on the screen for incident metering.

From the camera is also possible, if we use a an ISO calibrated RAW digital image we have to account the for the transmission, which can be calculated directly from the aperture plus some correction. Mr Sammuel Bigler kindlly teached me how:



(Sorry for the math) But going to practice, we can get a precise incident metering of the incident power from a digital image shot in the light sourde direction, still with the limitation that we only consider the angle of view of the camera, and also with the limitation that strong bright points (like the sun) will saturate the sensor.

Anyway, if wanting to use the phone to know the incident light power then today we'll be using the light sensor (I was wrong in that), so we have to check if our light sensor is directional or not, and if we should adjust a correction.

Beyond technical considerations, what I have just learned is that with my particular phone model I can get perfectly accurate incident meterings, I've checked it well.

 

[Lachlan Young]

That's it.
Moreover, it is inconceivable to me that photographers like H.C.B, E. Adget, R. Doisnau, S.Leitner and countless others have been so intensively involved with their light meter. Experience, intuition, imagination and other factors come into play here.

Most of those cited only seem to have largely only referred to a meter if using colour. HCB was notorious for not caring for meters & for liking quite generously exposed negs (which irritated at least one of his printers - if it was Tri-X in certain developers, I can see why). And Atget wasn't really dealing with what we'd call a 'narrow latitude' system. The EV system is pretty accurate.

 

[Donald Qualls]

How would one get a phone based app calibrated? If it is off what would one do?

I tested mine (the same Light Meter -- Free mentioned above) against Sunny 16, and against my Sekonic (which has given me good exposures in the past). On my Pixel, it seems to do well. I shoot negative films almost exclusively, so a partial stop error isn't very significant.