Advice on using a lightmeter

[elphesadente]

I'm really enjoying this thread as I'm also learning lots. I'm looking forward to Garry's findings.

I really don't want to start another thread as I do have a related question if anyone would please help?

I understand (I think?!) about metering the correct exposure of a subject and then dialing in to the camera. But can someone please explain how I do the opposite, so set up 2 lights to light up the subject at a given camera reading...say 1/125, f.8, ISO 200? Both lights would be in front of the subject at around an angle of 45 degrees to the subject. Do you need anymore information? Thank you.

 

[HoppyUK]

We seem to be going round in circles on this one. I will hazard a guess and say that some people use a meter to determine exposure, and others use a meter to check the image matches the exposure they were aiming for. Others use the meter for checking a lighting ratio, and others to check is a background is evenly illuminated. For others it is a combination of most of the above

Whatever the reason a few things shine out of the comments
- there often is more than one way of doing things
- often the reading you end up with ends up being "interpreted" or adjusted anyway

Very good summary

The points you're raising are clouding the issue.

The question raised in the thread is which direction is the correct one to point one's lightmeter in when measuring flash.

Any other discussion is beyond the scope of that and just clouds the answer to that question.

Proof of which direction to point the lightmeter is above. When the lightmeter is pointed at the lightsource, the subject isn't blown out. When the lightmeter is pointed at the camera with neither the subject or the light being adjusted, the meter reading gives a blown out exposure. It really is that simple.

Not.

Light source was a large dish in same plane as subject. Aimed slightly forward to feather the light across the subject and not hit the background (ambient in the room gave some small illumination on that).

Metering was taken from the nose of the polystyrene head pointing towards the lightsource and then from the same position towards the camera.

Your point that the front of the subject would be in partial shadow is absolutely correct and illustrates EXACTLY why the lightsource is the direction the meter needs to be pointed. This point is why I gave the head a split-lit (close enough for a quick and dirty point-prover) pattern instead of something more frontal.

When the meter isn't pointed at the lightsource, it isn't picking up the light which is hitting the subject and thus reflecting off to the sensor.

Metering really IS that simple

No it isn't. If metering straight at the light source was so reliable, why was the invercone domed attachment invented? And that's completely leaving aside the whole concept of 'correct' exposure.

I hesitate to say again that the most accurate way of determining exposure is to look at the LCD/histogram/blinkies... though meters are great for setting ratios and checking stuff as RK said.

 

[Garry Edwards]

I'm really enjoying this thread as I'm also learning lots. I'm looking forward to Garry's findings.

I really don't want to start another thread as I do have a related question if anyone would please help?

I understand (I think?!) about metering the correct exposure of a subject and then dialing in to the camera. But can someone please explain how I do the opposite, so set up 2 lights to light up the subject at a given camera reading...say 1/125, f.8, ISO 200? Both lights would be in front of the subject at around an angle of 45 degrees to the subject. Do you need anymore information? Thank you.

My only question really is why would you want to set up lights like that? Have you been reading Practical Photography or something?
OK, your choice.

1. Assuming that you want each light to have equal effect (to make sure that the face looks really fat and that the lighting is completely flat) Meter to each light in turn with the other light switched off, and adjust one light if necessary to get the same meter reading.
2. Switch both lights on and now meter to the subject, which will give you the correct exposure.
3. Adjust the power of each light equally until to meter to camera reading matches what you want, in this case f/8

 

[GDHphotography]

Be nice to know where you metered from (also the position & size of the light source) for the first image. Based on where the shadows are falling it looks as though the light source was slightly to the rear of the subject. So if metered from front/centre it would have been in partial shadow so wouldn't be able to meter correctly.

Paul

Looks like a perfect split light by the position of light and shadow, I would put money on the light being at 90 degrees to axis .
Size of the light source shouldn't make a scrap of difference as to meter, you meter where the light is closest to the subject.

 

[arad85]

But can someone please explain how I do the opposite, so set up 2 lights to light up the subject at a given camera reading...say 1/125, f.8, ISO 200? Both lights would be in front of the subject at around an angle of 45 degrees to the subject. Do you need anymore information? Thank you.

Yes. If you want equal lighting set the meter to 1/125th (although this doesn't matter really) and ISO 200. Metering one flash at a time, meter it for half power - so adjust the setting so it is f/5.6 decimal 5 on it's own. Do the same with the other on it's own. Switch both heads on and you should be at f/8 reading.

At least I think I have my maths right....

 

[Mattys]

My only question really is why would you want to set up lights like that? Have you been reading Practical Photography or something?
OK, your choice.

1. Assuming that you want each light to have equal effect (to make sure that the face looks really fat and that the lighting is completely flat) Meter to each light in turn with the other light switched off, and adjust one light if necessary to get the same meter reading.
2. Switch both lights on and now meter to the subject, which will give you the correct exposure.
3. Adjust the power of each light equally until to meter to camera reading matches what you want, in this case f/8

Forgive me Mr Edwards if you think I'm having a go at your statements (I'm not having a go at you, just your incorrect statements), but I wonder why you're going on to your steps 2 and 3?

If you're going to have your steps 2 and 3, why bother with step 1?

I'm really, really, really struggling to understand this.

With both lights measured to be the same output onto the subject, the effect of that light will be additive, will it not? That means, you adjust that reading by one stop and that's your exposure. Quite simple use of the physical laws there.

 

[elphesadente]

My only question really is why would you want to set up lights like that? Have you been reading Practical Photography or something?
OK, your choice.

1. Assuming that you want each light to have equal effect (to make sure that the face looks really fat and that the lighting is completely flat) Meter to each light in turn with the other light switched off, and adjust one light if necessary to get the same meter reading.
2. Switch both lights on and now meter to the subject, which will give you the correct exposure.
3. Adjust the power of each light equally until to meter to camera reading matches what you want, in this case f/8

Thanks for your reply. I want consistent and equal lighting for each picture although a different subject each time. The subject will be in exactly the same spot each time. How would you suggest to light up with only 2 lights being used/available? Thanks

Yes. If you want equal lighting set the meter to 1/125th (although this doesn't matter really) and ISO 200. Metering one flash at a time, meter it for half power - so adjust the setting so it is f/5.6 decimal 5 on it's own. Do the same with the other on it's own. Switch both heads on and you should be at f/8 reading.

At least I think I have my maths right....

Thank you for your reply. So, f/5.6.5 on each individual light, right? Which 'should' equal f/8 when both turned on?

 

[Mattys]

Very good summary



Not.



No it isn't. If metering straight at the light source was so reliable, why was the invercone domed attachment invented? And that's completely leaving aside the whole concept of 'correct' exposure.

I hesitate to say again that the most accurate way of determining exposure is to look at the LCD/histogram/blinkies... though meters are great for setting ratios and checking stuff as RK said.

The most accurate way of determining correct exposure with film is not a LCD/histogram/blinkies - it's too flipping late by the time you can see the histogram if you're on film. Exposure has no real practical difference for digital as opposed to film (pushing or pulling exposures and similar techniques are beyond the discussion).

And using a meter truly is that simple. If you're split lighting, pointing the meter in any direction other than the lightsource is just not going to tell you anything useful to your exposure.

 

[arad85]

Thank you for your reply. So, f/5.6.5 on each individual light, right? Which 'should' equal f/8 when both turned on?

Yes, if my maths is right If it isn't you should be able to work it out by trial and error...

 

[elphesadente]

Yes, if my maths is right If it isn't you should be able to work it out by trial and error...

Cheers! Trial and error....pah! If you're wrong, I'll be knocking on your door very loudly

 

[Mattys]

Thank you for your reply. So, f/5.6.5 on each individual light, right? Which 'should' equal f/8 when both turned on?

Yes

 

[Garry Edwards]

Thanks for your reply. I want consistent and equal lighting for each picture although a different subject each time. The subject will be in exactly the same spot each time. How would you suggest to light up with only 2 lights being used/available? Thanks

That's fine if that's what you want.
But equal lighting from two sides will equal very flat lighting with no shadows, no interesting features and will look unnatural, because there's only one sun in the real world.

 

[HoppyUK]

The most accurate way of determining correct exposure with film is not a LCD/histogram/blinkies - it's too flipping late by the time you can see the histogram if you're on film. Exposure has no real practical difference for digital as opposed to film (pushing or pulling exposures and similar techniques are beyond the discussion).

And using a meter truly is that simple. If you're split lighting, pointing the meter in any direction other than the lightsource is just not going to tell you anything useful to your exposure.

If you want to bring film into it, then slide and neg film have very different exposure characteristics and incident readings are only optimum for slides. Slide film is critical, and the reality of that is the prudent photographer will make their best 'guess' at exposure, or call it 'informed estimate' if you like, and then either bracket it or do a clip test.

Digital is different to both film types, more tolerant than slides because you can post proces, but less so than neg. If you want to optimise data capture with digital, then you'll expose to the right (of the histogram) and shoot with a more generous exposure than an incident reading suggests, though how much more generous depends on the subject and how far you want to push it.

 

[HoppyUK]

Yes

What if it's flat copying?

 

[Mattys]

Again, this is clouding the original question. I accept that was my fault, but was a response to the histogram/lcd/blinkies comment. However, whilst on that subject, you know the response from the film stock you're using and you know your meter, so you mentally adjust the reading it gives you for the stock you're using in your kit. You still point the meter in the right direction.

The question of where to point the lightmeter has been answered and even the person who said to point towards camera has since, in another reply, said to point the meter towards the lightsource.

 

[Mattys]

so you mentally adjust the reading it gives you for the stock you're using in your kit. You still point the meter in the right direction.

That isn't saying guess your exposure, it's saying make an informed decision based on your knowledge of how your film-stock responds and on the reading you're given by your meter when it's been pointed in the right direction

 

[Mattys]

What if it's flat copying?

I don't have any experience of that. Therefore I don't have an answer to that question.

 

[Garry Edwards]

Again, this is clouding the original question. I accept that was my fault, but was a response to the histogram/lcd/blinkies comment. However, whilst on that subject, you know the response from the film stock you're using and you know your meter, so you mentally adjust the reading it gives you for the stock you're using in your kit. You still point the meter in the right direction.

The question of where to point the lightmeter has been answered and even the person who said to point towards camera has since, in another reply, said to point the meter towards the lightsource.

If you're referring to me, please refer accurately. I said point towards the light to get an accurate reading of the amount of light reaching the subject - which, depending of course on angle, can be very different from the amount of light reaching the camera after reflecting from the subject, which is why we point the meter at the camera in the first place...

 

[HoppyUK]

I don't have any experience of that. Therefore I don't have an answer to that question.

I mentioned flat copying as that's the only occasion that I can imagine you'd want two lights at 45 degrees, normally at least. And the answer would be, in theory, if each light read f/5.6 d.5 individually, f/8 d.5 as all areas of the subject would receive double the light equally from both sides. I say in theory, because it assumes no hot spots and that you've taken the inverse square law into account.

It's also relevant because the final exposure is always cumulative with multiple lights, but the calculation for that using a meter only to measure individual lights directly would be extremely difficult.

Take a typical situation - portrait in a normal room. You have a main subject key light, an on-axis fill or reflector, and a background light. Just to make it easy, let's say they all read f/8 when metered individually and directly towards the light. What would your final exposure be?

What exposure would you set for either side of the face? And it would take you a month of maths to work out how much light was coming off the background and bouncing around the room to the front. Ditto off the floor and walls, depending on the tone of those. Easier to take a final reading facing the camera.*

* Edit: or you could check the LCD

 

[Mattys]

If you're referring to me, please refer accurately. I said point towards the light to get an accurate reading of the amount of light reaching the subject - which, depending of course on angle, can be very different from the amount of light reaching the camera after reflecting from the subject, which is why we point the meter at the camera in the first place...

But why are you pointing your meter at the camera????????????


A LIGHT-meter measures LIGHT. A LIGHT-meter does not measure CAMERA.

It makes no sense whatsoever to measure the camera with a lightmeter. And even if you're trying to see how much is heading towards your camera, all you can do is hold the meter in front of the camera and measure the reflected light with it. Holding the meter at the subject and pointing towards the camera makes no sense to me. I'm sure you can enlighten my dark lack of understanding because I really cannot, right now, see why you point at the camera.

 

[Mattys]

I CAN explain why we point the meter at the light and I proved it with the images earlier in the thread.
I cannot see why you are telling people to point it at the camera, I proved that wrong with the images posted earlier in the thread.

It doesn't matter how many times you repeat the mantra of pointing at camera, unless you have PROOF, it just does not wash.

PROVE why you say you should point the meter at the camera instead of just repeating it.

 

[Garry Edwards]

I CAN explain why we point the meter at the light and I proved it with the images earlier in the thread.
I cannot see why you are telling people to point it at the camera, I proved that wrong with the images posted earlier in the thread.

It doesn't matter how many times you repeat the mantra of pointing at camera, unless you have PROOF, it just does not wash.

PROVE why you say you should point the meter at the camera instead of just repeating it.

Stop jumping up and down.
I've said that I'll take some images and prove it, and I will. Then, hopefully, you'll understand.

 

[bryan elliott]

Take a typical situation - portrait in a normal room. You have a main subject key light, an on-axis fill or reflector, and a background light. Just to make it easy, let's say they all read f/8 when metered individually and directly towards the light. What would your final exposure be?

What exposure would you set for either side of the face? And it would take you a month of maths to work out how much light was coming off the background and bouncing around the room to the front. Ditto off the floor and walls, depending on the tone of those. Easier to take a final reading facing the camera.*

* Edit: or you could check the LCD

Having a key, fill and background light all measuring the same output isn't a typical situation and why would you do that in the first place, because it's going to be horrible regardless

 

[Mattys]

Stop jumping up and down.
I've said that I'll take some images and prove it, and I will. Then, hopefully, you'll understand.

I'm not jumping up and down. I'm trying to undo misinformation which is why I have lots of emphasis on my words.

I've proven why the meter points to the lightsource and not the camera. Now you either have to prove it otherwise or accept that pointing a lightmeter at somewhere other than the light is just plain incorrect.

 

[Richard King]

But why are you pointing your meter at the camera????????????


A LIGHT-meter measures LIGHT. A LIGHT-meter does not measure CAMERA.

A meter measures the light that falls on it, and in this instance, it will be measuring the illumination falling on the subject from the camera's eye view/axis, in the place you decided to place the meter. The measurement as Garry describes it will be the incident metering version, as opposed to the cameras spot metered version (camera measures light reflected from the object, in this instance the hand held light eter measuring light falling on the object)

The difference being that regardless of the colour or texture of the object, the incident (light meter) reading will be the same, whereas from the camera meters point of view, if you metered says black object and a white object, the camera would come up with 2 different readings

So potentially, you end up with 2 different meter readings, and you then need to interpret the answer from your choice of meter reading and come up with the exposure you want to set your camera too

The reason why the incident reading is so useful, is that it ignores the subject matter, and gives you an exposure based on the light falling on the subject. If you have to take a series of shots of different objects all on the same background, the objects being different in texture, colour and shade, using the incident reading will give you consistent accurate colour and tone between all of the shots. All the photographer needs to do is decide how much to tweak the base reading by, and stick with it

 

[Mattys]

A meter measures the light that falls on it, and in this instance, it will be measuring the illumination falling on the subject from the camera's eye view/axis, in the place you decided to place the meter. The measurement as Garry describes it will be the incident metering version, as opposed to the cameras spot metered version (camera measures light reflected from the object, in this instance the hand held light eter measuring light falling on the object)

The difference being that regardless of the colour or texture of the object, the incident (light meter) reading will be the same, whereas from the camera meters point of view, if you metered says black object and a white object, the camera would come up with 2 different readings

Correct. Your incident meter measures what falls on it rather than what's reflected off it.

In the split lighting setup I posted to show why pointing at camera is incorrect, the reason for pointing at the lightsource only is very obvious. When I measured the flash while pointing the meter at the camera, I got a totally different reading. When I set this, the subject was blown out down the side close to the light. I don't know about you, but when I use split-lighting, I want a pleasing exposure and not blown out areas.

In that situation, pointing your meter at the camera is going to give you a wrong reading. It really is as simple as setting up your lights, getting your meter out and proving it to yourself instead of arguing it. I've proved the point that pointing at the camera is wrong. If you disagree, get your kit out and prove it otherwise.

I just cannot understand why this is being argued instead of proven. I've proven my statement. Instead of arguing that, prove it otherwise.

Proof is better than argument. Even politicians use proofs to back up their arguments and they're extremely GOOD at arguing things. Definitely better at it than I am.

I've proved me right, now it's your turn to prove me wrong.

 

[Mattys]

A meter measures the light that falls on it, and in this instance, it will be measuring the illumination falling on the subject from the camera's eye view/axis, in the place you decided to place the meter. The measurement as Garry describes it will be the incident metering version, as opposed to the cameras spot metered version (camera measures light reflected from the object, in this instance the hand held light eter measuring light falling on the object)

The difference being that regardless of the colour or texture of the object, the incident (light meter) reading will be the same, whereas from the camera meters point of view, if you metered says black object and a white object, the camera would come up with 2 different readings

So potentially, you end up with 2 different meter readings, and you then need to interpret the answer from your choice of meter reading and come up with the exposure you want to set your camera too

The reason why the incident reading is so useful, is that it ignores the subject matter, and gives you an exposure based on the light falling on the subject. If you have to take a series of shots of different objects all on the same background, the objects being different in texture, colour and shade, using the incident reading will give you consistent accurate colour and tone between all of the shots. All the photographer needs to do is decide how much to tweak the base reading by, and stick with it

You added before I finished my response.

Your final paragraph is correct. I have a problem understanding why you are making a tweak to your settings though. Unless you mean that you know your meter measures slightly different to your sensor and stick with that same minor tweak for every reading? If that's the case, I agree with that too

Still, none of that explains why you would point the meter at the camera. Your point about measuring the light falling on the subject is the same no matter the surface of the subject is the same in my argument about pointing the meter at the light and not the camera. It doesn't go to show any proof for metering your camera

 

[Garry Edwards]

Your point about measuring the light falling on the subject is the same no matter the surface of the subject is the same in my argument about pointing the meter at the light and not the camera. It doesn't go to show any proof for metering your camera

Sorry, but that isn't right. A complex shape will direct light back to the camera in a very different way to the way that a flat surface will direct back the light, and a flat surface at one angle will direct it back very differently to the same surface at a different angle.

And a highly reflective surface will direct far more back than a less reflective surface. Simple physics.

But thanks for saying that, I will now include PROOF of that

 

[Mattys]

I mentioned flat copying as that's the only occasion that I can imagine you'd want two lights at 45 degrees, normally at least. And the answer would be, in theory, if each light read f/5.6 d.5 individually, f/8 d.5 as all areas of the subject would receive double the light equally from both sides. I say in theory, because it assumes no hot spots and that you've taken the inverse square law into account.

It's also relevant because the final exposure is always cumulative with multiple lights, but the calculation for that using a meter only to measure individual lights directly would be extremely difficult.

Take a typical situation - portrait in a normal room. You have a main subject key light, an on-axis fill or reflector, and a background light. Just to make it easy, let's say they all read f/8 when metered individually and directly towards the light. What would your final exposure be?

What exposure would you set for either side of the face? And it would take you a month of maths to work out how much light was coming off the background and bouncing around the room to the front. Ditto off the floor and walls, depending on the tone of those. Easier to take a final reading facing the camera.*

* Edit: or you could check the LCD

Missed answering this one. Sorry.

In answer. I wouldn't. A 1:1 lighting ration is just flat. Whether the fill is on-axis, slightly off-axis towards key or on the opposite side (yuk), it looks horrible. And yes, I have setup and done this one. 36"dish for both key and fill and changing ratios all the way from 1:1 down to 1:7 (1:6stopsless and 1:7stopsless, I just couldn't see the difference in shadow density on my calibrated crt).

Taking a final reading towards the camera doesn't make sense here either. Allow me to explain that statement: Let's say that you have your subject directly against a wall. You'll have a lot of bounce coming off that wall back towards the camera (this is the most bounce you'll have from your walls unless your ceiling is closer to the subject as the subject is to the wall). If you wish to know what effect this has, you can measure FROM the camera towards the wall (or look at your LCD (chimping is brilliant)) and this WILL measure how much bounce is at your lens/sensor-plane. If you hold the meter in front of the subject and point it towards the camera, it just CANNOT measure how much bounce is coming off the wall behind. Even teh argument that the dome gives it a 180 degree measuring area doesn't help here because the wall is behind the back of the meter. You're pointing your meter away from what has become your light source (it's the source if you're measuring how much bounce you have). If you don't accept that, get your meter and hold it in front of you pointing away from the wall and ask yourself how it can measure how much bounce is coming off the wall.

^^^ No point in pointing the meter at the camera there

 

[Mattys]

Sorry, but that isn't right. A complex shape will direct light back to the camera in a very different way to the way that a flat surface will direct back the light, and a flat surface at one angle will direct it back very differently to the same surface at a different angle.

And a highly reflective surface will direct far more back than a less reflective surface. Simple physics.

But thanks for saying that, I will now include PROOF of that

And if you're pointing your meter towards the camera, it's pointing AWAY from those surfaces, so it doesn't matter what shape, texture or reflectivity it has. The back of the meter is towards the object/subject. The invacone isn't going to measure anything on the subject/object as it is hidden by the body of the meter itself.

Still not proven

 

[arad85]

And if you're pointing your meter towards the camera, it's pointing AWAY from those surfaces, so it doesn't matter what shape, texture or reflectivity it has. The back of the meter is towards the object/subject. The invacone isn't going to measure anything on the subject/object as it is hidden by the body of the meter itself.

I think if you read what has been said with a little less prejudice you'll see that people have said they only meter towards the camera when the light is generally in front of the object being photo'd. If the light is behind or at an extreme angle, then the light is metered. In your example, whether it is 90deg to the side or slightly behind, that's beyond the crossover point at where you'd meter the light vs metering incident light.

You can't meter incident light when your sensor can't see the incoming light behind, but for photography where the key light is largely in front of the subject, it works. It also takes into account the surroundings - something which metering the light doesn't as well..

Have a look at these posts from some well respected people, one of which you are arguing with :
http://www.talkphotography.co.uk/forums/showpost.php?p=4204965&postcount=7
http://www.talkphotography.co.uk/forums/showpost.php?p=4206011&postcount=19

 

[Mattys]

I think if you read what has been said with a little less prejudice you'll see that people have said they only meter towards the camera when the light is generally in front of the object being photo'd. If the light is behind or at an extreme angle, then the light is metered. In your example, whether it is 90deg to the side or slightly behind, that's beyond the crossover point at where you'd meter the light vs metering incident light.

You can't meter incident light when your sensor can't see the incoming light behind, but for photography where the key light is largely in front of the subject, it works. It also takes into account the surroundings - something which metering the light doesn't as well..

Have a look at these posts from some well respected people, one of which you are arguing with :
http://www.talkphotography.co.uk/forums/showpost.php?p=4204965&postcount=7
http://www.talkphotography.co.uk/forums/showpost.php?p=4206011&postcount=19

Forgive me if I don't accept the point that it's if the light is generally in front of the camera. I am being told that I'm wrong on pointing my meter to the lightsource. I proved that I'm right on that purely and simply by use of split lighting. The argument overall is being posited that you measure towards the camera not the light source as that is what gives the final reading.

I'm sorry to say that if you have respect for someone who is arguing that, I think it is time for you to find someone else to respect for their knowledge because that argument is just wrong.

Another argument for pointing the meter towards the camera has been that you get lots of bounce. I've explained why that is still incorrect and I gave a way for every reader to prove that to themselves.

Quite simply, any argument that pointing the meter to the camera is correct is just plain and simply wrong UNLESS the light source is on the camera. In that case, pointing the meter at the camera is as right as right can be

 

[HoppyUK]

Having a key, fill and background light all measuring the same output isn't a typical situation and why would you do that in the first place, because it's going to be horrible regardless

Missed answering this one. Sorry.

In answer. I wouldn't. A 1:1 lighting ration is just flat. Whether the fill is on-axis, slightly off-axis towards key or on the opposite side (yuk), it looks horrible. And yes, I have setup and done this one. 36"dish for both key and fill and changing ratios all the way from 1:1 down to 1:7 (1:6stopsless and 1:7stopsless, I just couldn't see the difference in shadow density on my calibrated crt).

Taking a final reading towards the camera doesn't make sense here either. Allow me to explain that statement: Let's say that you have your subject directly against a wall. You'll have a lot of bounce coming off that wall back towards the camera (this is the most bounce you'll have from your walls unless your ceiling is closer to the subject as the subject is to the wall). If you wish to know what effect this has, you can measure FROM the camera towards the wall (or look at your LCD (chimping is brilliant)) and this WILL measure how much bounce is at your lens/sensor-plane. If you hold the meter in front of the subject and point it towards the camera, it just CANNOT measure how much bounce is coming off the wall behind. Even teh argument that the dome gives it a 180 degree measuring area doesn't help here because the wall is behind the back of the meter. You're pointing your meter away from what has become your light source (it's the source if you're measuring how much bounce you have). If you don't accept that, get your meter and hold it in front of you pointing away from the wall and ask yourself how it can measure how much bounce is coming off the wall.

^^^ No point in pointing the meter at the camera there

Chaps, I only said they all read f/8 just to make things easier. Let's say f/8 for the key light, f/5.6 for the fill, and f/16 on the background because it's black and you want to put a grey spot in the middle? In a domestic room with white ceiling and light walls.

That is all the information you have, so what's your final exposure setting?

 

[Richard King]

You added before I finished my response.

Your final paragraph is correct. I have a problem understanding why you are making a tweak to your settings though. Unless you mean that you know your meter measures slightly different to your sensor and stick with that same minor tweak for every reading? If that's the case, I agree with that too

Still, none of that explains why you would point the meter at the camera. Your point about measuring the light falling on the subject is the same no matter the surface of the subject is the same in my argument about pointing the meter at the light and not the camera. It doesn't go to show any proof for metering your camera

Bluntly, because thats generally the most significant part of the subject, and and from a lighting point of view the most equalised point to measure it for a normal sort of shot

Say you do a head shot, to a ratio, do you meter on the left light the right light? Say you meter to the left and you get f8, and 4.5 from the right what will you meter too?

You need to do an adjustment, for the same reason we use 18% grey cards, it's to give you an assumed average. The incident reading gives you a REAL measurement, the assumed average grey card takes into account the range of tones we often find in shots

 

[Garry Edwards]

Chaps, I only said they all read f/8 just to make things easier. Let's say f/8 for the key light, f/5.6 for the fill, and f/16 on the background because it's black and you want to put a grey spot in the middle? In a domestic room with white ceiling and light walls.

That is all the information you have, so what's your final exposure setting?

That's easy, just point the meter at the light, that will work.

Oh, hang on a minute...
Which light shall I point it at?

 

[arad85]

Forgive me if I don't accept the point that it's if the light is generally in front of the camera. I am being told that I'm wrong on pointing my meter to the lightsource. I proved that I'm right on that purely and simply by use of split lighting. The argument overall is being posited that you measure towards the camera not the light source as that is what gives the final reading.

Yes, you're doing exactly what the people said they would do and proving them right. Repeat your experiment with the light generally to the front of the object. I don't think people are helping themselves though as what you did is exactly my understanding of what others would have done lighting like you did.

I'm sorry to say that if you have respect for someone who is arguing that, I think it is time for you to find someone else to respect for their knowledge because that argument is just wrong.

I respect people that can see both sides of the discussion.....

 

[Mattys]

And how close is the subject to the background? And how high is the ceiling? And how far from the point at which the subject is stood are the white walls? What modifier is on the key light? What is on the fill? What is on the b/g light? How much spill do you have from each of those modifiers? Where is the key positioned in relation to the subject? Where is the fill in relation? How close to the background is the b/g light? (this is very relevant for inverse square problems). The question cannot be answered without the answers. As an example, if every single one of those lights is through a grid (or fresnel), they're not going to spill much around the room. If they're all bare-bulb (or just unmodified speedlites), you'll get masses of spill. Question cannot be answered without the answers to this lot.

However, as you set a question without filling in the required parameters, I'll give you an answer that fits without parameters. It doesn't make sense to do anything other than to set your key to what you want to shoot (by measuring the light from it) and shoot that setting.

However, even with those parameters, I still don't see how pointing your meter at the camera will overcome the spill issue.

Note on the inverse square problem mentioned above:
As example:
Subject to background distance is 4 meters.
Key light to subject distance is 4 meters and the light is directly in front (you're butterfly lighting).
Background is therefore double the distance the subject is, so that gives us (from inverse square law) 1/4 the power. Or, in practical terms, 2 stops lower. Normally, if we have something white only 2 stops lower lit than the subject, we can see it easily.
How about now having your light at 2 meters from your subject. Light to background distance in is now 3 times the light to subject giving us 1/9 the power.
Move your light to only 1 meter from the subject and you now have a light to background of 4 times the distance which is 1/16 the power hitting the background relative to what hits the subject. Now increase your subject to background distance to 6 meters and keep your light 1 meter from the subject. What do you get? A light to background distance of 6 times the light to subject and squaring that up gives you 1/36 the power hits the background compared to the power which hits your subject. The further you can move your subject away from the background, the darker you can make it.

When you put a b/g light into that mix, the only thing which changes it is the fact that you're now illuminating the b/g with that light.

 

[Richard King]

ISL is irrelevant

your camera records the photons that land on the sensor, once they leave the subject and start travelling, they dont suddenly diminish in power

A incident reading measures the light falling on the subject, at the subject, how many photons are reflected or absorbed depends on the subject

 

[Mattys]

That's easy, just point the meter at the light, that will work.

Oh, hang on a minute...
Which light shall I point it at?

Answer me this please.

I fail to understand why you're laughing at this quite serious question.

Which is the light giving you the majority of what's hitting your sensor? The key? The fill? You decide.

Once you've decided that, you can explain WHY pointing your meter at the camera will give you an exposure reading which is accurate for the lights? The light isn't coming from the camera unless that's where you've put the lights. It just doesn't make any kind of sense. Just stating that you should pont it at the camera doesn't prove it; stating it repeatedly just reinforces the perception that you can't debate or prove your point.

Prove the point or stop stating it.

In answer to the question you pose here: Point it at the main light

 

[Mattys]

ISL is irrelevant

your camera records the photons that land on the sensor, once they leave the subject and start travelling, they dont suddenly diminish in power

A incident reading measures the light falling on the subject, at the subject, how many photons are reflected or absorbed depends on the subject

And that tells me that I need to point my meter away from the subject and towards teh camera why? Previously noted is the fact that the body of the meter is between the sensor in it and the light at the subject. Not relevant