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Mark_Levesque
02-05-2008, 01:40 PM
Ch 12 Lighting

Q1) A meter reading of the shadow side of the face is 2 stops less than a meter reading on the highlight side. The light ratio is thus:

A) 2:1
B) 3:1
C) 4:1
D) 8:1

Q2) To emphasize texture, you would:

A) front light the subject
B) use diffuse light at an angle to the subject
C) use a large lightsource
D) use a small lightsource at an angle to the subject

Q3) In short lighting, the main light is placed:

A) to strike the side of the face away from the camera
B) directly in front of the face
C) on the shadow side of the face
D) to strike the side of the face closest to the camera

David_A._Lottes
02-05-2008, 02:05 PM
1. C
2. B
3. A
I think.....?
Thanks Mark!

Andrea_Chapelo
02-05-2008, 02:41 PM
Well this is my weak point so I really need to go read the book, but I am guessing CBA.

Stephanie_Millner
02-05-2008, 02:42 PM
C, B, A? Thus proving my inability to properly light in the studio...

Michael_Gan
02-05-2008, 03:18 PM
Here's a hint on the lighting ratio. Remember that 2 stops is not twice as much light.

Also, remember that light from the fill source is added to the main light.

Michael_Gan
02-05-2008, 03:21 PM
Another hint. Think in terms of what the word "difuse" means.

Cassandra_Sullivan
02-05-2008, 03:23 PM
1) C
2) D
3) A

KirkDarling
02-05-2008, 04:32 PM
Here's a hint on the lighting ratio. Remember that 2 stops is not twice as much light. Also, remember that light from the fill source is added to the main light.

With regard to answers thus far: This hint has not yet been taken into account.

Mark_Levesque
02-05-2008, 04:36 PM
Yes. The question was asked in a very specific manner to differentiate between a light ratio and a lighting ratio. It is the latter to which Michael's hint applies. Personally speaking, I think there oughtta only be one nomenclature, but so long as they ask the question both ways on the test, you need to be prepared for both and know the difference!

David_A._Lottes
02-05-2008, 05:15 PM
So with Michaels lighting vs light ratio tip what would be the lighting ratio if a subject had an f2.8 shadow side and an f8.5 highlight side?

Or from the perspective of the lights, what would be the lighting ratio if the key light were set to output f8 and the fill light were set to output f2.8. Both lights are at an equal distance from the subject but the key light is at a 45 degree angle to the subject.

I'll need Michael or someone else to answer this cause I don't know. I'm guessing 5:1. :)

Or is the lighting ratio 4:1 producing a 5:1 light ratio?

Cassandra_Sullivan
02-05-2008, 05:25 PM
Yes. The question was asked in a very specific manner to differentiate between a light ratio and a lighting ratio.

Can you explain the difference between the 2? I think I know but would like to hear you explain it, if you don't mind.
And if Michael's hint applies to 'lighting ratio', but your question asks the 'light ratio' - how does Michael's hint apply to the question? :confused:

Mark_Katz
02-05-2008, 05:37 PM
With regard to answers thus far: This hint has not yet been taken into account.

Well 2 stops is actually 4 times the amount of light, so is the ratio of 4:1 not correct? It seems that is what you are implying. But since everyone seems to answer C (4:1), why is it wrong?

Eric_Merrill
02-05-2008, 09:34 PM
Can you explain the difference between the 2?

I'll take a stab. It's been a while since I've studied light ratios, so I may be off.

By asking the question in terms of the meter readings, it's a straight forward question.

One side of the face is getting 4 times the light as the other.

Now, if the main light by itself produced a 2.8 reading and the fill light by itself produced a 5.6 reading, then you'd be looking at a 5:1 ratio because the side lit by the main light is also receiving light from the fill.


Eric

TerryMiller
02-05-2008, 10:14 PM
C
D
A
glad this was easy... I think:D

KirkDarling
02-05-2008, 10:31 PM
I've taken a closer look at this ugly puppy.

Looking more closely, there is an ambiguity in this question, in that it's not satisfyingly clear whether we're talking about making independent measurements of a main light and a fill light (or with the flat receptor) or simply pointing the meter one way and then another with all lights on in both cases with the hemispheric receptor, nor is it even clear if we're talking about an incident reading or a reflected reading.

Case 1: Metering each light independently with an incident meter.

We measure the fill light and get f/4. We measure the main light and get f/8--two stops diffference.

From f/8 to f/5.6 is twice as much light. From f/5.6 to f/4 is twice as much more than f/5.6.

Let's say 200 watt-seconds of light are striking the subject. Up one stop makes it 400 watt-seconds of light striking the subject. Up another stop makes it 800 watt-seconds of light striking the subject.

The two-stop jump from 200 to 800 watt-seconds is not two times more than 200, it's four times more. Or to put it conversely, in order to get a two-stop difference, we have to have a main light of 800 watt-seconds and a fill light of 200 watt-seconds.

Then, remember that what the camera sees as the "highlight" area is actually illuminated by the main light (which covers only part of our view of the subject at 800 watt seconds) plus the fill light (which covers our entire view of the subject at 200 watt seconds).

So now we have a ratio of 1000 watt-seconds in the highlights to 200 watt seconds in the shadows, which would be 5:1.

But that's not a choice, so let's back the truck up and run over that dog again.

Case 2: Metering each direction of the subject with a reflected-light meter

Let's say measuring the subject on the side of brighter light, we get f/8. Measuring the subject on the side of lesser light, we get f/4--two stops difference.

From f/8 to f/5.6 is twice as much light. From f/5.6 to f/4 is twice as much more than f/5.6, so there's our two-stop difference, which is 4:1.

But in this case, the reflected light measurement of the shadow side already takes the highlights into account because it's seeing what the camera sees (light from both directions), not just the light incident to the subject from one direction.

So I look at the stem again: "A meter reading of the shadow side of the face..."

Dang it, this is not a good question. It calls for reading too much into it. A good question should be straightforward and reasonable only one way. Moreover, taking multiple reflected light measurements is something only Zonies like me are likely to do on a portrait--it calls for taking a non-standard practice into account.

Michael_Gan
02-05-2008, 10:47 PM
Q1) A meter reading of the shadow side of the face is 2 stops less than a meter reading on the highlight side. The light ratio is thus:

A) 2:1
B) 3:1
C) 4:1
D) 8:1

Before Kirk has a major conniption fit :D

Note that the question does not say that there is a fill light source...

BUT, if there was a fill light source, remember that the fill light source adds to the shadow/fill side, so you are adding that "X" amount of light in addition to the main source, so the main light is not 2 stops more than the shadow side it's less because the mainlight side is the combination of both the fill and the main.

Yes, this question IS ambiguous and unfortunately, it's on the exams.

GeorgeannChambers
02-06-2008, 12:48 AM
Before Kirk has a major conniption fit :D

Note that the question does not say that there is a fill light source...

BUT, if there was a fill light source, remember that the fill light source adds to the shadow/fill side, so you are adding that "X" amount of light in addition to the main source, so the main light is not 2 stops more than the shadow side it's less because the mainlight side is the combination of both the fill and the main.

Yes, this question IS ambiguous and unfortunately, it's on the exams.
The question I saw on the exam this weekend (long story) - was as Michael references, but they actually asked the ratio from the shadow side. Make sure you read the question closely.

Georgeann

Heather_L._Smith
02-07-2008, 02:28 PM
Ugh... I think I thought too much about #2...

C) 4:1
D) use a small lightsource at an angle to the subject
A) to strike the side of the face away from the camera

Heather_L._Smith
02-07-2008, 02:35 PM
The question I saw on the exam this weekend (long story) - was as Michael references, but they actually asked the ratio from the shadow side. Make sure you read the question closely.

Georgeann

I read this to mean that the answers could look something like:
1:4
4:1
1:2
2:1

Or some variation of that?

Larry_Weathers
02-09-2008, 04:23 AM
1. C - 4:1
2. D - small lightsource at an angle
3. A - strike side of face away from camera

Mark_Levesque
02-09-2008, 11:51 AM
Q1) A meter reading of the shadow side of the face is 2 stops less than a meter reading on the highlight side. The light ratio is thus:

C) 4:1

Q2) To emphasize texture, you would:

D) use a small lightsource at an angle to the subject

Q3) In short lighting, the main light is placed:

A) to strike the side of the face away from the camera

KirkDarling
02-09-2008, 02:09 PM
Q1) A meter reading of the shadow side of the face is 2 stops less than a meter reading on the highlight side. The light ratio is thus:

C) 4:1

That's what I was trying to say with my "Case 2" above--they're measuring the subject (reflected reading) rather than the light (incident reading). But if I were writing the question, I'd have made that much clearer in the stem.

I think the idea of the writers was, "If they figure it for incident measurement, none of the responses will be correct." But that's the kind of question our test psychologist would have beat us about the head and shoulders over.

Elizabeth_Pokela
02-13-2008, 12:13 AM
C
D
A

I am way behind in my reading . . .

Elizabeth

GeorgeannChambers
02-14-2008, 03:20 AM
I read this to mean that the answers could look something like:
1:4
4:1
1:2
2:1

Or some variation of that?
Yes, that is format of the answers in the test.

Brian_Coleman
02-26-2008, 12:12 AM
4:1 is my guess

Gene_Paltrineri
02-27-2008, 05:05 AM
Let me make a stab at this.

When we are talking about "Light Ratio" we are talking about the intensity of the TOTAL light on, or reaching (reflecting off), one side compared to the other.(Assuming both sides are the same shade - if a gray card were in its place. If not then we would be talking about "contrast" ratio and would need to get into the Zone System for that discussion)
Highlight vs shadow.
If one side is two stops brighter (whether measured with a reflective or incident meter, dome or flat) then it is four times as bright as the other side, because each stop represents doubling the light.
We always talk in terms of light to dark so it would be 4:1.

Lighting Ratio, on the other hand, is measuring the amount of light coming from each light source(independently). It is best to use a flat, rather than a dome to prevent stray light from effecting the measurement. (Or block the main with your hand)Even better would be to turn off the other lights if you are using independent light sources.

We use a Lighting Ratio to achieve a Light Ratio.
Think of it as painting layers of light on the subject.
The fill light will paint one layer of light over the entire subject.
The main light will paint another layer(s) over the parts of the subject it reaches. The intensity determines how many additional layers.
If they are of equal power, the highlight side will receive two layers of light, one from the main and one from the fill, and the shadow side will receive one layer of light resulting in a 2:1 light ratio.

If the main light is one stop brighter than the fill, then you would have a 3:1 light ratio because the main light would be adding two units (layers) to the highlight side and the fill light would be be adding one more to make it three on the highlight side and still only one on the shadow side.

If the main light were two stops brighter, then the light ratio would be 5:1.
Four units from the main plus one from the fill on the highlight side and still only one unit on the shadow side.

So to get a 4:1 light ratio you would have to have the main light be 1.5 stops brighter than the fill.

Now aren't you glad they didn't ask the question this way?:(
"How many f-stops brighter would the main light have to be in order to achieve a light ratio of 4:1?


Gene Paltrineri, M.Photog, Cr. CPP

Mark_Levesque
02-27-2008, 10:37 AM
Read this and reread this until you understand it! Thanks, Gene.

Heather_L._Smith
02-27-2008, 12:07 PM
Wow... I think I totally get it now. Thank you, Gene! Great explanation!

Gene_Paltrineri
02-28-2008, 04:35 AM
Thanks
Come to NH in April
Don Chick and I are hosting a SuperMonday on Lighting and Posing.
Gene Paltrineri, M.Photog, Cr, CPP

Mark_Levesque
02-28-2008, 11:23 AM
She is coming to NH in April, and she will be studying with the Don*, but not on the Super Monday. ;)

* of the lighting mafia :D

Heather_L._Smith
02-28-2008, 12:15 PM
Hahaha! That acutally made me laugh out loud, Mark!

The Don.

Hahaha! I love it!

Ella_Carlson
03-15-2008, 01:09 PM
Hi Mark and Gene (and Don Chick)

They SURE do need to change the wording since lighting ration and light ratio seems unclear for so many, including me. According to Mark's answers on this chapter, the light ratio is the amount of light coming from each light source, not the amount of light striking the subject since his answer is 4:1, and 2 stop difference would mean there is 4 times as much light coming from the main light than the fill light. But Gene's explanations basically says, if I'm reading it correctly, that the LIGHT ratio is 5:1 since it is a measurement of the combination of light from the two light sources as it strikes the subject. Gene is saying that the LIGHTING ratio is the pure measurement of light coming from each distinct light source which would be the 4:1 ratio.

So... could you enlighten me? It's the same question I asked at the lighting workshop last weekend with Gene and Don where they also seemed to disagree on which was which, and we really didn't get that straightened out. Help.

KirkDarling
03-15-2008, 03:25 PM
Ella,

This is simply a poorly worded question, and as you can see, it's caused confused explanations even from people who surely know what they're talking about because they're trying to make sense of poor wording.

What you've said is correct--you understand what's happening. Let's hope the ratio questions on the test you take are better worded!

Stan_Lawrence
03-15-2008, 04:07 PM
"the light ratio is the amount of light coming from each light source, not the amount of light striking the subject"

Ella, from a practical standpoint, the amount of light coming from the light source really isn't important, it's the amount of light hitting the subject that creates the portrait.....I'm not sure how the question is worded, the reality is the fill is added to the main, so the one stop ratio is 3-1, two stop 5-1. I think folks tend to make this more complicated than it needs to be......:cool:

Gene_Paltrineri
03-15-2008, 10:24 PM
I will fall on my sword on this one.
The terms are confusing at best.
I Googled the terms "Light Ratio" and "Lighting Ratio" and found the terms used both ways, even some interchanged them within the same sentence to describe the same thing.
I think that one could semantically justify the use of either word, either way.
Is the "Light" the actual photons coming from the source or the source itself?
Is the "Lighting" a description of the set up of light sources or the result of what they produce?
My head is starting to hurt.
I deleted my message to reduce further confusion.
Sorry for any confusion I may have caused.

Michael_Gan
03-15-2008, 11:42 PM
I've restored Gene's post because it does make sense what he wrote, and because their were replies to that post. However, Gene, you could edit the message however way you like :)

Michael
Forum Moderator

Heather_L._Smith
03-15-2008, 11:56 PM
I just had a question about this the other day - and while I had the theory correct, I had the "term name" backwards. Now, I have not taken the CPP exam, but will be in April, so I feel confident that as long as I know the theory, I can figure out the correct answer.

So, in Mark's question (A meter reading of the shadow side of the face is 2 stops less than a meter reading on the highlight side. The light ratio is thus: 2:1 - 3:1 - 4:1 - 8:1) we can safely answer 4:1. However, if one of the options was 5:1, we could be in trouble :)

Heather_L._Smith
03-15-2008, 11:58 PM
Oh, and Gene, I meant to mention that I think your explanation was very helpful - the visual of "painting on layers" was remarkably easy for me to remember.

Michael_Gan
03-15-2008, 11:59 PM
<other hat on> In the context of certification, a big suggestion is to not read too heavily into the questions. The questions are designed to reflect what pertains to practicing professional photography. That is, how you would use this application on a day to day basis. Light Ratios as being a very important arsenal in your professionalism. A good understanding of light ratios may separate you from the many amatuer shooters out there.

When you start getting into the point of the science of light beam particles, then you're missing the applicable points of this exercise. I know how it goes, which is mainly why I always had are hard time taking multiple guess question exams when I was a kid. As my professor once said, "answer the question that is before you, leave the out of the box thinking for your art".

The context of this question is the amount of light that is reaching (or "hitting")your subject. Do not get too involved with the source itself because there are too many variable in light sources, such as the speed of which the light is emitted from the flash tubes, watt seconds, bare bulb vs. reflectors, etc. You could literally go nuts over that stuff. The questions were not designed to take all those things into account (or, at least the authors are trying their best, anyway).

Michael_Gan
03-16-2008, 12:12 AM
Think of a 3:1 light ratio as two lights at 5.6 on one side and one light at 5.6 straight on the subject. You thus have f11 on one side and 5.6 on the other. 2 stops not 1. (5.6 + 5.6 + 5.6=11)

Ella_Carlson
03-16-2008, 01:08 AM
Thanks everyone. As my old Spanish teacher used to say, "Que lio" which translates roughly as a 20 car pile-up in the fog.

Heather's right. If there is only one answer that could be correct based on logic and light, no problem. The issue will be if the test has a correct possible question for both light ratio and lighting ratio ---whichever is which. Since people seem to pass the exam in spite of this wording insanity, I guess I'll just trust logic to see me through.

I got the concept down. It's just the wording that PPA uses that's causing the issue. Anyone responsible for designing the PPA certification test listening???

Michael_Gan
03-16-2008, 01:10 AM
Now we get to the Lighting ratio. This is expressed, in this question as lighting that is independent of each other. In this instance, what the tester want you to understand is the relationship of the amounts of light in comparison to the other. I agree that it seems ambiguous, but you need to understand that the amounts of light are like the basic knowledge of the difference of amount of light that are expressed in f/stops. Yup, even harder to explain.

Take, for example 5.6 as one unit of light. To get to f/8, you need two units of light. To get from 5.6 to 11, you need 4 units of light. In this instance, your 4:1 is expressed in 4x1=4

Unlike a 3:1 light ratio that is expressed in amounts of light in relation to each other.

KirkDarling
03-16-2008, 01:13 AM
So, in Mark's question (A meter reading of the shadow side of the face is 2 stops less than a meter reading on the highlight side. The light ratio is thus: 2:1 - 3:1 - 4:1 - 8:1) we can safely answer 4:1. However, if one of the options was 5:1, we could be in trouble

Heather,

I don't have that book, so I can't speak to how they wrote their questions (there have been a couple quoted here that I haven't liked). I did take the test, and I found those questions to be well-written and unconfusing.

Keep what Michael said in mind:

1. Don't try to read too much into them.
2. The questions are designed to reflect what pertains to practicing professional photography.

Lighting ratios express the light striking the subject. The only tricky point is to remember the overlap of the fill and the mainlight in the areas struck by the mainlight that the camera sees.

So when you measure the light in a way that measures the overlap (incident with dome receptor pointed first at the main light and then at the fill light {camera}), the ratio the measurement gives you is the true ratio.

But when you're measuring the lights in a way that does not measure the overlap (incident with flat receptor pointed first at the main light and then at the fill light {camera}), you have to calculate effect of the overlap yourself to get the ratio.

In the same way, if you're talking about setting the lights themselves, again that doesn't take the overlap into account, so you have to figure that yourself to get the ratio.

I think you understand the concept. Just be sure to understand the situation the question presents: Is it taking the overlap into account or not? That's where you'll have to understand such things as measuring with the dome versus the flat receptor.

The question on the test will be clearer on which of those situations you're dealing with, whereas this question was pretty murky.