confusion regarding f-stop and studio lighting VS f-stop and camera


Status
Not open for further replies.

cryder

New Member
Dec 7, 2006
330
1
0
#1
2nd & 3rd paragraph <--- link
Our main or “key” light is fitted with the same silver umbrella and placed at the side position as before. In addition to this we have used our second head, fitted with a translucent, or “shoot through” umbrella. This fill light is placed close to the camera position slightly higher than the subject. It is set to give one f-stop less light than the main light onto the model.

This can be easily set up using a flashmeter and by taking readings from each head individually. e.g. if the main light is giving a reading of f/11, the fill should give a reading of f/8. Don’t forget to take another exposure reading with both lights and set that as your aperture.



2nd paragraph <--- link
In the diagram below you can see that we have placed a flash head quite close to the camera position and we have fitted a shoot-through umbrella. The power of this head has been reduced so it gives a meter reading at the subjects face of one f-stop less than the main light on the right. This ensures that we do not have flat lighting on her face and will give a very pleasing result. In this example the reading from the main light was f/11 (this was set on the camera) and the fill light was f/8.


isnt f/8 got more light than f/11? i understand that "f/8 let in more light than f/11 in camera term" but why is f/8 less light than f/11?:think: oya, i'm assuming everything is constant(iso, shutter speed, distance of flash etc) except for the f-stop in the above 2 links.
is the f-stop terminlogy different for camera and studio lighting?
 

Mar 22, 2008
300
0
0
www.alteredvision.net
#2
Not that I'm familiar with meter readings so making some assumptions that may be wrong here. Going by logic, if you set at f11 instead of f8, the part that reads as f11 will be okay, but the part that reads as f8 will be darker because you need to set at f8 (which lets in more light) to get the same brightness as f11.
 

flipfreak

Senior Member
Nov 26, 2007
7,030
0
36
Singapore
www.rogerchua.com
#3
in metering with a lightmeter, the reading is the other way round. high key lighting will be using like f/16 and low key would be your f/4.
 

camoptics

New Member
Mar 16, 2008
23
0
1
#4
I read through and tried to find what your problem is.
It seems to me the light intensity is half the value, so you need fast shutter speed. Nothing is wrong. You may need take more time understand the two sentences you highlighted.
 

jOhO

Senior Member
Apr 20, 2003
6,485
0
0
41
Singapore
www.expressivelyjoho.com
#5
if a READING is f11, it means the light is brighter than a READING at f8 because the brighter light will need a bigger f-stop (smaller aperture) to get the same exposure - which for light meters, is to expose for 18% gray.
 

blazer_workz

Senior Member
May 8, 2006
3,118
0
0
ClubSNAP Community
#6
Meter reading returns the aperture value you need to dial into your camera for a correct exposure.

the higher the f number returns, the higher the power of ur strobe..

U r oso right that.."f/8 got more light than f/11"..but this term is with respect to aperture size..f8 allows more light into the camera sensor than f11..

But do note again..meter readings return the aperture to set for correct exposure..

With the setup u mention..if u choose to shoot at f8..u will get correct exposure from the fill and overexposure (by 1stop) from the main light..
 

catchlights

Moderator
Staff member
Sep 27, 2004
21,903
46
48
Punggol, Singapore
www.foto-u.com
#7
2nd & 3rd paragraph <--- link
Our main or “key” light is fitted with the same silver umbrella and placed at the side position as before. In addition to this we have used our second head, fitted with a translucent, or “shoot through” umbrella. This fill light is placed close to the camera position slightly higher than the subject. It is set to give one f-stop less light than the main light onto the model.

This can be easily set up using a flashmeter and by taking readings from each head individually. e.g. if the main light is giving a reading of f/11, the fill should give a reading of f/8. Don’t forget to take another exposure reading with both lights and set that as your aperture.



2nd paragraph <--- link
In the diagram below you can see that we have placed a flash head quite close to the camera position and we have fitted a shoot-through umbrella. The power of this head has been reduced so it gives a meter reading at the subjects face of one f-stop less than the main light on the right. This ensures that we do not have flat lighting on her face and will give a very pleasing result. In this example the reading from the main light was f/11 (this was set on the camera) and the fill light was f/8.


isnt f/8 got more light than f/11? i understand that "f/8 let in more light than f/11 in camera term" but why is f/8 less light than f/11?:think: oya, i'm assuming everything is constant(iso, shutter speed, distance of flash etc) except for the f-stop in the above 2 links.
is the f-stop terminlogy different for camera and studio lighting?
No, you get mixed up.

think this way, when a subject received a certain amount of light to get a exposure of f8, you need to give it double amount of light to make the exposure become f11.

and when the subject received a certain amount of light to get a exposure of f8, if you half the amount of light on the subject, the exposure become f5.6.

hope this help.
 

cryder

New Member
Dec 7, 2006
330
1
0
#8
Not that I'm familiar with meter readings so making some assumptions that may be wrong here. Going by logic, if you set at f11 instead of f8, the part that reads as f11 will be okay, but the part that reads as f8 will be darker because you need to set at f8 (which lets in more light) to get the same brightness as f11.
hmm:think: still didnt answer why is f8 is 1 stop less light than f11?

from what i know, lightmeter measured the flash or surrounding light level. thou i'm not sure that value is it for us to input into the camera or is the value of the subject/surrounding basing on the our input on the lightmeter. oh man, what am i writing. hopefully someone can understand what i write.
 

Dream Merchant

Moderator
Staff member
Jan 11, 2007
9,660
6
38
#9
What you read (all the blue and red) referred to the light OUTPUT from the LIGHTS.

What you asked about (isnt f/8 got more light than f/11? i understand that "f/8 let in more light than f/11 in camera term" but why is f/8 less light than f/11?) refers to the LENS APERTURE.

They're totally opposite, but both correct. That's why you're confused.

When talk about output from the LIGHTS, a smaller number (f/8) is less powerful than a larger number (f/11).

When talk about LENS aperture, direct opposite. Smaller number (f/8) means MORE light goes through the lens, aka, 'brighter' (to the sensor POV) but larger number (f/11) means lesser light goes through the lens, aka, 'darker' (to the sensor POV).

Kinda like (but not exactly) it's like someone facing you in the street asking for directions, and you say (looking from your perspective) turn right ... then he (looking from his perspective) says, OK, I turn right, and puts out his right hand, and to you, looking at him lifting his right hand, say, no, not left, turn RIGHT but to him is correct because he looking from his right whereas you looking from your right so both are right but one's right is another's left.

See, easy.
 

blazer_workz

Senior Member
May 8, 2006
3,118
0
0
ClubSNAP Community
#10
Do you noe of this rule?

f-number = GN / Distance

Distance fixed at 1m:
Higher GN..higher the strobe power > more light > must use smaller aperture > bigger f number
Lower GN..lower the strobe power > lesser light > must use bigger aperture > smaller f number

the f-number here is the f-number return by ur lightmeter..
lightmeter works exactly like this formula less the mathematics..
 

Prismatic

Senior Member
Feb 25, 2003
1,323
0
36
38
In the void.
Visit site
#11
Maybe this will be easier to understand.

-The main lights are set to give a f/11 reading on your meter.
If you want the parts illuminated by the main lights to be correctly exposed, then you have to set your aperture to f/11.

-The fill lights are set to give a f/8.0 reading on your meter.
This means that you have to set your camera to f/8 if you want the parts illuminated by the fill lights to be correctly exposed. f/8 is a bigger aperture than f/11, which means the parts illuminated by the fill lights is actually dimmer and thus the output from the fill lights are lower. (Assuming the distances are the same).

In a studio environment, the existing ambient lights usually has little effect on the photo because the lighting level from the strobes will be a lot higher than the ambient level.
 

cryder

New Member
Dec 7, 2006
330
1
0
#12
Do you noe of this rule?

f-number = GN / Distance

Distance fixed at 1m:
Higher GN..higher the strobe power > more light > must use smaller aperture > bigger f number
Lower GN..lower the strobe power > lesser light > must use bigger aperture > smaller f number

the f-number here is the f-number return by ur lightmeter..
lightmeter works exactly like this formula less the mathematics..
ya, saw this in my sb-800 manual. totally ignore these:sweatsm:. regrettably, i havent try using other mode other than TTL on the flash.
 

yanyewkay

Senior Member
Sep 22, 2004
3,924
0
0
Cons digger.
#13
hmm:think: still didnt answer why is f8 is 1 stop less light than f11?

from what i know, lightmeter measured the flash or surrounding light level. thou i'm not sure that value is it for us to input into the camera or is the value of the subject/surrounding basing on the our input on the lightmeter. oh man, what am i writing. hopefully someone can understand what i write.
f/8 and f/11 is 1 stop apart. As explained by catchlights,
catchlights said:
think this way, when a subject received a certain amount of light to get a exposure of f8, you need to give it double amount of light to make the exposure become f11.

and when the subject received a certain amount of light to get a exposure of f8, if you half the amount of light on the subject, the exposure become f5.6.
to get the same exposure (with fixed shutter speed) when varying the strobe light output you have to change the aperture. More light from strobe, smaller aperture, less light from strobe, bigger aperture. So if the strobe is stronger (brighter) you have to use smaller aperture (f11) if the strobe is dimmer you have to use bigger aperture => f8. THere you have it. brighter => f/11 darker f/8. It is correct.
 

cryder

New Member
Dec 7, 2006
330
1
0
#14
i BIG head liao.
maybe i should go with just the practical and ignore those theory(wordings):sticktong, more easily understand and goes with my heart. hehe...

oya, i will still go thru all of ur posts and try to 'visualize' and understand it.
 

alexj

New Member
Apr 10, 2004
77
0
0
Singapore
#15
The confusion you face is the lack of complete understanding.
For a start, foot-candles quantifies the amount of light where kg quantifies weight. The higher the number the greater the amount of light, same goes for weight. Find out more about foot-candle on wiki (http://en.wikipedia.org/wiki/Foot-candle).

(The following numbers are not accurate, but more for illustrative purpose)
Say in the shot you compose, the amount of light falling is 1000ft-candles, which say is f8. So to have a "decent" exposure, you set f8 on your camera.
Same thing, if its 2000ft-candles you set f11.
The more the light in the scene, the more light you have to reduce from hitting the film/sensor of your camera. Makes sense right? Think shooting at night and during the day.
To further explain:
The difference in one-stop is the double of the amount light. f8 to f11 is one stop (1000ft-candles to 2000ft-candles is double the amount of light)
*again please note that these are figurative numbers, but their relationships are what's important, i.e. the doubling of light.

The concept of aperture for lenses (f-stop) is to control the amount of light passing through the lense. Different from the concept of measuring the amount of light (foot-candles). When you say the amount of light you have produced is f8, you are translating your foot-candles amount to give you an f-stop based on a given shutter and iso.
 

cryder

New Member
Dec 7, 2006
330
1
0
#16
f/8 and f/11 is 1 stop apart. As explained by catchlights,

to get the same exposure (with fixed shutter speed) when varying the strobe light output you have to change the aperture. More light from strobe, smaller aperture, less light from strobe, bigger aperture. So if the strobe is stronger (brighter) you have to use smaller aperture (f11) if the strobe is dimmer you have to use bigger aperture => f8. THere you have it. brighter => f/11 darker f/8. It is correct.

hmm...this make sense. will try to read thru a few dozens:sticktong times to have a better grasp of it.

below same same too.

The confusion you face is the lack of complete understanding.
For a start, foot-candles quantifies the amount of light where kg quantifies weight. The higher the number the greater the amount of light, same goes for weight. Find out more about foot-candle on wiki (http://en.wikipedia.org/wiki/Foot-candle).

(The following numbers are not accurate, but more for illustrative purpose)
Say in the shot you compose, the amount of light falling is 1000ft-candles, which say is f8. So to have a "decent" exposure, you set f8 on your camera.
Same thing, if its 2000ft-candles you set f11.
The more the light in the scene, the more light you have to reduce from hitting the film/sensor of your camera. Makes sense right? Think shooting at night and during the day.
To further explain:
The difference in one-stop is the double of the amount light. f8 to f11 is one stop (1000ft-candles to 2000ft-candles is double the amount of light)
*again please note that these are figurative numbers, but their relationships are what's important, i.e. the doubling of light.

The concept of aperture for lenses (f-stop) is to control the amount of light passing through the lense. Different from the concept of measuring the amount of light (foot-candles). When you say the amount of light you have produced is f8, you are translating your foot-candles amount to give you an f-stop based on a given shutter and iso.
 

catchlights

Moderator
Staff member
Sep 27, 2004
21,903
46
48
Punggol, Singapore
www.foto-u.com
#17
i BIG head liao.
maybe i should go with just the practical and ignore those theory(wordings):sticktong, more easily understand and goes with my heart. hehe...

oya, i will still go thru all of ur posts and try to 'visualize' and understand it.
the theory is very fundamental, if you don't try to understand it, you will not know when you are doing right or wrong, and just anyhow test here and test there, even by luck you get a good result, you may not know how to repeat or adapt the same results in future.
 

foxtwo

Senior Member
Mar 11, 2004
2,522
0
0
singapore
#18
1.) Fact: Light meter measuring for 18% grey every time.

2.) Theory: You need to open aperture to let in more light, assuming shutter speed/ISO is unchanged.

3.) Main light measured f1/11 where shutter speed is constant (x).

4.) Fill light measured f1/8 with shutter speed x.

5.) Deduction: Fill light is giving out 1 stop less light than Main light, thus light meter 'opens' aperture to correctly meter 18% grey.
 

cryder

New Member
Dec 7, 2006
330
1
0
#19
the theory is very fundamental, if you don't try to understand it, you will not know when you are doing right or wrong, and just anyhow test here and test there, even by luck you get a good result, you may not know how to repeat or adapt the same results in future.
true! that's why i would still try to understand it. dun1 be a mocking fun to others(old birds) and not to give wrong info to the new birds(if some1 ever ask me).

hehe, think wont any how test here test there one la, think i would get the hang of it when i have more exposure to studio shoot. i trust my left brain:sweat:.

OT
anyway, imo photography is more of an arts(creativity) than science(logic) or isit so; read: "more, not's not"? been dealing with IT stuffs(logic) for almost 2 decades, thus weeds has grown on my right brain that is dealing with creativity. a photo's is 1 man's meat but another's poison; thou it will mostly be meat;p.
 

catchlights

Moderator
Staff member
Sep 27, 2004
21,903
46
48
Punggol, Singapore
www.foto-u.com
#20
Ok, the main light is giving 1x amount of light, so you get f11 from main light only,

the fill light is giving 1/2x amount of light, so you get f8 from the fill light only,

since the fill light is weaker than the main light, so your aperture need to open up to f8 to received same amount of light as the main light.

however, since you need to expose for the two lights combine together, the total exposure will be 1x + 1/2 x = 1 1/2x, so your lens aperture will not able to set at f11 now, the recommended exposure will be f11 and a half.

hope this is clear enough.
 

Status
Not open for further replies.
Top Bottom