Inverse sqaure law and size of source

jlafferty said:

BillNi said:

All light from all sources obeys the inverse square law because it is a law. The clue is in the name.

Click to expand...

Not a reasonably collimated light source.

https://hackaday.com/2020/11/13/artificial-sun-lighting-via-old-satellite-dishes/

Click to expand...

It is a law. I stated focusing mirrors or lenses can change the apparent location of the source.

A light in a perfect and perfectly focused parabolic reflector will appear to be located at infinity. The video in the page you linked says as much around 2:09 and specifically around 10:03.

The law applies, but, has no observable effect when the distance is infinity.

BillNi said:

jlafferty said:

BillNi said:

All light from all sources obeys the inverse square law because it is a law. The clue is in the name.

Click to expand...

Not a reasonably collimated light source.

https://hackaday.com/2020/11/13/artificial-sun-lighting-via-old-satellite-dishes/

Click to expand...

It is a law. I stated focusing mirrors or lenses can change the apparent location of the source.

A light in a perfect and perfectly focused parabolic reflector will appear to be located at infinity. The video in the page you linked says as much around 2:09 and specifically around 10:03.

The law applies, but, has no observable effect when the distance is infinity.

Click to expand...

Right, so when you say “applies” but “has no observable effect” this is the pedantic way of saying “it no longer applies in any practical way for photography at human scale, and simply exists in an academic vacuum.”

A-Marc said:

another factor is the flash unit not firing very consistent.

i am gonna start a war with what i will say next, there will be enough number counting photpg who will go mad...

the inverse square law is based on a point like light source. basically the law refers to a light bulb. what most of the time never is the case in photography. so the modifier u use does affect the inverse square law by the way it gathers the light rays. therefor the inverse square law is mostly to be seen as a guide line, for sure it is not a law.

each modifier does have its characteristics, its wisely to study each modifier, to get to know the habit of the light at certain distances.

if the modifier still doesnt do what you are looking for, there s a big chance that its the wrong modifier for the look you are after. The inverse square law wont help you, another modifier will.

Click to expand...

One of the things I like about parabolic mods, especially silver ones, is that (undiffused) they yield less falloff with distance by focusing the light into a column.

jlafferty said:

BillNi said:

jlafferty said:

BillNi said:

All light from all sources obeys the inverse square law because it is a law. The clue is in the name.

Click to expand...

Not a reasonably collimated light source.

https://hackaday.com/2020/11/13/artificial-sun-lighting-via-old-satellite-dishes/

Click to expand...

It is a law. I stated focusing mirrors or lenses can change the apparent location of the source.

A light in a perfect and perfectly focused parabolic reflector will appear to be located at infinity. The video in the page you linked says as much around 2:09 and specifically around 10:03.

The law applies, but, has no observable effect when the distance is infinity.

Click to expand...

Right, so when you say “applies” but “has no observable effect” this is the pedantic way of saying “it no longer applies in any practical way for photography at human scale, and simply exists in an academic vacuum.”

Click to expand...

No. When I said it applies I meant it applies and when you said "Not a reasonably collimated light source" you were wrong.

I was wrong to say it has no observable effect. The lack of fall off with changing subject distance is an observable effect and consistent with the law. Being one of the touted benefits and uses of parabolic reflectors there is no 'academic vacuum' about it.

boldcolors said:

...

So the optimal solution would be a big 2m softbox say...3 meters away from the subject. And perhaps use flags on the sides to shape the light and give the model some sculpting since I suspect the light will be quite flat and boring right out of the gate.

Click to expand...

Curious, what kind of shoot are you doing ?

2m modifier, placed 3m away, will give a pretty wide spread of light.

--
https://www.ronchauphoto.com/
https://www.instagram.com/rchau.photo

BillNi said:

No. When I said it applies I meant it applies and when you said "Not a reasonably collimated light source" you were wrong.

Click to expand...

No. If you've got a collimated source in a confined location, like a photo studio, you're not going to observe the light source behaving consistent with inverse square. Sure, it technically still "applies", just not practically.

BillNi said:

I was wrong to say it has no observable effect. The lack of fall off with changing subject distance is an observable effect and consistent with the law.

Click to expand...

Not really. The law is based on a point source, but the minute you stray from a point source, there are all sorts of observable exceptions to the behavior, which is to say, as the exceptions become more dramatic, you'd say they no longer apply practically.

Saying a lack of fall-off "is consistent with inverse square law" is a bit like saying the way airplanes fly is consistent with how laws of gravity describe things falling to earth. Sure, technically that's true, but falling very slowly isn't how you'd describe flying in any practical sense, you'd say "a well designed plane does a good job defying the laws of gravity." It’s the opposite of falling that gives airplanes their appeal.

In the context of a photo studio, a parabolic reflector, a fresnel, a snoot, an optical spot - they all defy the inverse square law.

--
http://jimlafferty.com
Evocative beats academic.

ronscuba said:

As a guideline I place a modifier distance roughly equal to it's diameter. 100cm diamter, 100cm away. A 150cm diameter modifier at 150 cm distance should give similar softness with wider coverage.

Click to expand...

Thank you! That is exactly what I am after

Basically shooting regular headshots/halfbody in modified clamshell setup. Currently using a 100cm deep octa as main and I really like the punch from that modifier but one needs to pay close attention to allignment of the octa itself and the models or I end up with harsh shadows where I don't want them.

Figuring a bigger 150-ish Octa is more forgiving and gives me some leeway in terms of exposure and fall-off consistency while keeping similar softness and contrast from the 100 octa.

boldcolors said:

ronscuba said:

As a guideline I place a modifier distance roughly equal to it's diameter. 100cm diamter, 100cm away. A 150cm diameter modifier at 150 cm distance should give similar softness with wider coverage.

Click to expand...

Thank you! That is exactly what I am after

Basically shooting regular headshots/halfbody in modified clamshell setup. Currently using a 100cm deep octa as main and I really like the punch from that modifier but one needs to pay close attention to allignment of the octa itself and the models or I end up with harsh shadows where I don't want them.

Figuring a bigger 150-ish Octa is more forgiving and gives me some leeway in terms of exposure and fall-off consistency while keeping similar softness and contrast from the 100 octa.

Click to expand...

Just some modest suggestions and questions, hopefully helpful:

Are you in an especially confined shooting space? If not, then consider a 72” PLM soft silver with a sock. It’s super gorgeous light, and up close, maybe 3-4ft, sufficiently punchy.



Curious about your harsh shadows. Are you positioning the light centered over camera? I shoot with a 90cm octa for the kind of work you’re describing, and when I do so, the only change I make is to it’s height, relative to subject height. Super simple change. But I’m also using a big fill behind me, to shadows get opened up nicely and the key light’s narrower coverage gets hidden a bit.

jlafferty said:

boldcolors said:

ronscuba said:

As a guideline I place a modifier distance roughly equal to it's diameter. 100cm diamter, 100cm away. A 150cm diameter modifier at 150 cm distance should give similar softness with wider coverage.

Click to expand...

Thank you! That is exactly what I am after

Basically shooting regular headshots/halfbody in modified clamshell setup. Currently using a 100cm deep octa as main and I really like the punch from that modifier but one needs to pay close attention to allignment of the octa itself and the models or I end up with harsh shadows where I don't want them.

Figuring a bigger 150-ish Octa is more forgiving and gives me some leeway in terms of exposure and fall-off consistency while keeping similar softness and contrast from the 100 octa.

Click to expand...

Just some modest suggestions and questions, hopefully helpful:

Are you in an especially confined shooting space? If not, then consider a 72” PLM soft silver with a sock. It’s super gorgeous light, and up close, maybe 3-4ft, sufficiently punchy.

Curious about your harsh shadows. Are you positioning the light centered over camera? I shoot with a 90cm octa for the kind of work you’re describing, and when I do so, the only change I make is to it’s height, relative to subject height. Super simple change. But I’m also using a big fill behind me, to shadows get opened up nicely and the key light’s narrower coverage gets hidden a bit.

Click to expand...

Space is somewhat confined. The ceiling height is good but I am close to walls (which I have flagged so that is fine in terms of spill)

The harsh shadows is just me not paying enough attention. Ususally around the jawline which in some cases can make women look really bad. Either my key has been too high or my fill from underneath not enough. When I noticed this I moved the models a bit closer to key and raised my reflector. Basically my setup has been:

100cm Deep octa key. About 30 degrees camera left
Silver reflector under the key. Same position (about 30 degrees camera left)
100cm shallow octa on axis right above me to open up shadows on models left side a tad. Approx 1 stop below main

I am thinking the same setup and positions but

150cm indirect deep octa as key
100 cm shallow octa underneath for clamshell fill. 2 stops below key
100 cm shallow octa for on axis fill

Only reason I am looking for a bigger key is to get more leeway in terms of adjusting the position of lights in order to reduce the risk for mistakes. Or....make life a bit easier

boldcolors said:

John Vickers said:

boldcolors said:

John Vickers said:

boldcolors said:

OK, sorry for a stupid question but is the Inverse Square law also affected by the size of the modifier or only distance from the lightsource?

Click to expand...

Sure it's affected by the size (and shape) of the modifier.

If you're far enough away, you'll always get an inverse square law.

In most cases, for example if you have a diffuse modifier, you'll get an inverse square law if the distance from subject to the modifier is more than a few times the size of your modifier.

If your modifier is a large parabolic reflector with your light source at its focus, or some other kind of beam-forming optics, you might get fairly constant illumination over a distance many times the size of the optics.

If the distance between the subject and the modifier is small compared with the size of the modifier, the fall off will likely be slower than inverse square, and in some cases, there may be almost no falloff at all.

For example, if you have a large diffused LED panel, or a double-diffused softbox, so the light output is very even across the surface, the illumination will be nearly constant for distances up to something like half the size of the diffuser.

Click to expand...

OK, so...if I put my model....say 3 meters away from

A: a 100 cm octa

B: a 190 cm octa

the fall-off - or to put it in another way; working area for my model with the same light output/exposure will not be the same?

Click to expand...

By "working area" you mean the space in which your subject can move without the lighting changing significantly ?

You want to make the illumination of the model less sensitive to the position of the model ?

Click to expand...

Yes, exactly this. But still keep my light soft and pleasing

boldcolors said:

Using a bigger softbox (for a given design), or moving the softbox closer to the subject, will do that.

A 1m softbox at 3m will make shadows, and the illumination will be more sensitive to small changes in the position of the subject than a 2m softbox at 3m. A 2m softbox at 1m would be much less sensitive again, but at that point the big softbox can interfere with other lighting, and with the freedom of movement of your subject.

Some experimentatation with inanimate objects may be helpful.

Click to expand...

Thanks for that! Although I am not sure about the "moving the softbox closer" part in this situation. Yes, the light would be softer but isn't it the other way around about sensitivity to movements? The falloff is more rapid closer to the lightsource?

Click to expand...

Not for a uniformly radiating flat surface.

I'd been trying to think of a good way of explaining this. Without a load of calculus.

...

Suppose we have a sphere with a uniformly radiating (outside) surface.

The intensity of the radiation (outside the sphere) falls as 1/r^2, but r is measured from the centre of the sphere, not the surface of the sphere.

What's the difference between the light intensity 1m from the surface of the sphere and 2m from the surface?

If the sphere is has a radius of 1cm, the relative difference is (very close to) 1^2/2^2 = 1/4. The distance from the surface and the distance from the centre are practically identical.

If we do that sum more accurately, we get 101^2/201^2 = 0.2525

If the sphere has a radius of 100m, the relative difference is (very close to) 100^2/100^2 = 1.

If we do that last sum more accurately, we get 101^2/102^2 = 0.980

A large, flat, uniformly radiating surface behaves like a patch of a very big sphere, so long as the distance from the surface is much smaller than the size of the surface. And there is very little light falloff with distance from the surface.

At distances much larger than the size of the surface, the surface behaves more like a point source, with the familiar 1/r^2 point-source falloff.

...

Another way of looking at it is: starting very close to the surface, only a small part of the surface effectively lights up the subject. As we move the subject away from the surface, the area of the surface lighting up the subject grows as the square of the distance from the surface, exactly balancing the 1/r^2 falloff from each point of the surface.

...

A symmetry argument:

Suppose we have a horizontal (just for concreteness) uniform flat radiating surface, radiating upwards, extending infinitely in all directions.

Consider a transparent rectangle in a vertical plane, above the surface. Call the sides left and right.

What is the net light flow through the rectangle?

The light flow from left to right and right to left must be the same. So there can be no net light flow through the rectangle.

Suppose we make a transparent rectangular box, above the radiating surface, with four sides all in vertical planes, and the top and bottom ends horizontal.

What's the difference between the light flow into the bottom, and out of the top?

We've already found that there can't be any light flow through the sides, so the light flow into the bottom, and out of the top must be the same.

So there is no light falloff, however tall the box is.

(Similar arguments lead to a 1/r law for an infinite rod radiator, and a 1/r^2 law for a spherical radiator).

...

Any other folk here who have a better explanation ?

...

As I said, some experimentation with an inanimate subject may be helpful.

boldcolors said:

So the optimal solution would be a big 2m softbox say...3 meters away from the subject. And perhaps use flags on the sides to shape the light and give the model some sculpting since I suspect the light will be quite flat and boring right out of the gate.

Click to expand...

[Edit: fix thinko confusing radii and diameters of spheres. Result unchanged.]

boldcolors said:

jlafferty said:

boldcolors said:

ronscuba said:

As a guideline I place a modifier distance roughly equal to it's diameter. 100cm diamter, 100cm away. A 150cm diameter modifier at 150 cm distance should give similar softness with wider coverage.

Click to expand...

Thank you! That is exactly what I am after

Basically shooting regular headshots/halfbody in modified clamshell setup. Currently using a 100cm deep octa as main and I really like the punch from that modifier but one needs to pay close attention to allignment of the octa itself and the models or I end up with harsh shadows where I don't want them.

Figuring a bigger 150-ish Octa is more forgiving and gives me some leeway in terms of exposure and fall-off consistency while keeping similar softness and contrast from the 100 octa.

Click to expand...

Just some modest suggestions and questions, hopefully helpful:

Are you in an especially confined shooting space? If not, then consider a 72” PLM soft silver with a sock. It’s super gorgeous light, and up close, maybe 3-4ft, sufficiently punchy.

Curious about your harsh shadows. Are you positioning the light centered over camera? I shoot with a 90cm octa for the kind of work you’re describing, and when I do so, the only change I make is to it’s height, relative to subject height. Super simple change. But I’m also using a big fill behind me, to shadows get opened up nicely and the key light’s narrower coverage gets hidden a bit.

Click to expand...

Space is somewhat confined. The ceiling height is good but I am close to walls (which I have flagged so that is fine in terms of spill)

The harsh shadows is just me not paying enough attention. Ususally around the jawline which in some cases can make women look really bad. Either my key has been too high or my fill from underneath not enough. When I noticed this I moved the models a bit closer to key and raised my reflector. Basically my setup has been:

100cm Deep octa key. About 30 degrees camera left
Silver reflector under the key. Same position (about 30 degrees camera left)
100cm shallow octa on axis right above me to open up shadows on models left side a tad. Approx 1 stop below main

I am thinking the same setup and positions but

150cm indirect deep octa as key
100 cm shallow octa underneath for clamshell fill. 2 stops below key
100 cm shallow octa for on axis fill

Only reason I am looking for a bigger key is to get more leeway in terms of adjusting the position of lights in order to reduce the risk for mistakes. Or....make life a bit easier

Click to expand...

Seems like you already have what you need to control falloff/shadows. Adjust the positions of your fill light and reflector. Not just height but also angle.

Do you have a white reflector ? Silver will give a more powerful reflection, but be more sensitive to location.

ronscuba said:

boldcolors said:

jlafferty said:

boldcolors said:

ronscuba said:

As a guideline I place a modifier distance roughly equal to it's diameter. 100cm diamter, 100cm away. A 150cm diameter modifier at 150 cm distance should give similar softness with wider coverage.

Click to expand...

Thank you! That is exactly what I am after

Basically shooting regular headshots/halfbody in modified clamshell setup. Currently using a 100cm deep octa as main and I really like the punch from that modifier but one needs to pay close attention to allignment of the octa itself and the models or I end up with harsh shadows where I don't want them.

Figuring a bigger 150-ish Octa is more forgiving and gives me some leeway in terms of exposure and fall-off consistency while keeping similar softness and contrast from the 100 octa.

Click to expand...

Just some modest suggestions and questions, hopefully helpful:

Are you in an especially confined shooting space? If not, then consider a 72” PLM soft silver with a sock. It’s super gorgeous light, and up close, maybe 3-4ft, sufficiently punchy.

Curious about your harsh shadows. Are you positioning the light centered over camera? I shoot with a 90cm octa for the kind of work you’re describing, and when I do so, the only change I make is to it’s height, relative to subject height. Super simple change. But I’m also using a big fill behind me, to shadows get opened up nicely and the key light’s narrower coverage gets hidden a bit.

Click to expand...

Space is somewhat confined. The ceiling height is good but I am close to walls (which I have flagged so that is fine in terms of spill)

The harsh shadows is just me not paying enough attention. Ususally around the jawline which in some cases can make women look really bad. Either my key has been too high or my fill from underneath not enough. When I noticed this I moved the models a bit closer to key and raised my reflector. Basically my setup has been:

100cm Deep octa key. About 30 degrees camera left
Silver reflector under the key. Same position (about 30 degrees camera left)
100cm shallow octa on axis right above me to open up shadows on models left side a tad. Approx 1 stop below main

I am thinking the same setup and positions but

150cm indirect deep octa as key
100 cm shallow octa underneath for clamshell fill. 2 stops below key
100 cm shallow octa for on axis fill

Only reason I am looking for a bigger key is to get more leeway in terms of adjusting the position of lights in order to reduce the risk for mistakes. Or....make life a bit easier

Click to expand...

Seems like you already have what you need to control falloff/shadows. Adjust the positions of your fill light and reflector. Not just height but also angle.

Do you have a white reflector ? Silver will give a more powerful reflection, but be more sensitive to location.

Click to expand...

Yes, I think I actually might go with what I already have and pay more attention to adjusting the light for each person. No free lunch ey! Furthermore, putting a 150cm octa slightly to the left gives me no room for on axis modifier with a somewhat reasonable size.

As for the fill reflector I tend to prefer a regular softbox with all diffusers (and even feathered) rather than a silver reflector. The softbox fill gives me a bit more natural light but still that classic airy feel from clamshell. In the setup above I used silver reflector though since I used my other 100cm octa for the on axis fill. But I have two of those so I'll just bring them all the next time.

BTW! One thing that I have an issue with is that the harsh shadows tend to show up on shadow-side of the models chin with this setup. Not a nice gradation but rather a dark spot (like they missed shaving) which I have to correct in post - especially for women. I reckon I might kill that by either lowering the position of my key a bit, add more fill or simply move the underneath fill so that it is right in front of the model. Just not sure if this could mess up the ratio - I.e not balanced, more light on the lower part of the shadowed side. If that sentence makes sense

I have seen several versions of this. Some use what I do...full clamshell setup slightly to the left and either a V-flat as fill to the right or on axis (which I tend to prefer)

Some use just the key slightly to the left but keep the fill right under the camera (zero degree) and V-flat on the side.

boldcolors said:

ronscuba said:

boldcolors said:

jlafferty said:

boldcolors said:

ronscuba said:

As a guideline I place a modifier distance roughly equal to it's diameter. 100cm diamter, 100cm away. A 150cm diameter modifier at 150 cm distance should give similar softness with wider coverage.

Click to expand...

Thank you! That is exactly what I am after

Basically shooting regular headshots/halfbody in modified clamshell setup. Currently using a 100cm deep octa as main and I really like the punch from that modifier but one needs to pay close attention to allignment of the octa itself and the models or I end up with harsh shadows where I don't want them.

Figuring a bigger 150-ish Octa is more forgiving and gives me some leeway in terms of exposure and fall-off consistency while keeping similar softness and contrast from the 100 octa.

Click to expand...

Just some modest suggestions and questions, hopefully helpful:

Are you in an especially confined shooting space? If not, then consider a 72” PLM soft silver with a sock. It’s super gorgeous light, and up close, maybe 3-4ft, sufficiently punchy.

Curious about your harsh shadows. Are you positioning the light centered over camera? I shoot with a 90cm octa for the kind of work you’re describing, and when I do so, the only change I make is to it’s height, relative to subject height. Super simple change. But I’m also using a big fill behind me, to shadows get opened up nicely and the key light’s narrower coverage gets hidden a bit.

Click to expand...

Space is somewhat confined. The ceiling height is good but I am close to walls (which I have flagged so that is fine in terms of spill)

The harsh shadows is just me not paying enough attention. Ususally around the jawline which in some cases can make women look really bad. Either my key has been too high or my fill from underneath not enough. When I noticed this I moved the models a bit closer to key and raised my reflector. Basically my setup has been:

100cm Deep octa key. About 30 degrees camera left
Silver reflector under the key. Same position (about 30 degrees camera left)
100cm shallow octa on axis right above me to open up shadows on models left side a tad. Approx 1 stop below main

I am thinking the same setup and positions but

150cm indirect deep octa as key
100 cm shallow octa underneath for clamshell fill. 2 stops below key
100 cm shallow octa for on axis fill

Only reason I am looking for a bigger key is to get more leeway in terms of adjusting the position of lights in order to reduce the risk for mistakes. Or....make life a bit easier

Click to expand...

Seems like you already have what you need to control falloff/shadows. Adjust the positions of your fill light and reflector. Not just height but also angle.

Do you have a white reflector ? Silver will give a more powerful reflection, but be more sensitive to location.

Click to expand...

Yes, I think I actually might go with what I already have and pay more attention to adjusting the light for each person. No free lunch ey! Furthermore, putting a 150cm octa slightly to the left gives me no room for on axis modifier with a somewhat reasonable size.

As for the fill reflector I tend to prefer a regular softbox with all diffusers (and even feathered) rather than a silver reflector. The softbox fill gives me a bit more natural light but still that classic airy feel from clamshell. In the setup above I used silver reflector though since I used my other 100cm octa for the on axis fill. But I have two of those so I'll just bring them all the next time.

BTW! One thing that I have an issue with is that the harsh shadows tend to show up on shadow-side of the models chin with this setup. Not a nice gradation but rather a dark spot (like they missed shaving) which I have to correct in post - especially for women. I reckon I might kill that by either lowering the position of my key a bit, add more fill or simply move the underneath fill so that it is right in front of the model. Just not sure if this could mess up the ratio - I.e not balanced, more light on the lower part of the shadowed side. If that sentence makes sense

I have seen several versions of this. Some use what I do...full clamshell setup slightly to the left and either a V-flat as fill to the right or on axis (which I tend to prefer)

Some use just the key slightly to the left but keep the fill right under the camera (zero degree) and V-flat on the side.

Click to expand...

is your center of key directly pointed on the subject ? if your looking for softer shadows place the model into the edge light of the key, not in the center.

A-Marc said:

boldcolors said:

ronscuba said:

boldcolors said:

jlafferty said:

boldcolors said:

ronscuba said:

As a guideline I place a modifier distance roughly equal to it's diameter. 100cm diamter, 100cm away. A 150cm diameter modifier at 150 cm distance should give similar softness with wider coverage.

Click to expand...

Thank you! That is exactly what I am after

Basically shooting regular headshots/halfbody in modified clamshell setup. Currently using a 100cm deep octa as main and I really like the punch from that modifier but one needs to pay close attention to allignment of the octa itself and the models or I end up with harsh shadows where I don't want them.

Figuring a bigger 150-ish Octa is more forgiving and gives me some leeway in terms of exposure and fall-off consistency while keeping similar softness and contrast from the 100 octa.

Click to expand...

Just some modest suggestions and questions, hopefully helpful:

Are you in an especially confined shooting space? If not, then consider a 72” PLM soft silver with a sock. It’s super gorgeous light, and up close, maybe 3-4ft, sufficiently punchy.

Curious about your harsh shadows. Are you positioning the light centered over camera? I shoot with a 90cm octa for the kind of work you’re describing, and when I do so, the only change I make is to it’s height, relative to subject height. Super simple change. But I’m also using a big fill behind me, to shadows get opened up nicely and the key light’s narrower coverage gets hidden a bit.

Click to expand...

Space is somewhat confined. The ceiling height is good but I am close to walls (which I have flagged so that is fine in terms of spill)

The harsh shadows is just me not paying enough attention. Ususally around the jawline which in some cases can make women look really bad. Either my key has been too high or my fill from underneath not enough. When I noticed this I moved the models a bit closer to key and raised my reflector. Basically my setup has been:

100cm Deep octa key. About 30 degrees camera left
Silver reflector under the key. Same position (about 30 degrees camera left)
100cm shallow octa on axis right above me to open up shadows on models left side a tad. Approx 1 stop below main

I am thinking the same setup and positions but

150cm indirect deep octa as key
100 cm shallow octa underneath for clamshell fill. 2 stops below key
100 cm shallow octa for on axis fill

Only reason I am looking for a bigger key is to get more leeway in terms of adjusting the position of lights in order to reduce the risk for mistakes. Or....make life a bit easier

Click to expand...

Seems like you already have what you need to control falloff/shadows. Adjust the positions of your fill light and reflector. Not just height but also angle.

Do you have a white reflector ? Silver will give a more powerful reflection, but be more sensitive to location.

Click to expand...

Yes, I think I actually might go with what I already have and pay more attention to adjusting the light for each person. No free lunch ey! Furthermore, putting a 150cm octa slightly to the left gives me no room for on axis modifier with a somewhat reasonable size.

As for the fill reflector I tend to prefer a regular softbox with all diffusers (and even feathered) rather than a silver reflector. The softbox fill gives me a bit more natural light but still that classic airy feel from clamshell. In the setup above I used silver reflector though since I used my other 100cm octa for the on axis fill. But I have two of those so I'll just bring them all the next time.

BTW! One thing that I have an issue with is that the harsh shadows tend to show up on shadow-side of the models chin with this setup. Not a nice gradation but rather a dark spot (like they missed shaving) which I have to correct in post - especially for women. I reckon I might kill that by either lowering the position of my key a bit, add more fill or simply move the underneath fill so that it is right in front of the model. Just not sure if this could mess up the ratio - I.e not balanced, more light on the lower part of the shadowed side. If that sentence makes sense

I have seen several versions of this. Some use what I do...full clamshell setup slightly to the left and either a V-flat as fill to the right or on axis (which I tend to prefer)

Some use just the key slightly to the left but keep the fill right under the camera (zero degree) and V-flat on the side.

Click to expand...

is your center of key directly pointed on the subject ? if your looking for softer shadows place the model into the edge light of the key, not in the center.

Click to expand...

It is since I am using a clamshell setup. Only way to feather that setup would be to change the 45 degree downward tilt to zero, raise it and point the center of the light above the models head I guess. And by that also get some hairlight as a bonus

TBH I think you’re complicating what should be simple. I’d ditch the “clamshell” and just use a single, larger feathered source, with a reflector on the other side *maybe*. Then some sort of on axis fill possibly a single head shooting backward, behind me, into the room. But you probably don’t even need that.

The whole “harsh shadows” problem suggests you’re just not placing the key well. Do you understand when I say feathered, you’re basically turning the source so that the left side of the octa is lighting the camera right side of the subject? It’s almost as if you’re lighting past the subject. And you’ll swing it around, more frontal than side-y? But still on that 45 degree angle.

I did a whole series with a single source, varying skin tones, heights, etc. and it’s all about dialing in that initial placement:

jlafferty said:

TBH I think you’re complicating what should be simple. I’d ditch the “clamshell” and just use a single, larger feathered source, with a reflector on the other side *maybe*. Then some sort of on axis fill possibly a single head shooting backward, behind me, into the room. But you probably don’t even need that.

The whole “harsh shadows” problem suggests you’re just not placing the key well. Do you understand when I say feathered, you’re basically turning the source so that the left side of the octa is lighting the camera right side of the subject? It’s almost as if you’re lighting past the subject. And you’ll swing it around, more frontal than side-y? But still on that 45 degree angle.

I did a whole series with a single source, varying skin tones, heights, etc. and it’s all about dialing in that initial placement:

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Thanks! When I feather like that I usually keep the angle of key at 0, raise it so that the lower part of the octabox is at cheeklevel-ish. And just point it away so that the main direction of the light is travelling right across the models face. From left to right. The position of the octa is left or right and about a meter in front of the model. And white reflector on the other side. Soft and nice but I like the punch and character from clamshell. But then again - it doesn't fit everyone so maybe I should ditch it.

So you keep the angle of key downward 45 degree but otherwise feather it as I mention above?

If you check that IG link, 6th panel in shows the setup. Angle downward isn’t quite 45 degrees.

If it’s punch you’re after, just bring a smaller source in closer - raises contrast while, seemingly paradoxically, softens the shadow edge.

The important thing is bringing the light around front enough that you get good coverage/shaping on the side opposite the light.

If you want the benefit of clamshell without the finicky nature of the reflector under the face, you can put a e.g. 2x2ft white something on your floor (colorplast, cardboard, flexfill), and bounce a head into that, turning the floor into a reflector effectively. It’ll open up darker eyes, and provided you reduce power enough, it should mess with your contrast much.

boldcolors said:

ronscuba said:

boldcolors said:

jlafferty said:

boldcolors said:

ronscuba said:

As a guideline I place a modifier distance roughly equal to it's diameter. 100cm diamter, 100cm away. A 150cm diameter modifier at 150 cm distance should give similar softness with wider coverage.

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Thank you! That is exactly what I am after

Basically shooting regular headshots/halfbody in modified clamshell setup. Currently using a 100cm deep octa as main and I really like the punch from that modifier but one needs to pay close attention to allignment of the octa itself and the models or I end up with harsh shadows where I don't want them.

Figuring a bigger 150-ish Octa is more forgiving and gives me some leeway in terms of exposure and fall-off consistency while keeping similar softness and contrast from the 100 octa.

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Just some modest suggestions and questions, hopefully helpful:

Are you in an especially confined shooting space? If not, then consider a 72” PLM soft silver with a sock. It’s super gorgeous light, and up close, maybe 3-4ft, sufficiently punchy.

Curious about your harsh shadows. Are you positioning the light centered over camera? I shoot with a 90cm octa for the kind of work you’re describing, and when I do so, the only change I make is to it’s height, relative to subject height. Super simple change. But I’m also using a big fill behind me, to shadows get opened up nicely and the key light’s narrower coverage gets hidden a bit.

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Space is somewhat confined. The ceiling height is good but I am close to walls (which I have flagged so that is fine in terms of spill)

The harsh shadows is just me not paying enough attention. Ususally around the jawline which in some cases can make women look really bad. Either my key has been too high or my fill from underneath not enough. When I noticed this I moved the models a bit closer to key and raised my reflector. Basically my setup has been:

100cm Deep octa key. About 30 degrees camera left
Silver reflector under the key. Same position (about 30 degrees camera left)
100cm shallow octa on axis right above me to open up shadows on models left side a tad. Approx 1 stop below main

I am thinking the same setup and positions but

150cm indirect deep octa as key
100 cm shallow octa underneath for clamshell fill. 2 stops below key
100 cm shallow octa for on axis fill

Only reason I am looking for a bigger key is to get more leeway in terms of adjusting the position of lights in order to reduce the risk for mistakes. Or....make life a bit easier

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Seems like you already have what you need to control falloff/shadows. Adjust the positions of your fill light and reflector. Not just height but also angle.

Do you have a white reflector ? Silver will give a more powerful reflection, but be more sensitive to location.

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Yes, I think I actually might go with what I already have and pay more attention to adjusting the light for each person. No free lunch ey! Furthermore, putting a 150cm octa slightly to the left gives me no room for on axis modifier with a somewhat reasonable size.

As for the fill reflector I tend to prefer a regular softbox with all diffusers (and even feathered) rather than a silver reflector. The softbox fill gives me a bit more natural light but still that classic airy feel from clamshell. In the setup above I used silver reflector though since I used my other 100cm octa for the on axis fill. But I have two of those so I'll just bring them all the next time.

BTW! One thing that I have an issue with is that the harsh shadows tend to show up on shadow-side of the models chin with this setup. Not a nice gradation but rather a dark spot (like they missed shaving) which I have to correct in post - especially for women. I reckon I might kill that by either lowering the position of my key a bit, add more fill or simply move the underneath fill so that it is right in front of the model. Just not sure if this could mess up the ratio - I.e not balanced, more light on the lower part of the shadowed side. If that sentence makes sense

I have seen several versions of this. Some use what I do...full clamshell setup slightly to the left and either a V-flat as fill to the right or on axis (which I tend to prefer)

Some use just the key slightly to the left but keep the fill right under the camera (zero degree) and V-flat on the side.

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For what it’s worth, my preferred mod for single or small group portraits is a large soft silver Paul C. Buff parabolic umbrella. The light is contrasty, giving a “sunny” look, but the large size of the source helps soften transitions between light and shadow. Another advantage is that the relatively collimated cone of light yields very little falloff with distance, such that in a small group portrait there is very little difference in exposure on the subjects closer to and further from the source. I add a diffused umbrella or octa at the camera position for fill.

For women with wrinkles, I put a diffusion cover on the PLM to make it behave more like a softbox.

--
Event professional for 20+ years, travel & landscape enthusiast for 30+.
http://jacquescornell.photography
http://happening.photos

jlafferty said:

TBH I think you’re complicating what should be simple. I’d ditch the “clamshell” and just use a single, larger feathered source, with a reflector on the other side *maybe*. Then some sort of on axis fill possibly a single head shooting backward, behind me, into the room. But you probably don’t even need that.

The whole “harsh shadows” problem suggests you’re just not placing the key well. Do you understand when I say feathered, you’re basically turning the source so that the left side of the octa is lighting the camera right side of the subject? It’s almost as if you’re lighting past the subject. And you’ll swing it around, more frontal than side-y? But still on that 45 degree angle.

I did a whole series with a single source, varying skin tones, heights, etc. and it’s all about dialing in that initial placement:

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Click to expand...

arent we talking about clampshell ? thats one light on top one from below.

boldcolors said:

jlafferty said:

TBH I think you’re complicating what should be simple. I’d ditch the “clamshell” and just use a single, larger feathered source, with a reflector on the other side *maybe*. Then some sort of on axis fill possibly a single head shooting backward, behind me, into the room. But you probably don’t even need that.

The whole “harsh shadows” problem suggests you’re just not placing the key well. Do you understand when I say feathered, you’re basically turning the source so that the left side of the octa is lighting the camera right side of the subject? It’s almost as if you’re lighting past the subject. And you’ll swing it around, more frontal than side-y? But still on that 45 degree angle.

I did a whole series with a single source, varying skin tones, heights, etc. and it’s all about dialing in that initial placement:

View this content on Instagram

View this content on Instagram

Click to expand...

Thanks! When I feather like that I usually keep the angle of key at 0, raise it so that the lower part of the octabox is at cheeklevel-ish. And just point it away so that the main direction of the light is travelling right across the models face. From left to right. The position of the octa is left or right and about a meter in front of the model. And white reflector on the other side. Soft and nice but I like the punch and character from clamshell. But then again - it doesn't fit everyone so maybe I should ditch it.

So you keep the angle of key downward 45 degree but otherwise feather it as I mention above?

Click to expand...

you can have the modifier pointing on the floor (feathered) in front of the model, not above the model. appox so the model can barely touch the edge of the modifier with the hand when raising the arm.

its basicly the same as jlafferty describes with" left or right and about a meter in front" just that you light from top downwards.

if the center of your light source hits the subject, you get "harsh" shadows. if the edge of the light hits the subject, shadows are way softer. try it !