Specular Highlights/Direct Reflections

[kkamin]

I have read that the smaller the light source the brighter the direct reflection. I'm trying to wrap my brain around if that is a truism in all scenarios. I know if I have a soft box very far from my subject it will effectively be a small source and I will open up my aperture more to get a "normal exposure" thereby exposing the direct reflection of the light source more and rendering a brighter highlight. If I bring that soft box up super close to get an effective larger light source, I will stop down my camera and the direct reflection will be milkier and show more tone and texture through it. But does this hold up if you put on a larger or small light modifier rather than move the light? I feel if you swapped a smaller light modifier for a larger one to achieve a larger direct reflection, you would have to power up the light or open up the aperture and the highlight would get brighter.

Also I read that even if you have a milky highlight smaller pockets that catch the highlight can get brigher--why is this?

Confused. Please help.

 

[ac12]

I had to break your post into pieces, so I can try to understand it, and your question.
I suspect some of my problem is because English may not be your first language, and the translation is coming out confusing. Or the terms/words you are using are very different from my terms for the same thing. So we are effectively speaking different languages.

quote

1. I have read that the smaller the light source the brighter the direct reflection.
   
2. I'm trying to wrap my brain around if that is a truism in all scenarios.
   
3. I know if I have a soft box very far from my subject it will effectively be a small source and I will open up my aperture more to get a "normal exposure" thereby exposing the direct reflection of the light source more and rendering a brighter highlight.
   
   1. I know if I have a soft box very far from my subject it will effectively be a small source
      
   2. and I will open up my aperture more to get a "normal exposure"
      
   3. thereby exposing the direct reflection of the light source more
      
   4. and rendering a brighter highlight
4. If I bring that soft box up super close to get an effective larger light source, I will stop down my camera and the direct reflection will be milkier and show more tone and texture through it.
   
5. But does this hold up if you put on a larger or small light modifier rather than move the light?
   
6. I feel if you swapped a smaller light modifier for a larger one to achieve a larger direct reflection, you would have to power up the light or open up the aperture and the highlight would get brighter.
   1. if you swapped a smaller light modifier for a larger one to achieve a larger direct reflection,
      
   2. you would have to power up the light or open up the aperture and the highlight would get brighter
7. Also I read that even if you have a milky highlight smaller pockets that catch the highlight can get brigher--why is this?
   1. ... even if you have a milky highlight
      
   2. (then) smaller pockets that catch the highlight can get brigher

end quote

There are terms that you must clearly define, because they are the root of my not understanding your post. And anything that I guess is a guess, and likely to be wrong.

• direct reflection
• highlight
• milky highlight

#1 - You need to explain what you mean specifically by "the smaller the light source the brighter the direct reflection."
Because I don't understand at all what you mean by "direct reflection."

#3 - Sorry but this does not makes sense to me.
3.1 is correct
3.2 is correct
3.3 I just do not understand.
3.4 I do not understand.
If the light source is far or near, you MUST adjust the aperture as appropriate to get a correct exposure.
What I do not understand is what you mean by "exposing the direct reflection of the light source more and rendering a brighter highlight."
You need to define specifically what you mean by "highlights," cuz I do not understand the statement.

#4 - I do not understand what you mean by "the direct reflection will be milkier and show more tone and texture through it." You need to explain it better, or upload or link to a sample image of what you mean.

#5 - It is the apparent size of the light source to the subject that is the underlying issue.

• If you get a 2x2 softbox and position it that from the subject it covers say 60 degrees of arc.
• If you move it back so that it now covers 30 degrees of arc, you have a light that is 1/4 the apparent size that it was.
• If you want the same 60 degrees of arc coverage, you need a 4x4 softbox.
• So yes you need a larger light source, as you move it further from the subject.

The same logic applies in reverse if you move the light towards the subject, you need a smaller light source to maintain the same arc of coverage.

#6 - The sentence is confusing
6.1 The problem here is, what do you mean by "direct reflection"
6.2 This statement is confusing to me. It goes back to what do you mean by "highlight?" Because whatever you do to the light source, you need to properly expose the image.

#7 - I just cannot understand the question.
There appears to be an IF this, THEN that, but I can't figure it out.
I took a stab and breaking the question apart, but definition/meaning is the problem.
7.1 What do you mean by "milky highlights"
7.2 What do you mean by "smaller pockets that catch the highlight can get brigher"

 

[Derrel]

Keep in mind that at glancing angles from light-to-subject-to-camera, the specular highlight will be much brighter than when the light hits the subject at a less-steep angle. For example, with a hair light softbox, 24x24 inches, at 9 o'clock or at 10 o
'clock in relation to the subject, the highlights will be diffused. However, if the same,exact light is moved round back of the subject, so it rakes in at a shallow angle, with the light at say a 1 o'clock angle, the highlights will tend to be more-specular, brighter, more over-exposed, even if the light meter reading shows about the same flash power.

I am wondering if by "milky highlight" you are referring to a diffuse highlight, and not a brilliant, bright, specular highlight?

 

[Ysarex]

I have read that the smaller the light source the brighter the direct reflection. I'm trying to wrap my brain around if that is a truism in all scenarios. I know if I have a soft box very far from my subject it will effectively be a small source and I will open up my aperture more to get a "normal exposure" thereby exposing the direct reflection of the light source more and rendering a brighter highlight. If I bring that soft box up super close to get an effective larger light source, I will stop down my camera and the direct reflection will be milkier and show more tone and texture through it. But does this hold up if you put on a larger or small light modifier rather than move the light? I feel if you swapped a smaller light modifier for a larger one to achieve a larger direct reflection, you would have to power up the light or open up the aperture and the highlight would get brighter.

Also I read that even if you have a milky highlight smaller pockets that catch the highlight can get brigher--why is this?

Confused. Please help.

Basically, yes that is a truism but with some pragmatic qualifications some of which you're bringing up. For example an object surface that isn't uniform. Imagine an object covered in aluminum foil that has been crumpled and unfolded. each facet of crumpled foil becomes it's own surface with variations in surface angle and size while at the same time there can be an overall reflection area if the foil covers a curved surface -- you mentioned pockets catching highlights.

If you leave a lamp head on a stand in place and swap a smaller softbox for a larger softbox you'll get the same effect as if you had moved the smaller softbox closer once you've equalized exposure. What you're figuring out here is that it's the relative size of the light source that's determinant. The determinant size of the light source is a function of it's actual size and it's distance. Once you equalize exposure the ratio between the brightness of the reflection highlight and the rest of the subject will stay constant to a constant determinant light source size, decrease as the determinant light size increases, and increase as the determinant light size decreases. That's theory -- it is pragmatically possible to push past limits where for example you can't increase the determinant light source size by moving it closer once you've reached a certain limit. For example photographing a small object like a ceramic vase 10cm tall. If you bring a 1.5m square softbox to within 25cm of that vase, bringing it any closer isn't going to increase it's determinant size.

Joe

P.S. Thinking about that as I fixed lunch and I want to qualify that last example using the vase. With a huge light that extends beyond the limits of the subject's surface to fully reflect -- that would be the above scenario -- moving the light still closer should still reduce the ratio of reflection brightness to the rest of the subject but at a reduced rate (different math) since the full size of the light source can no longer be reflected.