Preferred Aperture For Studio

[smoke665]

I would ask why do you not see this at wider apertures since the reflected 'penetrated' light would be just as likely to return to the sensor and pass through a wider aperture?

Your question bothered me so I went at it from a different direction. It might be possible that the effect I'm seeing is at least partially a result of the light being softer. I used the guide numbers for my studio lights with a softbox at various watt/sec power settings. to compile this chart.

Using the full power rating of my AB800 at 320 with a guide number of 72, and using the formula distance = guide number/aperture, I came up with a distance of 9 ft to the subject for an aperture of f/8. Using the same power setting required moving the light in to 1/2 the distance to obtain the desired f/16. This was pretty much the same throughout the various power settings.

So would it not stand to reason that a softer light would be less likely to show blemishes by filling the shadows more? Plus the combination of the higher power, closer to the subject should also make the skin more luminous?

 

[JBPhotog]

I think what you are witnessing is the size relationship of the modifier to the subject at different distances. For example a 24" soft box will produce softer light at 5.54 feet than at 9 feet. The larger light source fills in the shadows, reduces contrast of the skin texture and wraps around the subjects face producing what you are calling more luminous. Yes a larger light source reduces blemishes but I don't think you are seeing dermal or subcutaneous light reflection since this tissue isn't white.

An analogy could be, the quality of light on a sunny day is hard shadows, contrasty and specular qualities versus a cloudy day, soft shadows, flatter and not specular. The sun is vastly larger than the planet by a magnitude. The cloud diffusing the sun is certainly smaller but due to its proximity to the subject is actually a larger light source and thus softer illumination is produced.

The gif examples are a visual of the same size soft box at different distances to the subject. The further you move the the light source away from the subject the harder the quality of the light simply by the proportion of the modifiers dimensions to the subject.

 

[photoflyer]

I've often wondered why the body makers don't have an aperture bracketing setting like they do for exposure. The camera would maintain a constant exposure and then take X number of shots below, at, and above the selected aperture. Maybe one does and I have not heard of it.

 

[zombiesniper]

I would prefer focus bracketing so I could still use a low f# and maintain a decent DOF in lower light.

 

[JBPhotog]

I've often wondered why the body makers don't have an aperture bracketing setting like they do for exposure. The camera would maintain a constant exposure and then take X number of shots below, at, and above the selected aperture. Maybe one does and I have not heard of it.

Have you checked your "P" mode? Although it isn't bracketing since that term usually is associated with bracketing the exposure, many cameras in P mode use the same exposure but the when the user shifts the shutter speed the f-stop changes so the exposure is the same.

 

[photoflyer]

I would prefer focus bracketing so I could still use a low f# and maintain a decent DOF in lower light.

Interesting idea.

Have you checked your "P" mode? Although it isn't bracketing since that term usually is associated with bracketing the exposure, many cameras in P mode use the same exposure but the when the user shifts the shutter speed the f-stop changes so the exposure is the same.

I will give it a try. Of course with bracketing it automatically takes X number of shots one after the other...automation makes us lazy perhaps.

 

[smoke665]

I think what you are witnessing is the size relationship of the modifier to the subject at different distances.

The size of the modifier in relation to the subject affects the "quality" of the light hard vs soft, but distance affects the "intensity" of the light at a given distance. (Inverse Square Law). Move your light closer at a given power setting the more intense it is.

but I don't think you are seeing dermal or subcutaneous light reflection since this tissue isn't white

The outer epidermis is relatively clear, while the pigmentation lies more in the 2nd dermis layer. The subcutaneous tissue or (hypodermis) you mentioned is a fat layer that actually absorbs more then reflects. My reasoning was, that more intensity would penetrate and be reflected back creating a more pleasing surface with a luminance depth quality, like looking at a clear coated paint surface on an automobile. In any case just an idea at this point, but one I will experiment with further.

 

[JBPhotog]

I think what you are witnessing is the size relationship of the modifier to the subject at different distances.

The size of the modifier in relation to the subject affects the "quality" of the light hard vs soft, but distance affects the "intensity" of the light at a given distance. (Inverse Square Law). Move your light closer at a given power setting the more intense it is.

but I don't think you are seeing dermal or subcutaneous light reflection since this tissue isn't white

The outer epidermis is relatively clear, while the pigmentation lies more in the 2nd dermis layer. The subcutaneous tissue or (hypodermis) you mentioned is a fat layer that actually absorbs more then reflects. My reasoning was, that more intensity would penetrate and be reflected back creating a more pleasing surface with a luminance depth quality, like looking at a clear coated paint surface on an automobile. In any case just an idea at this point, but one I will experiment with further.

I under stand the inverse square law but did you not say you changed the f-stop to f16 at 5.54 feet? If you did, then you compensated for the increased light output by stopping down 2 stops so there is zero increase in light intensity.

I would suggest that your working theory of epidermal, dermal and subcutaneous reflectance has never been discussed in any portrait lighting documentation I have come across. It would make for an interesting experiment but it would also be highly influenced by each unique persons complexion and body composition.

 

[Derrel]

I am wondering if perhaps the working f-stop represents shooting at a different position in the response curve of the sensor. For example with my old Nikon d2x in low light conditions the image looked kind of substandard, but when I was working with the camera in good light it performed admirably. Similarly at ISO 100 the image quality was quite stellar, whereas at ISO 250 the image quality was not so good, and by ISO 640 the image quality was very noisy.

Either way I am looking forward to testing a 2400 Watt-second power pack against a 400 pack. The main light in the first case would probably be about 1200 watt seconds and in the second case of the 400 pack the main light would probably be 100 watt seconds.

 

[smoke665]

I would suggest that your working theory of epidermal, dermal and subcutaneous reflectance has never been discussed in any portrait lighting

I love to read, especially the nerdy stuff. The reflectivity of the skin and the underlying layers gets quite a bit of discussion where lasers are used in medical treatments, but I'll admit I've found little in photography. That's another reason for my post, hoping someone else could comment.

Either way I am looking forward to testing

I am as well, Derrel.

 

[Derrel]

Speaking of testing, back in 2007 I tested an over/under twin umbrella setup. I had a 42 inch dull- white vinyl interior reflecting umbrella mounted on top of a heavy C- stand. The lowernlight had a 40 in Speedotron brand metalized silver umbrella. The idea is that the underneath umbrella fills in the shadows created at the pore level.I was quite impressed with how good the lighting looked on a woman in her mid-forties. No skin smoothing or retouching was needed. Both lights were at 100 watt seconds. The micro contrast is lowered by this well-known over /lighting setup. I used a clamp from Manfrotto to hold the bottom flash on the C-stand shaft. Both lights were on the identical axis, and the fill was more-specular than the main.

My experience has been that one way to get a difference in skin appearance is to change the inherent specularity of the light modifier. my experience has been that more-spectacular modifiers such as silver interior umbrellas look better in black and white than do modifiers that have dull,flat, vinyl interiors. Most current umbrellas made in China have a fairly shiny silvery white cloth interior which is just about halfway between flat non reflective white vinyl and metalized silver umbrellas.

 

[smoke665]

my experience has been that more-spectacular modifiers such as silver interior umbrellas look better in black and white than do modifiers that have dull,flat, vinyl interiors.

I might agree with you. My experience with silver seemed to produce a slightly unnatural skin tone. I have found them helpful in negating the red in thin skin on elderly.

Thanks for sharing the over/under tip. Something I'm going to try real soon.

Over the last month or so I've been going through old boxes of photos scanning them. One thing that's impressed me are how really good some of the old studio prints were, all done without benefit of PS. I've become fairly accomplished with both Lr and Ps, but I also see the need to step back to the beginning if I want to continue to improve.

 

[fmw]

I would ask why do you not see this at wider apertures since the reflected 'penetrated' light would be just as likely to return to the sensor and pass through a wider aperture?

Again just a thought and no experimental data to confirm, but assuming the more powerful the light the deeper it would penetrate and be reflected back.

That's a good suggestion on the gray card.

That is a matter lighting, not aperture. Light lessens with distance at every aperture.

 

[Zintle Gxowo]

When shooting portraits, set a wide aperture of around f/3.5 to f/5.6 to capture a shallow depth of field so that your subject is blurred beautifully.

 

[dxqcanada]

I've often wondered why the body makers don't have an aperture bracketing setting like they do for exposure. The camera would maintain a constant exposure and then take X number of shots below, at, and above the selected aperture. Maybe one does and I have not heard of it.

Can you not just set the mode to Shutter Priority, then add bracketing