I know that white reflective umbrellas produce less specular highlights than silver, but does it matter if you are using a diffusion panel on the front that makes it an octobox? My thinking is that the difference in light production wouldn't change if you use an umbrella in this manner, and if it does it will be minuscule. I only have silver reflective umbrellas so I can't experiment. Any input?
It depends on the panel material. With sufficient diffusion the result is identical. My umbrellas on hand include silver or white 41". Panels include china silk, polysilk, and Rosco Tough Rolux.
I don't think it's gonna matter much with a diffuser. Gold is usually used to warm up the light color. Even diffused it will probably be a very slight bit warmer.
Silver reflects more than white with slightly harsher light.
You can always warm it up by adding a gel.
With a diffuser panel on the umbrella you're talking about a Brolly Box. Good luck
John
If you are asking about the amount of light produced, with diffusion material in front you loose about 1 f-stop of light. It varies depending on manufacturer though so figure 0.6 - 1 f-stop reduction in light. If you are referring to the harshness of the light being produced they would be very close.
The softest (soft shadow area) would be a white umbrella with a white diffuser and the harshest (hard shadows with more specular highlights) would be produced with a silver umbrella without a diffuser.
I have the 86"/218cm Paul C. Buff umbrellas (they had a 3 pack for sale) with shoot-thru white, white interior, and silver interior.
From my experience, if you're diffusing with the same white fabric (1-stop white), the specularity will mostly be lost since you're throwing a white diffusion fabric over it. The light will be softened by the diffusion fabric + a bit more dispersed. You will however, get less light lost with the silver diffused, than a white diffused (because of the silver being more reflective than the white).
RDKirk wrote:
If the front diffusion is sufficient to actually achieve true diffusion, it doesn't matter what's going on behind it.
Agreed with one exception. What is the actual dispersion of the reflected light off of the umbrella surface, white vs silver. If the silver creates a hot centre and more falloff towards the edges at the surface of the diffusion then you will get a more defined shadow transition on your subject. Essentially a silver umbrella may be producing a smaller "effective" light source than a white umbrella. Testing this is required to define your results.
JB, not sure if my standard approach with soft boxes and umbrellas to feather it and use the edge of the light negates most hot spot issues. Also, with the silver Buff parabolics, you can defocus the light so you are still filling the umbrella edge to edge but the rays are dispersed ie, not as parallel off the silver lining. For me, the silver is a quickly set up soft box and out doors in low wind, it puts out more power than a white. I am often scratching for power out doors at 640 ws per strobe.
mrca, you are correct in the defocussing approach for silver umbrellas. I may be assuming people are doing this but those who don’t test their gear will be unaware of the best approaches. The one aspect to watch for, is will the head be defocussed properly with the diffusion panel attached as each head, umbrella and diffusion cover may be slightly different.
p.1 #10 · Silver or White Umbrellas with Diffuser?
JBPhotog wrote:
Agreed with one exception. What is the actual dispersion of the reflected light off of the umbrella surface, white vs silver. If the silver creates a hot centre and more falloff towards the edges at the surface of the diffusion then you will get a more defined shadow transition on your subject. Essentially a silver umbrella may be producing a smaller "effective" light source than a white umbrella. Testing this is required to define your results.
That's not an exception.
I said "If the front diffusion is sufficient to actually achieve true diffusion...."
If you have a hot spot, you have not achieved "true diffusion."
p.1 #11 · Silver or White Umbrellas with Diffuser?
RDKirk wrote:
That's not an exception.
I said "If the front diffusion is sufficient to actually achieve true diffusion...."
If you have a hot spot, you have not achieved "true diffusion."
I disagree. A focussed silver umbrella will always produce a delta from centre to edge across diffusion. All you achieve by adding layers of diffusion is reduce light output but the centre will be hotter than the edge, due to the focussed photons hitting that area. Sure maybe the delta will get to a third of a stop but how many stops of light are you willing to give up, 2, 3, 4 . . . ?
Defocussing a silver umbrella can lower the delta, one will need to test their gear to see where the sweet spot resides and how many layer of diffusion are required for acceptable diffusion.
p.1 #12 · Silver or White Umbrellas with Diffuser?
With diffusion, pretty much a wash between the silver and white umbrella.
That said, sans diffusion the silver umbrella will be more directional, and will "scatter" less light around a room, which may be an issue if you're in a tight space and want more control.
I personally only have one silver interior umbrella, the westcott 7 ft. I find the white umbrellas generally more flexible for most situations. And when I truly want direction control, I generally use a softbox and if needed, a grid.
p.1 #13 · Silver or White Umbrellas with Diffuser?
I come back to the same question, are you aiming your umbrella directly at your subject? I never do that with an umbrella or soft box, I feather the modifier nearly 90 degrees to the subject and the rear of the umbrella slightly ahead of subject. It gives me the maximum softness and directs the main light away from my background so I can light it independently. With grids on my octas, can start with a pure black bg even if it is light gray in color then get precise colors out of gels by controlling the delta between bg reflective and subject incident. ie, the chromazone concept of Dean Collins.
p.1 #14 · Silver or White Umbrellas with Diffuser?
JBPhotog wrote:
I disagree. A focussed silver umbrella will always produce a delta from centre to edge across diffusion. All you achieve by adding layers of diffusion is reduce light output but the centre will be hotter than the edge, due to the focussed photons hitting that area. Sure maybe the delta will get to a third of a stop but how many stops of light are you willing to give up, 2, 3, 4 . . . ?
Defocussing a silver umbrella can lower the delta, one will need to test their gear to see where the sweet spot resides and how many layer of diffusion are required for acceptable diffusion.
If you have a delta across the diffusion surface, then you don't have true diffusion. Whatever is necessary to achieve true diffusion--and that is no delta across the diffusion surface--then do it.
When you have no delta across the diffusion surface, it makes no difference what's behind the diffusion surface.
Are you not paying attention to what I'm actually saying?
p.1 #15 · Silver or White Umbrellas with Diffuser?
On a defocused umbrella, I wonder if a hot spot on the diffusion surface is an area where the light is diffused, just more concentrated. It may not be even brightness but still all diffused. Like I said, feather, I don't aim a softbox or umbrella directly at my subject, and that hotspot of light is going perpendicular to the subject. If the hot spot bothers you, do what my largest octa does, it has an extra layer of diffusion on the inner diffuser, so why not add one to the outer on the umbrella.
