Parabolic umbrellas (flatter not deep) - anyone experimented ?

MidnightUK said:
I thought the first couple of photos might be helpful to someone.
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IMO, not really. I don't think he really knows what he's doing. Images are small and low quality. BG is cluttered and hard to discern shadows, so it's hard to judge. I don't think the head is positioned quite right (light seems to be getting around it a bit), and I don't know if 10ft is an optimal distance for it as a "parabolic." To my eyes, the first shot could be any silver umbrella. Which at 10ft isn't much different from a large reflector/bare bulb.
In the second shot he's changed his lighting ratios by adjusting the aperture and having the power at full in both shots (the main difference I can discern). Additionally, he's lit up the entire smallish white room with spill. And yet the shadows I can discern still seem very similar in hardness, which isn't a big surprise because 10ft is too far for a modifier that is about 4ft in diameter (est) to be particularly "soft."

Basically it shows his results as used, but I don't think it shows what it is especially designed for (and if it's well designed) or what it is potentially capable of.
 
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I don't know whether there's any point in this post of mine, because various people have already explained it very well, but my take on it, and to summarise what other people have said is...
1.. Parabolic is indeed an over-used, misleading, deceptive ane meaningless marketing term
2. Regardless of the design, positioning of the light source is critical, and mostly, it's impossible to adjust the positioning adequately, if at all
3. With a true parabola, there is no discernable spread of light over distance
4. Fitting any kind of diffuser destroys any parabolic qualities
5. The fall off of light is a product of distance, not of design.
 
Garry Edwards said:
I don't know whether there's any point in this post of mine, because various people have already explained it very well, but my take on it, and to summarise what other people have said is...
1.. Parabolic is indeed an over-used, misleading, deceptive ane meaningless marketing term
2. Regardless of the design, positioning of the light source is critical, and mostly, it's impossible to adjust the positioning adequately, if at all
3. With a true parabola, there is no discernable spread of light over distance
4. Fitting any kind of diffuser destroys any parabolic qualities
5. The fall off of light is a product of distance, not of design.
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Thank you! Physics had nearly convinced me of (4) but so many prominent people use things labelled as paras with a diffuser on the front that I was questioning my reason.
 
juggler said:
Thank you! Physics had nearly convinced me of (4) but so many prominent people use things labelled as paras with a diffuser on the front that I was questioning my reason.
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It almost kills me sometimes, so many talk about the BD w/ diffuser as being something special... it's not, it's a small round softbox, and quite likely rather uneven.
 
juggler said:
Thank you! Physics had nearly convinced me of (4) but so many prominent people use things labelled as paras with a diffuser on the front that I was questioning my reason.
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As I've said so many times, a lot of these "celebrity photographers" are really just snake oil salesmen - or, as I like to put it, lost sheep masquerading as sheepdogs.
sk66 said:
It almost kills me sometimes, so many talk about the BD w/ diffuser as being something special... it's not, it's a small round softbox, and quite likely rather uneven.
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I take your point, but with enough distance between the deflector and the outer diffuser, plus an inner diffuser, the deflector can prevent a central hotspot and the overall effect can be very even.
 
Garry Edwards said:
I take your point, but with enough distance between the deflector and the outer diffuser, plus an inner diffuser, the deflector can prevent a central hotspot and the overall effect can be very even.
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Double diffusion on a BD? I've never seen it. But yes, just how uneven it is rather depends on the original design/output... some are *much* more even than others.
 
sk66 said:
Double diffusion on a BD? I've never seen it. But yes, just how uneven it is rather depends on the original design/output... some are *much* more even than others.
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The Lencarta ones have a double diffuser
 
HoppyUK said:
Garry means the fairly new Lencarta folding beauty dishes https://www.lencarta.com/s-fit-80cm-silver-folding-beauty-dish

They actually have triple diffusers with the inner one being double thickness in the centre. They're very versatile and make good softboxes :)
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You're right, I totally forgot that the inner diffuser is double thickness in the centre, which I shouldn't have done as it was my idea and my spec:)

But, 4 years from design start to finished product, so that's my excuse for forgetting...
 
Phil V said:
I would have thought if they did work as true parabolic, they would focus the light and be less use for fill or large groups? Or have I got that wrong?
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That is the main reason of the parabolic shape, to control the
three zones of the light: the spot, the spread and the falloff.

Depending on the position of the light source in the modifier,
the proportions between the three zones may be affected to
the point where, as Phil said, it be undesirable for group or
the contrary if pulled out before spill.
 
I think the easiest way of understanding an adjustable parabolic umbrella is to think of it as a "zooming reflector" much like a focusable flashlight. With the light source very close it produces a wide scatter of light (inefficient), and as the source is moved farther away from the reflector it starts to focus into a tighter pattern. First it will focus at some distance near infinity, and then the point of focus moves progressively closer. In order to focus/concentrate the light you are necessarily taking light away from the other portions of the pattern (but not completely).
 
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