kenyee wrote:
Hence my mentioning the 2xdiameter range for the beauty dish "effect", after which is looks like an umbrella for a while (not sure of cutoff point before it becomes a bare head).
Sounds like a similar limitation applies to parabolics, and also your experience shows their max useful distance is 4-10' away? A broncolor 220 is 5'7". Profotos range from 10' in diameter to a little under 5'. I'm guessing the max limit is still closer to the diameter of the parabolic?
The problem with assumptions is the premise upon which they are founded.
With these modifiers you are dealing with two very different issues that affect light quality.
First in terms of design, I can't think of two more diametrically opposed modifiers than a beauty dish and a parabolic reflector. I believe it is a mistake to equate optimum working distances of one to another. For one thing you are not dealing with a dead zone or peripheral hot spot on a parabolic. And although you might be able to alter the dead zone, you can't defocus a BD either. Oddly, it is often easier to control spill with a large parabolic than it is with even a small BD. A similar sized parabolic should have a much broader sweet spot than a BD, in both coverage and distance.
The other part of the equation is the size of the light source, which everyone understands has major influence on light quality. The good news is that the relationship between modifier size and distance to your subject is very predictable since it is governed by Inverse Square Law. ISL states that halving the distance to subject quadruples apparent size. Conversely, doubling the distance to subject quarters the modifiers apparent size, making a very big modifier small in a hurry. As an example that huge parabolic may be relatively the same size to your subject at 10' as a small BD is at 3'. Size diminishes exponentially with distance.
And this doesn't even touch on ISL's effect on fall off, which is something else that must be confronted when moving lights around.
It's interesting to watch folks running off to buy a "parabolic reflector" with no idea of how they intend to use it, apparently because it's their affordable entry into the rarefied world of the Briese, Para, Giant or EL-Octa. Sadly, I think this is similar to the recent BD rage, where everybody had to have one and then had no idea how to use it. No wonder Benji hates umbrellas.
I bow to the marketing master though. Long live King Luap.
Carmen Miranda wrote:
It's interesting to watch folks running off to buy a "parabolic reflector" with no idea of how they intend to use it, apparently because it's their affordable entry into the rarefied world of the Briese, Para, Giant or EL-Octa. Sadly, I think this is similar to the recent BD rage, where everybody had to have one and then had no idea how to use it.
If this does act like 80% of a true parabolic, like the AB BD did compared to the Mola BD, it wasn't just marketing. It lets us amateurs play with something close enough to what the pros use, at a much lower cost. The final images made by folks like CD will let us know how well Paul did. And people will have to ask dumb questions and make mistakes to learn how to use this. I'm certainly doing my share of asking dumb questions as I try to understand what it should be doing
Thanks for the clarifications all...hopefully we'll have some good examples by this weekend.
Carmen's points are extremely valid and well said.
I pre-ordered a full set of 6, not because I want parabolic reflectors, but to experiment with. I'm after fast setup, lower cost EL Big Octa's to equip our wedding photographer's with. If the light quality is 80% as good (when used outside, on location) as the world's greatest soft box (as the El Octa is often called), at 1/20th of the cost (including the strobe), I think I'm on a winner.
My concern is the diffuser fabric has been deliverately made slightly loose, so it doesn't bend the ribs in, changing the angles. This won't be great in the wind. However, the white versions without a front difuser, might turn out work nicely- though brolly's without front diffusers tend to catch the wind more...
Carmen Miranda wrote:
The problem with assumptions is the premise upon which they are founded.
With these modifiers you are dealing with two very different issues that affect light quality.
First in terms of design, I can't think of two more diametrically opposed modifiers than a beauty dish and a parabolic reflector. I believe it is a mistake to equate optimum working distances of one to another. For one thing you are not dealing with a dead zone or peripheral hot spot on a parabolic. And although you might be able to alter the dead zone, you can't defocus a BD either. Oddly, it is often easier to control spill with a large parabolic than it is with even a small BD. A similar sized parabolic should have a much broader sweet spot than a BD, in both coverage and distance.
The other part of the equation is the size of the light source, which everyone understands has major influence on light quality. The good news is that the relationship between modifier size and distance to your subject is very predictable since it is governed by Inverse Square Law. ISL states that halving the distance to subject quadruples apparent size. Conversely, doubling the distance to subject quarters the modifiers apparent size, making a very big modifier small in a hurry. As an example that huge parabolic may be relatively the same size to your subject at 10' as a small BD is at 3'. Size diminishes exponentially with distance.
And this doesn't even touch on ISL's effect on fall off, which is something else that must be confronted when moving lights around.
It's interesting to watch folks running off to buy a "parabolic reflector" with no idea of how they intend to use it, apparently because it's their affordable entry into the rarefied world of the Briese, Para, Giant or EL-Octa. Sadly, I think this is similar to the recent BD rage, where everybody had to have one and then had no idea how to use it. No wonder Benji hates umbrellas.
I bow to the marketing master though. Long live King Luap.
Looking forward to your stuff c.d.
Good luck. ...Show more →
You're analysis is fundamentally flawed. Inverse square law applies to light intensity, but not to apparent source size. A 6' source will appear the same size at 6' as a 3' source at 3' both in shadow structure and catch light size.
kenyee wrote:
If this does act like 80% of a true parabolic, like the AB BD did compared to the Mola BD, it wasn't just marketing. It lets us amateurs play with something close enough to what the pros use, at a much lower cost. The final images made by folks like CD will let us know how well Paul did. And people will have to ask dumb questions and make mistakes to learn how to use this. I'm certainly doing my share of asking dumb questions as I try to understand what it should be doing
Thanks for the clarifications all...hopefully we'll have some good examples by this weekend. ...Show more →
PLM, when used with a properly placed light unit, acts as a 100% true parabolic, less the focal anomalies associated by 16 segments vs an absolute circular geometry and the slight defocusing effect of silverize fabric vs a polished metal surface. By contrast, the "giant "paras" allow on the order of 20 - 30% of the light from the tube to escape the parabolic surface and to appear as unfocused peripheral stray light. The aforementioned anomalies are, of course still present - to an even greater degree with eight segment "paras".
The softening action on the fabric is, for most uses, a good thing because it results in a soft feathering of the edges of the pattern rather the harsh cutoff line that would result otherwise.
Deezie wrote:
Paul - you have several posters on here gushing about your products, then you come onto this forum and post defensive, glib comments. You continually self-destruct and do damage to your brand. How is it you just don't understand this? Let the photographers gush while you sit back and take all the credit. Telling someone that they're not dealing with the real world is insulting. When you get defensive, it gives people a reason to believe that there's a motive to do so.
I really don't give a rat's ars about your opinion of my demeanor, marketing methods or other quirks you might perceive. I think your opinion of about everything I do is quite well known to readers here so I suggest you go take some pictures or something. Oh darn, I hope I don't lose you as a customer and friend or personal analyst/business mentor.
Paul Buff wrote:
You're analysis is fundamentally flawed. Inverse square law applies to light intensity, but not to apparent source size. A 6' source will appear the same size at 6' as a 3' source at 3' both in shadow structure and catch light size.
Paul,
I'm no physicist, but here is what I have to support my claim:
Carmen Miranda wrote:
The problem with assumptions is the premise upon which they are founded.
Words come back to haunt us, don't they.
Paul, I think I see the error of my way. The problem with my analogy is that ISL relates to quantity emanating FROM a point source, not necessarily TO a subject, which is rarely a point (other than maybe to one's eye).
However, I'm still convinced that apparent size is inversely proportional, but since I lack the academic chops to prove it, I'll stand down for now.
Here are some photos from this afternoon. All f/4.0, 1/250, ISO 200. Profoto AcuteB 600R providing the illumination, about six feet/seven feet away. Small PLM. NO FILL.
http://img.photobucket.com/albums/v509/cdembrey/IMG_9881-a-8x5.jpg
The PLM is about 2' from the wall. The Profoto Disc reflector is doing a good job killing spill, note thin line of light on the wall. Also note the very small amount of stray non-collimated light on the wall, compare to what you would get with a conventional umbrella.
The following pix are of a supercharged racing engine. Just pices, no overall shot.
http://img.photobucket.com/albums/v509/cdembrey/IMG_9911-a-8x5.jpg
This is the supercharger. Nice crisp photo showing texture in the cast housing. On the lower part of the housing is cast the name Magnuson, See how this is bottom lit by the reflected light from the polished rocker cover. Not much difference in specular highlights from PLM and reflected light from the polished aluminum.
I'll post some people shots in a couple of days.
BTW what I shoot is mostly product. Doesn't make much difference if it's engine parts, jewelry or clothing -- they all benefit from crisp light.
Carmen Miranda wrote:
Words come back to haunt us, don't they.
Paul, I think I see the error of my way. The problem with my analogy is that ISL relates to quantity emanating FROM a point source, not necessarily TO a subject, which is rarely a point (other than maybe to one's eye).
However, I'm still convinced that apparent size is inversely proportional, but since I lack the academic chops to prove it, I'll stand down for now.
Never mind.
Carmen,
Your latter statement is probably closest to true. ISL is based off the fact that a point source will distribute its energy in a spherically symmetric manner, a shell of energy if you will. Since the area of a sphere is based on the square of its radius, you arrive at ISL. Kinda like the amount of rubber in a balloon doesn't change as you blow it up--just gets thinner.
Put a reflector in the way of half of the sphere of propagation and collimate the propagated light (ideal parabolic reflector source), and you'll see that ISL will fall apart. Sorta like why lasers don't follow ISL. ISL works well enough on umbrellas/softboxes/reflectors/etc since the face of the modifier can be thought of as a distribution of point sources.
Now, for the math geeks amongst us, we could do some ray tracing and find out the propagation characteristic of a parabolic reflector setup with reasonable accuracy.
Or we could just go shoot the dang things and figure out how they work.
Hope this helps, and doesn't obfuscate the idea. While I have shot very little with non-continuous light sources, I appreciate your contributions a bunch, along with many others.
John Ng wrote:
Great photos. So the PLM fits Profoto Acutes without filing the shaft? I may have to look into one.
Thanks.
Thanks John.
The shaft diameter is OK -- but the end of the shaft is square. So you will have to chamfer (bevel) the end to be able to insert it past the locking ball. Look in from the back side to see the shiny ball.
You should be able to easily (?) do this with a file. The end of the shaft seems to be made of brass. Mine were machine with a lath, nice to have a client with a machine shop
BTW you also have to do this with Hensel umbrella shaft ends to use with Profoto. Elinchrom doesn't need to be modified.
bugaglo wrote:
What exact diameter of the shaft in mm? My old profoto heads has hole less than 8mm, around 7.9mm, Thanks.
I have no idea. All I know is that the Buff and Hensel 8mm shafts fit. From watching other photographers work I've never seen an umbrella that didn't work.
I've seen a very old Profoto head that seemed much tighter than the present one
If I remember I'll check the shaft diameter the next time I'm in a machine shop.
I am 500 miles from home burying my mother in law today and tomorrow and have to work from a tiny laptop, so I can't answer things in the detail I like. Things are getting way complicated here and much is not understood about some relatively simple relationships. Go out and look at your satellite tv dish for clues - this is a classic parabolic dish tuned for maximum focus and efficiency. The points to remember are simple:
1. The light source should be a bare bulb with back plate - ie AB/WL, and should be located approximately at the edge of the ribs . . . never extended out far from the umbrella - this just defeats the whole design and serves no purpose. The useful range is plus or minus about 5" from this focal point. Any other light placement destroys the parabolic relationship.
2. Don't us any sort of reflector other than a spill kill plate. Reflectors will simply focus the light into the center of the PLM and diminish it's effective size and effectiveness.
3. This all by design to yield maximum light transfer and to minimize the need for heavy mounting hardware and unproductive cantilevered weight. You can easily use the 86" PLM on a light to medium weight standard light stand without tipping or sandbags, etc. Someone commented "This thing is heavy" . . . absolutely not true. Far lighter than any softbox or other modifier of this size.
4. The 16 sided design approximates a circle far better than standard 8 spoke umbrellas. This yields nice circular catchlights with minimal appearance of spokes and segments associated with 8 spoke umbrellas.
5. The 64" PLM is approximately the same size as the large Softlighter. If the white front diffuser panel is used on the silver PLM the effect is very similar to the Softlighter, but the light output is about 3/4f higher. This is what we recommend for most users . . . 64 or 86" Silver PLM plus optional front diffuser panel. The 7" PLM reflector has little effect on the pattern or light output, but eliminates any side spill. They're due next week.
6. The White PLMs are totally different and result in typical white umbrella in shoot through or bounce mode. Again, the 16 spoke design and large size, together with the well engineered positioning and shape result in extremely even lighting of the surface and maximal transfer of light to the subject. The low cantilevered weight and close mounting allow very large light source to be used in small studios without obtrusive hardware and expensive bulky mounting.
7. Outdoors, anything this size is going to act like a sail and cannot be kept from blowing away in the wind without someone standing there and hanging on to it!!
8. The most outstanding use of the silver PLM is for overpowering the sun with a giant light source, from substantial distances with smallish light units. With 600WS it is easy to obtain f22 to 32 at 10', ISO 100. If that won't get it you've aren't dealing with the sun we have on earth or you need to study the use parameters of distance, power, placement and general lighting physics.
I hope I am not coming off abrupt here - just trying to clear up some basic misconceptions in the small time I have.
Last note: To use modifiers like this with camera flashes the first rule is to convert the flash to a bare bulb sort of pattern. You cannot effectively use a parabolic like this with a focused beam flash stuck out away from the focal point of the parabola - this just destroys the relationships and yields no substantial result, particularly with silver versions.
I will prepare more detailed info when I get home. We have a basic instruction document that is available upon request. photos examples of coverage and output are coming ASAP.
First, that you're taking time to answer your customers concerns at a time like this shows a real dedication and it is noted.
Second, when you have time, could you let us know whether you'll be considering a 7mm shaft version of the product and / or an official adaptation kit? You have the attention of some of the "big boys"' customers.
Sean Baker wrote:
Second, when you have time, could you let us know whether you'll be considering a 7mm shaft version of the product and / or an official adaptation kit? You have the attention of some of the "big boys"' customers.
Not gonna happen. That's like asking Nikon to use the 5D2 sensor in their D300 at the same price point so you don't have to fork out $8k for a D3X.
