MadCityPhotog NYC NJ wrote:
One great photographer karl taylor explained this here..I cant do better

https://fstoppers.com/studio/what-diffe … tobox-8268

My design is for deep para reflectors like brise and brons. Open or shallow umbrella, even if parabolic, will have focus outside the umbrella (following laws of physics) and keeping light at focus will allow lot of light to escape without hitting the umbrella. Also the magic is seen when para is deep (depth almost same as opening diameter)

I have seen and worked with many para and beauty dishes.

My design can be used for making deep or shallow para..my offers for photography para are deep para only.

also, mine has light mount, crank assembly and strong sturdy design..something impossible to manufacture at the cost of a regular umbrella.
And has open modular design that almost anyone can make or diy at home.

This is a particularly good video.
Makes me want to break out my 8' deep parabolic more.

It also is a good introduction to real parabolic modifiers (as historically the name has been applied), to those who think PCB's offering is a parabolic (even if it is technically a parabolic shape), as the term is normally used for photography. I have a supper dish that is technically a dish, but I probably won't trade my big beauty dish for it.

J O H N  A L L A N wrote:

This is a particularly good video.
Makes me want to break out my 8' deep parabolic more.

It also is a good introduction to real parabolic modifiers (as historically the name has been applied), to those who think PCB's offering is a parabolic (even if it is technically a parabolic shape), as the term is normally used for photography. I have a supper dish that is technically a dish, but I probably won't trade my big beauty dish for it.

there's a whole generation of people lacking that knowledge, myself included, for lack of being able to afford or even have access to see what the real thing can do

I wonder how PCB gets away with using the parabolic term if it's not an actual parabolic light modifier?
kind of misleading IMO

Solas wrote:

there's a whole generation of people lacking that knowledge, myself included, for lack of being able to afford or even have access to see what the real thing can do

I wonder how PCB gets away with using the parabolic term if it's not an actual parabolic light modifier?
kind of misleading IMO

Yeah, it's specifically meant to mislead. They get away with it because (as you stated there are a lot of people who've not used a real one because of cost) and technically it's a parabolic shape that modifies light.

Herman Surkis wrote:
Interesting that the local PCB hater is not taking shots at Wescott who have a similar offering and design.

? who ?

Solas wrote:
........I wonder how PCB gets away with using the parabolic term if it's not an actual parabolic light modifier?
kind of misleading IMO

Well, PCB "get(s) away with it" for exactly as my good friend John Allen so correctly stated:

J O H N  A L L A N wrote:
........to those who think PCB's offering is a parabolic (even if it is technically a parabolic shape), as the term is normally used for photography.

Yes, there you have it from one of the great mathematical minds of our time: ".... PCB's offering is a parabolic...." BECAUSE "....it is technically a parabolic shape".

In fact, if they (any reflector) wasn't parabolic in shape it wouldn't be a parabolic reflector! (Technical or otherwise.I mean what does "technical" have to do with it? It's either a parabolic or it isn't.)

If you pay close attention to what Karl Taylor is saying, he goes to great length to help people understand that a parabolic reflector only functions as a parabolic when the light is in the focused  position (and he correctly refers to this, which is rare in these discussions).

Karl then goes into how it changes the light when you move it to any other position (so it's not acting as a parabolic reflector). Push it in and the light focuses closer (Karl notes that the light gets brighter), pull it out and the light has no focus and becomes more diffused. I noted an odd point, when the light is moved into the reflector, Karl mentions it does "appear" to become brighter, but only if you are still within the focus field of the reflected light (studios are small spaces). If you move far enough away, beyond where the light would be focused as a single point, the light will actually become diffused and quite a bit less strong than the light from the same reflector, but with the light at the focus point of the parabolic.

And now for this piece of "interesting" if confusing, piece of information:

MadCityPhotog NYC NJ wrote:
My design is for deep para reflectors like brise and brons. Open or shallow umbrella, even if parabolic, will have focus outside the umbrella (following laws of physics) and keeping light at focus will allow lot of light to escape without hitting the umbrella. Also the magic is seen when para is deep (depth almost same as opening diameter)

(I'm having trouble following this, I suspect English is not the writer's first language.)



There would indeed be some light loss if the focus point was in fact outside the plane of the umbrella opening. The PCB Parabolic's all have the focus point across the rim of the umbrella, and there is even a small reflector plate to prevent light spillage. There is no light loss (with PCB's Parabolic), all the light (except that that would somehow go back through the body of the strobe head) is reflected off the umbrella surface.

Math, the final frontier. Ahh,  that Greek guy Euclid, gotta love those Greeks (and the Geeks like Karl Taylor!)

John
Sponsored Photographer, Paul C. Buff Companies (Alien Bees, White Lightning. Zeus, and Einstein)
And I'm not a Geek. Actually passing plane geometry as a freshman in High School does not qualify me. However, I do (please note) actually live on Euclid Avenue! (Even I can't make some of this up!)
--
John L. Fisher
700 Euclid Avenue, Suite 110
Miami Beach, Florida 33139
(305) 534-9322
http://www.johnfisher.com

John Fisher wrote:

Ok in that case.. is the PCB PLM the same concept and works the same way as the bron one Mr Taylor is using? What about the one in the kickstarter ?

John Fisher wrote:
Math, the final frontier. Ahh,  that Greek guy Euclid, gotta love those Greeks (and the Geeks like Karl Taylor!)

I quite enjoy math, though am a bit slow to it due to dyscalculia.. however that does not stop my interest..when I do get it, it's quite enjoyable. In university I became a big fan of statistical inferences, quantum physics, and fluid dynamics.. bedtime reading as a kid was "hyperspace"

MadCityPhotog NYC NJ wrote:
Dear John n all my friends,
I didnot open the thread with an intention of PLM comparison or blaming one product over other. .

Yes of course, that came from my interest to see if this device had similarities as the PLM. If so, it has to be clear what those features and advantages are. If not, I'm intrigued to know why or if it produces results that are closer to that as the ones in Mr. Taylor's vids.

MadCityPhotog NYC NJ wrote:
My english may not be perfect..but my goal is clear..

That's quite all right, I speak from 4 different languages.. often my english slips, despite it being my native, I often flip in between languages or get the words mixed up I think most people in globalized society recognize that, and i don't think it influences anything in any way because it is an intriguing project.

Solas wrote:
Ok in that case.. is the PCB PLM the same concept and works the same way as the bron one Mr Taylor is using? What about the one in the kickstarter ?

You ask an important question (perhaps without realizing it). First, yes, all parabolics when the light source is positioned at the focal point of the parabola, produce the same light. It is a very unusual light which up until now had been missing from the studio. This light source (a parabolic umbrella with the light positioned at the focal point of the parabola) produces light waves in parallel to each other. This is exactly as sunlight appears to us. The sun is so far away that the light appears to be striking any subject evenly, but very directionally. As you turn your subject in the sun light, you will see shadows appear in different lengths, on different sides, or disappear all together. A parabolic umbrella with the light source at the focal point of the umbrella is like having a sun in your studio!

One of the phenomenons of this light is that in order to light your subject full length, the umbrella has to be quite large. Typically the umbrella has to be at least as wide across its diameter as your subject is tall. You can get some relief by moving the umbrella slightly up in the air and angling it down (creating a longer shadow path), but you obviously need a lot of ceiling height to do this.


Model: Destinee Smith, lit with a single large PLM located slightly to the stage left.

While Karl was showing how to use the light for beauty work (he positioned himself right in front of the umbrella), I like to move it slightly to the side (particularly for full length catalog work) so I get some shadowing which adds depth to the image. There is even one of my more well known images where I positioned the light way to the side for a very dramatic lighting effect.


A single light source, Parabolic Umbrella located stage right. The background was a white studio backdrop. the light source was clearly very directional.

Parabolic reflectors have become one of the most frequently used light modifiers today because of this "sunlight in the studio" effect. While I do not object to people using really expensive parabolics (I personally have used a very big Profoto parabolic), I do recommend that anyone should own a Paul C. Buff Parabolic (get the big one!) for the simple reason that it is a very effective parabolic, and allows you to use and understand one of the premier new light modifiers of the last few decades. And it's cheap. (Or as I'm sure my sponsor would prefer, inexpensive!) If you don't own Paul Buff lights, get the PLM with the shaft mount, you can use it with any light that can be used with an umbrella. You have to be more careful setting it up so that the light is in the proper position, but Karl's demonstration shows how you can do this. (Or do what I used to do, sight the light across the umbrella opening, and you're very close to the proper location.)

I am a huge fan of parabolics (and the Paul C. Buff PLM system), I use them all the time and learn more about how to position them every day.

John
Sponsored Photographer, Paul C. Buff Companies (Alien Bees, White Lightning, Zeus, and Einstein)
--
John L. Fisher
700 Euclid Avenue, Suite 110
Miami Beach, Florida 33139
(305) 534-9322
http://www.johnfisher.com

Herman Surkis wrote:
Now here is an interesting question.
If you mount your light at the focus point. Take the umbrella out in the Miami sun, and point it at the sun, will you melt your light?
John could you try this and let us know. 

That is an interest ing q..
I want to try it on one of our sunny days here..this city gets some of the most sunny in canada !

J O H N  A L L A N wrote:
Just because something is mathematically a parabola doesn't mean it is producing the same lighting. It's not the same modifier.

Shallow or deep.
If it has the same number of ribs and is the same size, and using similar fabric, at the focus point they will all produce parallel light rays, which strangely enough will be the *same* quality and look of light.

Stop arguing your hate of PCB and start arguing the facts.

You are correct that a deep dish style, which can be focused is a different modifier, but when the light is not at the focus point it is NOT a Para. It is simply a huge umbrella that can be focused. And the focusing changes the quality of light. Funny thing is that you can do that with any umbrella (change the quality of light). It is just that the big boy deep umbrellas do it better.

And perhaps the real problem might be that the umbrellas that you like were misusing the term Parabolic, since the only time they were true para's was when the light was at the focus point.

An interesting design would be one where you could focus it, by moving the light source to change the focus point, and the umbrella would change shape to keep the light at the focus point. And if you you think a Briese is expensive, you ain't seen nothing. Actually, I vaguely remember seeing such a thing, and it was hugely expensive, and used for research.

Solas wrote:

That is an interest ing q..
I want to try it on one of our sunny days here..this city gets some of the most sunny in canada !

Don't try it!

The answer is given by the OP, where he talks about using his stuff to boil water.
Precisely how a portable solar heater works. Takes the parallel rays of the sun and reflecting them brings them to a focus point. And strangely enough a lens does that as well, only differently.

Herman Surkis wrote:

Don't try it!

The answer is given by the OP, where he talks about using his stuff to boil water.
Precisely how a portable solar heater works. Takes the parallel rays of the sun and reflecting them brings them to a focus point. And strangely enough a lens does that as well, only differently.

..good point.. on second thoughts, knowing me.. i could burn water (actually managed to set a boiling tea kettle of water on fire...believe it or not).

Solas wrote:

..good point.. on second thoughts, knowing me.. i could burn water (actually managed to set a boiling tea kettle of water on fire...believe it or not).

However if lost in the bush...
Could be useful to boil tea or start a fire.

Herman Surkis wrote:
Shallow or deep.
If it has the same number of ribs and is the same size, and using similar fabric, at the focus point they will all produce parallel light rays, which strangely enough will be the *same* quality and look of light.

Stop arguing your hate of PCB and start arguing the facts.

You are correct that a deep dish style, which can be focused is a different modifier, but when the light is not at the focus point it is NOT a Para. It is simply a huge umbrella that can be focused. And the focusing changes the quality of light. Funny thing is that you can do that with any umbrella (change the quality of light). It is just that the big boy deep umbrellas do it better.

And perhaps the real problem might be that the umbrellas that you like were misusing the term Parabolic, since the only time they were true para's was when the light was at the focus point.

An interesting design would be one where you could focus it, by moving the light source to change the focus point, and the umbrella would change shape to keep the light at the focus point. And if you you think a Briese is expensive, you ain't seen nothing. Actually, I vaguely remember seeing such a thing, and it was hugely expensive, and used for research.

I'm willing to accept that you (you Herman) could not tell the difference visually in light produced between the two.

J O H N  A L L A N wrote:

I'm willing to accept that you (you Herman) could not tell the difference visually in light produced between the two.

So basically you are saying that parallel light rays that are the same colour temp, and coming off similar fabric (the type of fabric gives a granular particularity to the combined rays), and the same intensity, would be visually different if from a PLM, Profoto, Bron, Briese umbrella.

Ok, interesting physics going on, but whatever.

Herman Surkis wrote:
So basically you are saying that parallel light rays that are the same colour temp, and coming off similar fabric (the type of fabric gives a granular particularity to the combined rays), and the same intensity, would be visually different if from a PLM, Profoto, Bron, Briese umbrella.

Ok, interesting physics going on, but whatever.

What I'm saying is that I believe that it is entirely plausible that you Herman Surkis are incapable of seeing the visual distinction in the light produced between a PCB PLM and a Briese or Broncolor parabolic.

Herman Surkis wrote:
Question for MadCity

So as you move the light in and out of a deep Para, does the light exiting the umbrella remain Parabolic?
If so how is that done?

Light isn't parabolic or non-parabolic, you're misusing the term. The reflector is parabolic in that it is in the shape of a parabola.

MadCityPhotog NYC NJ wrote:
Shallow umbrella is good for collecting sunlight or satelite signal. Coz for this purpose the area of opening (diameter) is the key, as we dont worry about spill, in this case.
A medium deep (focus just below the opening) works better for parabolic microphones. Again for collecting and focusing sound wave at the focus.
google for "parabolic mic".

The quality of light coming out will vary to some extent depending on reflecting surface. Glossy curved and mirrored surface is best for cooking and heating.
BUT it is the shape of the para (deep shallow etc) defines the quality of light. For a deep para u can move the light all the way back for hard light, and move to focus which it is the brightest spot and at the very edge to get almost a huge ring light effect. This actually works very well for fabric and fashion shoot.

For a shallow one this difference is not significant (transition from harsh to soft) and internal reflection happens differently.
This is just how they are..

Thanks

Which is why a deep Para is such a neat light modifier.

But the question is still, does the light exiting the Para remain parallel as you move the light in and out of the reflector?
Or is the light only parallel at that one point where it is at the focus point for the design of that Para reflector?

Herman Surkis wrote:
True, I misused the term.
No reason why, since it is just as long to type parallel as parabolic.
So to be correct, lets pretend that I was asking if the rays remain parallel on exiting the reflector.

I believe the rays are at their most parallel with the light positioned at the focus point.

J O H N  A L L A N wrote:

I believe the rays are at their most parallel with the light positioned at the focus point.

I think that is a bit like you are either pregnant, or not pregnant.

But I get what you mean.
They approach being parallel as you approach the focus point and are parallel at the focus point.

J O H N  A L L A N wrote:

I believe the rays are at their most parallel with the light positioned at the focus point.

There are a number of issues here. Some with the optics and some with the terminology.

The defining characteristic of a parabolic reflector is that when the light is at the focal point, the light rays exiting the parabola are parallel to each other.  This is true whether you paid $100 for the reflector or $1,000.

This is not to say that there aren't differences between various brands of parabolic reflectors.

One possible difference is whether or not the reflector is a true parabola.   My understanding is that this isn't an issue for commercially available parabolic reflectors.

Another difference is the ability to "defocus" the system.  If the light is moved forward or backward from the focal point, the rays exiting the reflector will not be parallel.  You can get them to focus at a finite distance in front of the reflector, or you can have them diverge as they exit the reflector.   Although some will argue that this is no longer a parabolic system, it still provides useful light.   Different styles of parabolic reflector offer different methods for de-focusing the light source.  Generally, the shallower the parabola, the more sensitive it is to positioning differences.  A 1" movement on a PCB PLM, may give you as much change as a much large movement on a deeper modifier.   Which is better depends on your style.


Many parabolic reflectors mount the light in front of the reflector, pointing away from the subject, and into the reflector.  If the reflector was perfect, and all exiting light was absolutely parallel, the light would cast a shadow.  For a 5' diameter reflector, you would get a 5' circle of light, with an 8 inch hole in the center (the shadow of the light fixture).  The actual focal point is infinitesimally small.  It turns out the flash tube is bigger than this and therefore the light rays exiting the reflector are not perfectly parallel.  If they are close, you may way to defocus a bit to eliminate the shadow of the light source.

All of these issues and differences are relatively minor.  If you know what you are doing, you can get excellent results from either a $100 or a $1,000 parabolic reflector.   The problem is that if you get used to one style (deep or shallow), you will hate the other.  Your intuition on how far to achieve various effects will be wrong.  If you're not careful, you may wind up dismissing the other style as being unusable.

The bottom line is that there is a big difference between non-parabolic reflectors, and parabolic reflectors that allow the light source at (or near) the focal point.  This difference is far greater than the differences between various brands of parabolic reflectors.  When it comes to parabolic reflectors, the fundamental difference is the diameter of the reflector, not whether it is deep or shallow.