Speedlite difuser

This illustrates my point about size affecting shadow presence. First photo is flash lens only, second lens has a diffusing paper (bond) in front and exactly the same size as the lens, and the third has a 5x7" softbox in front.

PacAce wrote in post #6177079
That is exactly my point. Light path through a diffusing material would be unpredictable. However, light path through the wide panel of the flash would be just like it is through a lens and, hence, it's not technically a diffuser. That's the only point I was trying to make. I do agree with your other points, though.

I understand what you're getting at, I just don't see how light passes through a wide panel any more or less predictably than a white piece of paper or frosted glass. In all cases there will be a broad area in which the light rays will land and a maximum angle of spread but within that, which ray lands where is, for all practical purposes, random. Fire a single light ray into that wide panel and it could be redirected anywhere within an angle of around 114 degrees. Without analysing the wide panel at a microscopic level, there's no way to predict where specifically it will land.

I should say that the above isn't really my point - just trying to interpret what the authors wrote.

Hermes wrote in post #6177352
I understand what you're getting at, I just don't see how light passes through a wide panel any more or less predictably than a white piece of paper or frosted glass. In all cases there will be a broad area in which the light rays will land and a maximum angle of spread but within that, which ray lands where is, for all practical purposes, random. Fire a single light ray into that wide panel and it could be redirected anywhere within an angle of around 114 degrees. Without analysing the wide panel at a microscopic level, there's no way to predict where specifically it will land.

I should say that the above isn't really my point - just trying to interpret what the authors wrote.

Based on your post here, I can only suspect that you do not have an EX flash with a wide panel on it. If you actually saw what it looks like, I'm sure you'll have a different opinion about it.

PacAce wrote in post #6177787
Based on your post here, I can only suspect that you do not have an EX flash with a wide panel on it. If you actually saw what it looks like, I'm sure you'll have a different opinion about it.

Believe it or not I have 3. In fact, I actually got my 430 out of my camera bag and double checked that I wasn't remembering it wrongly when I read this.

My point is that if a single light wave or a thin laser pointer were fired through a pane of glass it would go (more or less) straight through, in which case you'd say its path was predictable. The same can be said for a mirror. If you fired it through a wide panel, depending on the exact point it strikes, it could go anywhere. If it hits a shallow point in between four micro-prisms it will go roughly straight, if it hits a prism at its peak it will be redirected sharply up, down, left or right depending on which side it strikes, and every in-between scenario is also possible.

Are you honestly telling me that if I put you in a square room with a laser set up pointing through a wide panel, you'd be able to mark the exact spot on the wall that the laser would end up hitting when turned on, and be able to keep doing it accurately as the laser was moved a few millimetres down, sideways, e.t.c.? - if its output was predictable, surely you'd be able to. The user manual for my 540EZ actually recommends pulling the wide panel out when bouncing the flash upwards to produce a catchlight in the subject's eyes - to me that's a pretty clear indication from Canon that it's designed to diffuse light.

Hermes wrote in post #6178289
Believe it or not I have 3. In fact, I actually got my 430 out of my camera bag and double checked that I wasn't remembering it wrongly when I read this.

My point is that if a single light wave or a thin laser pointer were fired through a pane of glass it would go (more or less) straight through, in which case you'd say its path was predictable. The same can be said for a mirror. If you fired it through a wide panel, depending on the exact point it strikes, it could go anywhere. If it hits a shallow point in between four micro-prisms it will go roughly straight, if it hits a prism at its peak it will be redirected sharply up, down, left or right depending on which side it strikes, and every in-between scenario is also possible.

Are you honestly telling me that if I put you in a square room with a laser set up pointing through a wide panel, you'd be able to mark the exact spot on the wall that the laser would end up hitting when turned on, and be able to keep doing it accurately as the laser was moved a few millimetres down, sideways, e.t.c.? - if its output was predictable, surely you'd be able to. The user manual for my 540EZ actually recommends pulling the wide panel out when bouncing the flash upwards to produce a catchlight in the subject's eyes - to me that's a pretty clear indication from Canon that it's designed to diffuse light.

Yes, I am. The behavior of prisms, like optical glass, can be predicted and, hence, so can the path of the light traveling through it. Why do you supposed prisms are used in SLR cameras and binoculars. And how about their use on focusing screens in the form of ring microprisms and split prism focusing aids?

BTW, the flash manual tells you to pull out the white panel for the catch light, not the wide panel. Yes, the white panel could be considered as a diffuser although it's rightly a reflector since light isnt' really passing through it. But the wide panel is not.

I think we've taken this thread way off topic so this will be my last post on the subject.

PacAce wrote in post #6180445
Yes, I am. The behavior of prisms, like optical glass, can be predicted and, hence, so can the path of the light traveling through it. Why do you supposed prisms are used in SLR cameras and binoculars. And how about their use on focusing screens in the form of ring microprisms and split prism focusing aids?

BTW, the flash manual tells you to pull out the white panel for the catch light, not the wide panel. Yes, the white panel could be considered as a diffuser although it's rightly a reflector since light isnt' really passing through it. But the wide panel is not.

I think we've taken this thread way off topic so this will be my last post on the subject.

It can't tell me to pull out the white panel as there is no white panel on the 540EZ, only a wide panel which acts as a diffuser Have a look at page 23 if you don't believe me - http://66.49.230.119 …es_meters/canon​_540ez.pdf

Anyway, I agree that we're probably getting into an endless debate and that the OP's question about the practical effect of the wide panel and of diffusion has been answered. One of them 'agree to disagree' ones.

Hermes wrote in post #6181047
It can't tell me to pull out the white panel as there is no white panel on the 540EZ, only a wide panel which acts as a diffuser Have a look at page 23 if you don't believe me - http://66.49.230.119 …es_meters/canon​_540ez.pdf

Anyway, I agree that we're probably getting into an endless debate and that the OP's question about the practical effect of the wide panel and of diffusion has been answered. One of them 'agree to disagree' ones.

Hermes, I don't understand why you insist that any lens that throws the light to a FOCUSED area which happens to be wide enough to cover 14mm lens is a 'diffuser' Q: What is the difference of a 14mm focused area and a 105mm focused area? A: The area of focus.

The point of a diffuser is that at each and every point on the diffusers's area, rays of light go out at random angles. The diffusion pertains to the directionality of light at each point...a frosted surface provides diffusion, the wide lens provides focused light within a wide area (there may be some diffusion effect, but the light is primarily directed by the lens system).

Wilt wrote in post #6181205
Hermes, I don't understand why you insist that any lens that throws the light to a FOCUSED area which happens to be wide enough to cover 14mm lens is a 'diffuser' Q: What is the difference of a 14mm focused area and a 105mm focused area? A: The area of focus.

The point of a diffuser is that at each and every point on the diffusers's area, rays of light go out at random angles. The diffusion pertains to the directionality of light at each point...a frosted surface provides diffusion, the wide lens provides focused light within a wide area (there may be some diffusion effect, but the light is primarily directed by the lens system).

Wilt, if you read back you'll see that I am questioning the notion that diffusion is inherently 'unpredictable' and 'random'.

A wide panel will produce a pool of light which is consistent in its coverage and angle of spread and so will a piece of paper or a sheet of tough spun. If you fire a flash through any of them, the results you get will be consistent and repeatable. I therefore don't see how you could say that a wide panel is more predictable or consistent than materials which are accepted to be diffusers (e.g. commercially available diffusion filters), and so a definition of 'diffusion' which rests on the notion of unpredictability or randomness (such as the one PacAce highlighted) is inadequate. By their definition, nothing would be classified as a diffuser as you can always analyse a material and calculate what effect it will have on light passing through it.

My original point wasn't about finding a detailed definition of 'diffusion' but simply to point out to the OP that diffusion was not, as you and some other posters stated, concerned with with the size of a light source but concerned with with its coverage, as I felt that the advice they were getting was inaccurate and misleading. Now that has been established, I tend to agree with PacAce that debating this further would pull the thread even more off-topic so this is the last you'll hear from me on the subject

Hermes wrote in post #6181508
Wilt, if you read back you'll see that I am questioning the notion that diffusion is inherently 'unpredictable' and 'random'.

A wide panel will produce a pool of light which is consistent in its coverage and angle of spread and so will a piece of paper or a sheet of tough spun. If you fire a flash through any of them, the results you get will be consistent and repeatable. I therefore don't see how you could say that a wide panel is more predictable or consistent than materials which are accepted to be diffusers (e.g. commercially available diffusion filters), and so a definition of 'diffusion' which rests on the notion of unpredictability or randomness (such as the one PacAce highlighted) is inadequate. By their definition, nothing would be classified as a diffuser as you can always analyse a material and calculate what effect it will have on light passing through it.

My original point wasn't about finding a detailed definition of 'diffusion' but simply to point out to the OP that diffusion was not, as you and some other posters stated, concerned with with the size of a light source but concerned with with its coverage, as I felt that the advice they were getting was inaccurate and misleading. Now that has been established, I tend to agree with PacAce that debating this further would pull the thread even more off-topic so this is the last you'll hear from me on the subject

Hermes,
Look at my illustration of effect of a lens (photo 1) vs. effect of diffusion (photo2) ...the diffusion offered by the paper softens the edges of the shadow. If you had put the wide lens over the flash, the total area of illumination changes but the shadow edge is fundamentally the same as without the wide lens, because it is still focused.

The diffusion effect of the paper is that (if you treat the paper as a grid of 10000 light emitting points) from each of the points on the surface of the paper, light is going out in all directions. That is the 'random' nature. Diffusion in liquid says that a dye would randomly disperse if you dropped a single drop into the water...and after enough time it is 'in all directions'

I don't want to step into heated territory, or unwelcome territory, but I do have a question about diffusers and since that is the discussion here, and you all seem to be more knowledgeable than I am, I figured I'd pick this discussion to ask my question. I am a fairly inexperienced photographer, I usually shoot in manual without a flash. I have never used a diffuser. I do have a Canon 430EX flash. I have used it and am comfortable using it, I just don't use it much. I am taking classes twice a week, I am up to advanced photography and getting ready to start Creative Portraiture classes, and then Studio Lighting classes. My friend from class says she thinks that if I use a diffuser at my next wedding, which is next week, that I'll be able to lower my ISO to get better quality pictures, but she wasn't sure. We are going to ask our instructor tonight, but I wanted to get some input from POTN members as well.

Is that true? Attached is a picture of what she told me a diffuser was, I want to make sure I am talking about the correct item! lol

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FergusonFotos wrote in post #6182755
I don't want to step into heated territory, or unwelcome territory, but I do have a question about diffusers and since that is the discussion here, and you all seem to be more knowledgeable than I am, I figured I'd pick this discussion to ask my question. I am a fairly inexperienced photographer, I usually shoot in manual without a flash. I have never used a diffuser. I do have a Canon 430EX flash. I have used it and am comfortable using it, I just don't use it much. I am taking classes twice a week, I am up to advanced photography and getting ready to start Creative Portraiture classes, and then Studio Lighting classes. My friend from class says she thinks that if I use a diffuser at my next wedding, which is next week, that I'll be able to lower my ISO to get better quality pictures, but she wasn't sure. We are going to ask our instructor tonight, but I wanted to get some input from POTN members as well.

Is that true? Attached is a picture of what she told me a diffuser was, I want to make sure I am talking about the correct item! lol

On the contrary, if you use a diffuser such as that shown in the link you provided, you'll actually end up having to increase the ISO. This is because you lose light intensity when the light has to pass through the diffuser material and you also loose light intensity per unit area because the light is spead out over a larger area than without it. But, if it's used indoors, you may get better quality pictures compared to shooting the flash straight on at the subject because the increase in the apparent size of the flash softens the shadow areas and lessens the overall contrast of the picture.

Thanks! That answers my question!

Linda,
Use of a diffuser does not permit lower ISO...if anything, the absorbtion of light by the diffuser might force you to use a high ISO to offset the loss of light caused by the diffuser!
The 'diffuser' shown in the photo does 'scatter light in all directions'...the light that goes up to the ceiling or adjacent walls and bounces back to the subject turns those surfaces into 'large apparent light source' and thereby softening shadow edges and reducing shadow contrast. But what goes off in other directions (which is most of the light, when you are outdoors!) is wasted light that provides no illumination of your subject. You depict what a lot of us will disparage as 'Tupperware' because the 'photographic diffuser' costs a lot more but is not more effective photographically than simply using a piece of Tupperware from the kitchen!

Thank you! That helps alot!