Friday, December 18, 2009

19. Discussion about 3 Different Flash Diffusers

I decided to capture a post that I made to Nikonians.com for the Flash Forum:

The question I was answering was that the person had tried verious diffusers and was asking why he didn't see much difference between them. The bottom line is that there isn't much difference between them until you put them in specific situations.

***************

First, you have to understand exactly why diffusion is needed in the first place. The basic problem is that all the light from an undiffused flash comes effectively from a 'point' source. This means all the light hits the subject from one direction, and that's what makes it harsh. To soften the light hitting your subject, you have to make it hit your subject from multiple directions. This causes tiny shadows to form in multiple directions, that merge into one another adding definition to facial features giving your subject a more natural look.

To make the light from the flash hit your subject from multiple directions, you have to use a diffuser, and the bigger the diffuser, the more paths the light will follow while traveling to your subject, and the softer it will be.

When you are indoors and have a white ceiling (that is not too high), and white walls, you can make your flash really soft if you send the light in all directions, so it bounces off every wall and ceiling before arriving at the subject. Then, you get amazingly soft light.

So, any diffuser that will send the light in all directions indoors in a room with white walls and ceiling, will make equally soft light. The small snap-on diffuser that comes with the SB-800 will do a remarkable job of this if you simply point it straight up.

However, there is more to this. In addition to making your light soft, you normally want to send a bit of light directly toward the subject to make catchlights in the eyes and lift shadows on the face. This is called 'direct' light, and if the direct light is coming from a tiny source, then you are adding harsh light into the image, which cancels out some of the softening you have created with the bounce.

So, the overall quality of the light on your subject depends on controlling the softness of both the direct light and the bounced light and the ratio between them.

So, let's look at the various diffusers you mentioned. If a bounce card is used without any other diffusion, you may already see that the direct light will be coming from a source that is the size of the bounce card. If this card is small, then the direct light will be harsh. This is what happens with the pull-out bounce card in the SB-800. It makes very harsh direct light, so it provides no diffusion at all by itself. Only the light that gets around it and is allowed to bounce off walls and ceiling will be soft. You can make it do a good job by pointing it up and adjusting how much of the bounce card is sticking out.

With the Demb flash diffuser pro, it uses a larger bounce card which softens the light more than the small card in the SB-800. You can compare softness of bounce cards by comparing the area of the bounce cards. The SB-800 card is 1.4 x 1.75 or about 2.5 sq inches. I don't own a Demb Flash Diffuser Pro (DFDP), but from the pictures it looks like its bounce card is about 3 x 3 inches or 9 sq inches. This will provide slightly more softening of the direct light than the smaller SB-800 card. Then, the DFDP adds a 'Front Diffusion panel'. This adds about 2 sq inches to the overall size of the direct light source and will cause part of the light to scatter, assuming an inverted funnel shape towards the subject. By itself, this diffusion panel will not add any softening, because the active area is about the same size as a flash. However, if you are indoors, some of the scattered light may hit the walls and arrive back at the subject. This light will be soft, but much of it will hit the subject from the sides, so it won't soften the face that much. The DFDP is a very versatile system that can produce great results once you fully understand how to use it.

The Lumiquest Mini Softbox softens only the direct light. It produces no bounce, so the area of the active surface of the box can be used to compare it to bounce cards. From the website, it says it will fold flat to 3.25 x 4.5 inches. This is about the same size as the active surface of the box so the area is about 15 sq inches. Therefore this will provide more softening of the direct light than the DFDP.

Then there is the Light Sphere II (LS) which comes with its 'inverted dome'. With the dome installed, and with it pointed straight up, it will cause the flash to scatter in all directions. Light will then bounce off the ceiling and every wall in the room, just exactly like the small snap-on diffuser that comes with the SB-800. This makes the effective light source the size of the entire room. This could be a total effective area of 500 sq feet. Compare that size to any bounce card there is and you see that there is no comparison. You get extremely extremely soft light, probably only to be outdone by an overcast day, when the entire sky becomes the diffuser size.

However, the advantage of the LS over the small snap-on diffuser, is that its active cross-sectional size is about 3 x 4 inches or 12 sq inches. This means that its direct light will be much softer. The direct light from the LS is not as soft as the Lumiquest Mini Soft Box and about the same as the DFDP.

The real power of the LS is that when you have a good ceiling bounce, you can remove the inverted dome and take full advantage of it. This is when you get maximum softening. Not only do you get a maximum bounce off the ceiling, but you still get a bounce off the walls and nice soft direct light as well. You also have the option of tilting the LS backwards to reduce the direct light while still retaining maximum room bounce. This is why the LS works so well.

Lastly, I should point out that as you move farther from your subject, the apparent size of the source grows smaller and smaller. This makes the direct light get harsher and harsher. Once you are beyond about 15 feet, none of the diffusers will have much of a softening effect on the direct light. When you are 15 feet or more away, you have to rely entirely on the room bounce for softening. Then, if you are outdoors (and within 15 feet), where there is no bounce, you have to rely entirely on the softness of the direct light. This is when the Lumiquest Mini Softbox beats the DFDP and the LS.

53 comments:

Raymond said...

Hi Russ,

How about some DIY bounce cards or something similar to this (http://www.abetterbouncecard.com/)?
I have seen some good results with this and am trying to figure out how to use it effectively. Thanks.

Russ MacDonald said...

Hi again Raymond,

There is no reason you can't make your own bounce card. And the bigger it is the better is will work (as I indicated in my article). Many photojournalists attach a white card to the flash with rubber bands, and it works better than the built-in bounce card in the SB-800 (simply because it is larger).

I am just not a fan of DIY, so I usually use things other people have made.

Regards,

Russ

Anonymous said...

Dear Russ

Thanks for your kind answer

Regards

Victor

Vivek said...

Russ,

When is post #20 coming?

We are all waiting in high anticipation!


Vivek - www.sacredpixels.com

Russ MacDonald said...

Hi Vivic,

Soon my friend - LOL. I'm working on a new post, but I only get to work on it between photo assignments, and my photo work has increased this year (finally)!

Russ

vive said...

Cool Russel! Can't wait!

V

vivek said...

Could you give away a hint about the subject of the next post?

THX

Russ MacDonald said...

Hi Vivek,

Well, I am working on several blogs, actually. The next one will probably be about speedlight batteries; different choices, which ones are best for particular use, how to keep track of them, ones to avoid, etc.

I have been working on a blog discussing how to take great portraits with Wireless CLS. The problem with this is that this information starts to come close to the info at the Strobist website. I don't want to encroach too much on David Hobby. So, I have to think about it.

Russ

Vivek said...

Thank you Russ!

Looking forward to it very much.

Vivek

Cameta Deals said...

Cant wait. I wil post a link on my site at Nikon Deals

JackW said...

Russ,

I have a question about this diffusion / bounce stuff, but before I post it here I thought I would ask if you mind, or would you prefer such topic broadening questions asked at The Nikonians?

Russ MacDonald said...

Hi Jack,

I try to answer all questions asked here and on Nikonians. However, if it is off-topic for my blog, then I prefer Nikonians.

Russ

R.Campbell said...

I have made my own bounce cards following advice from http://www.abetterbouncecard.com/ and they do the job remarkably well. Thanks again for your post Russ.

Russ MacDonald said...

Hi R Campbell,

I am aware of the 'Better Bounce Card'. Yes, they do work extremely well, as long as you make a big one.

They work especially well when there is no ceiling or walls to bounce off.

However, they don't make as good a full-room bounce as the Gary Fong Light Sphere, because they don't send light out in all directions. You just can't beat the Light Sphere for that.

Russ

Mark said...

Russ:

Just noticed Gary Fong has produced a collapsible lightsphere that collapses to 1.5". Wondering if you've heard anything about this or used it? Thanks.

Mark

Russ MacDonald said...

Hi Mark,

I know about the collapsable Light Sphere, but I haven't bought one. I am really happy with the regular ones that I own.

Thanks for the heads up,

Russ

Anonymous said...

Hi Russ, how about the whale tail?

Russ MacDonald said...

To Anonymous (wish you would leave your name),

I have not tried the Whale Tail, so I can't comment.

Russ

LUS said...

thanks for the info.
nice blog

Russ MacDonald said...

Hi LUS,

Thanks for the nice feedback!

Russ

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Russ MacDonald said...

Hi joven,

Thanks!

Russ

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D said...

It's still hard for me to grasp the idea stated by the last paragraph in your post. It would seem that the further away the light source is, the more diffused the light will be. But apparently, that's not the case. Color me confused :|

Russ MacDonald said...

Hi D,

Don't worry, lots of people find it hard to understand.

One way to think of it is that when the light source is close, the light can 'wrap around' the subject.

Another thing that may help is to think of the sun. It is over 100 times wider than the earth. Yet, it makes very harsh light since it is so far away and acts like a point source here on earth.

However, if you were up near the sun, (assuming you didn't burn up) the light would wrap all around you and be very soft.

One more thing to think about is the light when there is a complete overcast. The overcast diffuses the sun's tiny apparent source and makes it cover the whole sky. This makes the light very soft (and great for portraits, by the way). Now think about the shadows you see. You get a sharp shadow when the sun is shining directly without any clouds. But when there are clouds, the shadow basically disappears.

Maybe that helps?

Russ

Tomas said...

Hi Russ,

I've read through all your 19 blog posts and the Q&As after them over the last few days. Wow, what a wonderful compendium of practically useful information combined with great, clear explanations of how the flashes work as they do. Thank you so much for having taken the time to put all this information out here for everybody to benefit from.

Cheers,
Tomas

Russ MacDonald said...

Hi Tomas,

Thank you for the nice feedback! I'm really glad you found the information useful.

Russ

Kannan said...

Good post.

Russ MacDonald said...

Thanks!

Russ

Anonymous said...

Good post

radjabumi said...

it's a great article. nice blog....

Jan said...

Integrated bounce card in SB-800 is really not the best. My expirience is that the best is to find large plastic business card (they are a bit rare however very good quality and bigger than regular) and black silicon bracelet (its wide and hold enything perfectly) to hold it.

I also make a tinner one which is possible to get on the side of the flash when I shot portrait.

Russ MacDonald said...

Hi Jan,

Yes, you are right. The integrated bounce card in the SB-800 is very small and it offers no diffusion softening at all.

However, it is useful to get the source of the light a bit higher to reduce red-eye.

About the only time I use the integrated bounce card is when adding fill outdoors. Then, you don't need any softening anyway, so it works well.

Most PJ's (photo journalists) use a white index card and attach it with a rubber band to the flash head. That works very well!

Russ

Anonymous said...

If I use a stofen, the effective light source is the size of the entire room. If I pay for a Light Sphere or the other Gary Fong tupperwares, the effective light source is the size of the entire room. It may have impressive curves, but the flash shoots straight light, so what's the difference?

Russ MacDonald said...

To anonymous (wish you would leave your name),

You are right ... when shooting in a small room with a good bounce the sto-fen type diffuser works nearly as well as the Light Sphere (LS).

The improvement of the LS shows up when shooting in a large room with less bounce (or outdoors). The direct light from the LS is much larger and therefore softer than the direct light from the sto-fen. When the bounce is minimal, it is the direct light that exposes the subject. This makes the light sphere highly superior when the bounce is poor.

One other option with the LS is that you have the choice of installing the inverted dome or leaving it off. In a room with a high ceiling, I often remove the inverted dome so the flash fires much more powerfully into the ceiling. This reduces the direct light from the LS and increases the bounced light.

You can do a similar thing by removing the sto-fen and firing the bare flash at the ceiling, but then you do not get the nice catchlight in the subject's eyes that the LS always makes due to its direct light.

Russ

Anonymous said...

Thank You for all this great info. I am new to this and this will help me a lot.

Aaron Lavinsky said...

Very informative post!

You spoke about some of the flash diffusers that have been on the market for some time but I wish you had spoken a bit about the honl traveler 8. I often use this modifier in conjunction with the lightsphere and it offers beautiful quality and a much more controlled spread than the Fong lightsphere or the lumiquest.

The diffusion material is also thinner, similar to an opal gel, so you get much more light transmission. this is particularly important while shooting outdoors when you are fighting the sun.

but overall, great analysis on some of the standard diffusers. Looking forward to seeing more of your posts!

-Aaron Lavinsky
www.aaronlavinsky.com

Nikon L110 review said...

It is a bit advanced level for me as a beginner, but good to know where to come back to when I come to the level to understand everything in this post :). Thanks!

Russ MacDonald said...

Hi Nikon L110,

One thing that is very important to understand these things is to read ALL of my blogs starting with the first one. You have to read them in order, because I develop concepts in the early ones that I assume you know in the later ones.

Russ

Anonymous said...

Hi Russ,

I have just finished reading your 19 posts.

Very instructing. I have learnd a lot about my SB-800 flash.

Thank you for taking the time to write a blog of such quality.

Claude Carrier

Russ MacDonald said...

Hi Claude,

Thanks for the feedback. I'm glad my blogs are useful to you!

Russ

Haibin said...

Hi Russ,

Thanks a lot for your posts! I spend my whole week's spare time to read your posts line by line and tried myself. The information is really helpful!

After reading your posts about various diffusers, I am wondering do you recommend to use diffuser most of the time (use it to bounce light when possible for indoor shooting and use the Lumiquest Mini Softbox to point to subject directly as long as the subject is within the capable distance of flash and when bouncing is not possible ) along with all the approaches you listed in the "18 Camera & Flash Cookbook"?

Thanks!

Russ MacDonald said...

Hi Haibin,

Thanks for the nice comments!

The general rule is that if you are adding significant light with the flash, then you should diffuse it. To say this another way, if you are only adding a small amount of fill, diffusion doesn't make much difference, but if you are supplying a lot of light with the flash then harsh light is very obvious and needs to be diffused.

So yes, I do recommend using the diffuser almost all the time, and the methods in my cookbook all apply.

Hope that helps,

Russ

fotografia ślubna said...

hi there! thank for your article, I love reading about photography and cameras so it was great pleasure to spent some time here

Russ MacDonald said...

Hi fotographia slubna,

Thanks for the nice feedback. I'm glad you find it useful.

Be sure to read all the Q&A for answers to questions I haven't incorporated into the blog articles.

Russ

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Shawn Spencer said...

Now that I have a decent camera, the next step that I want to learn more about is lighting and I am tired of the harsh look of my standard flash, so thanks for this post. I need to get some flash diffusers for sure!

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Russ MacDonald said...

Thanks everyone for your feedback! I would have responded sooner, but I stopped receiving emails for some reason, and I didn't know you had posted.

Russ

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