Strobist: light modifiers

That link has been posted in this forum a time or two before. I used it when I decided to purchase the Softlighter II and a Morris Softbox.

I use the Softlighter II when around the house, and the Softbox when I go out For a couple of reasons. it's smaller size makes it a little easier to deal with, and it's design means that while the light isn't as diffuse as with the Softlighter II, it doesn't "waste" as much of my flash's power.

 

Frank, attaching a Softliter II to an SB800 is not complicated at all.

 

This is the exact article that I read before I bought my Wescott Appolo Jr. softbox. I had lost track of it so thanks in posting this. I now have it in my favorites.

 

I cannot speak for the Softlighter, but it does appear that its shaft should be right at the edge of the light. Studio lights are made that way, but (without some rube goldberg modifications), the SB-800 would be off center. The tilted and longer shaft of other mounts help to center the offset SB-800.

What is the diameter of your 32" umbrellas? Often the marketing number is the longer curved path over the top (fabric dimension if it could be laid out flat), but I am asking the straight across diameter? I dont know which way yours is marketed.

Page 121 of the SB-800 manual shows the beam angles for the various zoom angles. This is important to umbrella users. Specifically, it shows 60x78 degrees at the 24mm zoom, which seems right to fill an umbrella. No law says every inch of the umbrella has to be filled, maybe call it 75 degrees.

The SB-800 Guide Number is not large at 24 mm. With both metered in the same umbrella, a 24 mm SB-800 meters one stop less than an AlienBees B400, so my claim is that in this case at 24 mm, the SB-800 is about 80 effective watt-seconds. The link you posted saying the SB-800 is stronger than a B400 is dead wrong, she obviously doesnt understand GN is about the specific reflector used, and that the "stronger" number is only at the 105 mm zoom position. The B400 GN is for its 80 degree reflector. When the SB-800 is zoomed to 24 mm for 60x78 degrees, its GN drops to 98.

Back to the point, on the umbrella, suppose the straight across diameter is the 32 inches. Half of that is 16 inches. In trigonometry, call that the Opposite side. The effective shaft length (fabric to flash head) is the Adjacent side of the light beam angle. Maybe the effective shaft is 20 inches (in front of SB-800), just making up a number to have a number for the example. My 40/45 inch umbrella "effective" or usable shaft length of about 24 inches.

So, may be the umbrellas arc tan (16/20) is 39 degrees, and double width is 78 degrees. This is a good match at the 24 mm zoom setting, but you could hone it, either with zoom or shaft length. To judge this result closer, take some flash pictures of the wall BEHIND the umbrella, opposite the subject, to judge how much light spill you see back there.

What size of group? 8 people or 80 people? Umbrellas are inexpensive, no reason not to get what you want, and you probably do want larger, but I bet what you have would do 8 people. It becomes larger if you move it back a little, but it needs more power then.

For portraits, the idea is that moving an umbrella in close, as close as possible, stand pole at 2 feet instead of 4 feet, makes the fabric be larger in relation to the subject, for better smoother lighting, with more wrap around smoothing effect for portraits. The flash tube is the source for computing inverse square law, but the fabric is the source for computing width or angle of the beam. Substituting a larger umbrella appears the same size as a small one up closer, for this same better quality of light, so large is good for that reason. But of course, up close the illuminated area gets smaller... no room to spread out. A shoot though umbrella is great because it can be even closer. and larger... fabric at 2 feet instead of 4 feet on opposite side of pole. The general idea is large, and getting them up close is one way to appear large compared to subject, for the smoothing quality of light this large light produces.

Up close, you do see the umbrella spokes in the reflection in the eyes however (either way), which makes soft boxes popular for studio lights. My opinion is there isnt much difference other than the spokes and the spill. The key factor is "large", which may mean "close". I bought a 60 inch Photogenic Eclipse Plus white satin umbrella because it has white satin liner inside, over the spokes. It hides the spokes in the eyes, but I dont use it because it just doesnt give the same magic color image that the translucent white has (when used as reflected).

Anyway, instead moving the umbrella back, 12 feet instead of 6 feet, makes it smaller, and more "harsh" as a point source, but it illuminates a larger area for the group (needs considerable more power or more lens aperture). There is a large difference in the "quality" of light between 2 and 4 feet (due to relative size), but not much between 6 and 12 feet (because 6 is already small with respect to the subjects face).

The trick for groups is to have each flash wide, with the stands about inline with the edge of the group, and far enough out to be pointing in at a 45 degree angle towards center of the group, or very slightly past center (lights crossing, so to speak). The 45 degree angle is a magic number concerning the square root of 2, etc. The light at the center from TWO lights at 45 is about the same intensity as one light at the edge of the group... i.e., very even lighting across the group. The angle makes the shadows be worse however, so you pay close attention to the shadows. At minimum, each head has to have a clear view of both the camera and the lights.

That should cover the width of the group. As to height, point the shafts lower than the subjects eyes, if you need it to reach the floor. If centered on the heads, light going over the heads probably doesnt help anything.

 

Wow, Wayne, that was a fabulous explanation. Thanks. I'm sure I'll have to read it once or twice more to fulyl understand everything you mentioned.

Thanks again for taking the time.

 

Wayne this makes for very interesting reading and what you say makes sense as well. Your point about moving the light modifier in as close as possible for smooth soft lighting is something I learned early on. I have my softbox as close in as I can get it without interfering with the camera view of the subject. Thanks for sharing your expertise.

 

A very good post Wayne. One trick I use when I can't get enough power from one speedlight is to rubber band several together. Put them in the same group and use manual power control from the SU-800. When the power is turned down and using multiple flashes as a single source you have a much faster recharge for rapid fire style shooting. Also handy when you need the shortest flash burst possible for stopping motion.

I am starting to move away from umbrella and softbox modifiers. Starting to use diffusion panels and bounce, even with studio lights.

 

Frank, the knock off Softlighters from Amvona are one peice. The diffusion material opens with the umbrella, and it is very simple to attatch to/around a speedlight.

 

Yes you're right Frank, I misspoke slightly, sorry. I am prone to find the wrong word sometimes. But the point is still exactly the same : The link is dead wrong. It says:

> The SB-800 is a powerful flash. It has a guide number of
> 125 at 35mm (ranging up to 184 at 105mm).
> That is MORE powerful than an Alien Bee 400.


The first two sentences are correct. The third is dead wrong.

http://www.alienbees.com/specs.html says the AlienBees B400 GN
is 118. That is with the furnished 7 inch reflector, which has a coverage angle of 80 degrees (circular pattern), which is extremely suitable for umbrellas.

The author is just saying that 125 is a larger number than 118 without any regard to what it means. It does not mean what her conclusion suggests.

Because, at the 35mm zoom, the SB-800 is specified to cover only 45x60 degrees. This is a far cry less than the 80 degrees from the B400. Even at 24 mm, the SB-800 does not quite reach 80 degrees, but the GN is only 98 then. But it is true that if you only wanted this narrow coverage, it would be on even ground with the AB 7 inch reflector, however you could always use the optional 11 inch AB reflector with a 50 degree pattern, and a GN of 220. 220 is a larger number than 125.  

There is simply no way the SB-800 is "MORE powerful than an Alien Bee 400". More like half power, but which is still a very strong flash.

I own both, and have metered both lights in the same umbrella (B400 and the SB-800 at 24 mm to fill the umbrella), and in that situation, the way you would use them, the SB-800 meters about one stop less than the B400, and two stops less than the B800 (all at full power, manual mode). One stop less is half power.

But you really don't have to meter them. Just holding one in each hand ought to convince anyone.  

I am certainly not knocking the SB-800, I have two of them and they are great. But the fact is that they run from small AA batteries, and are only about half the power of the AB B400 when used in umbrellas. The SB-800 SU-4 mode does work great with the studio-type lights, but their fresnel lens makes them much less suitable for some modifiers.

For example, I am puzzled about bothering with attempts to put a SB-800 in a softbox. Umbrellas yes, certainly, but softboxes? What they want instead is a real studio light suitable for softboxes.

Because, the AB B400 is used bare-bulb inside the softbox (the reflector is removed). That means the light is going every which way inside there, 180 degrees, all around. Even slightly behind 180 degrees... The softbox has reflective walls to receive and disperse this 180 degree pattern, to scatter it everywhere inside there.

The SB-800 is still using the fresnel lens and even at 24 mm, is only going 60x78 degrees inside there, not 180 degrees. At this angle, over the 18 inch depth, the light is even not reaching the sides of the softbox to be reflected back around and mixed up, it is merely focused out the front fabric. My opinion is the result must be about exactly the same as just draping a handkerchief over the fresnel lens. Which no doubt helps, but I just dont see how it is the same as the studio light in the softbox.

I dont mean to step on toes, but if thinking it out, that is the result I get. I do like softboxes too, very much, but I use mine with the AB lights. The studio lights are much more versatile with the modifiers.

The umbrella seems the best light from the SB-800, because it works with the fresnel lens on the flash, the flash angle can cover the umbrella in its designed way.

I agree, there certainly comes a point where that must be true, and just guessing, but 12 feet may be it. It cannot be a major loss then.   I have not tried that comparison, but that was always done that way in the earlier days before umbrellas were common... 1950s with flash bulbs, 60s with early electronic flash...

 

Frank,

If this does not work out. I have a 28" Westcott Apollo I can give you a deal on......Since I got my Elinchrom Boxes I haven't used it. It's only been used about three times and still in new condition. I posted a couple of photos taken with the box and an SB-800 or two.

Send me a PM if interested.

GenoP

Nikon D2Xs ,Nikkor 105mm f/2.8G ED-IF AF-S VR Micro
1/60s f/3.2 at 105.0mm iso200 (1 SB-800 in Apollo Softbox & 1 SB-800 direct for fill)

Subscribe to see EXIF info for this image (if available)

Nikon D2Xs ,Nikkor 17-55mm f/2.8G ED-IF AF-S DX
1/60s f/5.6 at 48.0mm iso320 (1 SB-800 in Apollo Softbox & 1 SB-800 backlighting the beer)
View attachment 95532

 

Over list? I don't think so, but I can be wrong, but I know I sold it under list. Also remember the white ones cost more to begin with.

If you want more dispersion, you should go for an 48" umbrella.....I had a lot of luck with the Photoflex umbrellas, until I went with Elinchrom strobes, as they do not fit in the Elinchrom umbrella hole. You should also think about using silver if you are using SB-800s, as they will give you the most output.

One thing about soft boxes, is that even though they may be smaller, they give a softer and smoother output.

Personally, I think you should move up to a pair of AB-800s. The work you do is already great, and I think if you had the ABs, I think you would be simply amazed at the results.

GenoP

 

If you get one at the kind of price I got mine for and dont like it, I'll take it off your hands. I plan on getting a couple more down the road and putting them up on the shelf for spares.

 

thanks for heads-up, Roy ...i just won 2 of these gizmos,,.99 cents and 3 bucks and ebay kicked in 10 with some coupon thingy,,,,so after shipping and all that i'm out less than 20 bucks for 2 of em ..such a dilly