Large Softbox plus strobe

I have been reviewing lighting diagrams for portraits. One of the books I have makes frequent use of a 40x60 inch soft box as a key light source. I like the look of those portraits which use the softbox on one side and a reflector on the other side of the face. However, the book does not mention the power of the strobe in the soft box.

Am I right to assume that the larger the soft box, the greater the attenuation of the light from the strobe?

I will have Calumet Travelite 750 strobes with a 4x5 (or 8x10) camera with TMY-2 film. Will I have enough light output for such a large soft box? If not, what sort of power do I really need? Thanks.

Figure you'll lose around 2-3 stops compared to a small (like 5-6 inch) plain reflector with a softbox that size.

I think David's right. Remember, though, that with a softbox with a lip (like a Chimera) you'll usually be able to get it very close to your subject.

A 4x8' sheet of white foam core works very well as a reflector. If you butt up the long edges of two sheets, you can tape them together with white Gaffer's tape. (Tape both sides of the seam.) You now have a self-standing V-flat. If you get foamcore that's white on one side and black on the other, you can now either add or subtract light. If you do this, use black Gaffer's tape on the black edge.

Admittedly, big 4x8 sheets are best in the studio. Outside, you can use a white "silk". If you go this route, let me know. We found a fabric at local fabric store that's a dead ringer for Matthews' silk. Yes, we tested it. You can use A-clamps to clamp this to whatever, including C-stands. Be careful, though, as you now have a good sized sail if a breeze picks up.

An even smaller option is a collapsible reflector. White is good. Silver can kick up the light, but it can be very hard on the models. It's best to have an assistant hold the reflector, but you can use a stand with a disk holder. If there's a breeze, make sure to sandbag the stand.

Yes; the more the light is diffused, the more you lose at the subject, simply due to where the light ends up. It is kind of like using one of those hose nozzles or shower heads with various settings. The same amount of water always has to come out...but the difference in where and how it comes out affects the volume and intensity at any given point in one of the streams.

Soft boxes do eat up quite a bit of light, so your power settings may seem odd at first.

When using anything other than two identically powered lights with two identical modifiers, you must use metering at the subject, not power settings and distance alone, to determine how to set your packs. In other words, if the main light and the fill light, modified as you described, are in a 1:1 ratio at the subject, the power settings will not be equal.

The actual powers and distances of the lights do not matter, but the ratio of the lights' illumination of the subject, and the quality of the light does. In other words, don't think that you need a lot of power to get that effect.

Do not fear moving the lights very close to your subject. Having the lights close seems to be a chronic fear of most photographers that I see shooting in the studio. They shoot with a 500W pack, put the heads shooting through soft boxes 8 - 10 feet away from their subjects, and then they wonder why their lighting is so harsh even with soft boxes, and why they have to open up their aperture so much. A farther away light source equals a smaller light source equals a harsher light source and far less illumination (two stops less for each doubling of distance, and two stops greater for every halving of distance), and vice versa.

2F/2F said:

Do not fear moving the lights very close to your subject.

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This is a good point. I used to make the same mistake, and I could get away with it, because I was using a fairly powerful system and shooting 35mm, and then I had my portrait taken for some official use by a photographer who had to travel light with a small kit, and realized that as long as the lights were outside of the frame, they could be two feet away or closer if need be, and when shooting 8x10" or larger portraits with soft light, need tends to be.

While I don't have a softbox THAT big, I have used 30x40 inch softboxes on Travelites, and even a 20x70ish (for full length shots) and gotten enough output to shoot at modest fstops (f11-ish).

Dean Collins, the master of lighting, used to begin his portrait deoms with a porteait madde with a 5 watt bare bulb. Hi statement was,"It is not the quantity, but the quality of the light"

One thing about softboxes: their light is verrrry flat.

If you have the type that has a difuser in front of the flash tube, a silver inside and an other difuser at the outside: leave the out-side one off, it gives a much more interesting light.
I have used my Bowens 1x1 meter softboxes for portraits a lot and realy liked the results.
750 Ws should be enough, it will depend on the format you are shooting on, the desired aperture and the distance between light and subject.

Peter

It's the angular size of the light source relative to the subject that's important. A small source closer to the subject can have a greater angular size than a large source at a greater distance. The sun is 1.4 million kilometers in diameter, but at a distance of 150 million km, it appears to be only 1/2 degree in diameter, and produces deep, hard edged shadows. If you moved it closer, it could be a much softer light (and increasingly uncomfortable for portraits). So the distance at which a softbox is used is critical as others have noted.

When I was working in studios a quarter century ago, softboxes were all the rage, and they do give a wonderful enveloping light when used up close. We often used large boxes just inches above relatively small table top sets. One other great advantage of a softbox is the control of light spill. However, I knew studios that preferred to use various scrims, silks, diffusion panels that they could light with a bright hot spot, a broad diffuse light, or anything in between. This was more flexible and customizable, and made their work stand out from the majority softbox crowd.

Softboxes may be faster and easier for travel use, as they can require fewer stands and less set up time than a diffusion panel, and may be less to carry than a panel and supports. You also have to deal with spill light if you use a scrim/diffusion panel.

If you haven't got a copy of "Light, Science, and Magic", Fil Hunter et al, ISBN-10: 0240808193, ISBN-13: 978-0240808192, I very highly recommend it. It discusses all the important aspects of lighting without tying it so directly to specific photographic hardware, allowing you to "think outside the softbox" so to speak, and think about different ways to get a given quality of light.

Lee

You can also use the fabric mentioned above in embroidery hoops. Available in different sizes & shapes at the craft stores.
I once made one from the housing of a "LiteBrite" kids toy with a Vivitar 283 mounted at the back.

I always have the soft boxes as close as possible to the subject and meter the light very carefully. I'll meter the light as the camera will see it, directly at the soft box, the reflector. Whatever the set up is I meter it all around to be sure I know exactly what the exposure will be along with all ratios and then adjust as desired.

2F/2F said:

Do not fear moving the lights very close to your subject.

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But be very careful.
Not about heat, but how the light drops off.

Put a soft box, say, almost against the shoulder of a portrait sitter, and his or her ear will be much further away from the light source, the nose even further away.
And not by tiny amounts, but enough to see a steep drop off in light level.
Get the shoulder exposed properly, and the ear will be too dark, the nose even darker.

A soft box is made larger, so that you still have a large, diffuse light source, even when it is not close to the subject.
So unless you want to produce such a drop off in illumination, make sure your light is far away enough for the differences in distance to the several parts of your three dimensional subject to be small, compared to the overall distance to the light.

I, as well, would not put the soft box almost against someone's shoulder if I did not want the parts of the sitter's anatomy closest to the light to be markedly brighter.

IMO: Quality of the light is the primary concern. It comes first. You should tailor everything else to suit the quality of light that you want. Distance affects both quality (indirectly, by affecting the relative size of the light source) and intensity (directly). Never move something closer or farther just in order to obtain a change in intensity, without also taking note of the change in quality of light.

Great flexibility can be achieved by not using soft boxes, but large sheets of white 'plexiglass' (acrylic?).

While a lamp behind the diffusing sheet(s) of a ready-made softbox is at a fixed position (and orientation), and you can only change the position of the soft box relative to the subject, when using such sheets you can vary not only the position of the diffusing surface relative to the subject, but also how a light will shine through such a sheet: distance, position, angle.
You can also put more than one lamp behind the sheet, creating even more variety.

And you can even put an box lined with reflecting material (preferably white, but doesn't have to be that) between the sheet and the lamp, creating a 'regular' softbox.

Such sheets are not expensive (lots less than softboxes) too.

The only drawback is that you need more stands (and clamps) to keep the sheet in position.
Other than that, only advantages.

Q.G. said:

Great flexibility can be achieved by not using soft boxes, but large sheets of white 'plexiglass' (acrylic?).

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And you need to be careful about what plastics you use for this, because they sometimes impart a strong color cast that can be difficult to correct, or can cause a color imbalance between the light going through the plastic and other lights. The same is of course true for white diffusion fabrics that you pick up from a fabric store, where optical brighteners can sometimes cause problems.

Lee

I forgot to mention that you of course can also use fabrics, stretched over a frame.

But yes indeed, test them (you only need a small piece) for colour first.

jeroldharter said:

.....I will have Calumet Travelite 750 strobes with a 4x5 (or 8x10) camera with TMY-2 film. Will I have enough light output for such a large soft box? If not, what sort of power do I really need? Thanks.

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I don't think you will have any problems lighting a portrait subject with a 750ws light in a 40 x 60 softbox at close range with ISO 400 film.

For somewhat of a comparison, I can light a head and shoulders portrait with a 36 x 48 softbox placed 4 to 5 feet away, using 600ws or so. I normally use ISO 125 film, and fairly wide apertures.

My only caution is the size of that softbox vs. the available room. I find that I want lots of maneuvering room for my 36 x 48 softbox. With a 40 x 60 softbox, I would want at least 10-foot ceilings and several hundred square feet of floor space for the softbox, fill and modifiers, and their stands. A 40 x 60 softbox on a boom will require a huge stand.