Adjusting Background LIght Study

[smoke665]

In another thread I posted a question on lighting the background. Derrel put me on to Dean Collins which I understood but still had to wrap my mind around what he was saying in practice. While I still had everything set up, I decided to experiment.

The given: The background is a white sheet, approximately 6' behind the flowers. The flowers were lit from camera right at about 4 o'clock by an ocatabox. A flag was placed on the back side to prevent spill over on the background. A white reflector was placed on camera left at about 10 o'clock. . The back ground was lit by another strobe with a large umbrella modifier on camera left between the flowers and the background, high and angled down.

The objective: To light the background to produce either a pure white, or pure black, by only altering the reflected light reading from the background.

In the first shot, the key light was metered to an incident reading of f/8 the background was metered at a reflective reading of f/11 (1 stop over) at the camera. Sampling the background I'm getting an RGB: 252,252,252 in the bottom left quadrant to RGB: 242, 242, 242 in the upper right quadrant. Which I would expect given that I only had one light on the background. Had I had a second light to balance out the background, I believe it would have been fairly easy to get a consistent across the board reading of just under the pure white I was looking for.

In the second shot I was quickly reminded of why in the video Collins metered the subject at a higher aperture. The key remained at the same f/8, but the background was metered to a reflective reading of f/3, which was only roughly 2 1/2 stops under the subject. In order to get a true black, Collins recommended 4 1/2 stops. However even if I had started at a higher aperture on the subject, the ambient light in the room was such, that I could not have reach the -4 1/2 stops. While the ambient light isn't so much a factor in taking the background white, it is a major factor in going black. Also, the effect of uneven light is really apparent when trying to go black. Sampling the lower left quadrant I was getting RGB 127:127:127 with falloff into the upper quadrant of RGB: 52:52:52.

Interestingly when I went back to try to get a more even light on the background for a white. I metered the subject at f/7.6 and the background at a reflected reading of f/16 for a difference of just over 2 stops. The white still remained at RGB 252.252.252 in the lower quadrant but there was less change across the image until it got closer to the far side.

Conclusion: using Collins' method of metering the subject as an incident reading and then metering the background as a reflective not only works, but will give predictable results. I didn't post the middle one, but matching the background reading to the subject will as he said give you a neutral gray background. With some practice this could be a rapid way of dialing in your background lighting saving a ton of time over the trial and error method. While I didn't try it supposedly a black background will work the same way. The ability to change from black to gray to white backgrounds with only an adjustment to your lights fascinates me. While ambient light doesn't effect the white as bad, I suspect it would still be easier to start without a lot of excess light bouncing around.

My thanks to @Derrel for recommending the video.

 

[Derrel]

A nice write-up,smoke! I was gone all weekend, just got to this post tonight, Monday.

 

[smoke665]

A nice write-up,smoke! I was gone all weekend, just got to this post tonight, Monday.

Thanks Derrel, I'm really glad you recommended the video. Now that I did this I understand how it works.

 

[Derrel]

A nice write-up,smoke! I was gone all weekend, just got to this post tonight, Monday.

Thanks Derrel, I'm really glad you recommended the video. Now that I did this I understand how it works.

That's awesome, man. It is pretty cool to have the mathematical and practical knowledge of background density/tone/color control. As you've found out, this method is much more predictable than what that one guy's portraiture series had sort of glossed over.

I've found that working on Thunder gray paper is a good choice when you want to "drive up" the gray paper to white, or when you want to "pull it down" to a very dark gray, or even to black. In many shooting areas, there simply is not enough distance to get enough fall-off on light backgrounds to get them down to that four-EV minus zone; there's just too much light making it past the subject and onto the background, since we typically have only 6 to 8 feet of distance from the subject to the backdrop in many shooting situations.

I hope you do get a Thunder gray seamless paper backdrop; it is super-easy to lift it up, or to drop it down in value, to white, or to black, in normal, everyday shooting situations.

As far as lighting the background paper: for me, the easiest system is by using the "old-era" Speedotron Brown Line 11.5 inch diameter, 65-degree beam spread angle, deep parabolic shaped metal reflectors, with 2-way barn doors on them, to prevent flaring the lens; set them just off to the sides of the seamless paper, and aim them in toward the middle of the seamless, and easily "drive up" gray paper right up to pure white, or "drive up" black paper to gray. Using two identically-fitted lights eliminates fall-off across the width of the paper, and the metal, barn-door-equipped reflectors keep the light going the proper direction, with much more control and less bounce around the shooting area than an umbrella. (Softboxes could work too.) The Alien Bee flash system has similar reflectors, and barn doors, and gel holders, which will do the same thing.

When using gels, this type of metal "bowl" reflector + barn door set makes it easy to keep that colored light going toward the backdrop, but NOT bouncing all over creation.

 

[tirediron]

I love watching Dean's videos; to me, he's the poster child for "professional photographer". I'm sure there were multiple takes for some of those scenes, but the apparent ease with which he does all those calculations in his head always impresses the hell out of me.

 

[smoke665]

, 65-degree beam spread angle, deep parabolic shaped metal reflectors, with 2-way barn doors on them, to prevent flaring the lens; set them just off to the sides of the seamless paper, and aim them in toward the middle of the seamless

My first choice would have been two lights and reflectors, but with only one I was thinking the reflective umbrella would give me a larger spread. I believe it did, just not enough. For the future it will be two and I already have barn doors and gels

. It is pretty cool to have the mathematical and practical knowledge of background density/tone/color control. As you've found out, this method is much more predictable

As John @tirediron noted the apparent ease with which he did the calculations was a little intimidating for me, but the precise predictability is awesome. I suspect with use it will become easier.

 

[mrca]

Smoke, for an object this small, or say head and shoulders shot, you don't need 2 bg lights. I have a plate and stud screwed to a piece of wood that gets a strobe and 60 degree reflector low then place it right behind the seated subject about 7-9 feet from the bg. Or you can just place it on a low stand. Adjust it so you get an even reading across the camera frame, you don't have to have the whole bg evenly lit just what is in the frame. A longer lens helps. You can check to see if your blinkies pretty much cover the frame for pure white. For pure black, turn off the lights and take your shutter speed up to max sync speed to cut light as much as possible with curtains and blinds. Check the histogram and if it isn't stacked on the left, close down the shutter and keep testing til it is close. If you have too much ambient, then you won't be able to shoot wide open but you can get the bg black. I agree with Derrel on the thunder gray and have one and a pure white on chain drives. But if you have too much ambient, you may need to use something black. I keep a piece of black velvet about 4x6 with me and it sucks up all light. Clamp or gaffer tape it behind subject and you will have a pure black bg. I don't need a large black bg as I don't do full length on black. You can move the subject closer to the bg to keep the shot within the velvet since there is no reflected light like on pure white contaminating subject and the black doesn't show subject shadows. It is a multi tasker. I just used mine the other day to shoot the brides's shoes, corset and jewelry. It can be gaffer taped to a wall on location for an instant black bg. I have used it to pose new borns as well or something to hide a crummy seating object like a apple box. It cushions my lights in that case yet actually does other things. If you are lighting the subject, try to keep the spill from the main off the bg.

 

[smoke665]

@mrca this wasn't a typical setup I'd use for a portrait. It was an exercise to test/learn Dean Collins method, to be able to dial in a predictable background by the meter, without chimping. I have several different backgrounds, including black velvet, vinyls, painted canvas, plain canvas, white/colored sheets (Wally world brand works great).

This learning project was preparation for expanding my lighting set up to 5 light arrangements.

 

[mrca]

Excellent. Keep practicing. It is great to see someone working at mastering the craft.

 

[smoke665]

I hope you do get a Thunder gray seamless paper backdrop; it is super-easy to lift it up, or to drop it down in value, to white, or to black, in normal, everyday shooting situations.

I'd planned on white but this would probably be the better option. How does it work with gels?

 

[tirediron]

I hope you do get a Thunder gray seamless paper backdrop; it is super-easy to lift it up, or to drop it down in value, to white, or to black, in normal, everyday shooting situations.

I'd planned on white but this would probably be the better option. How does it work with gels?

Very well... Thunder grey gels more easily than any other colour out there.

 

[mrca]

Yes, I love thunder gray. It easily goes black and can be nuked to white. Upside of white is it can be used for full length pure white. With a couple sheets of white shiny board, it produces as grounding shadow as well and protects the paper somewhat. It's why I have both on chain drive. Third drive slot can be mottled, black, or other.

 

[Derrel]

I hope you do get a Thunder gray seamless paper backdrop; it is super-easy to lift it up, or to drop it down in value, to white, or to black, in normal, everyday shooting situations.

I'd planned on white but this would probably be the better option. How does it work with gels?

Gray background paper works extremely well with gels, as does black. White tends to be super-reflective (of course it is, since it's...white!) and while white can create some nice very pastel hues with gels, with my lights, I often have too much flash power to really effectively utilize white with gels, since I have Brown Line packs and big 2400 W-s Black Line packs, and do not have the really low-low power ratios at my fingertips (like 1/8 or 1/16 power settings) in the same way that many monolight users have, so I tend to go with gray for gel use. Like in the Dean Collins video, where he mentions starting "in the middle of the lens", so there's room at the top and bottom of the range, my lights are mostly in equal or 1- or 2-stop differentials,so I prefer to start with a gray paper if I want to gel the backdrop. So anyway...YES, gray is fantastic for using with gels, and it does not tend to cause "bounce-back" stray light to the degree that white paper causes with gelled light on the backdrop.

Smoke, you're right...a five-light setup allows a huge amount of control and style! Main light; fill light; separation light or accent light;and still two more lights for either hair or background! Like mrca was mentioning, a very low background stand (a factory-made or home-crafted backlight stand) of some type allows one, single light with a metal reflector to be placed on the set, easily. Speedotron offers a "clamshell" or "shovel" type reflector that bayonets onto their bigger heads, and looks a LOT like those old-fashioned metal, "hangs from a hook" shop or automobile 110volt AC work lights from the old days. It sends light ONLY in one direction, and the light spreads quite widely, so it covers the paper in a broad pop of light. Other brands (like the old Photogenic Studio Master system I used to use) have a "flood" type bare-bulb option that allows you to flood a 12-foot-wide backdrop canvas from about 6 feet or so from the backdrop. The practical purpose is, in most cases, to eliminate the need for two stands and two lights, and get that down to one stand and one light, while still lighting the backdrop widely, and effectively. This is where a 7-inch, 105-degree reflector (Speedo), or a flood-adapter used on the M90 Speedo Brown Line light can work well, while also preventing lens flaring.

As mrca was saying, one does not "have to" light the backdrop 100% evenly, but only what shows up in the shot! With a long lens, the angle of view behind the subject is narrow, so that can give you some wiggle room if the background is not lighted super-uniformly. But there _are_ some specific background lighting tools that help if one wants to light the BG with just one flash.

Paul C. Buff Alien Bees have their While Shovel Background Reflector, the traditionally-styled clamshell reflector of many decades' of use.
White Shovel Background Reflector

Alien Bees also have their 7-inch "standard" reflector, not the umbrella 7-incher, but the "standard", which has a 80-degree beamspread.7” Standard Reflector

 

[mrca]

Derrel, my favorite Alien Bee story is based on the shovel back ground reflector. I wondered what the shape of light it produced on the bg. I phoned a human answered the phone and she asked for my email address, went and shot it against a bg and sent me a photo of the pattern. Amazing service! For what about a $25 item. gave up reaching manfrotto recently. I didn't buy it because can create the same pattern with the light on the floor stand/plate. You use one to give even wide illumination? Interesting. May have to re think it. I was going to use it for it's vignette shape. Is it more even than the circular standard reflector? I guess you would place it centered height behind the subject? What kind of distance to bg? I usually place my strobe on a wood mounted stud then aim it up from against the back of the posing stool, about 8 feet then restrict it with a grid and get plenty of even light with inverse square at that distance. I You are absolutely right on the standard reflector and they take grids and the pattern can be sized with those. One of the things I like about Einsteins is they go down to 2.5 watt seconds down from the 640 max. It enables shooting at 1.4 to 2.0 with soft box. If not quite, I just clothes pin another translucent panel over the light.

 

[smoke665]

Paul C. Buff Alien Bees have their While Shovel Background Reflector, the traditionally-styled clamshell reflector of many decades' of use.
White Shovel Background Reflector

Alien Bees also have their 7-inch "standard" reflector, not the umbrella 7-incher, but the "standard", which has a 80-degree beamspread.7” Standard Reflector

I have the standard 7" reflectors already. You know that Shovel Reflector looks a whole lot like a DYI reflector I questioned John( @tirediron ) on in one of his setups. He said he made it out of large can. LOL I was thinking 2 lights on the background for even lighting, but I may have to rig one of these up to experiment with.

@mrca I can't say enough good about the company. I've always found them super great about answering questions, providing top notch customer service, and solid equipment. I go through Nashville every so often, and one of these day's I'm going to stop by.