DIY Softbox with TL950 bi-pin T8 bulbs?

[dh003i]

vinny,

Can you explain the suggestion for aluminum for reflector material? From what Behr told me when I called them, their ultra premium flat paint is 95% reflective, which is pretty good. A source online (now no longer up, but still cached...maybe because the poster made a not-so-subtle reference re "sleeping easier at night" if they had a certain reflective material, because it is 90% IR proof):

Aluminum Foil:

Aluminum foil is no more than 55% reflective - if used, make sure that the dull side is the one that is used to reflect the light. When it becomes creased its reflectivity is even lower (around 35%.) It is also very dangerous to use because it creates hotspots easily, is electrically conductive, and is a fire hazard when it is in close contact with HID lighting. Attaching this to walls is a pain and usually using aluminum tape or glue is the best way. This should only be used as a last resort, and even then its usefulness is questionable.

[vinny]

Nearly all continuous lighting sources us aluminum reflectors (including every fluorescent light). Higher output and no introduced color shift. Does behr make lights for the still or motion picture industry? No, they make paint.

[dh003i]

Nearly all continuous lighting sources us aluminum reflectors (including every fluorescent light). Higher output and no introduced color shift. Does behr make lights for the still or motion picture industry? No, they make paint.

Point taken about aluminum reflectors being a sure bet, but that doesn't mean flat white paint would do poorly...95% reflective, and color shift is just up to a matter of testing out. A test I found shows mylar coming ahead of regular flat white paint and aluminum foil on a DIY design...but that's foil, not polished aluminum (and although it may not be a concern with CFLs, mylar is a fire-hazard).

In any event, I'll look into some of those aquarium hobbyist reflectors.

[vinny]

Mylar will melt w/o good ventilation but it's your best bet if u can't find aluminum. Attach w/ super77 spray.

[erie patsellis]

dh,
You're shooting film or instant capture digital, right? Are you aware that 1600+ w/s pack head systems go for next to nothing these days? Especially the older ones with limited adjustability. I have a different situation, I have to use continuous light due to the use of a scan back.

Wiring a ballast is simple, the wiring diagram is on the ballast, the same socket is used for both T8 and T12 bulbs as well. No offense meant, but if you are having trouble figuring out the wiring diagram, you may want to reconsider the DIY approach.

As far as reflector material, you can buy thinner aluminum sheets fairly inexpensively, .025 to .032 3003 cuts pretty easily with hand shears, and can be pop riveted (or using aircraft style bucked rivets), which makes a rather rigid box.

Out of curiosity, what work are you doing that requires such a methodical, calculated approach? You can obtain soft lighting with nothing more than a silk (white ripstop) on a frame between the light source and subject, very inexpensive, versatile and no reflectors needed.

[Bruce Watson]

Re the 150W CMH bulbs and Philips 575MR bulbs used in HMI lights (I've been unable to find the 575MR bulbs), these are less efficient, hotter running bulbs than the fluorescents, right? (also, the 150W CMH lists a CRI of 85, although I'm not sure that means it is worse than the Philips TL950, because it may have a smoother spectral distribution without spikes).

It's my understanding that all arc lights, regardless of their "presentation mechanism" (direct, fluorescence, whatever) have spikes in their output. HMI's, like fluorescents, are kinds of arc lamps. The spikes may differ in frequency and size, but they'll be there. Which is why HMIs top out around CRI of 85 or so.

[Bruce Watson]

I found yet another bulb for you to consider. RPImaging sells the GTI bulbs. Supposedly seven phosphors (as opposed to two or three in the vast majority of the so-called "cinema bulbs". Closest thing to true D50 or D65 illumination that I've found, but the spectral power curve still shows some sizable spikes. And these bulbs aren't cheap.

[dh003i]

dh,
You're shooting film or instant capture digital, right? Are you aware that 1600+ w/s pack head systems go for next to nothing these days? Especially the older ones with limited adjustability. I have a different situation, I have to use continuous light due to the use of a scan back.

I shoot 4x5 film and an Olympus E-3 (4/3rds, the smallest DSLR sensor size format). Yea, I know that there are plentiful flashes available that produce lots of power, but I rather like continuous lighting to start out with. i.e., my 3 softbox idea will allow me to position things around and see how that changes the effect of the lighting, WYSIWYG. I am just starting out with lighting, and I've seen many (such as Frank Petronio, who introduced me to LF a few years ago) recommend continuous lighting to start out (and I figure fluorescent to keep things cool for me and the subject).

Frank Petronio recommend Dynalites for Flash. I've seen the Dynalite L2040 and 1836 sell for $118 - $150 used on eBay. What do you recommend and what is you definition of "next to nothing"?

Wiring a ballast is simple, the wiring diagram is on the ballast, the same socket is used for both T8 and T12 bulbs as well. No offense meant, but if you are having trouble figuring out the wiring diagram, you may want to reconsider the DIY approach.

LOL, well, I haven't actually looked at any of them yet. I am just trying to figure out what is needed to make a portable softbox unit that plugs into the wall outlet (ya know, 3-prong plug). So-far, I've found TL950 lights, electronics ballasts, medium bi-pin socket lampholder. Ok, so I don't see anything there that is going into a plug which goes into an outlet. This is what I'm trying to figure out.

I want to know exactly what I need to do before I go off like a loose cannon and start buying stuff.

As far as reflector material, you can buy thinner aluminum sheets fairly inexpensively, .025 to .032 3003 cuts pretty easily with hand shears, and can be pop riveted (or using aircraft style bucked rivets), which makes a rather rigid box.

Thanks.

Out of curiosity, what work are you doing that requires such a methodical, calculated approach?

Will be taking portrait shots of friends, as well as a sports photo shoot for a friend's portfolio to showcase his work. Being methodical and calculating is just in my nature. I like to have a solid idea of precisely what I need to do before I go out and do it. I'm not one for just trying stuff an experimenting...unless the experiment costs around $10.

You can obtain soft lighting with nothing more than a silk (white ripstop) on a frame between the light source and subject, very inexpensive, versatile and no reflectors needed.

Well, without the reflecting material behind the tubes, I'd be wasting half of their lumen output, right?

[dh003i]

I found yet another bulb for you to consider. RPImaging sells the GTI bulbs. Supposedly seven phosphors (as opposed to two or three in the vast majority of the so-called "cinema bulbs". Closest thing to true D50 or D65 illumination that I've found, but the spectral power curve still shows some sizable spikes. And these bulbs aren't cheap.

Yea, they definitely aren't cheap! The GTI D50 48inch F32T8/GL50 bulbs are $675 for a case of 30 ($22.5/bulb) vs. $102 for 25 TL950s ($4.08/bulb). As expected, they're better than the cheaper TL950 bulbs. The spectral distribution charts from this site:

GTI D50 Spectral Power Curve: two major peaks
Attachment 44692

Philips TL950 Spectral Power Curve: 3 major peaks, 1 more gradual peak
Attachment 44693

But alas, I think the GTI bulbs are a little too pricey for me at this point. But I'll keep them in mind. From talking with the kind GTI representative, the their T8 48" F32T8/GL50 bulbs have a lumen-output of 1787, as measured under their conditions (vs. 2000 for Philips TL950s). He also reiterated to me that as spikes are smoothed out, lumen output decreases because that energy output is lost. This makes sense. They seem like great fluorescent bulbs.

[Bruce Watson]

How about something like this fixture from Lithonia Lighting? Got ballast built in, got reflectors already made. Stack as many together as you want.

Won't be as nice as a Kino Flow or Cool Lights biax unit. Doesn't have the light stand mechanicals built in. But you can use bi-pin bulbs and get the higher CRI you're after.