rheostats on studio lights?

Discussion in 'Beyond the Basics' started by jaybird-7, Nov 25, 2006.

  1. jaybird-7

    jaybird-7 TPF Noob!

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    I'm fairly new to studio photography, am interested in doing portraiture, and have just bought a pair of Smith Victor Q120 photo lights to get started with. This will be continuous lighting rather than flash, which I figured would be the simplest and cheapest way to get started. These lights use very bright, hot halogen bulbs (420 to 600-watt, two-prong DYS or EKB bulbs), and I am wondering whether a rheostat could be used to dial down the power and hence the brightness of the bulbs, both to reduce the amount of light when required for photography and to extend the life of the bulbs. Some Smith Victor lights have dimmer switches built right into them (to extend bulb life, I presume), which gave me the idea. Places like Radio Shack have rheostats that can be used between a wall plug and an appliance. My question is, can these somewhat expensive halogen bulbs be damaged by dialing their power up and down like that? Is anyone else using a rheostat on his continuous studio lighting?

    Any info or thoughts would be appreciated.

    Tom
     
  2. jaybird-7

    jaybird-7 TPF Noob!

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    Guess no one in the forum here has any info or experience with putting rheostats on studio lights, since it's been a few days since I posted with no replies. I did find out from a seller of the light bulbs that in his opinion using a rheostat on a photo light would work fine, and extend the life of the bulbs, although he did warn about turning the power up too fast with the rheostat. He said a sudden surge of power could "shock" a bulb's filament and shorten its life, or blow it out entirely, if one isn't careful. A slow, steady return to full power is the way it should be done. He also warned that as the light dims or brightens, the color temperature will vary (it's 3200 degrees at full power). Thus, in a situation where you might lower the light level to improve the photo, you would also be changing the color or white balance somewhat. Shouldn't be too much of a problem, especially with digital, but it's something to be aware of.

    My only remaining worry would be that the Smith Victor Q120 light itself might not be happy with diminished power and might be damaged somehow by running the power up and down through it frequently, since I don't know how these lights work internally. However, in the absence of any information about that, I guess I'll go ahead and try it. I bought these studio lights second-hand and didn't pay too much for them, so if I ruin one I haven't lost too much, except for the inconvenience of having to look for replacements.

    Tom
     
  3. kilgtfish

    kilgtfish TPF Noob!

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    I have used (dimmers) on hot lights before with no ill effects to the bulbs......just a lot of sweat on the subject. I purchased regular dimmer type switches from Lowes and put them in plastic wall boxes(usually placed inside walls) and mounted them on a board(crude but effective). The dimmers I used are not rheostats....... actually they are electronic choppers and do not generate a lot of heat like a rheostat would. Just make sure you select switches which will bear the high wattage of the bulb you are using.
     
  4. jaybird-7

    jaybird-7 TPF Noob!

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    That's a neat solution. Actually I was in a Lowe's yesterday and saw those dimmer switches, if you mean the ones with sliders on them instead of knobs. Did you splice the wires from the studio lights right into those dimmers, or did you put receptacles on either side of the dimmers for the lights and extension cords to plug into?
     
  5. morydd

    morydd TPF Noob!

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    Tungsten-Halogen is what most lighting in theater is, and we dim the heck out of them. Most theatrical dimmers are electronic rather than resistance, but electronic dimmers cost more. The kind you usually find at hardware stores are usually resistance dimmers.
    Keep in mind, the dimmer you make them, the more amber the light will be.
    As far as building your own, if you're at all comfortable doing wiring, it's easy. If you're not comfortable with it... well trust your instincts and don't touch. :)
    What I usually have done is gotten a double-gang box (wide enough for 2 outlets/switches) and put the dimmer on one side, and the outlet on the other. (They make covers that accomodate this.) Add a tail with a plug in the side, then you can plug any light into it. Keep in mind, most household dimmers are only rated to 600 watts, so if you're using lights over 300W, don't try to plug 2 in.
     
  6. kilgtfish

    kilgtfish TPF Noob!

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    Morydd has given you the info you need, I think. I did pretty much the same as he, and used recepticles which were wired with the dimmer switches. You can engineer whatever convenient mount that you feel will work. Just remember the wattage requirements, and if you use metal boxes....ground the boxes to the bare wire in the romex that you use to wire the stuff together. If this is all greek to you.....then it would be wise to get help with the wiring.
     
  7. jaybird-7

    jaybird-7 TPF Noob!

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    Thanks mucho guys. I can do the wiring as you describe it, in double-gang boxes, each box with a receptacle on one side for the light to plug into and the dimmer on the other side, with a tail to plug into a wall socket. I have two studio lights (Smith Victor Q120s), each using a 600 watt bulb, so I'd better make a separate dimmer for each light to avoid possible overloads.

    I'll have to go back to Lowe's now and see if I can tell whether those dimmers they have are electronic or not, and try to find electronic ones.

    As to the color changes with dimming, I guess experimenting with the digital camera (an Olympus 8080) will sort out that problem. On the auto exposure setting, the camera usually does a pretty good job with white balance, and gives plausible skin tones, but it also has presets for tungsten if the auto setting can't handle it. And there's always Photoshop to remove color casts with.

    Anyway, I may just use the dimmers to cut down on the heat and extend bulb life during pauses in the shooting, rather than shooting with dimmed light. I'm using diffuser screens (white fabric stretched over PVC pipes) and it may take all the power to push enough light through the diffusers.

    I already shot a bunch of student portraits for my daughter's school using two ordinary 300-watt work lights, diffused through white fabric, and got very good results with individual portraits, although the lights were only barely strong enough for groups. These new genuine studio lights should work much better for the next shoot. The parents really liked the absence of the flash on the kids, especially the smallest ones, since my continuous lighting didn't startle or excite them, and as a result the photo sessions were pleasantly relaxed. It shows in the pictures.

    I'd really like to find or make some softboxes to attach directly to these lights (each one has a mounting hole under the reflector for clamping in some sort of umbrella or other diffuser, if I could only figure out what), because I can only run a light up so high before it goes above my stand-alone PVC diffusion screen. Of course, there's the heat to deal with with attached diffusers. Diffusers are a different topic, of course. Has anyone addressed diffusers for continuous lighting in this forum?
     
  8. kilgtfish

    kilgtfish TPF Noob!

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    I used white umbrellas to bounce the the light. Of course you need light stands with umbrella mounts. This worked very well for me. The dimmers allowed proportional adjustment of Key, fill, hair, and background lights. Softboxes are ideal, but the heat problem would be a worry, and they cost more than umbrellas. Since you are using hot lights, I think cost is a big factor for you. I bought light stands and light+umbrella holders on e-bay to get started. The smith victor lights are cheap and work pretty good. When I shot with film I used a blue filter to correct the incandescent color. It is a lot easier now with white balance.
     
  9. jaybird-7

    jaybird-7 TPF Noob!

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    Thanks for the info. I too bought my two Smith Victor lights and extra bulbs for them on Ebay, and now I guess I should look around there for unbrellas or softboxes or some such to diffuse the harsh light they emit. Seems like a softbox that could be held a little away from the hot lights somehow would work. I have a pretty good assortment of woodworking and welding tools, and might be able to make something, but of course I'd rather buy ready-made stuff if possible than do any real work.

    I like these continuous lights because I can not only do still photography from them but also light and paint models (I mean paint pictures of the models, not paint the models themselves, although that might be interesting). I also plan to do some video interviews and you can hardly do that with flash.

    On the other hand, softboxes bursting into flame at odd moments would probably distract from any of these pursuits, so diffusing the light must be done correctly and safely. In the past I used work lights on my models, which were usually sufficient visually, when painting, (as you can see in this photo: <http://www.nmia.com/~jaybird/ThomasBakerPaintings/>) but cameras want and need more light than your eyes do. The cloth panels stretched over PVC pipe frames work all right at diffusing light but are large and clumsy to set up. Guess only time will tell what I eventually end up using.
     
  10. Philip Weir

    Philip Weir TPF Noob!

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    Good morning, Just noticed this post and it reminded me of when, many years ago portrait photographers were using tungsten lighting, and quality studio flash was in its infancy. I personally used a studio flash pack that was like a small fridge. Slowly but surely flash with modeling lights became the norm for the vast majority of studio photographers for portrait, still life and fashion photography etc. My question would be, why don't you use flash for all your work, it is a much better way to go.

    www.philipweirphotography.com
     
  11. kilgtfish

    kilgtfish TPF Noob!

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    I don't know about the origional poster, but when I first attempted studio phtotography, I started using hot lights, because they are cheap, and I did not have a flash meter. Hot lights are easy to set up, and you can actually see the lighting result so you don't need a meter. Setting the lighting ratio is easy when you can see the result as you adjust the dimmers.
    Stobes, on the other hand, are more difficult....even if they have proportional modeling lights built in. It is fairly easy if you have a flash meter. If you don't then I guess you can shoot and adjust over and over again to get it right. Digital has opened up that possibility.
     

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