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Old Apr 14, 2011, 5:33 PM   #1
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Default Range of wattage for light bulbs!

Hello!
-I want to photograph my acrylic paintings (2-D & not varnished) in my 14 X 24 ft. garage & I will cover all windows with black block out fabric so that ambient light should be close to zero.
-I will be using a Nikon D5000 on a Slik 700 DX Pro tripod with an IS0 of 100 or lower, F8-f stop, bracket exposure. I will need to experiment.
-My artwork is, at the largest 24 X 28 inches & will be shot on an easel thatís parallel with the camera & the back wall thatís covered in black fabric. So the furthest away Iíll need to be for these paintings is no more than 7 ft. with the lens set at 55mm.
-I will be shooting in RAW & be using a Whi Bal card for reference in ACR & a color calibrated monitor.
-I need 2 lights on stands that I can utilize the 45 degree techniques.
-Iím thinking that I need not spend more than $300.00. Iím not adverse to using tungsten quartz but I donít want the bulbs to be so hot that they can damage my art or become a fire hazard. That is why:
1.) I need to know what is a good range of wattage for light bulbs that will work for me in my shooting situation.
2.) What is a good range of wattage for tungsten so that I have enough of wattage to get even light & what is excessively dangerous.
3.) Likewise with the (cool) florescent lights, what is enough wattage? Iím looking for ball park figures, not precise formulas. Iím lost!
-thanks!
-Dave Zippi






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Old Apr 14, 2011, 6:27 PM   #2
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Dave - I was a lighting consultant for 5 years (20 years ago, lol) and your question is extremely complex, because there are so many variables to take into account. It's not just about wattage. You have to determine what type of reflector, the desired shape of the reflector to achieve the desired effect, color temprature, etc. etc. To get the most accurate color, I would think you would want to get what is called a full spectrum fluorescent lamp with kelvin temperature of at least 5,000, & make sure that the lamp (light bulb in layman terms) is the highest CRI (color rendering index) possible. The best lamps will give you a CRI of 90 or above. You will also have to deal with the effect of the reflection of the acrylic paint. Then you need to determine brightness or lumen output. The luminaire (fixture) design, it's efficacy, it's distance from the art and the desired lumen level are all factors that will determine what wattage. There may be some guide out there that will help you with your answer, but if it were me, I would start with a single flourescent luminaire (fixture) with 5000K T8 or compact flourescent lamps with a CRI of at least 90. If you're only taking pictures of one piece of art at a time, I would be surprised if one or two fixtures wouldn't do the trick. My company represented Philips products, & here is an example of what you would need:

PHILIPS TL 950 - T8, 5000 Kelvin, 98 CRI Full Spectrum Fluorescent Lamps
The Philips TL 950 Full Spectrum fluorescent lights offer unmatched Coloring Rendering in T8 Fluorescent Technology!!! The Philipus TL950 series is a very high CRI lamp which is available in 24, 36 and 48 inch sizes. Its low color temperature combined with a high CRI translate to a longer acceptable life.
Full Spectrum Fluorescent Lamps, particular the philips TL 950s Are Ideal for ..
  • High- End Retail Shops
  • Hotel Ballrooms and Restrooms
  • Museums and Art Galleries
  • Graphic Arts
  • Photography Studios
  • Avicultural Lamps
The Philips F32T8 TL950 Full Spectrum Fluorescent Bulbs and Lamps Feature:
  • The philips TL950 Full Spectrum Fluorescent Bulbs are Perfect for Color Critical Applications

    Provides distortion-free fluorescent lighting
  • 5000 Kelvin at 98 CRI

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Old Apr 14, 2011, 6:55 PM   #3
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You don't need to buy an expensive fixture from a photography supply. You can probably get everything you need from a lighting wholesaler in your area that sells Philips products (or the GE equivalent, etc.).
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Old Apr 15, 2011, 9:11 AM   #4
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Jerry,

Thanks for the informative advice.
-Dave Zippi
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Old Apr 15, 2011, 9:53 AM   #5
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Dave - I wish I could be more helpful than just a light source recommendation. I took quite a bit of training on how to make these kind of calculations, but I don't have the books & workbooks anymore and my 50 yr old mind can't recall something like that from 20 years ago. :-) By the way, not only will you get much better color rendering using the full spectrum fluorescents, they also give out more lumens per watt, which means there will less heat for the equivalent amount of light as compared to a tungsten light source.
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Old Apr 16, 2011, 6:04 PM   #6
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Default Thanks, Jerry!

Jerry, Thanks!

I've been to 4 photography forums asking for some advice on my situation & you've been the only one who has steered me in the right direction. Probably has something to do with you doing this as a career. I've gotten a lot of confusing off the subject amateur advice elsewhere!

I truly appreciate your help & feel more confident in searching for florescent lights.
-Dave
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Old Apr 18, 2011, 9:19 AM   #7
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Dave- you're more than welcome. I'm just glad my old business experience was able to help you out. I'm always amazed at the help I get on this forum. There are a lot of folks on here much smarter & more experienced than I will ever be and they are almost always happy to help. Welcome to Steve's by the way.
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Old Apr 20, 2011, 8:02 AM   #8
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Setting your camera 7' away from the object with an f-stop of 8 will drastically increase your lighting needs, without any benefit I can perceive. That set-up might be preferred for a portrait photo of a person, but for a flat painting I recommend opening up the aperture as wide as you can to let more light at the sensor. The shallow depth of field will be of no consequence for the painting as long as the focus is accurate.

An on-camera flash will probably create a harsh reflection back to the lens. This might be eliminated with a polarizing filter. Another option would be to buy a couple of those job lights - they are simply an aluminum reflector that holds a bulb and has an integral clamp for mounting. Pop a 200w equivalent 5500K compact fluorescent bulb in there, cover with cheese cloth (buy a reflector that has the wire cover to prevent the cheese cloth from getting close to the bulb, and do not leave in unattended) and you're in business. 200w CFL = $10-$15 each, job light = $7-$10 each, cheese cloth = $4, total $40-$55.

Aim the lights at a 45 deg to the painting from both sides and see what happens. A polarizing filter may still be necessary to cut the reflection. And if the light is not diffuse enough, replace the cheese cloth with a very thin cotton fabric.
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