 Wayne A. Renfrew |
Mixing flash with fluorescent light I need to take photos at night in a Scout hall, under fluorescent light. I need to use flash, as the kids don't stop moving for photos! I have a Pentax K20D and Sigma EF530DG Super flash. I find the problem where the area covered by flash is fine, but the rest (walls etc.) are green-tinted. I'd read a bit on the net, suggesting to use a green gel on the flash and to set the WB to fluoro. However, when I went to the local photo shops (Melbourne Australia), they looked at me like I was an idiot. So, I have some questions... firstly, is the gel solution reasonable and, if so, what specifically do I ask for at a photo shop and how do I attach it to the flash? Secondly, instead of a gel on the flash, can the photos be corrected in PaintShop Pro or Photoshop (remembering that the kids in the foreground are shown correctly as they're in range of the flash)?
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A C |
you're not an idiot! I have some roscolux gels (the sample pack) that I haven't had enough time to play with. The gels are the same type you use for theater lighting (so a theater store might be able to help you more than a photography store). You can buy sheets of them and cut them down to size. When I put my gels on, I use tape. I just can't fire at full power or it can melt the gel. Otherwise, I have no problems. There are some companies that make nice little thingys to fit on your flash. I had a bunch of sites bookmarked but my computer is dead and I don't have access to my list of favorites, sorry. But if you do some searching on google, you can find 'em like I did. Stofen makes a set: http://www.amazon.com/Sto-Fen-Green-Colored-Omni-Bounce-Canon/dp/B00097D5XI/ref=pd_cp_p_3/002-4468674-0324801?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-41&pf_rd_r=08DMS96MM95WYBBY743C&pf_rd_t=201&pf_rd_p=413862901&pf_rd_i=B00098FFN0 I wouldn't try to fix it in photoshop ... that's a lot of work!
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Alan N. Marcus |
Hi Wayne, No filter will force your flash to match florescent. The principle is an evacuated tube filled with a tiny droplet of mercury. The vacuum inside the tube causes the mercury to evaporate and fill the tube with mercury vapor at low pressure. This mixture will conduct an electric current. As the current transverses the tube the mercury vapor emits UV light. Since UV is invisible to us humans, the inside walls of the tube are coated with phosphorus. UV energy strikes the phosphorus which converts this energy to visible light. It’s popular because florescent is far more efficient than tungsten. The color of the fluorescent light outputted lacks a continuous spectrum. However it stimulates the human eye; we see approximately white light. However films and digital cameras see this light quite differently. Usually subjects illumined by florescent record with a greenish cast. Meanwhile your electronic flash emits simulated daylight. The problem is compounded by the fact that the phosphorus used is different per manufacturer. Additionally they are blended to produce different colors. To name a few – Daylight – Warm White – Deluxe Warm White – Cool White – etc. What I am trying to tell you, it’s impossible to filter the camera and correct to achieve perfect color balance. Your digital can do a reasonable job on its own. However when you mix electronic flash a florescent, the camera can’t cope. Filter the flash: Kodak and others make CC (color correcting filters). These are gelatins, designed to be placed on the camera. Also they make CP (color printing) made of acetate to be placed in front of light source. They are labeled as to their color and strength: Strength 2 f/stop = 60 – Strength 1 f/stop = 30 – Strength 2/3 f/stop = 20 – Strength ½ f/stop = 15 – Strength 1/3 f/stop = 10. Color M = magenta – Y = Yellow – C = Cyan Table of corrections for various Fluorescents Daylight fluorescent 40M + 30Y Any camera shop worth their salt knows about CC and CP filters. Alan Marcus (marginal technical gobbledygook)
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Wayne A. Renfrew |
Hopefully this might give a better idea of what fluoro type is present. Thanks
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