Kino Flow Diva Lite vs. 4-banks

[Yannick Hagman]

Unfortunately the thread seems to have disappeared with the forum crash. Someone recommended me to get a 4-bank instead of diva lite 400. What causes the magenta shift? And why doesn't the 4-bank suffer of it? I also noticed that they anounce the thungsten diva lite bulbs with 2900k instead of 3200k. Why?

[Kinosaur]

Unfortunately the thread seems to have disappeared with the forum crash. Someone recommended me to get a 4-bank instead of diva lite 400. What causes the magenta shift? And why doesn't the 4-bank suffer of it? I also noticed that they anounce the thungsten diva lite bulbs with 2900k instead of 3200k. Why?

I suggested that you consider the 4 banks, I cant answer your questions I'm afraid. Perhaps the best thing would be to rent a diva and a 4-bank for your next shoot and see what you think. at the end of the day all that matters is how they look on camera, and how you find them to work with.

[Richard Andrewski]

I had a posting on that thread to answer your question about magenta shift. I'll repost it again.

On the 4 foot tubes and why so many people report that they don't see a color shift with them: firstly, these T12 tubes (like the Kino 75w or 40w 4 foot tubes) aren't continuously dimmable like the newer CFL technology of biax T5 type 55w lamps as used in the Diva, Cool Lights, Flolights, etc.

The 55w tube is quickly becoming a standard in video use where they do want to go the flo route--perhaps film people don't like it so much because of a problem with color shift during dimming, but you haven't heard the whole story of why that is.

Let's cover why you see no problem with color shift in a T12 tube. The fixtures that feature these tubes, will have an intensity switch to switch to 50% intensity. If these tubes were continuously dimmable you would see a color temperature change on them just like the 55w tube, as all discharge tubes whether fluorescent or HMI exhibit the same characteristics. It's not the ballast or fixture that's at fault, its the tube and how it works and it's just the nature of it. The Diva, Cool Lights dimmables, etc.: these just happen to use a technology that you can continuously dim below 50% so you see the problem and they get a bad reputation for that. Again, if your Kino 4 foot tube could be dimmed below 50% you'd see it there too and you'd understand that this is a fluorescent issue, not an issue inherent in one kind of tube and not in another one. Also, on the subject of the HMI type discharge tubes: they're part of the metal halide family and all metal halide can't be electronically dimmed below 50%, it's just not possible and maintain ignition. Any tricks to dim it below 50% usually are mechanical in nature. Thus--people don't see a color temp shift so much with HMI because you can't dim it below 50% anyway.

As it is, most people that report negatively on the 55w tube and it's dimming characterstics do so because it is continuously dimmable when you have a dimmable ballast on the fixture. You can go to 75% or 35% or even 5%. The major color shift starts to occur at around 50 to 60%. Thus, this is why people don't report a problem with the T12 tubes. They can't be dimmed below 50% anyway so you why would the problem pop up?

Then, on the subject of why some lamps shift toward one color or another during dimming: Kino Flo has some 55w tubes made primarily for film use that have more magenta coloring in the phosphor mix. Magenta is chosen for its minus green effect for the same reasons you also use a magenta backlight for green screen work--to counteract green spill on the subject. More specifically, magenta is chosen because it's the color opposite of green on the color wheel. If you wanted to counteract blue, for blue spill on a blue screen, you'd choose amber, etc.

Anyway, when you dim any fluorescent tube, not just a 55w one, if it can go below 50% it will exhibit color temperature shift and will shift toward one dominant phosphor in the tube--in the case of the special magenta kino lamps, you can guess why it favors the magenta coloring during dimming. I've noticed that my 3200K tubes get a bit more red during dimming. So do Osram tubes and probably most of the other ones. The normal 5600K tubes perhaps seem a bit more gray during dimming, etc.

By the way, there shouldn't be any particular reason to choose Kino magenta coated lamps for use with a RED camera or any digital camera as they already do a great job of filtering out the green spike (and as long as the CRI of the tube is high enough in the 80's range or higher) that all discharge tubes from flo's to HMI/metal halide will normally exhibit on real film. Video and digital cameras are a far more forgiving medium in this respect than film and I see no reason why the RED camera should behave more like a film camera in this particular respect. It should behave like a digital camera or a video camera with discharge lighting. Time will tell though.

[pablokorona]

i can personally vouch for fantastic flexibility of the diva light. It, and a bounce/fill have been my run and gun staple. It being dimmable, allows for fantastic flexibility especially with many talking head setups per day in a lower budget testimonial shoot. As for the magenta cast, don't drop it past 50%, which color shift happens no matter what the bulb type is. There's a switch to drop it from 4Lamp output to 2Lamp output.

(youtube darkened this: )
http://www.youtube.com/watch?v=suy0PmgQbyk

if i remember reading the stats correctly, its light output is actually greater than a 2 ft4Bank, even close to if not more than a 4ft 4Bank

[Kinosaur]

i can personally vouch for fantastic flexibility of the diva light. It, and a bounce/fill have been my run and gun staple. It being dimmable, allows for fantastic flexibility especially with many talking head setups per day in a lower budget testimonial shoot. As for the magenta cast, don't drop it past 50%, which color shift happens no matter what the bulb type is. There's a switch to drop it from 4Lamp output to 2Lamp output.

(youtube darkened this: )
http://www.youtube.com/watch?v=suy0PmgQbyk

if i remember reading the stats correctly, its light output is actually greater than a 2 ft4Bank, even close to if not more than a 4ft 4Bank

I'm reliably informed that the Diva light is Kino flo's best selling fixture, so I guess I may be in the minority in not liking it, however when Ive used one I found that it needed 1/4 green correction to match tungsten fittings (when at 100%) this was with brand new tubes, also with the 55w single ended tubes the orientation is an issue, they have to be the right way up or one end has to be a bit higher than the other or the colour shifts further, the fixture is clearly marked to show you which way up, this isnt an issue with the double ended 4 bank tubes, and I found the warm up time can be rather long, and the bulb life isnt great. apart from that they're fine. LOL
There has been some mention of a 50% swith on the 4 bank ballast, what it actually has is a switch to select either 2' or 4' fixture, with a 4' fixture this can be used to reduce the output, by selecting 2' , but its not recommended to over run the 2' fixtures although I have on occaision accidentally with no apparent harmful effects. you can switch each individual lamp on or off though.

[Rick Darge]

I heard that if you run a 2' with the 4' setting, it gives you a green shift spike, that's all...and it wears out the life of the bulb.

[Yannick Hagman]

Thanks for all the recommendations and insights. What are cheaper shops except for bhphotovideo.com (which only have diva lite kits for European current) ? Here in Europe, they simply overcharge everything for no reason. And with the low Dollar importing is the way to go for me.

[Yannick Hagman]

What about the one from Lowel: http://www.evsonline.com/merchant2/merchant.mvc?Screen=PROD&Product_Code=CF40
?