Continuous Fluorescent Light (Technical)

[wahgongzai]

Hi all, after consideration and advise by fellow CS members. I decided to move all the technical/tips/knowledge stuff from the galleries thread to here instead.

As I am busy with my work, I can only move part by part at a time if I am free.

Before I start anything I hope you guys will read first before posting anything.

This thread is strictly to share with one another on topics relating to CFL on:
Technical knowledge in using CFL
Tips and tricks
How different brand of camera behave when using CFL
Auto White balance issues/theories/troubleshoot
Lights/CRI/Color temperature/full spectrum theory
Getting good images and how you achieve it with CFL
How different brand of fluorescents behave (heat/CRI/and etc)
Types of CFLs
DIY CFL, interesting stuff relating to CFL

Please don't post things like:
Sourcing for CFL (Please please don't do it here, you go google yourself or post your own WTB in Buy/Sell)
Comparing with others equipments (I truly believe that different type of photography equipment has it own unique strength and weakness) If you really want to compare, please post your own thread.

Hope everyone will find this thread useful in someways. For guys who are CFL owners/non-owners, I hope we can make use of this and learn from each others.

Just to share a interesting quote:
instead of giving a person a fish and feed him a day, why not teach him to fish so he can feed himself forever. So now we are fisherman and try to teach each others to fish with CFL :bsmilie:

 

[wahgongzai]

A general guide

Light Temperature
1500 K Candlelight
2680 K 40-watt incandescent lamp
3200 K Sunrise/sunset
3400 K One hour from dusk/dawn
5000-4500 K Xenon lamp/light arc
5500 K Sunny daylight around noon (Full spectrum)
5500-5600 K Electronic photo flash
6500-7500 K Overcast sky
9000-12000 K Blue sky


CRI Range and Rating/indicator (contributed by Alvin and Prismatic)
100 - The Sun
90 - Full Spectrum lights with temperature of 5400-5600K
80 - Common Household lights

Some bulbs manufacturer will have this rating/indicator numbering on the bulbs. Example 865 means it has a CRI rating of 80-89 and the light temperature is 6500K. For 955 means it has a high CRI rating of 90-99 and has a light temperature 5500K. Please note not all brands will have these indicator.


Bulb Watts conversion on Fluorescent (a general guide)
8W=40BW
20W=100BW
26W=130BW
30W=150BW
32W=160BW
36W=180BW
40W=200BW
65W=325BW
70W=350BW
Basically just multiply by 5 and you can get the BW. However please be careful with bulbs that only indicate 30W/40W and nothing else. These can be only 6W/8W fluorescent instead.

 

[wahgongzai]

Types of Continuous Fluorescent Lights

The Lamp Socket: Common in Singapore, normally need a (Soft thru/Reflective Silver) Umbrella to insert into it to create a diffuse light source.

Flolight Fluorescent Light Tubes: Very Powerful lights, normally it uses a few Fluorescent tubes instead of fluorescent bulbs. And it ranges from 4-8 tubes, thus can get 1000BW and above. Normally this come with barndoors, which allow a person to control the light more efficiently. I think I saw two at Sony show room which they used it to light up objects for people to test the Sony DSLR.

Lamp Socket with multi bulb heads: Something like the lamp socket, but this one has a bigger head with multi bulb adapters (4-6) which you can insert the bulbs. It also has switch controls behind it which you can control the power by switching off one or more of the lights. Normally these lights come with a silver round metal dish and a diffuser cloth.

Fluorescent Lights with Softbox: Basically is a Lamp Socket but has a softbox attached to it. Come with varies sizes/shapes. I am using these for my work. So far I have the 40cm Square, 50cm Octagon, 50cm square, 50x70cm CFL

DIY CFL: I read it from one China Photography magazine. The photographer uses a ordinary lamp and one of those A4 paper carton box to create one. It works great, he even uses cardboards to create the barn doors. If anyone has created his/her DIY CFL please share with us

 

[wahgongzai]

(Contributed by alexj) thanks alexj

For lighting, normally what's important is the CRI (http://en.wikipedia.org/wiki/Color_rendering_index) and if the ballast is flicker-free. colour temperature is usually constant. As mentioned in some CFL posts around the forums, kinoflos (and similar brands most commonly used for video) are pretty popular as its pretty high on CRI and ballast is flicker-free (when in factory condition).

Normal fluorescents in the house are subject to colour cast (green or magenta), flickering at speeds other than multiples of 50hz (our power line frequency; 1/25 works, not sure about 1/100 and above), inconsistent colouring due to CRI (they might not produce certain colours of the 7 basic wavelength ROYGBIV)...

Some details are recalled off hand so pardon if their wrong or terms misused.

Generally, you wouldnt know if your light meter is off in its calibration, unless you send it in, or it's consistently off by more than (+/-) 1-stop, which then would be obvious. A simple test would be one you are doing but setting the exposure on ur camera to what ur meter tells you. I'm sure if ur using a dslr, manual mode should be possible, so check the reference book. Once you do that, look at ur shots on a calibrated screen and see if the exposure if off... change different lenses (but keep the same setup on tripod). So the only variable is the lens. If your exposure if not ideal then 1) compensate mentally for the light meter or 2) send it in.

If the exposures given by the different lenses are not similar, then you know that there are some differences in the lens - i.e. one exposes slightly brighter or darker. Not sure about your lighting kit, so it may or may not reproduce the same light consistently (which is not ideal for this test).

 

[wahgongzai]

Hi all, an update on this thread

Today I will be sharing on Full Spectrum Fluorescent Lights, below is the 5500K bulbs (also know as Full Spectrum)

Basically I have tested this FS bulb for a few product shoots and the result is good, no more green cast for all the shoots :bsmilie:. But most of the time, I used AWB on my Sony A100. Will try to test with other WB mode and see how it reacts.


Sample taken with continuous burst shoots on my A100

Condition Specs
One 50x70 CFL with Diffuser
4 x 36W 5500K = 720BW
Camera used : Sony A100 (Hand Held, Anti-Shake on)
ISO 200 F5 1/125
WB: Auto White Balance

Conclusion (In my opinion): Overall all the images turns out good, and no green cast can be found. Regarding the flickering issue thingy, I think no issue on my side. The only problem I had is I hand held the camera so the images is a bit up and down from the sequence (due to my super unsteady hands :sweat

I think the result will be better If I mount on tripod and use remote trigger instead.

One important point is all the test images is taken in a pitch dark room at night time, I discovered if I switch on my room ceiling lights (6500K). The green cast will return. So conclusion, if anyone wants a true 5500K no other lights interference is allow.

Will post more test shoot based on different WB modes if I have time

 

[hanqiang1011]

Hi,

To copy artwork, when we use tungsten light nowadays in DSLR, besides setting WB to tungsten, what sort of things we nedd to keep in mind?

Thanks.

 

[wahgongzai]

when we use tungsten light nowadays in DSLR, besides setting WB to tungsten, what sort of things we nedd to keep in mind?

Hi, I afraid I am not able to answer your question as I don't own or used any tungsten.

 

[wahgongzai]

Hi, long time never update this thread, so decided to share something on Full-Spectrum

Recently I have purchase some different watts Full-Spectrum bulbs from oversea, but found out that these bulbs were actually not Full spectrum even if they claim they are... :dunno:

image taken with a 75x75cm CFL with 3x85W 5500K bulbs (1275 BW) @ 1/125sec, F5.6 AWB
from left: 36W 5200-5500K, 85W 5500K, 55W 5400K

Result quite disappointing... Almost all the images turn out yellowish. I try with 5500K custom WB and AWB the result is the same. So I suspect this is actually below 5000K maybe around 4000K something near to warm light. Even if I on the light I can see slight yellow.

The 55W 5400K I tested out a few weeks back, the result also not so good, about 50% of the image have slight green/blue cast on it. I passed the 55W to a friend who use a color meter to measure, it turns out that the color temperature is 5900K. :sweat:


image taken with a 75x75cm CFL with 6x36W 5200K-5500K bulbs (1080 BW) @ 1/125sec, F5 AWB

36W variable is still the most accurate, very hard to find Full-Spectrum bulbs in Singapore. So far I have seem one 12W (60BW) 5000K bulb selling at AMK. But 12W is too low for any use. So guys if you have seem any full spectrum selling in Singapore, do share with us.

Something interesting about CFL:
Recently, I also came across a photo mag mentioning about CFL, instead calling it Full-Spectrum Light, they call it the Daylight Balance Light. :think:

 

[calebk]

Spectrum is a reference to CRI
Colour balance is a reference to Kelvin colour temperature.

I can have a "full spectrum" light of 90CRI but in tungsten balance, and I can have a 90CRI light in daylight balance. They are both almost full spectrum, but are of different colour temperature.

Aren't they both referring to different things?

 

[wahgongzai]

Spectrum is a reference to CRI
Colour balance is a reference to Kelvin colour temperature.

I can have a "full spectrum" light of 90CRI but in tungsten balance, and I can have a 90CRI light in daylight balance. They are both almost full spectrum, but are of different colour temperature.

Aren't they both referring to different things?

Hmmm... I not sure about this, maybe technically this are really two different terms.

By the way, this is part of the extract portion from the magazine:
"Unlike Hot Lights, DBFs (Daylight Balance Fluorescent) have the same color temperature as natural light and allow you to easily introduce daylight as an ancillary light source..."

its a cool and informative article, I enjoy reading it

 

[calebk]

Hmmm... I not sure about this, maybe technically this are really two different terms.

By the way, this is part of the extract portion from the magazine:
"Unlike Hot Lights, DBFs (Daylight Balance Fluorescent) have the same color temperature as natural light and allow you to easily introduce daylight as an ancillary light source..."

its a cool and informative article, I enjoy reading it

See here:

http://www.edbergphoto.com/pages/Tip-fluorescents.html

They are referring to different things - colour spectrum rendition and colour temperature.

 

[wahgongzai]

See here:

http://www.edbergphoto.com/pages/Tip-fluorescents.html

They are referring to different things - colour spectrum rendition and colour temperature.

Interesting indeed :think:

 

[wahgongzai]

Hi all, yesterday I finally manage to convert my softbox CFL set into a "portable camera flash set". Now I have the options of using Continuous Lights (fluorescent) or remote camera flash mount into it :bsmilie:. Have been looking into this mod since day one I own a 40cm CFL two years back.

Of course I can also just use a umbrella (reflect or thru) to do the same job, but with the softbox it does resemble a strobe in some ways, and since I own different shapes (octagon, square, rectangle) of CFLs. I have now more options and a bit better control in lighting.

Below is a image of the remote flash attached to my 70cm octagon CFL.

At first, my original idea is try to convert the CFL into something like a 400/250W strobe. So I plan to have at least 2-3 camera flash heads inside. I intend to do this by detaching the flash head from its body and extend its wiring so the head will be inside the CFL and the body attached to the light stand. This way I can on and off it from outside. Anyway I did manage to extend the wiring but it did not work. I think I connect something wrong somewhere :sweat: Hmmm... Now I am considering bringing it to a electrical technician (Sim Lim Tower) to help me.

(Please take note: Do not do this if you are not sure, certain risk is involve. Inside all camera flash, it has something call a capacitor (I think...) which store the charges before firing off. If someone touches this without precautions and it contain charges, than the electric charge will hit the person:faint:. For my side, I will fire the flash and immediately off it, this will make sure than the flash have minimum charge in it (Note: It still have some but just not full). So now I decided to find someone who is able to do this and not me.)

Anyway, I decided to mount the one camera flash into the CFL and it work fine. I than covered the CFL with its diffuser cloth and trigger it with a PT-04. It work perfectly. You can refer below to see the test image. Will post more images If I manage to upgrade and modify this in terms of construction and power.

 

[wahgongzai]

Test image references:
Equipment used: Sony A100/ Minolta 28-70 F2.8G/ Minolta Flash Meter III
Positioning: about 2.3 meter at a 20 degree angle aiming at the subject
Minor Note: I am using cheap used camera flash which I bought from Hong Kong for this experimental purposes. Its kinda old, My A100 has a max sync speed of 1/125sec (with AS on), it does not have power output control (eg 1/1 1/2 1/4 1/6...). Every time I fired it will be full blast.

If anyone will like to share constructive ideas and tips for this mod do post or PM me. Will update this if I manage to improve this mod further.

thanks

 

[wahgongzai]

CFL portable camera flash MOD set part II

Hi all just an update on this mod

With the help from a good friend. He manage to mod the flash for me. So now I am able to fit two flash head into my CFL.

The Flash body is attached outside (eg. to my light stand). Now I can on and off the flash from the outside, I can also change my PT04 channels easily if require. The reason for me to do this is because in the future, I will be using camera flash that has flash power output control (eg. Full 1/2 1/4 1/16). Which means more control to it :bsmilie:

 

[wahgongzai]

Test image references:
Equipment used: Sony A100/ Minolta 28-70 F2.8G/ Minolta Flash Meter III
Positioning: about 2.3 meter at a 20 degree angle aiming at the subject
Minor Note: My A100 has a max sync speed of 1/125sec (with AS on), The flash does not have power output control (eg Full 1/2 1/4 1/6...). Every time I fired both flash will be full blast.

With two flash, I am now able to increase the power. And ISO100 can be achieve at F5.6. Next step I will be testing this mod CFL in a portrait shoot and see how it fair

 

[wahgongzai]

Hi all saw some informative cool videos regarding color temperature, do check out if you free :bsmilie:

Color temperature on video
http://www.youtube.com/watch?v=NTUPEFXaBq8

Color temperature on video also but more in depth
http://www.youtube.com/watch?v=KX1ibvWW0tE

Very theoretical but excellent video on Color temperature
http://www.youtube.com/watch?v=7-5753PjB0E

Day Light Balance bulbs and its effect relating to photography. must check out
http://www.youtube.com/watch?v=Zm87f9grBJ0

Photography with Continuous Fluorescent Lights

 

[wahgongzai]

Hi all, long time never update. Will like to share something I just experimented few days back on CWB (custom white balance) with a expo/white balance filter cap on CFLs.
(before I start anything, will like to state that CWB is very new to me. Most of the time I use AWB. So if I mention/suggest anything which is incorrect do correct me and share with us your knowledge. thanks)

Specs/Details:
75x75cm CFL 3x85W (1275BW) x1
50x70cm CFL 4x36W (720BW) x1
Ambient light: None (pitch dark)
Flash/Strobe: None

Below is the cap that I used, its a third party cap commonly found in Singapore. In the market, there are large variety of brands ranging from S$18/- to S$100+++. Do take note that this is just a guide/reference as different brands/DSLR/Lens may give different results.

Below is the results with different white balance settings

Auto White balance (AWB), the image appear yellowish because of the 85W fluorescent which is between 4600-4900k.

Custom White Balance (CWB), the CWB is set by aiming at a white space from the scene. You need to fill the frame with white and than record a custom setting. The image improve a bit but yellow still can be seem in the image...

Custom White Balance (CWB) with expo/WB filter. The filter have to attached to the front of the lens and extend to its longest telephoto zoom, than aim at the scene and take a reading. The result is much better.

 

[wahgongzai]

Another two examples:

Custom White Balance (CWB).

Custom White Balance (CWB) with filter.

So, if you are not using any full spectrum bulbs or you DSLR AWB/CWB sucks. And you want to get rid of the green/yellow cast from the images. This is one of the method you can consider using.

Next time I will be sharing on using 18% grey card with CFL. Something similar from using a expo/WB filter cap. But with a 18% gray card, you have the option of doing post production adjustment using software instead of setting CWB on your DSLR.

 

[wahgongzai]

A cool video showing how to use the "Expo/WB filter Cap", do check it out

how to use the "Expo/WB filter Cap" 01