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Flash versus continuous lighting are we at the crossroads?.
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Len Willan



Joined: 22 Mar 2009
Posts: 84
Location: Como West Sydney Australia

PostPosted: Sun Dec 02, 2012 8:13 pm    Post subject: Flash versus continuous lighting are we at the crossroads?. Reply with quote

For a long time I have been using Nikon Sb-R200 flashes, and with the current rate of change in lighting technology I have been considering for when focus stacking for use with Zerene Stacker to use some form of continuous lighting.
Cree lighting was the first LEDs to draw my attention (they are even installing Cree Lights in Sydney as street lights)

Then my attention was drawn to an article http://ledsmagazine.com/news/9/11/10
That stated;
"The ability to adjust the color temperature of a white-light LED fixture provides benefits in a number of applications. In retail applications, for example, when a sales display is changed the color temperature can be altered to show the goods at their best. In offices, hotels and other scenarios, the color temperature can be adjusted throughout the day to optimize comfort, productivity and well being.
The usual method to achieve an adjustable color temperature is to have an array of different LEDs, for example a mix of warm- and cool-white LEDs. These are controlled separately so that the output of each set of LEDs can be adjusted, which in turn changes the color temperature of the mixed light from the fixture. "

Now we have another choice a 105W E27 5400K Photo Video Photography Studio CFL Daylight Lighting Lamp Bulb
The Seller states "Why choose bulbs with colour temperature 5500K/5400K for shooting?
Please check the graph above.
Only the colour temperature 5500k/5400K enjoys colourless spectrum while 6400k is blue,and 4500k yellow.
So not the highest the best,5500k/5400K is your right choice for photography."
Specification:
• 105W (525w equivalent) Continuous Light Bulb, pure white daylight
• 5500K, just made for photography
• General colour rendering index(CRI) Ra > 90
• 10000 hours long life bulbs
• E27 socket, suitable for any light holder with E27 socket
• Voltage: 220V-240V
• Weight: 0.6kg

http://www.ebay.com.au/itm/360527372002?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Some of the problems arising from using flash systems were comprehensively discussed in Riks post here: http://photomacrography.net/forum/viewtopic.php?t=16414

Where to now, comments appreciated,
Len
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elf



Joined: 18 Nov 2007
Posts: 1308

PostPosted: Mon Dec 03, 2012 12:15 am    Post subject: Reply with quote

Why mess around with a wimpy 105 watts when you could use one of these: http://yongshi.en.alibaba.com/product/672807366-213888356/high_power_energy_saving_lamp_8U_17mm_220V_250w_cfl_6500k.html

Unfortunately you'll be limited to purchasing 120,000 per month Smile
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Len Willan



Joined: 22 Mar 2009
Posts: 84
Location: Como West Sydney Australia

PostPosted: Mon Dec 03, 2012 12:28 am    Post subject: Reply with quote

Thank you elf .
That is a great increment, what do you think of the colour temperature of 6500 Kelvin compared to the suggested 5500 on the initial one?
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elf



Joined: 18 Nov 2007
Posts: 1308

PostPosted: Mon Dec 03, 2012 12:39 am    Post subject: Reply with quote

I have several Ott lamps that are around 5500k, but only 15 watts so the required shutter speeds are too slow. I don't think the color temperature will usually make a difference as you can set the white balance. It will, however make a difference if you're mixing light sources.

I suspect the price of these lights should be dropping pretty fast after the last election in the US (at least in Washington and Colorado) Smile
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rjlittlefield
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PostPosted: Mon Dec 03, 2012 1:48 am    Post subject: Re: Flash versus continuous lighting are we at the crossroad Reply with quote

Len Willan wrote:
Where to now, comments appreciated

Back when I was shooting video, I observed with several different types of fluorescent bulbs that they changed color systematically on each cycle of AC power. I assume this was because the phosphor coating had several components with different colors and relaxation times.

I just now set my DSLR on 1/320 second, pointed it at a fluorescent fixture, and ripped off a series of 10 shots. The differences in color and brightness were striking -- much worse than anything I've ever seen with flash. Even more interesting, from time to time the two bulbs would swap places, first one brighter, then the other. For your amusement:


So I think one key issue you need to consider is what exposure times you want to use. If you're comfortable shooting with say 1 second exposure time, then you'll be averaging over 100-120 half-cycles of AC power and CFLs would probably be fine. But with shorter exposures I think you'll experience variation that is increasingly painful.

This is very different from the situation with DC or high frequency AC regulated incandescent bulbs commonly found in halogen illuminators. Even my inexpensive halogen illuminator gives exposures that vary by only about +-1 pixel value over a series of 10 exposures at 1/320 second. Here's the brightest/darkest pair in that case:


I have not checked out commercial LEDs so I have no idea how they behave. But I'm skeptical...

--Rik
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Len Willan



Joined: 22 Mar 2009
Posts: 84
Location: Como West Sydney Australia

PostPosted: Mon Dec 03, 2012 2:08 am    Post subject: Reply with quote

Rik thanks for checking it out , if the latest CFL lamps are not a satisfactory proposition, I will revert to my old Schott KL 1500 fiber optic set up, even if the bulbs have a short life and are only about 3200 Kelvin and a low lumen yield. So much for progress,
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rjlittlefield
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PostPosted: Mon Dec 03, 2012 2:21 am    Post subject: Reply with quote

What can I say? Progress in light bulbs is normally measured against a sensory system with about 60 Hz flicker fusion frequency and lousy color memory. Our camera sensors can be a lot more demanding, depending on how they're set.

--Rik
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Chris S.
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PostPosted: Mon Dec 03, 2012 3:03 am    Post subject: Reply with quote

Len, since you asked for comments, perhaps what follows is welcome--but a long-windedness warning is officially issued. Smile

That Ledsmagazine article was an interesting link. But like Elf, I don’t think this particular development (LED light with adjustable color temperature) changes the playing field much for studio macro, where we can use light sources with matched color temperatures and set the white balance of our camera or raw file conversion accordingly. A color-adjustable light source might be nice for mixed-light situations that we get outside the studio, but we’ve long had gels to help us with that. And LEDs are probably not yet powerful enough for most of those situations.

Also, the eBay vendor hawking daylight-balanced CFL is, I think, oversimplifying and overstating his case, though his light bulbs may still be pretty nice. The same argument applies as with adjustable LEDs—we can set our cameras’ white balance for a wide range of color temperatures, and I’d be leery of claims that we get a huge benefit in shooting with lights said to be at “5500k/5400K.”

Fanatics could consider the following: Adjusting color temperature in camera or in raw conversion amplifies or attenuates individual color channels (R, G, or B), so there might be some benefit in shooting at whatever color temperature is optimal for a particular sensor. While I’d suspect that this would be a daylight color temperature, I wouldn’t bet my life on it without testing. And I’d expect that any benefits would show up as reduced noise in certain color channels, perceptible mostly in dark regions when operating close to the limits of a sensor’s dynamic range. If so, such an advantage should not emphasized beyond the limited circumstances in which it might show up.

Something I’m leery about with “white” LEDs is that if one looks at their emissions spectra, most have “valleys” at certain wavelengths. Suppose one were to shoot a subject having areas of a color nearly absent in the emissions spectrum. Since there would be no light waves hitting those areas with the proper wavelength to bounce off, would it happen that the area would be rendered as too dark or otherwise inaccurate? I don’t know, but am skeptical enough that I’d want to test this before committing to an LED lighting approach. Lots of attractive photographs have been taken with LED light; but if a project requires color accuracy, are there holes in the spectrum that a particular LED can’t deliver? Again, I don’t know—but it’s something I would want to test.

Your “crossroads” postulate--bless it--gives us a chance to ponder a vital topic. I would say that we have not newly arrived at this crossroads, but have long been there, even with decades-old technology. The continuous lights I use for studio macro are halogen, as I want very bright, concentrated sources directed through fiber optic light guides. LEDs have not yet reached a price/performance level for this use that makes me ready to integrate them, though I look forward to that time coming.

As you say, some pros and cons of flash vs. continuous light were discussed in Rik’s thread. But I don’t think the list was comprehensive—so let me do a partial recap, and add a couple more items. Flash is often a miracle cure for movement problems; most beginners would be well-advised to start with flash and not consider continuous light until something about flash cramps their style. But ironically, in other situations (especially with light-weight, dark-colored subjects in regimes requiring a lot of light), flash can induce violent subject motion during even the shortest exposures, and can be an irrecoverable cause of motion problems. Some have described this situation as “rare”—and it is probably so for many photographers—but for others of us, it is a very common problem. Certain subjects simply cannot be imaged with flash, so some of us have no choice but to add continuous light to our bag of tricks. But this has other advantages—flash can vary in intensity and color from one shot to the next, which continuous light does not. And during long stacks, battery-powered flashes can run out of juice. Flash units can overheat. In order to get full capacitor recharges and avoid overheating, a rest interval may be needed between shots, which can add up to hours for deep stacks. For me, doing deep stacks with continuous light is much faster than doing them with flash. Plus, continuous light has the great virtue of being WYSIWYG; flash is emphatically not. But one’s setup needs to be very stable in order to use continuous light. So for every macro image I make, I ask myself which devil I want to wrestle with—flash or continuous light. Neither is perfect.

What changes if we substitute LED or CFL for halogen? Either technology can produce continuous light with much less heat than halogen—all the better to avoid cooking our subjects and to save electricity. The halogen light’s cooling fan may no longer be necessary, removing one possible source of vibration (from the fan motor) and air movement (from the fan itself). In what strikes me as a largely unrecognized benefit, LED light can be gated electronically—so the light can be turned on after the camera shutter is open and consequent vibration has dissipated. Few photographers seem to be making use of this advantage, but I think it is substantial; with halogen, one needs to mitigate camera shutter vibration with a mechanical shutter on the lights, a long enough shutter speed to make shutter-induced-vibration unnoticeable, or electronic first shutter curtain (“EFSC”—a feature unavailable with many cameras, including Nikons, which I use).

So the continuous vs. flash dilemma is, I think, a very pertinent issue, even if not a new one. My present approach is to have both available, and choose either tool for a particular job. Increasingly often, I’m choosing continuous halogen light. If LED replacements for my halogen bulbs ever become attractive in price and performance, I’ll substitute them.

I see that Rik has also responded while I was typing. Rik, out of curiosity, did the fluorescent bulbs you shot have a modern electronic ballast, or an older one? In the back of my mind is a thought that the two have quite different flicker characteristics, with the older technology being much worse. I do know that some portrait photographers are now using fluorescent light--but principally with modern, electronic ballasts. If memory serves, they say that they don't have to worry about shutter speed vs. flicker anymore. NB, this is with long fluorescent bulbs, not CFLs--no clue if observations about one apply to the other.

--Chris
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rjlittlefield
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PostPosted: Mon Dec 03, 2012 3:28 am    Post subject: Reply with quote

Chris S. wrote:
Rik, out of curiosity, did the fluorescent bulbs you shot have a modern electronic ballast, or an older one?

That was an older one, with 4 foot straight tubes.

Here's a CFL, replaced a couple of months ago. Again with the 1/320 second shutter speed.



Cheers,
--Rik
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Chris S.
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PostPosted: Mon Dec 03, 2012 4:22 am    Post subject: Reply with quote

Eek! Guess that CFL isn't going to work. Nice demonstration, Rik.

Here is a link to a thread on the Fredmiranda Lighting & Studio Techniques forum by "gintasr," who made a portrait light out of four-foot fluorescent bulbs with electronic ballasts. Having an interest in DIY lighting projects, a statement of his stuck with me: "For a ballast, you MUST make sure it is ELECTRONIC, otherwise you will be getting flicker and your exposure will vary frame to frame. The electronic ballast will let you use any shutter speed without a hint of flicker." I have not tested his assertion. If correct, it must not apply to CFLs--or at least not to all CFLs.

Is the CFL you photographed dimmable? If so, I wonder if a non-dimmable CFL would also exhibit flicker? I don't know how dimming is accomplished in CFLs, but wouldn't be surprised if an induced, variable flicker rate were involved, as it is in some adjustable LED lights.

--Chris
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johan



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PostPosted: Mon Dec 03, 2012 4:33 am    Post subject: Reply with quote

Chris S. wrote:
in other situations (especially with light-weight, dark-colored subjects in regimes requiring a lot of light), flash can induce violent subject motion during even the shortest exposures, and can be an irrecoverable cause of motion problems. Some have described this situation as “rare”—and it is probably so for many photographers—but for others of us, it is a very common problem. Certain subjects simply cannot be imaged with flash


Fwiw, I use flash to get around vibration problems. The biggest limitations I've come across are mechanical ones, of positioning, so I use all sorts of homemade things like barn doors to focus the light where I need it. I'm curious about this quoted section though. What would be some examples of this?

Coincidentally I came across this today on the BBC, about field-induced polymer electroluminescent (Fipel) technology, which looked interesting. They seem to stress its colour output which can't be bad for types like us.
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Craig Gerard



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PostPosted: Mon Dec 03, 2012 5:37 am    Post subject: Reply with quote

Johan,

Light is energy (as you know) ...I believe Chris may be specifically referring to the photon dance (that's what I call it). This matter was discussed in a thread sometime recently...too late here for me to track it down at the moment.

Possibly this one from August 2011:
http://www.photomacrography.net/forum/viewtopic.php?p=90774#90774


Craig
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johan



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PostPosted: Mon Dec 03, 2012 6:33 am    Post subject: Reply with quote

Thanks Craig, I get what he is referring to now
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NikonUser



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PostPosted: Mon Dec 03, 2012 9:31 am    Post subject: Reply with quote

What is the problem with the SB-R200s - apart from the cost of batteries?

I do a lot of focus stacking using Zerene and SB-R200s and SB Speedlights and have yet to see any reason to switch to continuous lighting.

I use a Nikon camera with Live View and connect the camera to a 19" TV via a HDMI cable. A test shot shows up instantaneously on the TV and shows the effect of the lighting; simple to change the flashes' positions and fire another test shot. Perhaps not quite as easy as if I had continuous lighting but works well. I guess one could use a continuous light source to check illumination and shadows, using Live View and a TV, and them place flashes in the same positions for the photos.

PS/ A single SB-R200 on its stand lines up exactly with the lamp at the back of an Olympus BHS microscope. I use the bare 100w bulb on the BHS to get setup for an image and then simply slide the SB-R200 into position with the front of the flash touching the lamp.
Very important not to let the flash get close to the bulb when the bulb is lit, also wait until the bulb cools before sliding the SB-R200 into position.
Why you ask? the microscope lamp get so hot that it melts the flash - been there done that!
A single SB-R200 gives enough light for brightfield photos; I substitute a SB-900 when using polarization or DIC
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Nikon camera, lenses and objectives
Olympus microscope and objectives
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Len Willan



Joined: 22 Mar 2009
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PostPosted: Mon Dec 03, 2012 11:20 am    Post subject: Reply with quote

Thank you all
It is great to see the constructive comments that members are making.
My thoughts for my own use are to two setups.
1) Horizontal,and Flash for the 1 to 1 range
2)Vertical,and Continuous lighting for higher magnification and deeper Zerene Stacking.

Here is an example of the vertical set up with continuous lighting that I am presently building using fiber optic lighting.



The two different choices are clearly shown in the links below.
Len
SCHOTT® LLS This LED based light source is a hybrid solution pairing LED technology with fiber optic light guides. It is the ultimate in light control, boasting a simple user interface with versatile remote control abilities (analog, RS-232, and ethernet). The SCHOTT LLS fits all SCHOTT COLDVision light guides, optimal performance is achieved when using the light source with larger bundle diameters, 9-14 mm.
http://www.us.schott.com/lightingimaging/english/machinevision/products/fiber-optic-illumination/led-lightsources.html
Setting Up the Visionary Digital Passport II - Part 2 well illustrates the “ Vertical Flash”solution’
http://www.youtube.com/watch?v=A7KfJ5tvO34
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