Does the quality of light vary between studio flashes and portable speedlites?
The first time I used speedlites, the light was very good. Then I purchased an Elinchrom D-Lite kit. My first impression was that the light is a little on the warm side, and the quality of light lower than Canon 580-EX speedlites.
Then I got an Elinchrom Quadra kit, and after my first shot I said, "WOW!" The light has a metallic color, the subjects looks better and have a good light/shadow definition. Of course I used a softbox of similar size in all cases. One Hollywood photographer said that he can recognise if a photo was made with expensive lights or cheap lights.
What have you discovered about flash light quality? Are all the same? What differences have you seen?
I have made a review here on my site with quadra vs d-lite color temperature
A softbox is a light modifier. Light can be modified a zillion ways.
There is a huge amount of literature on light modifiers and making lights be better for your photos. Check out the Strobist blog. http://strobist.blogspot.com/
It is fairly easy to see quality, and its easier to get good quality from ProFoto or Elinchrom, but that doesn't mean its impossible to get great quality from inexpensive lights.
Gear does not take the photo, photographers take the photos. Gear is simple a tool.
Yes - Personal experience has shown me that, in particular "speedlights" (IE on-camera / battery powered flash guns) have very differing characteristics in 2 main ways:
I have found that cheap (what i like to call Chinese eBay specials) tend to be inferior in both, as they are designed to a price, and use "a flash tube" as opposed to a specially designed tube filled with a special gas mix. So therefore have varying "histograms" (if you like) in the same way that fluorescent lighting lacks certain wavelengths.
Of course we must not forget that all speedlights / flash guns have BUILT-IN Light modifiers, so the design of the reflectors and fresnel lenses within make a huge difference to the spread and uniformity, especially in the zoom models.
The same can be said for studio flashes, although the light modifiers are usually detachable, so cant really be considered in this case.
DONT FORGET - White Balance CANNOT cure everything if the wavelength was missing in the first place, that "information" cannot be re-created. A prime example being near-monochromatic sodium street lighting - if you try to get rid of the orange cast via white balance, you will end up with a near B&W image.
Assuming the light is fairly full spectrum and all of your lights have similar color output, the differences are negligible for all but the most critical environments (i.e. scientific documentation). You can document the differences in light color output just by changing settings in some strobes. See this for such an example. But in the world of portrait photography there are so many more factors that have a much higher degree of impact on the final result.
One good rule of thumb about improving your image quality is to buy the best lens you can afford and stick with a decent body rather than keep a decent lens and upgrade to a top tier body. I've seen several "experts" say the same thing about lights and modifiers: get a decent light and the best modifiers you can afford. Scott Kelby says in Light It, Shoot It, Retouch It, "You just need something that creates a bright flash of light, which is pretty much any strobe. It's not so much the type or brand of light, it's the modifier (soft box, beauty dish, strip bank, etc.) that you put in front of that flash, and how you aim and position it, that makes the difference." Of course Kelby's main emphasis and expertise is post processing, where differences in color temperature are managed.
Speedlights (meaning, in this case, flash guns with variable output) and the Quadra both run a bit "hot" (cool tones come from higher Kelvin temperatures), and for the same reason: they cut off the flash output electronically and suddenly. With portable units, that's as much to conserve battery power as anything else. (Some high-speed units, like the Paul C. Buff Einstein 640, when in "Action mode", do it specifically to limit flash duration.)
Most studio flashes take a different approach to power adjustment, charging the capacitors only to the level required for the desired output, then letting the flash "burn out" naturally. In a well-designed system, this means both that the colour temperature of the total flash output will be lower (warmer-toned) since both of the lower-temperature ramp-up and decay portions of the flash output are used, and that colour will be more consistent throughout the output range.
There is one small fly in the ointment, though, and that is that in order to adjust the power downward on a full-duration flash, any charge already in the capacitors needs to be dumped, and the capacitors recharged to the correct level. That's not exactly conducive to TTL (or "automatic") metering. The Flash WB setting on your camera is set to approximately the middle range of temperatures expected from TTL flash under typical shooting conditions, which would be somewhere in the upper 5000s Kelvin, although "enthusiast" use (off-camera flash much closer than your average consumer would take it) often means that the light is considerably cooler (higher colour temp) than the camera is set for. As a result, we've come to think nothing of using a quarter- or half-cut of CTS or CTO as a matter of course when mixing with daylight ambient. The thing is, though, that we're not so much "adding warmth" as "correcting coolth" in those circumstances.
The DLites (well, I don't know about the Ones, but the 4 and 2, certainly) are, apart from the non-metal case and the resulting modifier weight restrictions, as good and capable as any of the monolights we had available for studio use in my day. Better, in most respects, than the vast majority of breathtakingly expensive pro gear available then, since the adjustability and shot-to-shot consistency are better thanks to modern electronics, and radio triggering (and remote control on the new RX versions) were just a silly dream we had back then. I'd have traded my EL Compacts for them in a heartbeat (except for the 1000s, since there's no power equivalent in the DLite range). The Portalite softboxes, though, aren't so great (no softbox that's all straight lines will have distribution as nice as one that's more-or-less parabolic and designed for the light source, even if you use all of the available deflectors and inner diffusers). If colour temperature was your problem, then adjust for it. That can mean adjusting your camera for the relative warmth, or it can mean gelling the lights bluer (or using the optional blue deflector), depending on other light sources in the image. If it's distribution and fall-off, then it's probably the modifiers to blame -- the basic head shape and light distribution is the same across the entire Elinchrom line. Both the Rotalux and the EL Indirect range are much, much better than the Portalites.