1. The abiility to accurately see shadows and highlights. The lack of modeling lights make it impossible to see beyond the basics
Did you know that light travels in a straight line? I do not need modeling lights to know where the light will fall. All I do (if in doubt, which is REALLY rare nowadays), is stand behind the light stand and look in the direction it is aimed. I offer you the opinion that all modeling lights are crutches for people who just got lazy and cannot or wish to not visualize what they desire.
I am thankful for the 500w modeling lights, as they are bright enough to accurately see what areas need fill cards or goboing.
If you cannot see flare or light contamination from any light source, you are simply not paying attention. Modeling light strength (1 watt or 500 watt modeling lights), mean nothing to help decide if you need a gobo or not. If you are STILL in doubt, a fast shot and a 4 second look will tell you, however, thats really reaching. I can stand where the camera will be, and know /see if I am getting contamination or not.
Part of the "quality of light" talked about by people isn't just the quantity @ power level / color temperature, but also the accuracy of modeling lights
Modeling lights are NOT used in the picture. They could be blue, green or hot pink and not make a difference. They should be turned off once you are set anyways. Basically, I say that they are used by people so that they can "see" where the light is going to fall before the flash happens. An experienced photographer needs not to do such things. If one is really in doubt, snap off a shot and look, it takes like 4 seconds total.
I am no professional, but I can walk into a room, look at a lighting setup and tell you pretty freaking accurately where the light is going to fall on your subject without flashes or modeling lights. Did I mention that light travels in straight lines? (lol)
Using my Nikon speedlights, I've used from 1/128th to full power and my WB is *always* set to 5600k. My skin tones don't stray, the grey card is always close, even on a speedlight thats already delivered 250 flashes from a simple set of four AA batteries. Thats a test that I did a while back too. If there were changes, I would be the first to say that this is so. I cannot speak for all setups, but for my meagre one, it doesn't waver and is not an issue... unless I gel them.
3. Consistency of output. Portable and lower end flash units output vary, some by as much as a stop from pop to pop.
A possible advantage of the higher end studio units. Before that happens on the speedlights, though, recycle times drop severely and I know to change batteries before that (usually by that point, I am well past 400 shots). Batteries do not fire the strobe, they charge the capacitors. When the cap is full, whether from an old or new battery, it fires consistently at the the same intensity... it just may take longer to charge up as the battery weakens.
However, by the time that happens, I've taken 400+ pics. So, not only is it time to replace the batteries, its usually time to swap CF cards and likely go for lunch too (lol). In effect, I can charge my batteries faster than I can drain them. Also, at 1/2 power, I am looking at a maximum 2 second recycle times (~ 3-4 seconds at full power) with the AA batteries, less if I use external power packs. At 1/8th-1/4th power I can pop off 15-20 shots at 4 FPS before it starts to become a factor to consider. No matter what, at these levels, I cannot burn out my flash heads using ordinary AA batteries. At 1/8th power and lower, I have no mental considerations for battery life or recycle times, its near instantaneous and more than what I will require from any given session.
Now, I *could* easily burn out my strobes if I used an external Quantaray battery pack (guaranteed continual 1 second recycle times at anywhere from 1/2 to full power for 800 shots... thats what that battery pack can do), but thats just nuts. I do not know anyone that needs that many cycles in that short a time. I can also guarantee that your speedlight is toast after that as well.
4. The above noted lack of Modifiers/insufficient power.
There exists no modifier that doesn't already exist for a speedlight or that cannot be easily made. Scrims, gobos, snoots, gridspots, softboxes, umbrellas, gels... you name it, someone can or has already done it.
Lack of power? The one HUGE advantage for the big guns! I will ceded that there are no existing speedlights that can match the output 1 for 1 on even a mid-range 500Ws studio strobe. However, there is nothing stopping me from putting 4 umbrellas in a shoot-through scenario (2 up, 2 down, very close and tight) and get the same final results as a single ProPhoto 500Ws setup in a $400 4 X 6 foot softbox. Been there and done that. Only difference, the 500Ws softbox can be 10-15 feet away, and I have to be 5-6 feet away. Thats no biggie for most.
I will also counter that with 500ws of lights in a 10 X 20 foot room dialed down to it's lowest power settings, you still cannot get the light strength low enough without ND filters, massive diffusion or a really high F-stop to light the scene on 2 different planes (ie: first plane being between the front strobes to the subject and 2nd plane being from the subject to a backdrop). With the tiny strobes on the other hand, I can open my camera's lens to F/1.4, blur the heck and/or blacken out ANY ambient light out of the picture within a total physical depth of 4 feet from camera lens to backdrop and still get perfect exposure on my subject, and I'll be working at 1/8th to 1/32nd of my maximum strobe power on the strobes. To do the same result with a 500WS studio unit dropped to it's lowest setting of 100-125Ws, you would need 50 or more feet to reproduce a similar result or smaller apertures, massive filtering or diffusion, not to mention a really nice 200mm lens at that distance!
I frequently use a 4'x6' softbox, and on occassion a 5'x12' scrim, even with 4800 w/s on tap, it's tough to get sufficient light levels to shoot at the required aperture at times.
Again, the fact that speedlights are weaker? No contest and no argument. It is also a fact that the average person on this forum (let's expand that to 90% of ALL photographers that use flash), will never need to light a 20 X 40 foot room at F/11. However, there will always be someone that does, and for them, that justifies their needs perfectly.
In addtion to the above, 2 sec. recycle times, at max power level
2 second recycle times are actually quite slow. As mentioned, if I wanted to use 1/2 to full power, the external battery packs are good for 800 flashes with 1 second recycle times... but you can then go and toss that $300 flash into the garbage... lol.
Leave that speedlight at 1/2 power and you can go all day at 5-6 continual flashes with a 10-15 second break in between. Do you really need that, though? The average person... of course not. The pro? Even that is likely too slow for them sometimes.
ability to adjust power levels symmetrically/assymetrically from the shooting location,
Adjusting settings manually is no biggie honestly, but being able to do it while from behind the camera is an awesome choice to have. On a smaller scale, I can do this using Nikon's CLS and can tell you, it IS convenient, but its not mandatory nor what I would call a deal breaker. Also, to be able to do this in the studio is definitely going to cost you some pretty coin, as these units do not come cheap. For $1000 to $3000 savings, I'll walk the 10 feet across to the light to change settings. Now, if your strobe is 25 feet in the air... thats another story!
...it's take a quick shot, see what needs adjusting, repeat...
That would be the same with strobes or studio flashes. However size of the subject, room and distance makes the big advantage that a full-out studio setup offers. You pay big bucks for that big light. In some cases, absolutely nothing else will do, I know that.
It all boils down to what your expectations are, and what your clients (if any) expect and will pay for.
You are 100% right on that. They are the ones that will decide if you get paid or not. I definitely understand that if you don't have the equipment needed to get the job done, it costs you big time. The thing is, very few people need that level that we are discussing.
