The big question is, "do you want to shoot colour?" If so, CRI is very important or you will end up with muddy pictures. You need a CRI of over 90 for acceptable results. For B&W, CRI doesn't matter and you can use pretty much any cheap LED, though really bad colour quality might result in some filter effects the odd subtle artifact.
For a simple build process, you're best off buying complete mains-powered LED or CFL bulbs that are labelled as "dimmable" and then controlling them with a light-dimmer knob. That won't be real cheap, but it is very achievable and it means you can simply replace your lamp modules with different ones at any time, as long as they're dimmable.
If you want to build more from scratch, it gets harder. For a decent bright light, you need a few hundred watts of electrical power (look on eBay for "COB LED 50W", they're about 10c/W from China but don't forget to budget for and design-in heatsinks or your LEDs will last only a fraction of a second), which is difficult to dim efficiently. You have a couple of options:
a) control the maximum current using a resistor, dim with pulse width modulation (PWM),
b) control the current with a buck-mode switching controller, or
c) control the current with a boost-mode switching controller.
Option (a) is the simplest, you just need a high-ish voltage power supply (probably 36V, most high power chip-on-board LEDs are about 32V), a HUGE resistor and a FET and 555 (or microcontroller, e.g. Arduino) to set the PWM duty cycle. The drawback here is that for 100W of LED (32V, 3A), your current-limit resistor needs to dissipate about 15W, so it's inefficient and that resistor is big, hot and expensive. 36V power supplies are also annoyingly expensive because they're not real common.
Option (b) is much more efficient. You can use a higher voltage (e.g. 48V) power supply that will be cheaper than a 36V, a low-loss inductor, couple of FETs, a bunch of other supporting components and a microcontroller. You need to write somewhat-complicated software and be passingly familiar with control theory.
Option (c): don't go there. Not if you're asking this question. It's cheap because you can use a 12V power supply, but controlling current in a boost converter is an inherently unstable process and you need to be a control-theory wizard.
You can also buy cheap off-the-shelf LED power supplies that will produce a fixed regulated output current, e.g. 1A, 2A, 3A, etc. They're NOT dimmable, but you could do simple dimming by turning banks of lights on/off. Say you put 16 banks of LEDs in, you could turn on 1, 2, 4, 8, or 16 banks to get 4 stops of light control in 1-stop increments. The cost of 8 or 16 controllers would start to add up, though you'd have a simple control scheme (row of switches) with no need to do any tricky electronics or software, you just hook up LEDs to power supplies. You still need to do the heatsinking.
and could use some help narrowing down the field! Any suggestions?
