I use a old Plume Wafer 100- it's 30 x 40 inches.
24" might work depending on what you're shooting.
Tons better than bare flash or the useless diffuser dome.
(not that bare flash doesn't have it's place)
Closer makes it softer, bigger makes it softer.

I'm not a portrait photographer, but here is a recent location head shot I did with two Nikon SB800's (one in the box, the other with a grid) and the IR controller. Sure beats draging powerpacks around.

Hi Joe . . no, I wasn't recommending the Pocket Wizards with your budget restrictions. I was suggesting any good set of flash radio triggers. If the Canon transmitter is within budget, go for it. It will be more reliable than most off-brand radio trigger sets.
I had the STE-3 years ago, but it was not RT (radio trigger). Got rid of it as I could do the same thing with my second flash camera mounted.

"I have been looking at the Canon Speedlite 600EX-RT as this can be used off camera"

Caution . . . the IR remote flashes are not so reliable out of doors. They are strictly "line-of-site" and can get confused in bright sunlight. Very frustrating trying to have the lights where you want them and where they will work at the same time. That's why the Pocket Wizard Flex TT5 is so popular. It accomplishes the TTL by radio waves instead of infra red. The 600EX-RT is a great piece of equipment, but the money saved going to a 580EX II would probably buy you two decent radio triggers. Also you will find that working out of doors, the flash will work better and more reliably on manual mode rather than in TTL mode.

Just a thought . . .

It came out early this year.
The transmitter is about $300
Pretty cool stuff, but alas, I shoot Nikon and more than happy with it.

http://pixsylated.com/blog/canon-600ex-rt-first-impressions/

Makes me wonder if the next round of cameras will have the transmitter built-in...and what price level.

My main concern with lighting is the quality of the light (softness and color) and the direction of the light. At a wedding you will normally see me carrying around a light stand with a 24x24 inch softbox with a Canon 580EX and Pocket Wizard FlexTT5. The advantage of the Flex is that it is can be used in manual or TTL plus it is automatically high speed sync that lets me use up to 1/2000th of a second for outdoor fill flash balanced with the ambient bright sunlight.
When, and only when, it isn't practical to carry the light stand, I have another 580EX mounted on camera with a flash modifier called a Lite-Scoop by Lite Genius. I NEVER point a direct bare flash at a subject because of the harshness of the light. For large groups outside I exchange the soft box for another Lite-Scoop because at a distance of 10-15 feet the small softbox loses it's softness advantage and wastes light.
I suggested earlier in this thread that for what you are trying to accomplish you should be using an off-camera flash with a radio flash trigger . . . on a stand . . . with some kind of light modifier to get rid of the harshness of direct flash. A softbox, shoot through umbrella, light scoop or even shooting through a scrim will work. Bounce cards are useless out of doors so please don't go there. Here are a few examples:

Would have been nice to have an accurate explanation in the first post, but at least you finally got there.

OK - it is STILL not on-camera flash IF the flash is your main light. An on-axis fill is a different story and can very attractive. The trick is do dial the flash EV down to somewhere at or less than 1 1/2 stops below ambient. Light is light is light. Crappy light from and on-camera flash inside can be just as crappy outside.

But now your main is ambient and the direction of that light has to be controlled just as though it were in the studio. You have to search areas that keep the sun off the faces, but do not contribute to flare in the camera. You usually need to block the top light. You need to ensure the background has a reasonable color harmony with the subject and is neither too bright nor too dark.

I did a group of 16 outside yesterday. Main was ambient, background a tree in autumn color, fill light was two 640WS Paul Buff Einstein lights at the camera distance of about 30 feet. 1/250 at f7.1 got me 40% of the light from the strobes and 30 to 40% is usually a good number for fill that does not look like flash, but kills the "down light" shadows and puts a nice catchlight in the eyes.

Really well-done outdoor portraits are beautiful. Bad ones are garbage. No different than in a studio. If you can light well, if you truly understand light, you can do so in any environment.


And by the way. characterizing studio location as. "...dull boring studio," shows you have no idea what you are talking about. Many of the MOST gorgeous images I have seen have been studio images. That kind of language is EXACTLY what the MWACs and DWACs say to their unsuspecting clients to attempt to trick them into thinking that taking them out in the woods and using a pop-up flash is OK. "Oh, that tree growing out of your head? Don't worry...that is REAL."

So promoting your "Lifestyle Portraits" as something out in the world int beautiful locations is great. Suggesting they are better than studio sessions is BS. They can BOTH be great or crap - depends you.

I guess searching for information on the internet is kind of like finding the right passage in the bible until you can interpret something to back your thoughts. Not everything you read on the internet is gosple . . . and not every article on the internet is written by knowledgeable people. For example there are over 10,000 recipes on the internet for "the best apple pie". Is that possible?

Nobody said that a portrait could not be taken on the street, but that hardly makes it "street photography". It's just an on-location portrait.
Getting back to the OP's request for information . . . where do you see on Eric Kim's site where he is recommending an camera flash????