I have a t3i the flash is acting up all of a sudden.

[becbec]

One min the flash goes off fine. Then the next thing it does is act as if it flashes but the picture is dark. I have tried manual mode, auto or all other modes and get the same result. PLEASE HELP!!!!!

[ScottyP]

Hi, becbec.

What do you mean it "acts like it flashes but the picture is dark"? Does the flash light up or not?

Also how long have you had this camera?

Note that the range of the onboard flash is really short; only about 12 feet, really, as I recall from the last time I read the manual. Could it be that the trouble is happening with shots taken at longer distances?

Either way, a speedlite external flash unit is a good buy. A 430 is pretty cheap these days. These have much longer range and have other benefits too. One, with a speedlite you can angle the head and bounce flash off of a ceiling or wall and avoid ugly direct flash with ugly shadows. Two, your on board flash does not sit high enough above the camera to fully "see" over the end of any lens longer than the kit lens. If you have a slightly longer lens, or a lens hood mounted, you will actually get a half-circle lens shadow on the bottom of your picture! Three, with a speedlite you can do off-camera flash for nice effects, with the flash unit sitting somewhere to the side or even the rear of the subject, and you triggering it as a slave using the on board flash as the trigger.

[becbec]

I've had the camera since about feb. 2013. It does flash but the picture is as if I took it without a flash. It does it with the lens it came with or with my 50mm. I was thinking I'm going to have to buy a flash as well. But it did not do this before. So I don't know what could of caused this.

[TCampbell]

As Scotty mentions... the range of the on-board flash is limited.  There's a table on page 90 of your owners manual which shows how far you can expect it to be and still illuminate a subject based on your ISO, lens, and focal length.  For example... at ISO 100 using the kit 18-55mm lens zoomed to 55mm the flash is only good for about 7.5'.  If you increase the ISO to 400 you can get that up to 15'.  You could even get to 30' if you went to ISO 1600 but you'd have more digital "noise" in the image as a result of using a higher ISO -- so there are trade-offs.

But there is one other aspect as well... 

The camera has a control called "flash exposure compensation".  Sometimes we deliberaetly want to change the power-output of the flash.  If I'm outdoors in the sun, I'm _probably_ using my flash as a "fill" light.  But when doing this, I want to de-power the flash a little.  It's possible the flash exposure compensation has been altered and is causing the flash to fire at a lower power level.

Page 104 of your T3i manual (here:  http://gdlp01.c-wss.com/gds/0/0300004720/02/eosrt3i-eos600d-im2-c-en.pdf ) explains how to do this.

Use the [Q] button and directional arrow keys to navigate on the LCD screen the the icon with a lightning bolt with a +/- next to it.  Select that and then you can use the arrows to dial the power up or down on your flash.  "0" means it'll fire at normal power output.  Each full value changes the power by either half or double (depending on if you're going down or up).  e.g. -1  means you want the flash to fire at exactly 1/2 of the power that would have otherwise used.  -2 means you want to cut in half a again (for a total of 1/4 power).  -3 is 1/8th power.     

You can go to the positive diretion as well if you want to overpower the flash but keep in mind that the onboard flash is a tiny flash so there's only so much power it can pump out.    For situations where you need more power, you'd want to use an external flash (external flash is much more versatile as well.)

My favorite use of an on-board pop-up flash involves using it outdoors in sunlight and setting the flash exposure compensation to approximately -1.  It provides a nice amount of "fill" light so that outdoor photos in full sun look better because your subjects wont have "dark" shadows... they'll have gentle mild shadows instead.

[becbec]

What external flashes do you guys have? Or recommend? 

[Skirball]

Either a Canon 430exII or a generic Yongnuo 565.

[TCampbell]

The Canon 430EX II is a good work-horse flash for your camera, fairly powerful but not too terribly expensive and rather full-featured with support for E-TTL, high-speed sync, 2nd curtain flash, and can function as a "slave" in a multi-flash setup.

The Yongnuo is good but a bit more basic (and low-cost).  It wont support E-TTL (manual only) or high-speed sync, nor 2nd curtain (that requires advanced communication between the flash and camera body).  That means you'll need to learn the relationship between subject distance, flash power, and camera f-stop and how all those work together.  It's not hard, but it's not auto-matic either -- you have to learn it.

E-TTL is Canon's electronic "through the lens" flash metering system where the flash and camera work together to automatically set the power level for the shot.   The camera pre-meters the scene, tells the flash to fire a test-shot at low power while the camera meters the light return, then the camera establishes how much the flash it should _really_ use, opens the  shutter and orders the flash to fire at the calculated/metered power level.  But this all happens so incredibly fast that you'd swear it only fired once.

There are better & more powerful flashes... but they'll cost a bit more.  I have a 270EX, a 430EX II, a 580EX II, and a pair of 600EX-RTs.  But for someone starting out with a Rebel body and single flash, my favorite for a combination of price, performance, size, power output, etc. is the 430EX II.  The 600EX-RTs are actually my very favorite... but those aren't cheap (about $500 each) and they're also noticeably larger and heavier than a 430.  The 270 and 320s are a bit smaller and less expensive, but not nearly as powerful.  I use my 270 with my G-series powershot body in small rooms and for outdoor fill flash -- but never with the DSLR or in any large room.  

[Skirball]

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@TCampbell wrote:

The Yongnuo is good but a bit more basic (and low-cost).  It wont support E-TTL (manual only) or high-speed sync, nor 2nd curtain (that requires advanced communication between the flash and camera body).  That means you'll need to learn the relationship between subject distance, flash power, and camera f-stop and how all those work together.  It's not hard, but it's not auto-matic either -- you have to learn it.

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The Yongnuo 565 that I mentioned supports both eTTL and 2nd curtain sync.  If you want high-speed sync the Yongnuo 568 does that, in addition to TTL and 2nd curtain.  They also have similar power outputs to the Canon 580.

[TCampbell]

I stand corrected.... I was thinking of the YN-560.