Flash Photography 101, Chapter 2 - (WHY) SHOULD I GET A FLASH UNIT FOR MY CAMERA?

[Curtis N]

(WHY) SHOULD I GET A FLASH UNIT FOR MY CAMERA?
A beginner’s guide

Many cameras, including some fairly expensive DSLRs, have a built-in (pop-up) flash unit, as well as a hotshoe for an attached flash unit. Beginners often ask why or if they should buy a separate flash attachment, and this tutorial is designed to answer that question.

I wanted to include some sample images before I posted this, but since I don't know if/when I'll ever get that done, I decided to go ahead with the text.

REASON #1: REDEYE
We’ve all seen pictures of people whose eyes have that diabolical red glow. It can ruin an otherwise very good shot. It is caused by light reflecting off the retina in the back of the eye. This phenomenon is worst when the subject’s pupils are dilated (indoors), and when there is a narrow angle between the light source (flash), eye, and lens. Geometrically, the two factors which affect this angle are the distance between the flash and the lens, and the distance between the camera and the subject’s eyes. One way to avoid this problem is to move the flash further from the lens. The more distance there is between the flash and the lens, the further away the camera can be from human subjects without causing red eyes. Typically, a hotshoe-mounted flash unit will be twice as far from the lens as a “pop-up” unit. A flash bracket can be utilized to make this distance even greater.

REASON #2: POWER
The effective distance of any flash is dependent upon the aperture and ISO setting used. For example, at f/8 and ISO 100, the built-in flash on today’s DSLRs will be effective only if your subject is within about 5 feet of the camera. Of course, you can increase this range by opening up the lens and/or using a higher ISO setting, but that comes at a cost - less depth-of-field and more digital noise. A good flash unit has about fifteen times the power of a built-in unit, with perhaps four times the effective distance. This allows the use of smaller apertures (for better depth-of-field) and lower ISO settings (to reduce digital noise). Power is also critical for bounced flash and fill flash in sunny conditions.

REASON #3: BOUNCED FLASH
The ability to point the flash at a wall or ceiling will do more for the quality of flash photographs than just about anything else. It can mean the difference between a harsh-looking “snapshot” and a pleasing photograph that doesn’t even look “flashed”. Illuminating the ceiling has the effect of making the light source much larger, creating softer shadows, a brighter background, and more natural-looking results. The power required for this technique varies widely according to the height and color of the ceiling and other factors, but even with a low, white ceiling it can require as much as four times the power of direct flash. With direct flash, you’re lighting up your subject. With bounced flash, you’re lighting up the whole room!

REASON #4: FLASH MODIFIERS
There are a wide range of “diffusers” and other attachments which somehow modify the direction of some or all of the photons flying out of the flash unit. They can be as simple as a 3 x 5 index card and rubber band. Other attachments include the Lumiquest Promax System, mini softboxes, the Sto-Fen Omni-bounce, and the Lightsphere II. They all work a little differently and they each have their place. Generally they are designed to make the light source larger from the subject’s perspective, or to provide some direct illumination with bounced flash. Another completely different modifier is the Better Beamer, which creates a powerful, narrow beam for long-distance wildlife shooting. When used properly, flash modifiers can dramatically improve flash photographs, but you need a flash unit to use them.

REASON #5: FLASH BRACKETS
Flash brackets come in a variety of styles and serve a dual purpose. In addition to moving the flash unit further from the lens (see reason #1), they also allow the camera to be rotated to vertical orientation while keeping the flash above the lens. This prevents those ugly side shadows on backgrounds which otherwise ruin vertical shots when using a hotshoe-mounted flash indoors. Some styles work by flipping the flash unit, keeping it oriented the same way as the camera. These allow the flash to be zoomed with the lens to avoid wasting light (and power) with direct flash. Other styles allow the camera to rotate while the flash remains over the camera. These make it easier to change orientation while mounted on a tripod, and they work better with some flash modifiers such as the Lumiquest Promax System. Use of a flash bracket requires a sync cord to electrically connect the flash to the camera.

REASON #6: BELLS & WHISTLES
Most good flash units have additional features not available with the built-in. They include:
1)A focus assist light - This light casts a pattern of lines on your subject to allow the autofocus system to work better in low light situations.
2) FP Flash (high speed sync) – This enables the use of high shutter speeds. If you’re using fill flash outdoors and want to use a wide aperture to blur the background, FP Flash is a necessity.
3)Manual mode – This allows you to set and adjust the flash unit’s power, rather than relying on automatic flash metering, and also enables the use of optical slaves. It’s more of an advanced option, but sooner or later you’ll find it useful.
4)Wireless E-TTL – Allows the use of multiple flash units at various power ratios in a master/slave arrangement with E-TTL flash metering.

To summarize, today’s Digital SLRs are packed with amazing technology, and with the right lenses they can produce wonderful images. But the built-in flash units on these cameras are lacking in power, too close to the lens, can’t be tilted for bounce flash and can’t be used with flash modifiers. In short, they rarely produce anything better than “snapshot” quality. Their usefulness is so limited that high-end professional camera bodies don’t even have a built-in flash.

My recommendation to people who buy a DSLR is to buy a good flash unit for it as soon as funds allow. While there are many types of photography that don’t require flash, most beginners photograph people more than any other subject. Flash can improve just about any “people” shot, whether indoors or outdoors. Before you buy another lens, before you get that fancy tripod or any other accessory, buy a good flash unit!

Not sure which one to buy? Take a look at Tim's thread: Which flash should I get for my EOS camera?

Next: Chapter 3 - A Systematic Approach to Bounced Flash
Chapter 4 - Guide Numbers and High Speed Sync

[lakiluno]

Thanks curtis - now you just need to write chapter 4, 5, 6, 7, 8, 9...or perhaps you might as well read the flash bible after that

[hard12find]

Great post Curtis, a lot of useful info...thanks for taking the time to research, and post all the info....
Jim

[gcobb]

Great material there. I have had my pop-up bail me out once or twice. But I rely on the 430 when I shoot people almost all the time.

[vvilko]

cheers i think you've made me broke!

i think im going to buy one after that!

[Moccatino]

Thanks for your information and time. NOW I understand why I need a flash, I just need to save up for one now!

[Venkateshmurthy.V.K]

Can I use my old non dedicated flash guns with my Canon 400D?

[Curtis N]

Originally Posted by Venkateshmurthy.V.K

Can I use my old non dedicated flash guns with my Canon 400D?

Probably, but check the trigger voltage first.

Take a look at this thread.
http://photography-on-the.net/forum/...d.php?t=228311

[zwollenaar]

Great info Curtis, I keep reading this again and again.

PS: I rather like your current logo =Master Flasher a lot more than a lady face you used weeks ago

[Cam101]

Good post!! Being new to the SLR world has made me realize the importance of a good flash unit. The points you made can not be underestimated.

[pratman64]

Very useful information, indeed. Thanks, Curtis.

It would have been nice to see some example shots of without and with flash to really appreciate an external flash unit.

Great work, nevertheless.

[euge]

this was very helpful! thank you

[sgogula]

Great Information. I don't miss any of the Curtis posts in this forum because all his posts have very useful information.

[Tigerkn]

Thanks Curtis for putting all these together!!!

Anyone know if there is a list of difference Flash Modifiers (Beauty dish, Umbrella.....) that would work best for difference Setting/Situation (Indoor head shot/group, Outdoor....). Thanks.

Originally Posted by Curtis N

....................

REASON #4: FLASH MODIFIERS
There are a wide range of “diffusers” and other attachments which somehow modify the direction of some or all of the photons flying out of the flash unit. They can be as simple as a 3 x 5 index card and rubber band. Other attachments include the Lumiquest Promax System, mini softboxes, the Sto-Fen Omni-bounce, and the Lightsphere II. They all work a little differently and they each have their place. Generally they are designed to make the light source larger from the subject’s perspective, or to provide some direct illumination with bounced flash. Another completely different modifier is the Better Beamer, which creates a powerful, narrow beam for long-distance wildlife shooting. When used properly, flash modifiers can dramatically improve flash photographs, but you need a flash unit to use them.

.................

[egordon99]

Originally Posted by Tigerkn

Thanks Curtis for putting all these together!!!

Anyone know if there is a list of difference Flash Modifiers (Beauty dish, Umbrella.....) that would work best for difference Setting/Situation (Indoor head shot/group, Outdoor....). Thanks.

Check out http://www.strobist.com

Lots of articles on umbrellas/softboxes/etc...