learning to use flash (Canon, Nikon, adjustment, cameras)

[mathjak107]

learning to use your flash can be one of the biggest improvements you can make in your photos.

you can open up shadows ,freeze action ,light up subjects who are backlite, even out histograms and a whole lot more.

understanding your flash can be quite complex.

i ran into russ macdonald on another forum. russ had an excellent way of teaching me about flash work. it was simple, it was good and it improved my capability 100x over.


i thought i would pass his teachings over to you.

again im not familiar with cannons flash system so i cant really say if the same techniques work so im only talking about nikon with seperate external flash.

its important to understand there are many modes you can put your flash in but the two we will discuss are TTL AND TTL-BL OR BALANCED MODE.

in TTL mode you really have 2 seperate exposure systems going on. the camera will control how light or dark the background is and how far back into it you can see. the flash controls the subjects exposure seperatly .

the two systems dont really influence each other by communicating.

that offers lots of different ways to do things.


continued

[mathjak107]

step 1 as russ taught me through his tutorials is learn what kind of light your in.

is it low light,medium light or a case with high ambiant light and we are just filling in rather than making our flash the dominant source of light.

heres how to judge.

1) Camera in Manual mode
2) Flash turned OFF
3) Fixed ISO 400 (not Auto ISO)
4) Aperture: f/4.0
5) Aim your camera at the area you want to measure
6) Adjust the shutter to zero the meter


The resulting Shutter speed then will indicate the ambient lighting condition you are in as follows:

1) Low Ambient: Shutter 1/30th or less
2) Medium Ambient: Shutter 1/30th to 1/250th
3) High Ambient: Shutter above 1/250th




LOW AMBIENT:In low ambient conditions, your flash will be primary the only light on the subject. The ambient will contribute only to the background exposure.

Recommended Initial Settings: Camera Manual, Flash TTL, ISO 400, f/4.0, 1/80th shutter.

The flash system will control the exposure of the subject no matter you you do to the ISO, Aperture, or Shutter (within the range limts of the flash).

this is important to understand. the shutter speed adjustment on the camera will control the brightness or darkness of the ambiant background . anything else you do effects the flash exposure.

The shutter will primarilly control the background exposure. Increase the shutter to stop the ghosts around moving objects at the expense of a darker background. Decrease the shutter to brighten the background, at an increased risk of ghosting.

The aperture will primarilly control depth of field. Widen the aperture to decrease depth of field, increase background exposure, and increase flash range. Narrow the aperture to increase depth of field, decrease background brightness, and reduce flash range.


there is alot to absorb here as the concept of the 2 different exposure systems can be confusing at first. its easily seen in a room where the background has a nice distance behind the subject.

turning the speed up or down has no effect on the subjects brightness ,only the background when using flash on the subject..


next:

[mathjak107]

high ambiant light conditions as taught by russ macdonald.

In high ambient conditions your flash will be adding FILL. This means the flash will be secondary to the ambient light in creating your images. The flash will brighten the shadows on the subject's face and clothing. The power of the flash must be adjusted to balance with the ambient light to make the subject equal brightness to the background ambient. You should use TTL-BL flash mode to allow the flash to adjust itself automatically to balance the subject with the ambient. THE BL MEANS BALANCED MODE

If direct sunlight is hitting the subject's face, move the subject into the shade. If that is not possible, turn off the flash to avoid overexposure (blow out) of the subject's face.

Recommended intitial settings:
Camera P mode, ISO 200, TTL-BL
This is the simplest setting I recommend at first until you more fully understand everything. These settings will add nice Fill to your shots.


why use program setting? because if you dont your camera isnt smart enough to not run up the speed past the cameras flash sync speed which typically maxes out somewhere between 1/200 and 1/320 in any other mode except program mode.

if you set your speed faster than your cameras max sync speed light output from the flash falls off drastically.
next

[mathjak107]

medium light shooting as taught to me by russ macdonald


Medium ambient is by far the most difficult situation to use your flash. It is also the time when if you use your flash right, it will greatly improve the quality of your images, but if you use it wrong, it will destroy your images.

In medium ambient you have to make several more decisions to determine the initial settings. You have to decide how you want to shoot:
Do you want the flash to be primary?
CAN you even make the flash primary?
Or do you want the flash and ambient to balance on the subject?
Or do you want the flash to be only light Fill and the ambient primary?
Or do you have to turn off the flash and shoot available light?

Then you might ask, why would I want the flash to be primary?
Well, the most frequent reason would be when the ambient light was some funny color, like bright mercury vapor lamps (gymnasium). The flash is the color of daylight, so you would then have a weird multicolored image since there is no single white balance that can be chosen. The only way to get proper colors in this situation is to either turn off the flash and use a white balance that matches the ambient or eliminate the ambient by making the flash primary.

A second reason you might want the flash to be primary would be if you are shooting a subject that is moving quickly (dancers, runners). You can eliminate ghosting and blur if you make the flash primary, since the flash will then freeze the motion because its duration is only about 1/1000th sec.

[mathjak107]

making your flash the primary light source as taught by russ macdonald

To make the flash primary, you have to make the flash overpower the ambient light. This must be done with the flash in TTL mode by decreasing the exposure by three stops or more with shutter and ISO from the ambient setting you measured with the camera meter above.

Example 1: Assume the results of your metering step above came out to f/4.0, ISO 400, and 1/60th. You would then recognize that you were in Medium Ambient Conditions, so you must immediately change the ISO to 200. This decreases the ambient exposure one stop.

Then increase the shutter by two stops to 1/250th (double it twice and pick the closest setting - 1/60th-->1/120th-->1/240th). Notice that the highest shutter speed you can select when in regular flash sync (on a D200) is 1/250th. Now, you have changed the settings so the camera will underexpose the ambient by three stops. This example is right on the edge of where you might have to turn off the flash and shoot available light or switch to TTL-BL and go for balanced fill. In fact, if your camera is a D80 it has a maximum flash sync speed of 1/200th, so you would not be able to fully overpower the ambient in this situation.

[mathjak107]

i want to thank russ macdonald for the effort he has put in to explaining how to use flash in a way thats easily understood by even dummies like me.

well done russ!

[RayinAK]

Everything there is to know about flashes with Canon, but in reality some of the flash uses apply to any camera brand:
Small Flash and Studio Lighting - Canon Digital Photography Forums

[mathjak107]

educate me..... does cannon have a mode like nikon ttl where there is next to no interaction between the flash system and you have the 2 distinct systems going on?

nikon has a balanced mode too. thats where the camera and flash talk .

if you were trying to remove the shadows of a backlite face the camera and flash interact to bring the subject up to the same brightness level as the background light and stop there. thats the ttl-bl balanced mode.

in ttl mode the camera and flash dont adjust each other, its just assumed there is no light at all and the flash is providing the light.

the end result is in ttl mode if your not careful with your settings the flash can easily expose the subject if there is to much existing ambiant light.


one thing i left off the above tutorial is the little pop up flashes on the nikon cameras only operate in balanced mode so they are not that great for trying alot of the techniques above.

does anyone think a tutorial on learning about the flash sync speed and FP MODE on the flash is anything they want to learn about?

i dont want to do one up unless there is interest.

[RayinAK]

I imagine that Canon flashes work in a similar way as Nikon and other brands. Canon uses TTL flashes, but some cameras sync with the flash at a different speed. All depends on the camera. While on my Canon 40D the built in flash does not trigger external flashes, my 7D does. I can set the 7D to only use the built-in flash, or both. For example, I can place the Canon external flash away from the camera at an angle toward the subject, the built in flash triggers the external flash, and both illuminate the subject. I can also program the built-in and the external flashes to regulate the amount of light output from each, or just so that the built-in flash stays off while only the external one that's several feet away from the camera illuminates the subject. Some of the Canon flashes can serve as "master" (to trigger other flashes), or "slave" (to be triggered by other flashes). This is probably true with Nikon flashes.

[mathjak107]

here is a little more about shooting with flash in medium ambiant light as per russ macdonald .

medium light offers the most in choices and can be the most difficult to shoot in with flash.


There are two approaches to balancing the flash to medium ambient conditions:

1) In TTL mode you reduce the flash compensation manually by trial and error until the right flash power is determined. I am not going to discuss this method.

2) In TTL-BL mode, the flash system will set itself automatically. This is the approach I will now discuss.

Recommended Initial Settings for allowing TTL-BL to balance automatically with medium ambient: Camera P mode, Flash TTL-BL, ISO 200. (notice that these are the same settings as for High Ambient conditions).

This will give you nicely balanced images with bright backgrounds and bright subjects. You might want to apply some negative flash compensation, say -0.3 ev, to keep it from looking like the subject is jumping out of the picture.

You might be tempted to use camera A mode, and it can be done, but you have to be very careful to prevent overexposure. The shutter is limited to 1/250th (or 1/200th) flash sync speed, and since it can't go any higher than that, if you choose an aperture that is too wide, the shutter will bang into the limit and your images will all be overexposed. P mode fixes this problem.

Incidentally, among professional photographers the joke is that P mode stands for 'Professional' mode, because most use it in bright ambient when shooting fill flash. For some reason, beginning photographers avoid P mode like the plague. P mode has its important uses, and shooting TTL-BL is one of them (especially in bright ambient).