Bounce flash technique?

peterharvey · Jun 24, 2016

I have a Canon 70D with Speedlite 600EX-RT.

When using ceiling bounce flash against a standard 8 feet white ceiling:

1) Is the angle of the bounce flash head estimated pretty much by trial and error?

2) After we rotate the flash head up to the ceiling, the flash's zoom defaults to "----". Should we leave the flash zoom at this default setting, or should we switch on the M Manual flash zoom to 20 mm, 24 mm, 28 mm, 35 mm, 50 mm etc?

3) I find that direct flash in evening social restaurant situations uses an ISO of 400, however my ceiling bounce flash appears very dark, and uses ISO of 1600.

It seems that my ceiling bounce flashes are very inefficient, light sapping, resulting in rather dark underexposed images, yet the 600EX-RT still flashes the LED "green" light indicating adequate exposure - however, I disagree.

Should I be using Exposure Compensation of say 2 stops, for 4x more light etc???

4) Because my ceiling bounce flash seems to be so underexposed, I no longer use the warm diffuser gel that comes with the Speedlite 600EX-RT. Previously, I would use the warm diffuser gel when I used the flash under traditional warm halogen downlights.

hotdog321 · Jun 24, 2016

I don't own the Canon 600, but I own 4-5 of the earlier Canons strobes.

As an editorial photographer, I use bounce flash all the time when circumstances allow. I keep a heavy rubber band around the head of the flash and put a white card or piece of paper (usually my assignment sheet) on the rear of the flash head.

The head is either angled straight up for nearby subjects or angled one click forward for subjects further away.

I set my camera on manual with a fairly slow shutter speed, but sometimes still need to dial the ISO to 800 or even 1600 to make the background ambient light look satisfactory. Using this combination with the bounce flash lets you generate quite flattering shots in office portraits, galas, parties, etc.

Anyway, two cents from a guy who has been shooting editorial work for 35 years.

Ellis Vener · Jun 24, 2016

peterharvey said:
I have a Canon 70D with Speedlite 600EX-RT.

When using ceiling bounce flash against a standard 8 feet white ceiling:

1) Is the angle of the bounce flash head estimated pretty much by trial and error?

it depends o your distance to whoever or what ever you are photographing. Use your eyes: take a shot and look at it. if it looks good carry on, if not change the angle and/or use your feet to get a better looking photo.

peterharvey said:
2) After we rotate the flash head up to the ceiling, the flash's zoom defaults to "----". Should we leave the flash zoom at this default setting, or should we switch on the M Manual flash zoom to 20 mm, 24 mm, 28 mm, 35 mm, 50 mm etc?

In bounce mode I usually use the wide angle diffuser and the little pop-up reflector.

peterharvey said:
3) I find that direct flash in evening social restaurant situations uses an ISO of 400, however my ceiling bounce flash appears very dark, and uses ISO of 1600.

Stop using auto ISO!

peterharvey said:
It seems that my ceiling bounce flashes are very inefficient, light sapping,

Think about what is happening when you use bounce flash: instead of heading directly at the subject , the light must first head upwards, bounce off of the ceiling or wall and then down towards the subjects to illuminate them, The light is not only traveling farther it also spreads as it travels and as it reflects off of a large area of the ceiling the light paths multiply randomly, making it far less efficient.

peterharvey said:
resulting in rather dark underexposed images, yet the 600EX-RT still flashes the LED "green" light indicating adequate exposure - however, I disagree.

What the green light may mean in this case is that the flash has fully discharged - done it's duty to it's upmost capacity.

peterharvey said:
Should I be using Exposure Compensation of say 2 stops, for 4x more light etc???

It is worth trying but keep in mind that just asa bucket can only hold so much water, the flash can only put out as much light as its capacitor capacity allows.

peterharvey said:
4) Because my ceiling bounce flash seems to be so underexposed, I no longer use the warm diffuser gel that comes with the Speedlite 600EX-RT. Previously, I would use the warm diffuser gel when I used the flash under traditional warm halogen downlights.

Without samples it is hard to judge. O the camera side, Exposure for all photographs are based on three factors;

-Sensitivity of the receiving media ( the sensor and however much gain you apply to the signal the tenor generates natively (AKA ISO setting)

- Aperture ( which controls how much light is allowed to stream in during the length of the exposure.)

-Shutter speed, or in the case of the flash lit portion of the total exposure, the flash duration.

With flash this is also complicated by the distance fro the flash to the subject and the reflectivity of the subject. For instances: a pale skinned blond wearing white clothes against an all white background in a white room reflects light a lot more efficiently than a dark skinned person wearing dark clothes against a dark or black background.

I hope that helps.

Nixon Glenn · Jun 24, 2016

peterharvey said:
I have a Canon 70D with Speedlite 600EX-RT.

When using ceiling bounce flash against a standard 8 feet white ceiling:

1) Is the angle of the bounce flash head estimated pretty much by trial and error?

2) After we rotate the flash head up to the ceiling, the flash's zoom defaults to "----". Should we leave the flash zoom at this default setting, or should we switch on the M Manual flash zoom to 20 mm, 24 mm, 28 mm, 35 mm, 50 mm etc?

3) I find that direct flash in evening social restaurant situations uses an ISO of 400, however my ceiling bounce flash appears very dark, and uses ISO of 1600.

It seems that my ceiling bounce flashes are very inefficient, light sapping, resulting in rather dark underexposed images, yet the 600EX-RT still flashes the LED "green" light indicating adequate exposure - however, I disagree.

Should I be using Exposure Compensation of say 2 stops, for 4x more light etc???4) Because my ceiling bounce flash seems to be so underexposed, I no longer use the warm diffuser gel that comes with the Speedlite 600EX-RT. Previously, I would use the warm diffuser gel when I used the flash under traditional warm halogen downlights.

How high was the ceiling? Does it have white/bright color or dark color?

Have you tried adding exposure compensation?

GG · Jun 24, 2016

I too use bounce off the ceiling with no issues, and I have an older Canon speedlite. ISO maybe at 400.

So, it would be interesting to know more as to why the poor results,, (dark ceiling?? etc).

rxb dc · Jun 24, 2016

You've already gotten valuable inputs from some of the resident experts including Hot Dog and Ellis. Some additional (probably duplicative points).

What I find is that ceiling bounce works well with low (9 - 10 feet) ceilings and relatively close subjects - typically kids birthday at home.

Events locations - ballrooms, halls etc. - tend to have much higher ceilings, sometimes 20-30 feet - and that is a lot of distance to cover when bouncing - at the minimum, twice the height of the ceiling. As Hotdog suggested, direct flash or bounce with white card is useful then but you do need fairly wide aperture and high ISOs.

Personally, I just do not like too dark ambient - so I end up with high ISOs (I've used 8000 !) and at that point, flash is basically doing fill duty rather than the primary.

peterharvey said:
...

1) Is the angle of the bounce flash head estimated pretty much by trial and error?

The way I think of it is that when you through light on the ceiling or wall, you are basically creating a 'window' in that space with a certain direction of light which depends on where you aim. The thing is that if you aim over someones head, the light will be pushing vertically down vs. bouncing closer to the camera wherein it will be more horizontal.

The second consideration is how far away you are - as the light will drop off faster from the ceiling compared to the flash.

peterharvey said:
2) After we rotate the flash head up to the ceiling, the flash's zoom defaults to "----". Should we leave the flash zoom at this default setting, or should we switch on the M Manual flash zoom to 20 mm, 24 mm, 28 mm, 35 mm, 50 mm etc?

3) I find that direct flash in evening social restaurant situations uses an ISO of 400, however my ceiling bounce flash appears very dark, and uses ISO of 1600.

While it could be a metering issue, the more likely case is that you have probably maxed out the capacity of the flash. This will depend on the height of the ceiling and hence distance to the subject, aperture and ISO.

peterharvey said:
It seems that my ceiling bounce flashes are very inefficient, light sapping, resulting in rather dark underexposed images, yet the 600EX-RT still flashes the LED "green" light indicating adequate exposure - however, I disagree.

Should I be using Exposure Compensation of say 2 stops, for 4x more light etc???

4) Because my ceiling bounce flash seems to be so underexposed, I no longer use the warm diffuser gel that comes with the Speedlite 600EX-RT. Previously, I would use the warm diffuser gel when I used the flash under traditional warm halogen downlights.

peterharvey · Jun 24, 2016

hotdog321 said:
I don't own the Canon 600, but I own 4-5 of the earlier Canons strobes.

As an editorial photographer, I use bounce flash all the time when circumstances allow. I keep a heavy rubber band around the head of the flash and put a white card or piece of paper (usually my assignment sheet) on the rear of the flash head.

The head is either angled straight up for nearby subjects or angled one click forward for subjects further away.

I set my camera on manual with a fairly slow shutter speed, but sometimes still need to dial the ISO to 800 or even 1600 to make the background ambient light look satisfactory. Using this combination with the bounce flash lets you generate quite flattering shots in office portraits, galas, parties, etc.

Anyway, two cents from a guy who has been shooting editorial work for 35 years.

--
photojournalist
http://craighartley.zenfolio.com/

-

You use manual.

Not sure what aperture you're using.

However, your FF has 2.25x more surface area than mine.

You're using slow shutter speeds.

Yet your ISO is 800 to even 1600.

You seem to be collecting much more light than me.

I use the automatic P mode.

peterharvey · Jun 24, 2016

Ellis Vener said:
peterharvey said:

I have a Canon 70D with Speedlite 600EX-RT.

When using ceiling bounce flash against a standard 8 feet white ceiling:

1) Is the angle of the bounce flash head estimated pretty much by trial and error?

Click to expand...

it depends o your distance to whoever or what ever you are photographing. Use your eyes: take a shot and look at it. if it looks good carry on, if not change the angle and/or use your feet to get a better looking photo.

Ellis Vener said:

2) After we rotate the flash head up to the ceiling, the flash's zoom defaults to "----". Should we leave the flash zoom at this default setting, or should we switch on the M Manual flash zoom to 20 mm, 24 mm, 28 mm, 35 mm, 50 mm etc?

Click to expand...

In bounce mode I usually use the wide angle diffuser and the little pop-up reflector.

-

The 600EX-RT's built-in flash zoom normally covers 20 mm to 200 mm.

Isn't the wide angle diffuser for use at short FL's less than 20 mm?

I will give the built-in flash card a go; last Saturday, at a wedding, a pro-photographer used a Fong light fitting, but then some people say they're a terrible waste of money.

-

Ellis Vener said:
Ellis Vener said:

3) I find that direct flash in evening social restaurant situations uses an ISO of 400, however my ceiling bounce flash appears very dark, and uses ISO of 1600.

Click to expand...

Stop using auto ISO!

Ellis Vener said:

It seems that my ceiling bounce flashes are very inefficient, light sapping,

Click to expand...

Think about what is happening when you use bounce flash: instead of heading directly at the subject , the light must first head upwards, bounce off of the ceiling or wall and then down towards the subjects to illuminate them, The light is not only traveling farther it also spreads as it travels and as it reflects off of a large area of the ceiling the light paths multiply randomly, making it far less efficient.

Ellis Vener said:

resulting in rather dark underexposed images, yet the 600EX-RT still flashes the LED "green" light indicating adequate exposure - however, I disagree.

Click to expand...

What the green light may mean in this case is that the flash has fully discharged - done it's duty to it's upmost capacity.

Ellis Vener said:

Should I be using Exposure Compensation of say 2 stops, for 4x more light etc???

Click to expand...

It is worth trying but keep in mind that just asa bucket can only hold so much water, the flash can only put out as much light as its capacitor capacity allows.

Ellis Vener said:

4) Because my ceiling bounce flash seems to be so underexposed, I no longer use the warm diffuser gel that comes with the Speedlite 600EX-RT. Previously, I would use the warm diffuser gel when I used the flash under traditional warm halogen downlights.

Click to expand...

Without samples it is hard to judge. O the camera side, Exposure for all photographs are based on three factors;

-Sensitivity of the receiving media ( the sensor and however much gain you apply to the signal the tenor generates natively (AKA ISO setting)

- Aperture ( which controls how much light is allowed to stream in during the length of the exposure.)

-Shutter speed, or in the case of the flash lit portion of the total exposure, the flash duration.

With flash this is also complicated by the distance fro the flash to the subject and the reflectivity of the subject. For instances: a pale skinned blond wearing white clothes against an all white background in a white room reflects light a lot more efficiently than a dark skinned person wearing dark clothes against a dark or black background.
I hope that helps.

--
Ellis Vener
http://www.ellisvener.com
Free your eyes and the rest will follow. (With apologies to George Clinton.)

peterharvey · Jun 24, 2016

Nixon Glenn said:
peterharvey said:

I have a Canon 70D with Speedlite 600EX-RT.

When using ceiling bounce flash against a standard 8 feet white ceiling:

1) Is the angle of the bounce flash head estimated pretty much by trial and error?

2) After we rotate the flash head up to the ceiling, the flash's zoom defaults to "----". Should we leave the flash zoom at this default setting, or should we switch on the M Manual flash zoom to 20 mm, 24 mm, 28 mm, 35 mm, 50 mm etc?

3) I find that direct flash in evening social restaurant situations uses an ISO of 400, however my ceiling bounce flash appears very dark, and uses ISO of 1600.

It seems that my ceiling bounce flashes are very inefficient, light sapping, resulting in rather dark underexposed images, yet the 600EX-RT still flashes the LED "green" light indicating adequate exposure - however, I disagree.

Should I be using Exposure Compensation of say 2 stops, for 4x more light etc???4) Because my ceiling bounce flash seems to be so underexposed, I no longer use the warm diffuser gel that comes with the Speedlite 600EX-RT. Previously, I would use the warm diffuser gel when I used the flash under traditional warm halogen downlights.

Click to expand...

How high was the ceiling? Does it have white/bright color or dark color?

Have you tried adding exposure compensation?

-

The ceiling is only 8 to 9 feet high, and stark white.

Adding exposure compensation is the only thing I can think of that I have not tried yet.

I was just wondering if it was normal for you guys to use bounce with exposure compensation at +1 of +2, since bounce seems to a relatively inefficient process, so something must compensate to maintain brightness?

Ellis Vener · Jun 24, 2016

peterharvey said:
Isn't the wide angle diffuser for use at short FL's less than 20 mm?
I will give the built-in flash card a go; last Saturday, at a wedding, a pro-photographer used a Fong light fitting, but then some people say they're a terrible waste of money.

Yes, with the W.A. lens deployed on the flash the beam pattern is more or less wide enough to cover the angle of view for a 14mm.

If the flash is around 6 feet or less from tje person and the ceiling isnt high tje collapsible Fong diffusion cup works very well. Especially if you get the flash off camera.

Ellis Vener
http://www.ellisvener.com
Free your eyes and the rest will follow. (With apologies to George Clinton.)

Sailor Blue · Jun 24, 2016

Don't limit yourself to overhead bouncing. Bouncing off walls, a ceiling-wall joint, or a corner between two walls and the ceiling can work very well.

Where you aim the flash depends on your subject distance. Think of angles like on a billiards or pool table. You want a bounce angle that will light up the subject from about 30°-45°.

If the projected pool of light on the ceiling is too close to the subject you get dark shadows in the eye sockets so angle the light so that the bounce position is further from the subject.

If the projected pool of light is too far from the subject you waste most of the light so angle the light so that the bounce position is closer to the subject.

If the projected pool of light is too wide you are wasting light. If the ceiling is high then you can zoom the flash to a longer focal length to limit the size of the pool of light.

If it is too small you aren't getting even lighting. One example would be bouncing off a wall behind you when you were only a couple of feet from the wall. In that case you might want to use the wide angle drop down of your flash to make the pool of light larger.

If you have to choose one then choose too wide, which is what your flash is doing when it zooms to the maximum focal length.

TTL is inherently flawed and it is amazing that it works as well as it does. It can NOT give you a perfect exposure more than rarely. Anytime you are using TTL you should expect to use Exposure Compensation and Flash Exposure Compensation and make lots of exposure corrections during post processing. Using bounce flash just increases the need to use FEC.

Ellis Vener · Jun 25, 2016

peterharvey said:
Nixon Glenn said:

peterharvey said:

I have a Canon 70D with Speedlite 600EX-RT.

When using ceiling bounce flash against a standard 8 feet white ceiling:

1) Is the angle of the bounce flash head estimated pretty much by trial and error?

2) After we rotate the flash head up to the ceiling, the flash's zoom defaults to "----". Should we leave the flash zoom at this default setting, or should we switch on the M Manual flash zoom to 20 mm, 24 mm, 28 mm, 35 mm, 50 mm etc?

3) I find that direct flash in evening social restaurant situations uses an ISO of 400, however my ceiling bounce flash appears very dark, and uses ISO of 1600.

It seems that my ceiling bounce flashes are very inefficient, light sapping, resulting in rather dark underexposed images, yet the 600EX-RT still flashes the LED "green" light indicating adequate exposure - however, I disagree.

Should I be using Exposure Compensation of say 2 stops, for 4x more light etc???4) Because my ceiling bounce flash seems to be so underexposed, I no longer use the warm diffuser gel that comes with the Speedlite 600EX-RT. Previously, I would use the warm diffuser gel when I used the flash under traditional warm halogen downlights.

Click to expand...

How high was the ceiling? Does it have white/bright color or dark color?

Have you tried adding exposure compensation?

Click to expand...

-

The ceiling is only 8 to 9 feet high, and stark white.

Adding exposure compensation is the only thing I can think of that I have not tried yet.

I was just wondering if it was normal for you guys to use bounce with exposure compensation at +1 of +2, since bounce seems to a relatively inefficient process, so something must compensate to maintain brightness?

i may be not understanding your question: is it the flash or the ambient portion of the exposure that is underexposed? If it is the ambient portion than the solution is straightforward: use a longer shutter speed. If you currently are using 1/200 try 1/60 or longer and at these longer shutterspeeds switch to rear curtain sync mode.

peterharvey · Jun 25, 2016

Ellis Vener said:
peterharvey said:

Nixon Glenn said:

peterharvey said:

I have a Canon 70D with Speedlite 600EX-RT.

When using ceiling bounce flash against a standard 8 feet white ceiling:

1) Is the angle of the bounce flash head estimated pretty much by trial and error?

2) After we rotate the flash head up to the ceiling, the flash's zoom defaults to "----". Should we leave the flash zoom at this default setting, or should we switch on the M Manual flash zoom to 20 mm, 24 mm, 28 mm, 35 mm, 50 mm etc?

3) I find that direct flash in evening social restaurant situations uses an ISO of 400, however my ceiling bounce flash appears very dark, and uses ISO of 1600.

It seems that my ceiling bounce flashes are very inefficient, light sapping, resulting in rather dark underexposed images, yet the 600EX-RT still flashes the LED "green" light indicating adequate exposure - however, I disagree.

Should I be using Exposure Compensation of say 2 stops, for 4x more light etc???4) Because my ceiling bounce flash seems to be so underexposed, I no longer use the warm diffuser gel that comes with the Speedlite 600EX-RT. Previously, I would use the warm diffuser gel when I used the flash under traditional warm halogen downlights.

Click to expand...

How high was the ceiling? Does it have white/bright color or dark color?

Have you tried adding exposure compensation?

Click to expand...

-

The ceiling is only 8 to 9 feet high, and stark white.

Adding exposure compensation is the only thing I can think of that I have not tried yet.

I was just wondering if it was normal for you guys to use bounce with exposure compensation at +1 of +2, since bounce seems to a relatively inefficient process, so something must compensate to maintain brightness?

Click to expand...

i may be not understanding your question: is it the flash or the ambient portion of the exposure that is underexposed? If it is the ambient portion than the solution is straightforward: use a longer shutter speed. If you currently are using 1/200 try 1/60 or longer and at these longer shutterspeeds switch to rear curtain sync mode.

BAK · Jun 25, 2016

Re >> a Fong light fitting, but then some people say they're a terrible waste of money. <<

Some people are not smart.

I know how, and most importantly, when, to use a Lightsphere.

Some people do not have the ability to figure out how to use one.

BAK

BAK · Jun 25, 2016

I'll try to be more helpful over the weekend.

Imagine you are throwing a bucket of water, rather than a bucket of light.

Notice how the water spreads all over the place, and your target does not get very wet.

BAK

Ellis Vener · Jun 25, 2016

peterharvey said:
Ellis Vener said:

peterharvey said:

Nixon Glenn said:

peterharvey said:

I have a Canon 70D with Speedlite 600EX-RT.

When using ceiling bounce flash against a standard 8 feet white ceiling:

1) Is the angle of the bounce flash head estimated pretty much by trial and error?

2) After we rotate the flash head up to the ceiling, the flash's zoom defaults to "----". Should we leave the flash zoom at this default setting, or should we switch on the M Manual flash zoom to 20 mm, 24 mm, 28 mm, 35 mm, 50 mm etc?

3) I find that direct flash in evening social restaurant situations uses an ISO of 400, however my ceiling bounce flash appears very dark, and uses ISO of 1600.

It seems that my ceiling bounce flashes are very inefficient, light sapping, resulting in rather dark underexposed images, yet the 600EX-RT still flashes the LED "green" light indicating adequate exposure - however, I disagree.

Should I be using Exposure Compensation of say 2 stops, for 4x more light etc???4) Because my ceiling bounce flash seems to be so underexposed, I no longer use the warm diffuser gel that comes with the Speedlite 600EX-RT. Previously, I would use the warm diffuser gel when I used the flash under traditional warm halogen downlights.

Click to expand...

How high was the ceiling? Does it have white/bright color or dark color?

Have you tried adding exposure compensation?

Click to expand...

-

The ceiling is only 8 to 9 feet high, and stark white.

Adding exposure compensation is the only thing I can think of that I have not tried yet.

I was just wondering if it was normal for you guys to use bounce with exposure compensation at +1 of +2, since bounce seems to a relatively inefficient process, so something must compensate to maintain brightness?

Click to expand...

i may be not understanding your question: is it the flash or the ambient portion of the exposure that is underexposed? If it is the ambient portion than the solution is straightforward: use a longer shutter speed. If you currently are using 1/200 try 1/60 or longer and at these longer shutterspeeds switch to rear curtain sync mode.

Click to expand...

Sailor Blue · Jun 25, 2016

Canon's Full Auto, P, Av and Tv all seem to try and balance the ambient light exposure with the flash exposure. I have no idea what Auto ISO does.

If you are using Auto ISO that might be the problem, or it might be that TTL with your camera and flash just don't work well with bounce flash.

The first thing I would do would be to go to a fixed ISO of 400 to 1600 with the camera in Manual Exposure Mode and try a few TTL bounce light test shots. If that works then it is Auto ISO that is the problem.

If using a fixed ISO doesn't work then it is TTL and your solution is to automatically dial in some FEC when doing bounce. Just be aware that if you dial in a positive value for FEC you will be working your flash harder so you may want to increase your ISO, especially if your shots are still underexposed after increasing the FEC.

peterharvey · Jun 26, 2016

Sailor Blue said:
Canon's Full Auto, P, Av and Tv all seem to try and balance the ambient light exposure with the flash exposure. I have no idea what Auto ISO does.

If you are using Auto ISO that might be the problem, or it might be that TTL with your camera and flash just don't work well with bounce flash.

The first thing I would do would be to go to a fixed ISO of 400 to 1600 with the camera in Manual Exposure Mode and try a few TTL bounce light test shots. If that works then it is Auto ISO that is the problem.

If using a fixed ISO doesn't work then it is TTL and your solution is to automatically dial in some FEC when doing bounce. Just be aware that if you dial in a positive value for FEC you will be working your flash harder so you may want to increase your ISO, especially if your shots are still underexposed after increasing the FEC.

BirdieMaker · Jun 26, 2016

I love your tech portraits. You capture the vibe wonderfully.

Sailor Blue · Jun 26, 2016

peterharvey said:
Sailor Blue said:

Canon's Full Auto, P, Av and Tv all seem to try and balance the ambient light exposure with the flash exposure. I have no idea what Auto ISO does.

If you are using Auto ISO that might be the problem, or it might be that TTL with your camera and flash just don't work well with bounce flash.

The first thing I would do would be to go to a fixed ISO of 400 to 1600 with the camera in Manual Exposure Mode and try a few TTL bounce light test shots. If that works then it is Auto ISO that is the problem.

If using a fixed ISO doesn't work then it is TTL and your solution is to automatically dial in some FEC when doing bounce. Just be aware that if you dial in a positive value for FEC you will be working your flash harder so you may want to increase your ISO, especially if your shots are still underexposed after increasing the FEC.

--
Living and loving it in Pattaya, Thailand. Canon 7D - See the gear list for the rest.

Click to expand...

-

Yes, presently I'm using P Mode with Auto ISO too. I'll give that fixed ISO a go.

In Full Auto mode the camera sets the ISO, shutter speed, aperture, and built-in flash usage and power via TTL.

From the manual for my Canon 7D: With P, only the shutter speed and aperture are set automatically. You can freely set the AF mode, drive mode, built-in flash usage, and other functions.

This means that when you use Auto ISO in P mode you are basically back in Full Auto mode.

In any of the Auto modes your camera will try to balance the ambient and flash exposures within limits.

Here are the limits with my Canon 7D for aperture and shutter speed where normally a fixed ISO is used. When you throw in Auto ISO you make these modes more like Full Auto. This chart is for the built-in flash but with an on-camera flash the same limits apply.

What you need to understand is that a flash picture is actually two exposures - one is the ambient light exposure and the other is the flash exposure.

The ambient light exposure takes place as long as the shutter is open. Once you settle on an ISO then the shutter speed and aperture determine the the ambient light exposure

The flash exposure only takes place when the flash is firing. Once you settle on an ISO then the flash power and aperture determine the the flash exposure.

Making a good flash image is all about balancing these two exposures to get the image you want. Typically you find the ambient light exposure then add light from the flash to make the subject brighter than the background. This of course means that the final total combined exposure is higher than the individual ambient light exposure or the flash exposure.

TTL is effected by many things, not just the subject to flash distance so when you use TTL flash you should expect to use FEC to correct the TTL exposure. FEC is also used to control the subject to background exposure ratio.

--

Living and loving it in Pattaya, Thailand. Canon 7D - See the gear list for the rest.

Bounce flash technique?

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