Can anyone explain this to me?

[Sam]

I have been doing some reading as well as practicing with my new flash. I do not understand why I get different shutter speed/aperture combinations on the different shooting modes.

Here is what I have been doing.



I'll set the camera to "P" mode take a reading. It is something like 1/60 f/5.6.
Then set it to "TV" mode and set the shutter speed to 1/60 the aperture shows up as f/5.6 but it is blinking.
So then I set the camera to AV mode at f/5.6 and I get a very slow shutter speed, somewhere around 1 second.
I know that P, Tv, Av and M modes handle flash illumination differently but why? When I am not using my flash and I go through each shooting mode with similar settings I get similar results.

This is making my head hurt. If you can explain this to me I would be very greatful.


The reason it is bothering me so much is that I would like to shoot in AV mode to have some control over my background. But if I get these slow shutter speeds I might as well just use M mode.


I would be interested in knowing what mode any of you more experienced photographers shoot in. Thanks in advance for any help.

[PacAce]

I have been doing some reading as well as practicing with my new flash. I do not understand why I get different shutter speed/aperture combinations on the different shooting modes.

Here is what I have been doing.



I'll set the camera to "P" mode take a reading. It is something like 1/60 f/5.6.
Then set it to "TV" mode and set the shutter speed to 1/60 the aperture shows up as f/5.6 but it is blinking.
So then I set the camera to AV mode at f/5.6 and I get a very slow shutter speed, somewhere around 1 second.
I know that P, Tv, Av and M modes handle flash illumination differently but why? When I am not using my flash and I go through each shooting mode with similar settings I get similar results.

This is making my head hurt. If you can explain this to me I would be very greatful.


The reason it is bothering me so much is that I would like to shoot in AV mode to have some control over my background. But if I get these slow shutter speeds I might as well just use M mode.


I would be interested in knowing what mode any of you more experienced photographers shoot in. Thanks in advance for any help.

When using the flash, in P mode, the camera knows that you are using the flash, so, in the lighting situation you are in (indoors with low lighting, I'm assuming), the camera will set the shutter to 1/60, which is the slowest it will use. The aperture will be set to the biggest the lens has which, in your case, I'm assuming is f/5.6.

In Tv mode, the camera does not care whether you have the flash on or not. It will meter as if the flash weren't there. So, since you have the shutter set at 1/60, the camera will set the aperture needed to get a good exposure. However, at 1/60, the aperture available is not wide enough for a good exposure so the camera uses what's available and flashes it to tell you that you are going to get an underexposed image even though you won't with the flash on.

In Av mode, again, the camera doesn't care that you have the flash on. It'll meter for ambient lighting. At f/5.6, the camera is going to set the shutter speed to something less than 1/60 since we already know that at 1/60, the image is going to be underexposed (from what we saw in Tv mode above).

Hope this makes sense to you. What you'll notice is that in Tv and Av modes, the settings won't change whether you have the flash on or not. In P mode, however, you should see a difference in camera settings selected between using the flash and not using it.

[Sam]

Thank you PacAce, I didn't know that the camera was not aware of the flash in AV or TV mode. That really clears up a lot of my frustration. In M mode am I correct in thinking that the flash is fully aware of the camera settings and will adjust acordingly as long as I keep it in auto mode?

So would my best bet be to go ahead and meter the scene in P then switch to M and change the settings as I see fit? I am not all that experienced but it seems to be a step backwards for me to just shoot in P mode when using my flash.

Would a light meter be a wise investment at this point or should I get through more of my learning curve first?

[lostdoggy]

No you don't need to meter in P mode since that will only meter ambient light. You would need to s flash meter to do that. If you have a TTL flash the flash will vary its duration depending on the TTL metering during the exposure.

[Sam]

OK, forgive me if this sounds a little ameteur (but I am one!)

If I press the * button on the back of my camera the flash pops and I get an exposure setting. This is what I meant by metering in P mode first. The exposure setting that I get here would not be useful?

[PacAce]

Thank you PacAce, I didn't know that the camera was not aware of the flash in AV or TV mode. That really clears up a lot of my frustration. In M mode am I correct in thinking that the flash is fully aware of the camera settings and will adjust acordingly as long as I keep it in auto mode?

So would my best bet be to go ahead and meter the scene in P then switch to M and change the settings as I see fit? I am not all that experienced but it seems to be a step backwards for me to just shoot in P mode when using my flash.

Would a light meter be a wise investment at this point or should I get through more of my learning curve first?
If you are going to be using the flash, you really don't need to meter anything because the metering will be for ambient light which you don't have enough of in the first place. And using the FEL (using the "*" button) doesn't buy you anything either because, in P mode, the camera will just set the shutter to 1/60 and the aperture to the widest available on the lens when you don't have enough ambient lighting.

Here's the logic you can apply in M mode to determine what settings to use. First of all, unless you are using a tripod, you will want to pick a shutter speed fast enough to allow handholding. For most people, that would be 1/60 with a normal lens. The problem with 1/60 is that if there is enough amblient lighting and people are moving, you may get a blurred image (or ghosting). That's one reason some people like to use a higher shutter speed, like 1/125 or 1/250. Just realize that with a higher shutter speed, you will capture less of the ambient lighting and could end up with a darker background. BTW, shuter speeds at or below sync speed has no effect on the flash usage. It only determines the ambient light exposure.

Determining the aperture is going to be a little more tricky because, unlike the shutter speed, the aperture used will have a direct effect on the maximum distance you can use the flash. The wider the aperture, the farther your subject can be from the flash. But the problem with using the widest aperture, especially with fast lenses, is that you end up with a shallower DOF than with a smaller aperture. So you have to come up with a compromise between maximum working flash distance and deeper DOF since they are inversely related to each other. You have to decide which is more important, distance or DOF. if you decide DOF is more important, then determine what aperture you need to achieve the desired DOF. Then determine what your maximum working distance is for that aperture (dividing the appropriate flash GN by aperture) and make sure your subjects are within that distance range.

[Sam]

If you are going to be using the flash, you really don't need to meter anything because the metering will be for ambient light which you don't have enough of in the first place. And using the FEL (using the "*" button) doesn't buy you anything either because, in P mode, the camera will just set the shutter to 1/60 and the aperture to the widest available on the lens when you don't have enough ambient lighting.

Here's the logic you can apply in M mode to determine what settings to use. First of all, unless you are using a tripod, you will want to pick a shutter speed fast enough to allow handholding. For most people, that would be 1/60 with a normal lens. The problem with 1/60 is that if there is enough amblient lighting and people are moving, you may get a blurred image (or ghosting). That's one reason some people like to use a higher shutter speed, like 1/125 or 1/250. Just realize that with a higher shutter speed, you will capture less of the ambient lighting and could end up with a darker background. BTW, shuter speeds at or below sync speed has no effect on the flash usage. It only determines the ambient light exposure.

Determining the aperture is going to be a little more tricky because, unlike the shutter speed, the aperture used will have a direct effect on the maximum distance you can use the flash. The wider the aperture, the farther your subject can be from the flash. But the problem with using the widest aperture, especially with fast lenses, is that you end up with a shallower DOF than with a smaller aperture. So you have to come up with a compromise between maximum working flash distance and deeper DOF since they are inversely related to each other. You have to decide which is more important, distance or DOF. if you decide DOF is more important, then determine what aperture you need to achieve the desired DOF. Then determine what your maximum working distance is for that aperture (dividing the appropriate flash GN by aperture) and make sure your subjects are within that distance range.

WOW, great reply. Thanks I will play around with the advice you gave me. :)