Flash photos in AV canon 30d

Janice

Janice

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Janice
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OK Im baffled!! No change there then!!! :D :lol:

I put my 30d on AV mode (having set in the custom functions.. the mode for having shutterspeed set at 1/250" when flash is used) as NO.. which means it DOESNT do that and i can have slower speed if I wish.

now with the sigma 500dg super attached in ETTL-II mode (ie, auto) the camera tells me when shooting a normal daylight interior for instance... that if I want to use F8 which sounds quite normal....the shutter speed will be 1/10".

The resulting photo is way overbright.

If i put the shutterspeed to what Id have thought was normal...ie 1/60" or something...im getting an aperture of 2.8 which wont give me enough dof.


Im waaaaay confused now.! i thought perhaps that i should just set the aperture to what i want and forget the shutterspeed.... but then im getting shutter staying open a long time to expose the background and this is all doing my head in!!! Even more!! :D
 
Just start shooting everything in manual janice, flash power included. It saves the confusion.
 
The camera will meter for the scene using existing light so the f/8 @ 1/10 is right. The flash will be used for fill only. As Kev suggested switch to manual then you can decide how much of the scene light can be used for the exposure and the flash will do the rest.
 
me and a lad at work had a discussion about this a few months back, if you set the camera to manual and set your own requirements in that the flash tends to follow suit and expose the image correctly
 
Ahhh ww that explains it.

I did understand the problem Janice is having, because I was thinking about this the other week.

Basically the camera meters the scene for available light, and doesnt take the flash into account.
I didn't know if you set it up in manual, the flash then works out and exposes correctly.
 
Regardless of camera mode the flash basically does the same thing. A pre-flash is fired and is used to calculate how much power to use for the shot.

If you meter for the scene then you'll be using only a small amount of fill flash. The more you under-expose the more power the flash will use.

For example a night shot using manual mode. Meter for the street lights in the backgound, etc. and the flash lights the foreground.

web_5300.jpg
 
[S2]I HATE FLASH[/S2]

Janice you are not alone - I can;t get my head around flash !! - in P mode and Auto yep with the sigma it works great. In AV or TV NO CHANCE!!

So I then think Manual - but haven;t a clue what settings to use, do I go off the in camera meter? Does it know there is a flash - I wish i understood
 
Well I do always use manual usually....when not using flash.

My question was actually appertaining to this wedding in august which is at noon so im thinking of keeping the flash on to fill in the shadows under ladies hats etc with the sun being up above.

I dont really want to have to up and down the flash power with each shot.. Id rather it do it automatically.

I didnt want to use manual all day....although I know it well...as I thought there would be more scope to go wrong. Spot metering is what I use but decided on that day to use matrix.

P mode sounded a good idea but with flash you cant use the shift feature so thats out.
 
pxl8 said:
The camera will meter for the scene using existing light so the f/8 @ 1/10 is right. The flash will be used for fill only. As Kev suggested switch to manual then you can decide how much of the scene light can be used for the exposure and the flash will do the rest.
Click to expand...

But if it meters for the scene and decided F8 at 1/10" and I shoot at that..... the shutter speed is so slow you can hear it go click....click.
if someone moves Im buggered!
 
I think the problem is that people expect it to be more complicated than it really is, generally the flash will get it right without any effort. Try this when you've got 10 mins.

Get a willing subject, sit them in a chair with a table lamp next to them (switched on of course!).

Put the camera in manual and try the following.

Move in and get them to hold their hand near the light, take a reading from it and use those settings.

Take a shot with and without flash and compare. You should see that the flash shot has filled the darker side of the subject.

Now try another shot, this time take a reading from the table lamp itself so you're exposing for the brightest part of the scene. Then take a shot at the reading, -1 and -2 stops - all with flash. Now you can see how the flash automatically compensates to give the right amount of light for the shot.

If you feel the flash is too powerful you can adjust the FEC to knock it back a bit.

By controlling how you meter for the scene you are also controlling how much flash is used. The trick is to choose the right part of the scene to meter from in the first place and then balance the flash with FEC to get the result you want.

You can also try the same tests on a sunny day. Shoot with the sun behind and to one side of the subject. Expose for the highlights from the sun and let the flash fill the dark areas.
 
Janice said:
But if it meters for the scene and decided F8 at 1/10" and I shoot at that..... the shutter speed is so slow you can hear it go click....click.
if someone moves Im buggered!
Click to expand...

Well, yes and no. It depends on the scene. If the person is in the foreground then they will be lit by the flash so the exposure time for them is the duration of the flash not the shutter. If you keep the background OOF then any blur from camera shake probably won't be noticable.

But this is why manual mode is the way to go, you can balance the settings so you get a usable shutter speed for the situation. You might have to lose some light from the scene or up the ISO but at least you have a choice over the balance of flash and available light.
 
pxl8 said:
The camera will meter for the scene using existing light so the f/8 @ 1/10 is right. The flash will be used for fill only. As Kev suggested switch to manual then you can decide how much of the scene light can be used for the exposure and the flash will do the rest.
Click to expand...

Right...just been practising.:D Manual on camera (with spot metering) and manual on the flash.

I wanted a shot with a large aperture to give me small dof ... ie, of someone a fair way in front of the background so the background is oof. (ie, a bride's head and shoulders with some trees behind that are oof)

I exposed for the background using existing light .... and because the flash is attached to the camera I cant get a faster shutterspeed than 1/250" (as that is the flash sync speed) when using an aperture of F2.8 on my 50mm lens.

So when I shoot the subject the shutterspeed isnt fast enough adn there is way too much light. I assume the flash needs to be taken down a huuuuuge amount in manual in this situation?

This is where Im thinking that there's is going to need to be far too much fiddling between shots.


I also find it difficult that I dont meter off the bride's face for example.... and leave it to chance that the flash does it correctly...and if it doesnt i have to keep trying and turning it down and down.


Sounds terribly hit and miss to me. :shrug:
 
pxl8 said:
You can also try the same tests on a sunny day. Shoot with the sun behind and to one side of the subject. Expose for the highlights from the sun and let the flash fill the dark areas.
Click to expand...
How will the flash only fill the dark areas without blowing out the areas already lit by the sun? :shrug:
 
Does your flash do a high speed sync mode? I use it a lot on my 580ex for macro. I often shoot at 1/1000th or faster with flash.
 
Yes it does, Robert..... aaaarghhhh... more to get my head round!! LOL
 
Janice said:
How will the flash only fill the dark areas without blowing out the areas already lit by the sun? :shrug:
Click to expand...

When the flash pre-fires the camera works out how much flash is needed to stop that happening. The light from the flash doesn't reach the bright background which you've exposed for, only the subject. ETTL is also tied to the focus point or centre point in manual focus.
 
If half the face is lit by the sun and half isnt.......then they are both at the same distance from the flash as each other.............how can the flash only ligh the dark half?
Everyone says I should use the flash on manual.....does that use ETTL then?
 
I'm with pxl8 on this I think people are making it far more complicated than it actually is. As long as the flashgun is set on ETTL the balance of flash to ambient light wont be far out regardless of which mode you actually use on the camera - including manual.

If anything the result may be a little too much, and after a test shot all I usually find necessary is to reduce flash power a little. Using bounce flash it may be necessary to increase power a little due to light loss, although generally speaking I find the ETTL system copes with bounce situations very well apart from extreme condition - high ceilings etc.
 
Thanks for that CT... i think i was confused by earlier on in the thread... people said to use manual on the camera AND manual flash too!
ETTL II sounds easier.


Made me seem thicker than I am!! :lol: if that's at all possible!

would you use spot or matrix btw?

and it doesnt matter that the shutterspeed is slow and it goes "click......click" and doesnt enable me to take shots quickly?
 
Janice said:
Everyone says I should use the flash on manual.....does that use ETTL then?
Click to expand...
No it doesn't. Don't confuse Manual Mode on the camera with Manual Mode on the flash - they're two very different things.

When the flash is set to Manual - it's purely well... manual! It ouputs the exact same amount of light each time in accordance with what it's actual power is (indicated by it's Guide No). The only effect you can have on the flash power is either manually reducing it's output power, or by using the guide number to calculate the correct aperture for flash to subject distance, or the correct flash to subject distance for a given aperture setting.
 
If it makes you feel any better Janice - I'm as confused as you on this. I just did a dance show in a sport hall and the organiser asked me to do some group shots. The ceiling was too high to bounce so set AV so it was shutter 1/200 and f7.1, even with the flash head power setting on ETTL at +2 the flash was no where near good enough to light the kids, so had to change the ISO all the way to 1600 to get enough flash to light the pic. Should I have needed touch the ISO? What did i do wrong?
 
Janice said:
If half the face is lit by the sun and half isnt.......then they are both at the same distance from the flash as each other.............how can the flash only ligh the dark half?
Click to expand...

Using random figures plucked out of the air... If the sunlit stuff is say 2000 lux and the shadow stuff is say 200.... and the flash adds 200 to the light level..... the sunlit area becomes 2200 (or plus 10%) and the shadow becomes 400 ( or twice as bright). So the change in the bright areas is not noticeable... but the dark areas is.

that's my wine fuelled theory anyway ;)
 
RobertP said:
that's my wine fuelled theory anyway ;)
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Well, my cider-fuelled brain has caught on there Robert! Well explained! :thumbs:

And thanks to everyone too.... for putting up with my inane questions.....its a topic I find it hard to come to grips with. :thumbs:
 
Janice said:
would you use spot or matrix btw?
Click to expand...

In most situations Janice I'd use matrix. It's all to easy forget you're using spot metering and end up metering on a black suit or a white dress - using weddings as an obvious example. Thank gawd we can chimp like flip! ;)

and it doesnt matter that the shutterspeed is slow and it goes "click......click" and doesnt enable me to take shots quickly?
Click to expand...

Well it can matter depending on the situation Janice.

Remember that the duration of the flash is incredibly brief - much faster than the fastest shutter speed on your camera,, so the shutter is still open long after the flash has died away. This is exactly what you want with a fill flash situation indoors as the ambient exposure which happens while the shutter is still open (after the flash has died) is what gives you that natural looking interior shot instead of the sudden fall off into darkness behind your subjects. Sometimes the ambient light can be strong enough for secondary images to record from subject movement during this period before the shutter closes, so if it's typically an exposure of say 1/25 or less just ask your subjects to keep still. :)
 
Keltic Ice Man said:
If it makes you feel any better Janice - I'm as confused as you on this. I just did a dance show in a sport hall and the organiser asked me to do some group shots. The ceiling was too high to bounce so set AV so it was shutter 1/200 and f7.1, even with the flash head power setting on ETTL at +2 the flash was no where near good enough to light the kids, so had to change the ISO all the way to 1600 to get enough flash to light the pic. Should I have needed touch the ISO? What did i do wrong?
Click to expand...

Try to remember that flash lighting is only affected by two things during exposure which are ISO and Aperture. You'd have been better off opening up the aperture than upping the ISO to increase the effect of the flash but if you needed more light overall you could have decreased the shutter speed depending on the length of the lens you were using.
 
Keltic Ice Man said:
If it makes you feel any better Janice - I'm as confused as you on this. I just did a dance show in a sport hall and the organiser asked me to do some group shots. The ceiling was too high to bounce so set AV so it was shutter 1/200 and f7.1, even with the flash head power setting on ETTL at +2 the flash was no where near good enough to light the kids, so had to change the ISO all the way to 1600 to get enough flash to light the pic. Should I have needed touch the ISO? What did i do wrong?
Click to expand...

This is where the guide number comes into play. That tells you how powerful your flash is for lighting a certain distance. I don't remember much more about it as I only used it back when I had a basic manual flash on a film camera.

So yes it is possible you might need to up the iso. Diffusers and wide angles all make it harder for the flash.
 
Keltic Ice Man said:
If it makes you feel any better Janice - I'm as confused as you on this. I just did a dance show in a sport hall and the organiser asked me to do some group shots. The ceiling was too high to bounce so set AV so it was shutter 1/200 and f7.1, even with the flash head power setting on ETTL at +2 the flash was no where near good enough to light the kids, so had to change the ISO all the way to 1600 to get enough flash to light the pic. Should I have needed touch the ISO? What did i do wrong?
Click to expand...

Do this NOW in the room wherever you are... ;)

Set the camera on a tripod.- AV mode, 100 or 200 ISO, Meter for the room light - let's say its 1/25 or less with the lens wide open. USE THAT SETTING FOR YOUR FLASH SHOT. Attach the flashgun. Set it to ETTL and make sure it's on full power. Point the flash right up at the ceiling - take the shot.

Go on - tell us what happens. :)
 
Kev - If I had dropped the Aperture - with 2 lines of kids I wouldn't have had enough DOF would I?
I Couldn't drop the Shutter Speed - as I was in AV and had told it to set to 200, maybe I should have gone to Manual on the Camera.

Robert - I had the Gary Fong on - wonder if I should have overpowered the flash head by a bit more (+3 perhaps)
 
Yep, CT's on the same page as me. Everyone stop trying to figure it out and do it cos it just works :D
 
KIM, the shutter speed doesn't affect the flash which is a much faster burst. If you were using the Fong then I think you were trying to bounce the flash from the high ceiling. You would have been better shooting with the naked flash head.
 
K I M. Your flash has a maximum output that it can do. You usually know when it used all it has as the flash is bright and takes longer to recharge :)

Having just looked at guide numbers for a refresher.... If your flashgun has a guide number of say 40 then for a standard lens, direct flash (no diffuser) the aperture at 100 iso for subjects 5 meters away would be 40 divided by 5 = f8.
As the flash decides how much light to punch (using ETTL) you can choose any aperture wider than f8 too. Shut down more than f8 to say f11 and the flash does not have enough power and the shot will be under lit.

Caveat: The wine hasn't quite worn off yet ;)
 
RobertP said:
Shut down more than f8 to say f11 and the flash does not have enough power and the shot will be under lit.

Caveat: The wine hasn't quite worn off yet ;)
Click to expand...

why when you make the aperture smaller will the flash not have enough power?

cider hasnt quite worn off yet either! ;)
 
CT - So I gets my fluffy white polar bear, and white cat - lines them up in my room. Takes a reading at iso 200 of F2.8 and 1/8th. Then I switches on my flashgun - make sure its in ETTL point it to the ceiling (which is quite low) and Yep I get a well exposed shot!

So lets say that was a 7 year old kid instead of a polar bear would a shutter speed of 1/8th be enough or would there be motion blur on it?

PX18 - The Gary Fong was pointing straight towards the kids as the ceiling was a really long way up.

Robert P - :) Thanks
 
Janice,
Don't forget I was talking about using the flash at its maximum output. it can only give so much light. If you ignore shutter speed (cos it is fixed and not variable ie flash duration) the only way to control exposure is the aperture.

If you were stuck with say 1/1000th for an outdoor shot you don't have a choice of aperture unless the sun gets brighter.

need more wine my explanations are getting worse
 
Keltic Ice Man said:
CT - So I gets my fluffy white polar bear, and white cat - lines them up in my room. Takes a reading at iso 200 of F2.8 and 1/8th. Then I switches on my flashgun - make sure its in ETTL point it to the ceiling (which is quite low) and Yep I get a well exposed shot!
Click to expand...

There you go! :)

So lets say that was a 7 year old kid instead of a polar bear would a shutter speed of 1/8th be enough or would there be motion blur on it?
Click to expand...

That depends really on the strength of the ambient room light, but 7 year old kids are notorious for not keeping still aren't they? Do the time honoured professional thing - take a few shots and chimp like ****! :D
 
Keltic Ice Man said:
So lets say that was a 7 year old kid instead of a polar bear would a shutter speed of 1/8th be enough or would there be motion blur on it?

PX18 - The Gary Fong was pointing straight towards the kids as the ceiling was a really long way up.
Click to expand...

Re. Fong - the thing is designed for bounce flash, even pointing straight forward it will still chuck light in all directions as it's supposed to do that.

If you need to shoot a 7 year old and the metered reading is too slow you can either:

Up the ISO to increase shutter speed
Open the aperture to increase shutter speed
Increase the shutter speed and lose some of the light from the scene (the flash will use more power to compensate).

Or a bit of all 3 to find the balance, maybe another stop of ISO and a stop wider, etc.
 
Just think about that cheap compact we've all had where when light levels drop to a certain level, the flash comes on automatically at a default flash sync speed of 1/60 or faster. The assumption is made for you by the camera that the flash is going to be the main or only form of illumination. This is why these cameras produce those ghastly typical night out pics where the subjects look like frightened deer in the car headlights. Flash is very linear - it goes straight out from the camera - hits the subject - returns to the onboard camera sensor which deems the exposure correct and quenches the flash. The flash never reaches that dark background and the flash sync (shutter) speed was too quick for the camera to record any ambient light room detail.

You DSLR is a bit more sophisticated than that. If you choose a slow shutter speed it 'assumes' from the outset that the flash is going to be combined with ambient light. The normal camera metering system meters for the ambient room light, while the onboard flash sensor determines the flash exposure, but all the while calculating the best way to combine the two sources of light. In the main it works very well with minimum interference from us. ;)

Manual flash is fine in a studio situation, but it's the last thing you want to be doing at say a wedding - continually doing the guide no maths in your head to determine subject distance or aperture when you're under plenty of pressure anyway is no fun - I've done it and I don't miss it. :gag:

Modern flashguns are a bloody godsend, we just need to learn to trust them - most of the time anyway. :)
 
Keltic Ice Man said:
If I have 2 or 3 lines of 7 year olds, f2.8 won't give enough DOF, if I open it to say f11 I seem to go over the Shutter speed of 200 that AV allows me with a flash on. Is there a way around this, or perhaps as Shutter don't seem to matter - DOF works differently?
Click to expand...

You close down to f11 KIM, you don't open up from f2.8, so closing down to f11 would actually result in a slower shutter speed - not a faster one.
 
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