Auto mode & Custom mode not agreeing

[lmele]

Hi All
Was fooling around with my camera & Flash tonight and i noticed that when i took and shot in auto mode the reading was one thing and in custom mode the reading was something else.
Scenario
Camera mounted on tripod facing a chair with a toy on top of chair
Camera has a 17-85mm lens and a 580ex flash mounted on it.
In automode the setting is f5.6 apperature with 60 shutter speed and 400 iso and 80mm focal length
In custom mode i set the apperature to f5.6 but the shutter speed was at 0' '3 and without major adjustments to the iso and exposure settings i could not get the same reading
I'm a bit confused here , is there something ive missed or maybe my brain is in(its monday tommorow, today i rest dont bother me) mode and have missed something simple:oops: .

[Rigrider]

WARNING!!!! I HAVE NO IDEA WHAT I"M TALKING ABOUT!!!!!

Sounds to me like you were reading the flash when you were in your "custom" mode (manual??) When you goe to those modes, you have to tell the camera to use the flash. At least that is the way it is with my 300D and the pop up flash. I can only assume it'd be the same in your case. Did you hit the little flash button????

L8r,

[lmele]

My camera had my 580ex flash attached to it and i was taking the readings from the view finder, I'm not sure but i dont think i have to tell the camera that the 580 flash is attached do i?? now i'm more confused ( i wish my brain would wake up:lol: )

[robertwgross]

What do you mean by "custom mode?"

---Bob Gross---

[smasraum]

I ASSuME he's talking about the creative modes.

As he said, with the built in flash in the "creative" modes you have to pop the flash up or the camera won't use it. But since you had an external mounted I doubt that's the case. But it does sound like it's trying to shoot without the flash

Which creative mode were you using? Was it the "P" or one of the other modes. If it was one of the other modes you will have to manually set things like iso and if in Av or Tv you'll have to set the other.

[lmele]

What do you mean by "custom mode?"


Sorry guys i mean creative mode. Like i said i have the 580ex flash mounted on the camera not the pop up flash. I'm using AE mode set at f5.6, my question is do i also have to set the flash as well as the shutter speed . I thought that in creative mode say AE mode you select the f/stop and the camera sets the rest . I'm just confused that in auto mode it selected f5.6 with shutter at 60 with 580ex flash monted but in creative mode i selected f5.6 but the shutter was at 0' '3 just wondering why the difference
thanx

[Hellashot]

I believe if you put an 550Ex or 580EX on a camera and set it in normal mode (external flash) the camera will not consider it is using a flash in Av, Tv, or M modes. If you put the flash into high speed sync like 1/200th it will know it has a flash to use.

[lmele]

Hellashot:

From my understanding then is that if i use the 580ex flash in auto mode the camera knows that the external flash is connected , but if i use creative mode i have to set the flash in high speed sync to tell the camera it has an external flah on it?
I always thought that if the external flash was mounted that the camera automatically detected that the flash was connected. I still was able to take the shot in creative mode and auto mode without doing any adjustments to the flash or camera its just that i could not match the shutter speed in Av mode to that of the auto mode without adjusting other settings?

[Raj]

I have not used external flashes yet but in auto mode camera automatically boosts iso upto 400, which it wont in creative modes, there you have to set iso manually. You mentioned iso 400 in auto mode, which camera will boost by itself, ou have no control on it.
Certian variables need to be set manually in creative modes without which you wont get readings similir to auto modes. Boost iso to 400 manually in creative mode & then try again & see what happens. Keep all other variables same.

[robertwgross]

Your 20D must be different from my 20D.

Mine does not have any AE mode called that.

---Bob Gross---

[lmele]

I meant Av mode my mistake:)

[robertwgross]

Have you read the EOS Flash Sticky thread?

It is long, but it goes into explanations of how flash exposure is done differently from one mode to another. That might explain some of the things you are seeing.

---Bob Gross---

[lmele]

I'm at work at the moment but i will read it tonight thanx Bob

[robertwgross]

That document does not have 100% of all of the flash answers. However, the one document goes farther than any other single document in aiding your understanding of flash issues. Unfortunately, you might need to read it multiple times in order to really get it. I did.

---Bob Gross---

[Bodog]

Assuming by Auto mode you mean "P" mode, the camera limits the shutter speed to a "hand holdable" 1/60 of a second. ( I believe the same limit would apply in the "green box" mode) If you were using the kit lens at 80mm, then f5.6 is your max aperture, so the camera couldn't open it any further. That is why the "custom" settings do not match. Setting the aperture to f5.6 in AV mode would give you the actual (slower) shutter speed necessary to expose the background at the time.

[Jim_T]

Using a flash on an EOS camera is an art unto itself :)

http://photonotes.org/articles/eos-flash/

[lmele]

Jim_TUsing a flash on an EOS camera is an art unto itself



Jim_T you nailed that one on the head. I spent all night last night reading and testing the sticky thread that Robertwgross steared me to, and man my brian is now fried . I tried to store to much information at once and all i got was flashes in my dreams:cry: . I guess its back to school again and lots of testing and practice.

[robertwgross]

Don't feel bad. Lots of people get the same feeling when they read that for the first time.

I suggest you read a little, then practice a little with your camera. Then get a local Canon buddy to go over it with you. Then practice a little more.

It is not trivial. I will give you that. However, it eventually filters into the dark recesses of our brains.

---Bob Gross---

[Titus213]

EOS flash photography is really a deep black art with occasional bursts of light...