Author Topic: What flash mode to use  (Read 4853 times)

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Offline aelkays

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What flash mode to use
« on: April 16, 2010, 03:53:51 PM »
I was wondering what Flash mode I should use when I have my flash gun on. There is ADI & pre-TTL which one should I select and what is the difference?

I have a Sigma EF530 DG ST flash.

Thanks,

Ahmad.
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Offline tpe

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Re: What flash mode to use
« Reply #1 on: April 16, 2010, 04:37:09 PM »
You can use ADI with lenses with 8 contacts when the flash is pointed directly at the subject, what it does is use the focus distance information to illuminate the subject in focus properly. If you are bouncing the flash of anything, using a diffuser, have a very short focal distance (macro) or are not using a lens with 8 contacts then you should use TTL. The advantage of ADI is the thing in focus is generally exposed correctly. The advantage of TTL is that the amount of light entering the lens will be correct, but not necessarily the subject of focus. For example if you have focused on the wall behind the subject it may be underexposed and the out of focus subject will be correctly exposed. In theory that is. In practice, ttl is useful for everything but some people say that it gives annoyingly bright pre flashes.

Tim

Offline paul_b

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Re: What flash mode to use
« Reply #2 on: April 16, 2010, 05:15:27 PM »
Excellent information and easy to understand tpe. I had worked out ADI was underexposing, using my F42 and a diffuser, and that TTL was correct. Now I know why. saved me some research :)
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Offline REX (aka TG)

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Re: What flash mode to use
« Reply #3 on: April 16, 2010, 06:50:04 PM »
Just to att something more.
1#you have to check if your flash is ADI compatible.
2#you have to check if your lens is D or DT (ADI compatible)
3#If the two above exist then try to use always ADI except when you use a diffuser because the flash can not recognise that you have put something in front of the flash unit
4#When you bounce the flash will turn to TTL automatically so you don't need to switch between TTL and ADI when bouncing
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Offline chappo1

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Re: What flash mode to use
« Reply #4 on: April 24, 2010, 05:02:35 AM »
Much more concise and understandable than the 58AM manual Tim.....john
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Offline Stef.

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Re: What flash mode to use
« Reply #5 on: April 24, 2010, 06:34:10 PM »
One more little point to add: I leave mine on ADI always because as far as I know the camera will automatically change to TTL if needed.
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Offline REX (aka TG)

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Re: What flash mode to use
« Reply #6 on: April 24, 2010, 06:44:13 PM »
One more little point to add: I leave mine on ADI always because as far as I know the camera will automatically change to TTL if needed.
Stef.

When you put a diffuser in front on the flash the camera cant recognise this situation.As far as i know only Nikon have a switch so when diffuser is attach the camera is already informed

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Offline harveyzone

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Re: What flash mode to use
« Reply #7 on: April 24, 2010, 07:52:09 PM »
2#you have to check if your lens is D or DT (ADI compatible)

Point of correction - ADI works with non D lenses - it does not default back to TTL. The distance info is probably not as accurate as with a D lens, as it calculates the focus point by distance of focus ring travel, but it still uses ADI.

Personally I always use TTL as I get better results than with ADI, but both work. I would encourage the OP to  try both as mine is an older camera (A100) and this has probably been improved since.

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Offline Stef.

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Re: What flash mode to use
« Reply #8 on: April 25, 2010, 01:58:15 AM »
Harveyzone- I think with the newer models it is actually that the camera detects what kind of lens is attached as it will switch automatically to TTL depending on lens. TG is (I think) absolutely correct: if you attach a diffuser it will not know that. If you tilt or swifel the flash it will though. (Me thinks ;) )
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Offline REX (aka TG)

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Re: What flash mode to use
« Reply #9 on: April 25, 2010, 06:01:46 AM »
2#you have to check if your lens is D or DT (ADI compatible)

Point of correction - ADI works with non D lenses - it does not default back to TTL. The distance info is probably not as accurate as with a D lens, as it calculates the focus point by distance of focus ring travel, but it still uses ADI.

Personally I always use TTL as I get better results than with ADI, but both work. I would encourage the OP to  try both as mine is an older camera (A100) and this has probably been improved since.

I can not confirm what you say because even mhorner on his site he doesn't confirm this. In a topic by dyxum only one time mhorner spoke exactly about what you said now. So for me if i can not get any decent results i can not confirm it i can just say i have heard from mhorner that ADI can work also with no D/DT lens but not always accurate.

So for me
old lens only....> TTL
Diffuser attach only...... >TTL
New lens always......>ADI
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Offline boogaloo

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Re: What flash mode to use
« Reply #10 on: May 18, 2010, 02:00:18 PM »
Save yourself a huge headache, get a good understanding of lighting/exposure, and just shoot manual :)

Offline Stef.

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Re: What flash mode to use
« Reply #11 on: May 18, 2010, 06:55:22 PM »
I have just answered another thread: we have to state clearly what we mean by "manual" There is a manual setting on the flash and the is the M setting on camera and both work completely different! Manual setting on the flash does not take int account any of your surrounding lighting situation! It will shoot at full power if you don't adjust the setting ON the FLASH.
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Offline harveyzone

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Re: What flash mode to use
« Reply #12 on: May 18, 2010, 07:15:10 PM »
I can not confirm what you say because even mhorner on his site he doesn't confirm this. In a topic by dyxum only one time mhorner spoke exactly about what you said now. So for me if i can not get any decent results i can not confirm it i can just say i have heard from mhorner that ADI can work also with no D/DT lens but not always accurate.

You can easily test if it is true...

Put 5 contact lens on camera.
Put camera on tripod and point it at a plain bit of wall.
Set camera to manual exposure and heavily underexpose (so that only flash is lighting the subject).
Set flash metering to ADI
Manual focus to infinity - expose.
Manual focus to closest focus - expose.

If it is purely TTL then both shots will be the same.
If it uses distance information then the infinity focus will be over exposed and the close focus one under exposed.

This happens on my A100 with 50mm f/1.7, but I do not have a more recent camera body to test it on.

Tom Harvey

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