Auto mode and TTL problems

Ever had auto mode or TTL exposure problems at a wedding or event? What did this

occur? What solution did you produce for it? Were you successful? What alternative

solutions did you use to get by? What equipment did you use? What would you tell other

photographers?

I have had problems with auto and ttl mode. Equipment, Nikon D1H, SB80 DX, SB50 DX, Metz 45-CT3, Lense realy isn'nt an issue. In low light or fairly dark the auto ttl mode shines I get fantastic results. In average lit rooms where i need lots of light and everthing well lit and balanced I find I get much better results shooting manual with the metz It seems more natural and reliable. I was assisting a very sucessfull wedding and event photographer in the Toronto area and he was a manual fanatic so I guess he showed me the light so to speek :-). Overall I find Auto unstable and not very consistant it has to many variables and can be fooled to easily. I get very consistant results with manual and use my 80 DX many times in manual mode rather than auto. Thats not to say that its better than auto its just better for me. I'm sure many of you find auto ttl just fine.

 

Cheers.

Here is a good example of where TTL works well for me. This was shot full auto in a dark bar.<div></div>

Here is a good example of maual mode for me. If I remember it was shot at 1/90th at F6<div></div>

I never use Program or AV in dark conditions. I prefer Manual with the flash set to TTL.

 

The thing that throws some folks is that with many of these new cameras the TTL read is

done at the focus point selected. If you focus one place and then reposition the framing,

the flash exposure may be off because the camera read the focus point, not the new

framing.

 

For example, with Canon's ETTL if you just use the center point of focus, that's where the

pre-flash will be read. If you reposition the framing the pre-flash reading may well be off.

But, if you use the 45 point auto focus selection (where the camera determines the subject

to focus on), then the entire field of view will be what the ETTL pre-flash uses to

determine flash exposure... which is usually more accurate flash exposure because it is

reading the Matrix area. Canon provides a FEL button for the photographer to manually

trigger the pre-flash while training a single focus point on any subject area. The camera

holds this reading for the following shot no matter where the camera is then focused.

 

Frankly, there are times when I wished Canon also provided a straight Auto read that

wasn't TTL (like Nikon does).

I have a problem I need solving. I <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=007ukw">posted about it</a> in another group a while back. http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=007ukw<br>So far, I ran a test and it seems to correlate with shooting at 1/30 sec in any camera mode. The effect is less noticeable at small apertures. If anyone can help with this, I would appreciate it much.<div></div>

That problem is called light fall off (inverse square law). When direct flash is the primary light source, there is a distance that is exposed exactly right. Closer things are over exposed and farther away things are under exposed; and that's what's happened in your picture. There are two ways to get more even exposure: Use two lights - one for the foreground and one for the background. The other way is to bounce (or use an omni-bounce pointed up) to more evenly distribute the light.

Can't be light fall off. I've tested it at the same distance. The horizontal line happens at the same position in the frame, and it even happens in portrait orientation. I need to run more tests, but so far it only happens at 1/30 sec shutter speeds. I'm worried my shutter is going bad. But like I said, it happened to two independent setups (camera and flash) on the same night. What are the odds?

From the samples I would say it is shutter bounce or shutter hang-up, both of which

would produce the effect. When you shoot with a flash it normally fires as the second

shutter starts to close. If the shutter hung up 3/4 of the way closed, it would expose that

remaining 1/4 of the frame more than the rest. Same with shutter bounce, the shutter

would close completely, but bounce back open to expose the bottom portion of the frame

more than the rest. I actually had a case of shutter bounce that I had to get repaired so I

know the look. But either of these would also show up in non flash photos. You would

have to look closely at the negs to see it.

 

What is perplexing is the fact that 2 cameras did exactly the same thing. Which leads me

to believe 1) you got mixed up as to who shot what, with what camera. Or 2) there was a

common error involving the same piece of gear. Was the same Metz flash used for both

shots?

 

If you used 2 different flashes, and the effect is showing up on non flash negs then I

suspect the answer is # 1 and your shutter needs repair.

Doesn't the flash usually fire right after the first curtain opens, unless you set to rear curtain sync, in which case the flash fires right before the second curtain closes?<br><br>In any case, thanks for the insight, this is the first suggestion that makes sense. Although it's weird that it happend to two setups at once. I'm quite certain that it happened with both cameras, we kept our film separate. And we each have our own Metz flash.<br><br>I'm going to do a few more tests, then take them into the shop to have them checked out.<br><br>Can you describe any tests I could perform to verify that it's shutter bounce?

MP. have you resovled this problem yet?As I have encountered it 4 months

ago. Program with TTL and a Metz. Keep us posted.