Contax 645 TTL Flash Considerations

[john_coan]

I had a number of questions regarding the finer points of using TTL

flash with the Contax 645. Last week I spoke with Kyocera technical

support and got some answers which I thought might be helpful to the

group. I have a Metz flash but its SCA 3801 adaptor module emulates a

Contax TLA

360. The information should be valid for both flash units.

 

1. The pre-flash lever fires the flash sometimes but not at other

times. Its

operation is inconsistent. Answer: This could be caused by the

electronics

getting confused. If you find yourself in this condition, turn off

both camera

and flash. Turn them back on and see if the pre flash function starts

operation

working again.

 

2. Can the camera's compensation dial be used for altering fill flash

ratios

after locking in an ambient exposure value (instead of using the

compensation

switch on the flash unit itself.)? Answer: Yes. The on-camera

compensation dial

works by changing the camera's stored value of the ISO rating of the

film. Thus,

one can leave the compensation on his TTL flash at zero. Lock in an

ambient

exposure reading using the AE lock lever. Then, dial in the amount of

fill flash

compensation you want *on the camera*. The ambient exposure will be

retained at

the previously established EV, but the fill flash will be computed on

the "new"

ISO rating and thus be lower or higher. (This is good news because

now all

controls for ratioing fill flash are on the camera body. You can

leave the flash

controls alone, once you set them for TTL.)

 

3. The built in flash meter is a spot meter, about twice as large as

the

ambient-reading spot meter. Can you use the pre flash function to

measure flash

output on one part of a scene, say a face, and then recompose and get

the same

flash output? Answer: Yes. The pre flash lever locks-in the computed

flash

output value. Your flash unit will give the same amount of light,

exposure after

exposure, until that lever is pushed back in. Again, good news. Do a

pre-flash

with your subject's face centered. Leave the lever out, and recompose

and fire

away. The face will be correctly filled in.

 

I hope I got all these answers right. If someone thinks otherwise,

please let me

know and we can all experiment and see what works. All in all, this

seems like

great news and a cool way to work the equipment. ( Editorial comment:

Of course,

all this should have been explained in the instruction manuals.)

 

John

[john_coan]

One thing I forget regarding number one, above. Pre-flash does not work in Tv mode at all. This was confirmed by two helpful forum members who tried it on their cameras.

 

Anyone else with information regarding this topic, I would love to hear from. Opinions, how you use flash with the Contax 645, etc.

 

Also, I found out that the Contax off camera flash cable has only 3 pins, so all the information is not transmitted. However, the Metz unit puts the TLA adaptor itself on the camera, and thus preserves all functions when using off camera flash.

[michael_marks]

I have just purchased the contax 645 and have been successful using my canon eos off camera flash cord with the contax. the canon has a five pin system compatible with the contax ttl system.

[jhbeckman]

John -- that's very helpful info. thanks for posting it. I've got to admit to a little surprise at items 2 and 3, though. Still, if the instruction manual were better written, and 2 and 3 might not be a surprise.

 

So, the exposure compensation control will control only the flash output once the AE is locked? And the camera will essentially lock in flash output for TTL even if a scene is recomposed if you leave the pre-flash lever pulled? pretty nifty tricks to know.

[david_uschock]

If you want to be a perfectionist about it... Get an 18% gray card. I got four and stuck them on a poster board for a bigger target. Have your assistant place the gray card in the background. Zero out compensation. Set metering for spot.(located by viewfinder) Focus on the gray card. Turn lever to AEL.(auto exposure lock) Assumptions: 1. using aperature priority 2. The shutter speed that locks is 1/125th or slower. e.g. 1/125, 1/60, 1/30, 1/15 etc. Now move the gray card to where the people will be standing. Adjust exposure compensation to -2/3. Focus on the gray card and pull the pre-flash. Mine pretty consistently shows an "error" of -1/3, giving you a total of -1 stop under flash exposure. Enough to color balance skin perfectly. Not enough to give that hard flash look, burns included. Note: I also use a diffuser on my flash to soften the flash effect. This sounds complicated. It is not. AEL on a background gray card. Pre-flash -2/3 on a foreground gray card. You are now ready for one perfect shot after another. Simply trip the shutter release each time and adjust nothing else. Caveats: When you are done return compensation to zero, return AEL to on, return pre-flash lever to normal, return metering to average. You may have to use aperatures like f/4 in a dark church for formals and the shutter speed you get will probably necessitate a tripod. Having said all that, it is pretty automatic once you get it down and the images, background and foreground are bright, airy, perfectly exposed and the fill flash is completely unnoticable in your images. Very professional for formals.