Contax with flash consistently underexposes. Help!

[tom in mpls]

I am using a Contax 645 with P30+ back, prism viewfinder, and a Metz flash. I have tried shooting TTL and Av, and have also tried flash set to "A" and camera set to "M", 1/60 sec. All combinations result in pics that are 1 stop underexposed. I don't understand what I'm doing wrong here.

 

[gogopix]

with the backs the reflection is different from film . Contax and Phase both recommend a two stop exposure adjustment, but I thought it was the other way (unless you are using an aperture too small for the flash to fihope helps
regards
Victor
PS I use the two contax flash with the Phase backs and they are quite good with -1 adjustment on the 380. smaller flash doesnt have exposure adjustment. 380 should behaqve a lot like the Metz.
also I assume you have the adapter for the shoe? (1205 or some such number; sorry I dont use Metz)

 

[tom in mpls]

Yes, I have the correct Metz adapter (SCA 3802). I'm still trying to learn about this camera; since I got it the weather here in Minneapolis had been dreadful so I have used it very little. Some testing today suggests that it is a metering problem, as shooting with natural light has yielded the same 1 stop underexposures. At least I can correct for that with the camera EC, but I don't know if there is a way to adjust FEC.

I don't understand the reflectivity problem (I mean I have an inkling what you mean about different properties of film and digital). It seems to me that manufacturer could easily account for that by adjusting the ISO settings.

 

[fotografz]

Yes, I have the correct Metz adapter (SCA 3802). I'm still trying to learn about this camera; since I got it the weather here in Minneapolis had been dreadful so I have used it very little. Some testing today suggests that it is a metering problem, as shooting with natural light has yielded the same 1 stop underexposures. At least I can correct for that with the camera EC, but I don't know if there is a way to adjust FEC.

I don't understand the reflectivity problem (I mean I have an inkling what you mean about different properties of film and digital). It seems to me that manufacturer could easily account for that by adjusting the ISO settings.

How would Phase One universally adjust the ISO settings for every camera their backs fit? The Contax metering system was developed before digital was so dominate ... the TTL was based on average film reflectivity NOT sensor reflectivity. Besides, the metering system on a Contax 645 is different than the Mamiya 645 and different than the Hasselblad H ... all of which I have used extensively, or still own.

BTW, when I shoot with the H camera I've (generally) found the most consistency of digital exposure comes from using the older style center-weighted averaging. Of the three cameras, it has been the most accurate at digital metering ... and dead on for flash control ... perhaps a function of the type of photos I shoot, so your milage may vary

Also, I've found that almost every back maker errors on the slight underexposure side ... perhaps to prevent the sin of blowing the highlights. Easy enough to adjust your exposure compensation on any of these cameras once you are sure
that it's a truly consistent issue.

If you are using a Metz flash it may that the 3802 module is one that can be adjusted to permanently retain a plus-or-minus compensation, which is independent of the main +/- comp controls. My SCA 3502 has this feature.

Are you shoot an evenly lit digital test card to be sure it's an issue?

And lastly, how are you processing ... if with C1 what profile? Is your monitor calibrated? Sorry to ask this if you are experienced and know all this.

 

[tom in mpls]

How would Phase One universally adjust the ISO settings for every camera their backs fit? The Contax metering system was developed before digital was so dominate ... the TTL was based on average film reflectivity NOT sensor reflectivity. Besides, the metering system on a Contax 645 is different than the Mamiya 645 and different than the Hasselblad H ... all of which I have used extensively, or still own.

Also, I've found that almost every back maker errors on the slight underexposure side ... perhaps to prevent the sin of blowing the highlights. Easy enough to adjust your exposure compensation on any of these cameras once you are sure that it's a truly consistent issue.

If you are using a Metz flash it may that the 3802 module is one that can be adjusted to permanently retain a plus-or-minus compensation, which is independent of the main +/- comp controls. My SCA 3502 has this feature.

Are you shoot an evenly lit digital test card to be sure it's an issue?

And lastly, how are you processing ... if with C1 what profile? Is your monitor calibrated? Sorry to ask this if you are experienced and know all this.

OK, thanks for setting me straight on ISO adjustments.

It seems the SCA 3802 has no compensation adjustment; of course they're famous for poor documentation but looking at the stuff behind the flap on the adapter I see nothing that works for flash comp. I had thought of that earlier. I also have a Contax flash that results in the same underexposure that I see with the Metz.

Not shooting test card, but shot many different things, some with lots of light/dark areas, some very evenly lit. All show same underexposure.

I use C1, but for my testing I'm looking only at the histogram on the digital back.

And, Yes, I am an amateur, and quite new to MF. So go ahead and fire away at me so I can learn.:thumbup:

 

[fotografz]

What exposure mode are you using? Are you coming from shooting film prior to this?
What digital experience do you have besides this?

Open the files in C1 and see what they look like. Just auto adjust to see if they are okay or if it indeed is 1 or more stops under.

Have to leave for LA now ... will respond more if I get the chance.

 

[David K]

I wish I could offer some help but have never used a flash with my Contax kit... always strobes with a Sekonic light meter and Pocket Wizards. Might be worthwhile to pick up a light meter and set the camera to M. In my experience though, 1 stop underexposure is easily adjusted in C1.

 

[tom in mpls]

What exposure mode are you using? Are you coming from shooting film prior to this?
What digital experience do you have besides this?

Open the files in C1 and see what they look like. Just auto adjust to see if they are okay or if it indeed is 1 or more stops under.

Aperture priority for TTL. Long time since I used film. I've got a lot of experience and consider myself competent with Canon dslr's, also used the Metz with the Canons and it worked great.

My experience with pulling one stop underexposed shots is that I sometimes get lots of noise in the darker portions. I'm prefer to overexpose a bit rather than underexpose.

 

[fotografz]

Tom, I'd do a more controlled test to determine exposure specifics of that Contax, Phase One combination. Even light on a Grey card, or one of those digital white balance cards ... then zero in the WB in C1 to see where you are.

Your Canon experience is from a pure digital camera, where the Contax was a film camera adapted to digital with the meter calibrated for film reflectivity.

For years I used a Contax 645 with a Kodak Proback 645C, and it did slightly underexpose on a regular basis. However, it almost never blew the highlights. Your Phase One back has more exposure latitude than any Canon ever made,
so as David says, lifting a 16 bit MF digital file a stop is simple, and in my experience has little to no effect on the IQ.

However, it should be an easy thing to adjust your compensation to account for any difference once you test it in controlled conditions.

 

[gogopix]

from the P45+ use guide

"...TTL flash
Because the CCD element reflects light different than film, and this cannot be communicated to the Contax.Using TTL flash with the CONTAX 645 camera and the P+ back, will result in a 2 f-stop overexposure. When using TTL flash, the exposure compensation on the flash unit must therefore be set to –2 f stops.

..."

 

[tom in mpls]

from the P45+ use guide

"...TTL flash
Because the CCD element reflects light different than film, and this cannot be communicated to the Contax.Using TTL flash with the CONTAX 645 camera and the P+ back, will result in a 2 f-stop overexposure. When using TTL flash, the exposure compensation on the flash unit must therefore be set to –2 f stops..."

This is even more confusing. I looked at the manual and see this quote is correct. So that would put my flash pics at 3 stops underexposed since I am shooting with no FEC. Going from bad to worse, it seems.

 

[fotografz]

This is even more confusing. I looked at the manual and see this quote is correct. So that would put my flash pics at 3 stops underexposed since I am shooting with no FEC. Going from bad to worse, it seems.

That's why I think you need to do a controlled test. One where there are no variables in subject and light source. Fresh batteries in all items.

 

[tom in mpls]

I have been able to make some additional observations. Son loaned his 645 to me to use for comparison, and I found his Contax and mine behaved in exactly the same manner. This would suggest that the bodies are functioning properly.

When using the Metz flash (with SCA 3802 adapter) in TTL mode, camera set on Av, I got inconsistent results from both bodies. Some pics were 1 stop underexposed, some were 2 stops overexposed, and on occasion I would get one properly exposed.

However, I also tested with a Contax TLA 200 flash. Same settings all around. Now, both bodies shot 2 stops overexposed, consistent with the info from Phase regarding flash overexposure on this body. And when I set the EC to -2, I was able to get properly exposed pics with great consistency.

I don't know why the Contax flash behaved properly but the Metz did not. I would suggest that it is due to some problem with the Metz adapter, but I do not know if it is a malfunction or if the adapter just wasn't designed/programmed properly.

Oh, yes, one more thing. Under natural light, I found both bodies had a tendency to underexpose about 1 stop.

 

[fotografz]

"Oh, yes, one more thing. Under natural light, I found both bodies had a tendency to underexpose about 1 stop."

This is exactly what I experienced concerning ambient light exposures when using a Kodak Proback 645C on the Contax 645. I never used a Metz flash on that camera, instead used either a Contax 360, or more frequently a ball diffused Sunpak 120J bare-bulb with C/Y TTL module to shoot weddings. The Sunpak was fairly accurate, and provided better results than the Contax flash.