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Author Topic: Sekonic vs. Canon Meter Reading  (Read 4007 times)

svaughan

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Sekonic vs. Canon Meter Reading
« on: July 04, 2006, 08:22:43 pm »

I recently purchased the new Canon 30D. It was a definate up grade from my Sony F828.  Right now, I am just shooting different style shots to get comfortable with the camera, and settings. I have been doing some portraits for people and pets, but mostly outside. I have used fill flash on these at times, and I use incident metering on most of my shots.

I was playing with the camera inside comparing flash readings  from the sekonic to the camera meter.  The sekonic consistanly reads less light than the camera, using incident mode.

As an example I am shooting with the Sigma 17-70mm. If I set the ISO to 100, the shutter to 60, and apeture 4.5, when I fire the flash, my sekonic reads that as apeture 1.6, even though my ISO and shutter are set the same as the camera.

Why the big difference? If I bump my ISO up to 650 to get the sekonic to read around 4.5, the shot seems slightly over exposed.

My distance is around 6 feet, and I am using the flash on the camera, not an external. I would expect them to read closer than this.

Is the difference due to reflective vs incident?  Synchronization Problem? Calibration Problem?

Any Idea's. All comments are greatly appreciated.
Steve
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Anon E. Mouse

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Sekonic vs. Canon Meter Reading
« Reply #1 on: July 05, 2006, 04:55:08 am »

Are you sure your Sekonic is not reading the camera's pre-flash? Most modern on-camera flash units put out a pre-flash before the main flast to determine exposure. If you change your camera flash controls to manual, you may be able to turn off the pre-flash, but not all cameras can.
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svaughan

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Sekonic vs. Canon Meter Reading
« Reply #2 on: July 05, 2006, 07:18:04 am »

Yes, the camera does have preflash. Infact it is a part of the AF system, if the light is too dim to focus.  Maybe I should set the sekonic to read multiflash, where it accumulates the readings. But according to the sekonic manual, if I am measuring without a cord, it should autorest and take the reading anyway.

I will test it with the multiflash function to see if that makes a difference.
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Sheldon N

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Sekonic vs. Canon Meter Reading
« Reply #3 on: July 06, 2006, 11:10:31 am »

You are chasing something that you cannot fix. The 30D does not have any manual control over flash output, just flash exposure compensation adjustment. Every shot is metered by the ETTL II system (preflash) and then output is adjusted based on what the camera thinks is appropriate. Adjusting aperture, ISO, etc will not give you any control over the flash output. If you want to adjust it, use the flash exposure compensation control on the camera.

Your Sekonic was designed to be used with flashes that have manually adjustable output, not to be used as a replacement for the ETTL system.

I wouldn't worry about whether your Canon popup flash output matches your Sekonic's reading. They work in different ways, so its not a surprise that they don't match.
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Sheldon Nalos
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boku

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Sekonic vs. Canon Meter Reading
« Reply #4 on: July 06, 2006, 12:10:41 pm »

Quote
You are chasing something that you cannot fix. The 30D does not have any manual control over flash output, just flash exposure compensation adjustment. Every shot is metered by the ETTL II system (preflash) and then output is adjusted based on what the camera thinks is appropriate. Adjusting aperture, ISO, etc will not give you any control over the flash output. If you want to adjust it, use the flash exposure compensation control on the camera.

Your Sekonic was designed to be used with flashes that have manually adjustable output, not to be used as a replacement for the ETTL system.

I wouldn't worry about whether your Canon popup flash output matches your Sekonic's reading. They work in different ways, so its not a surprise that they don't match.
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I concur. In general, I have never found that using a flash meter worked with any form of auto flash. If you have manual flashes, a Sekonic flash meter, and working in a controlled environment, then you don't need auto flash. (But you already know that.) On the other hand, if you choose to use a built in flash that is controlled by the camera, even with flash exposure compensation capability, put the Sekonic away. You are at the mercy of the camera no matter what the meter says.
« Last Edit: July 06, 2006, 12:12:16 pm by boku »
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Bob Kulon

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svaughan

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Sekonic vs. Canon Meter Reading
« Reply #5 on: July 08, 2006, 08:57:02 am »

Thanks for the answers. I was thinking that was my problem. I was supprised to see that the flash level was controlled by the camera in manual mode. In the Canon customizing menu's, there are only two ways to use it, evaluative and average, but it can't be turned off.

What I found interesting, is when I did some fill flash shots outside, regardless of my shutter or f stop setting, the flash fired the same level of light to match my exposures.

Thanks. Steve
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