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FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
Thread started 07 Sep 2008 (Sunday) 23:27
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can someone help me redo this lil experiment

 
ccp900
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Sep 07, 2008 23:27 |  #1

a) Put your metering to evaluative
b) stick a falshgun on top of your camera (in my case a 580 EX)
c) now put a single color of anything in front of the lens, this is so that you get a constant reading from the reflective meter, maybe a colored paper.
d) put your camera on AV
e) set an fstop maybe lets say f4.
f) turn on your flashgun
f) read the shutter speed chosen by the camera (just set it to 0 for simplicity)
ok now do this
g) turn off your flashgun

my results....

after turning off the flashgun the meter will still be at 0 position but the shutter speed will be reduced. Ex, if i had f 4.0 and SS 80 when the flashgun is turned on, the moment i click the power off on the flash it will immediately go to f4 SS 40 but the meter is still at 0.

I know using a flashgun in AV mode defaults the flash to fill in flash. But i thought id keep my settings the same but the electronics will output a lower amount of flash to keep a -1 stop flash fill ratio. I never thought my shutter speed will move and flash isnt affected by shutter speed anyway.

Now do this, move your metering to Spot mode and you wont see the behavior.

If your camera is at manual you also wont see the behavior, it seems to happen only when you are at evaluative metering and AV (maybe TV but i didnt check that)


[Sony A7R Mark 3 | Sony A7S | Sony Zeiss 16-35m f/4.0 | Sony FE 28m f2 | Sony Zeiss 55m f1.8 | Sony FE 28-70m f/3.5-5.6 | Helios 44-2 | Helios 44-3 | Nikon 105m f/2.5 AIS | Contax Zeiss Planar 50m f1.7 | Contax Zeiss Planar 100m f2 | Voigtlander Nokton 40m f/1.4 | Canon 24-105m f/4.0L | Canon 85m f/1.8 | Sigma 30m f/1.4 | Canon 10-22m f/3.5-4.5 | Canon 100m f/2.8 Macro USM | Canon 580 EX Ver 1.0]

  
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evandavies
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Sep 08, 2008 05:20 |  #2

Just quirks of the metering programing I guess. They can't account for all possible situations especially turing flash on and off.


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ccp900
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Sep 08, 2008 05:42 |  #3

so you also saw the same results?

or am i the only noob here who has a camera malfunction hehe....any expert that can enlighten me?

thanks.


[Sony A7R Mark 3 | Sony A7S | Sony Zeiss 16-35m f/4.0 | Sony FE 28m f2 | Sony Zeiss 55m f1.8 | Sony FE 28-70m f/3.5-5.6 | Helios 44-2 | Helios 44-3 | Nikon 105m f/2.5 AIS | Contax Zeiss Planar 50m f1.7 | Contax Zeiss Planar 100m f2 | Voigtlander Nokton 40m f/1.4 | Canon 24-105m f/4.0L | Canon 85m f/1.8 | Sigma 30m f/1.4 | Canon 10-22m f/3.5-4.5 | Canon 100m f/2.8 Macro USM | Canon 580 EX Ver 1.0]

  
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SkipD
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Sep 08, 2008 06:25 |  #4

The meter in your camera (and the meter display in your viewfinder) responds ONLY to ambient light, regardless of whether or not you have a flash attachment connected to the camera.

Under certain conditions (and I don't know all of the details), the camera will choose a different shutter speed - typically 1/60 second - when it detects a Speedlite connected or is trying to use the built-in flash as compared to the shutter speed that it would use or allow use of for an ambient-light-only exposure.

I would suggest thoroughly reading the manual supplied with the camera.


Skip Douglas
A few cameras and over 50 years behind them .....
..... but still learning all the time.

  
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Lowner
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Sep 08, 2008 09:06 |  #5

Just tried all that with my 30D and 550EX. I used the back of a blue folder on a window sill and had to go up to f/8 before the camera was happy, but despite running the test several times, I only get 1/250s at f/8, with or without the flash switched on.


Richard

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PacAce
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Sep 08, 2008 11:54 |  #6

ccp900 wrote in post #6262429 (external link)
a) Put your metering to evaluative
b) stick a falshgun on top of your camera (in my case a 580 EX)
c) now put a single color of anything in front of the lens, this is so that you get a constant reading from the reflective meter, maybe a colored paper.
d) put your camera on AV
e) set an fstop maybe lets say f4.
f) turn on your flashgun
f) read the shutter speed chosen by the camera (just set it to 0 for simplicity)
ok now do this
g) turn off your flashgun

my results....

after turning off the flashgun the meter will still be at 0 position but the shutter speed will be reduced. Ex, if i had f 4.0 and SS 80 when the flashgun is turned on, the moment i click the power off on the flash it will immediately go to f4 SS 40 but the meter is still at 0.

I know using a flashgun in AV mode defaults the flash to fill in flash. But i thought id keep my settings the same but the electronics will output a lower amount of flash to keep a -1 stop flash fill ratio. I never thought my shutter speed will move and flash isnt affected by shutter speed anyway.

Now do this, move your metering to Spot mode and you wont see the behavior.

If your camera is at manual you also wont see the behavior, it seems to happen only when you are at evaluative metering and AV (maybe TV but i didnt check that)

What you're seeing is a phenomenon called NEVEC (negative evaluative exposure compensation). The amount of difference will vary depending on the Ev of the ambient lighting. The lower the Ev, the more the difference. At Ev 13 or higher, you may not see any difference with the flash on or off.

A previous discussion on the subject:

https://photography-on-the.net/forum/showthre​ad.php?t=172767


...Leo

  
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ccp900
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Sep 08, 2008 20:54 |  #7

ahh thanks leo, will read thoroughly on nevec, i sort of skipped on that whole nevec thing when i saw the discussions before, sort of threw me back to college and masterals mode which i wouldnt wanna go through again hahaha.

lowner, your camera is set to fixed 1/250 when a flash is used, you need to change a custom function to disable that.

skip, thanks for the reply man but im not very clear on what youre saying, probably another nevec discussion, ill go read up on it.

thanks again guys!!


[Sony A7R Mark 3 | Sony A7S | Sony Zeiss 16-35m f/4.0 | Sony FE 28m f2 | Sony Zeiss 55m f1.8 | Sony FE 28-70m f/3.5-5.6 | Helios 44-2 | Helios 44-3 | Nikon 105m f/2.5 AIS | Contax Zeiss Planar 50m f1.7 | Contax Zeiss Planar 100m f2 | Voigtlander Nokton 40m f/1.4 | Canon 24-105m f/4.0L | Canon 85m f/1.8 | Sigma 30m f/1.4 | Canon 10-22m f/3.5-4.5 | Canon 100m f/2.8 Macro USM | Canon 580 EX Ver 1.0]

  
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can someone help me redo this lil experiment
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