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12-29-2009, 06:01 PM   #1
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K7 Exposure With Flash Up

I just bought my K7 3 weeks ago.

I'm a little confused about how the camera does exposure compensation with the built-in flash. Here are some examples:

This picture was taken at 18mm with the flash up in Program mode. ISO is at 100. EV compensation is set to 0. Flash is set to "ON" with no compensation. The camera chose a shutter speed of 1/50 and an aperture of F3.5.


I immediately took a second picture. The only thing I changed is the EV compensation, which I set to +2. The camera did not change any other settings. Shutter speed remained at 1/50 and aperture remained at F3.5. Sensitivity also remained the same. Yet the picture is clearly much brighter.


My question is; why? What changed between the first and second picture (besides the EV compensation)? The camera settings are all the same!

When not using the flash, I can immediately see the effects of adjusting the EV compensation. Shutter speed goes up or down, aperture closes or opens, etc. But when the flash is up, nothing seems to change with the EV compensation, yet the picture does get brighter or darker with the compensation.

12-29-2009, 06:25 PM   #2
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QuoteOriginally posted by GoremanX Quote
when the flash is up, nothing seems to change with the EV compensation, yet the picture does get brighter or darker with the compensation.
Nothing seems to change but apparently something does change: It's the light output of the flash. To be exact, it's the duration of the strobe from the flash.

I assume you're using the kit lens (that's the only one listed in your signature). F/3.5 is max aperture. And I think 1/50 sec is the min shutter speed that camera thinks that does not create blur due to vibration.

I'm a bit confused as why you are surprised. What do you expect to happen when you change the EC to +2?
12-29-2009, 06:29 PM   #3
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With exposure compensation for the flash you change how much light you get from the flash. With +2 EV compensation you 4 times the light from the flash as with no compensation.
12-29-2009, 06:41 PM   #4
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QuoteOriginally posted by SOldBear Quote
Nothing seems to change but apparently something does change: It's the light output of the flash. To be exact, it's the duration of the strobe from the flash.
I didn't realize the flash output could be adjusted by the camera. I always figured it was a static thing that I could only adjust manually with the flash compensation. But now that I've read your reply, I tried a couple of experiments, and the flash is definitely way brighter at +5 EV than at -5 EV.

QuoteOriginally posted by SOldBear Quote
I'm a bit confused as why you are surprised. What do you expect to happen when you change the EC to +2?
That's the whole point, I didn't know. My previous camera (Canon S3 IS) didn't adjust flash intensity automatically, it just adjusted shutter speed even when the flash was up. I could only adjust flash intensity manually. So the more I increased the EC with the flash up, the more yellow the pictures would turn out because the white balance was set to "Flash" but the slower shutter speed would let in more incandescent light.

12-29-2009, 08:55 PM   #5
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which EV compensation?

There are two EV compensation settings that can be adjusted in this case.
One is the ambient light EV, the other is the flash EV. Which one did you change?
12-29-2009, 09:02 PM   #6
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QuoteOriginally posted by stanjo Quote
There are two EV compensation settings that can be adjusted in this case.
One is the ambient light EV, the other is the flash EV. Which one did you change?
The one that changes when I hold down the EV (+/-) button and turn the rear dial (using default dial configurations).
12-29-2009, 09:37 PM   #7
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QuoteOriginally posted by GoremanX Quote
The one that changes when I hold down the EV (+/-) button and turn the rear dial (using default dial configurations).
Hmmm, this is interesting. I will not expect this result from the ambient EV comp.

With my K100D, that EV control affects the ambient exposure. In your case, the ambient is underexposed and the camera cannot get more exposure as the f-stop and the speed are at their limit. Increasing that EV compensation should have no further effect - it's a wish (let more light in) the camera cannot fulfill (f-stop and speed already at limits).

Th flash EV comp serves a different purpose - it sets the exposure of the flash relative to the exposure of the ambient. No compensation means the flash will try to archive the same exposure as the ambient. Flash comp -2 sets the flash EV two stops lower then ambient (useful to balance ambient light with a certain fill ratio).

I am really puzzled why the K7 did that.
12-29-2009, 09:52 PM   #8
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QuoteOriginally posted by stanjo Quote
Th flash EV comp serves a different purpose - it sets the exposure of the flash relative to the exposure of the ambient. No compensation means the flash will try to archive the same exposure as the ambient. Flash comp -2 sets the flash EV two stops lower then ambient (useful to balance ambient light with a certain fill ratio).
On the K7 and K10D (I don't know about other bodies), if the built-in flash is up and enabled, the EC setting is for overall exposure and thus can change the built-in flash output.

To adjust flash output vs ambient light ratio:

- On the K7, hit the flash button (the one with lightning symbol), then turn the rear dial to adjust + or -.

- On the K10D, hit the Fn button, then the flash button, then turn the rear dial to adjust + or -.

12-29-2009, 09:59 PM   #9
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oops, K100D does the same...

I spoke too quickly - the K100D does the same.

I tried ambient and flash compensation. It seems like when the ambient light is not enough, the camera assumes "slow sync" flash mode and both compensation controls become flash compensation. They add to each other.
For example:
-2 amb, +2 flash = 0 amb, 0 flash
+2 amb, 0 flash = 0 amb, +2 flash.

Could very well be mentioned in the manual
12-29-2009, 10:02 PM   #10
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more confirmation from SOldBear - mystery is solved !
12-29-2009, 10:16 PM   #11
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QuoteOriginally posted by stanjo Quote
I am really puzzled why the K7 did that.
My initial thought was that my K7 was defective. I could swear it didn't act this way before. But I figured I'd ask a question rather than cry "DEFECT" for nothing. I guess it did always act this way, I just hadn't paid enough attention.

Here's another example of why this confused me. In Av mode, when the flash is up, changing the aperture does not make the camera adjust the shutter speed. Here are a couple of shots to illustrate my point:

This one was taken at F3.5


and this one at F8:


In both cases, the camera left the shutter speed at 1/50 and automatically adjusted the flash intensity to get the proper exposure. I didn't change either the EC (set at 0) or the flash EV comp myself, yet the exposure is the same despite the lens being closed a bunch of stops.

When using a flash, shutter speed appears to be dependent on focal length rather than EV. This probably has to do with proper flash sync speed. With this kit lens on a K7, at 18mm, shutter speed is always 1/50. At 24mm it's 1/60th. At 30mm it's 1/80. At 40mm and above it's 1/100.

Just when I thought I knew all the basics, I learn something new!

P.S. I realize the pictures above are horrible and show a shadow from the lens. I just took them quickly while sitting at my computer to illustrate a point.

Last edited by GoremanX; 12-29-2009 at 10:21 PM.
12-30-2009, 12:18 PM   #12
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QuoteOriginally posted by GoremanX Quote
My initial thought was that my K7 was defective. I could swear it didn't act this way before. But I figured I'd ask a question rather than cry "DEFECT" for nothing. I guess it did always act this way, I just hadn't paid enough attention.

Here's another example of why this confused me. In Av mode, when the flash is up, changing the aperture does not make the camera adjust the shutter speed. Here are a couple of shots to illustrate my point:

In both cases, the camera left the shutter speed at 1/50 and automatically adjusted the flash intensity to get the proper exposure. I didn't change either the EC (set at 0) or the flash EV comp myself, yet the exposure is the same despite the lens being closed a bunch of stops.

When using a flash, shutter speed appears to be dependent on focal length rather than EV. This probably has to do with proper flash sync speed. With this kit lens on a K7, at 18mm, shutter speed is always 1/50. At 24mm it's 1/60th. At 30mm it's 1/80. At 40mm and above it's 1/100.

Just when I thought I knew all the basics, I learn something new!

P.S. I realize the pictures above are horrible and show a shadow from the lens. I just took them quickly while sitting at my computer to illustrate a point.
I'm not sure with this since I don't have K-7, but if you have time try to check whether the K-7 apply the Auto EV Compensation on the setting.
My K20D has this option on the Custom setting which will cause the camera to adjust the exposure value AUTOMATICALLY when the camera thinks that correct exposure is not achieved.
12-30-2009, 01:10 PM   #13
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QuoteOriginally posted by HermanLee Quote
I'm not sure with this since I don't have K-7, but if you have time try to check whether the K-7 apply the Auto EV Compensation on the setting.
My K20D has this option on the Custom setting which will cause the camera to adjust the exposure value AUTOMATICALLY when the camera thinks that correct exposure is not achieved.
I have Auto EV turned off. I dislike that feature because I know better than the camera how much exposure I want. I only use the camera's metering as a tool to achieve my means faster.
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